Training at BARC(Bhabha atomic research centre)

INDEX

S.NO	Contents	Page no.
1.	Introduction to chiller A/C plant	2
2.	Technical specification of chiller	3
3.	Refrigeration & Refrigerants	4
4.	Refrigeration cycle & its process	5
5.	Compressors	9
6.	Oil Separator	13
7.	Condenser	13
8.	Drier	15
9.	Expansion valve	16
10.	Evaporator	18
11.	load calculation	21
12.	Human comfort	21
13.	Cooling Tower	23
14.	Pipe circuit of Chiller machine	25
15.	Pumps	27
16.	Troubleshooting	30
17.	Air Handling Unit	34
18.	Fan Coil Unit ( FCU)	41
19.	Precision unit	43
20.	Belt & Bearing	45
21.	Safety Devices	48
22.	Pump - Motor Alignment	50
23.	Readings & Observations	53
24.	Softening Plant	55
25.	Ozone layer depletion	58
26	Conclusion	59

1. INTRODUCTION

The chilling plant is use for the cooling of air and water. These are using the chillers which are work according to refrigeration cycle. Chillers are use either vapor-compression or absorption refrigerant cycle to cool the fluid for heat transfer. The basic refrigeration cycle used by chiller is same for both vapor-compression and absorption chillers.

The system utilize the liquid refrigerant that changes phase to a gas within an evaporator which absorbs heat from water to be cooled.

The refrigerant gas is then compressed to a higher pressure by a compressor.

Then it converted back into a liquid by rejecting heat through a condenser.

And then expanded by expansion valve to a low pressure mixture of liquid and vapor that goes back to the evaporator section. The cycle is repeated.

The chillers we studied about are using R-134a as a refrigerant gas. The system was installed by BLUE STAR Pvt. Ltd. in HBNI Plant for providing air conditioning in HRDD and Convention center.

There are two chiller machines in the HBNI chiller plant and both having the capacity of 350 TR. Here, induced draft cooling towers are using for cool and maintain the condenser water temperature separately. These cooling towers having capacity of 500TR both.

2. TECHNICAL SPECIFICATION OF CHIILLER:-

S no.	DESCRIPTION	DETAIL
1.	Make	BLUE STAR LTD
2.	Model	LCWX2-350F
3.	Rated capacity	1225 KW
4.	SR no.	910J07
5.	Compressor no.	RC2-830A-F
6.	Compressor sr no.	7E83602/04
7.	Refrigerant	R134A
8.	Charge Qty	523 KG
9.	Oil charge Qty	40 LTS/ COMPRESSOR
10.	Power supply	400-3PH-50Hz
11.	Rated current	360A
12.	Max current	440A
13.	Rated power input	221.8 KW
14.	Operating weight	8800KG

3. REFRIGERTION AND REFRIGERANTS:-

Refrigeration:-

Refrigeration is a process of removing heat from an area that is not desired and transfers it out to where it is unobjectionable, in a control manner.

Refrigerants:-A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. Many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became common, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane.

Desirable properties:-

The ideal refrigerant would have favorable thermodynamic properties, behavior to mechanical components, and be safe, including freedom from toxicity and flammability. It would not cause ozone depletion or climate change. The desired thermodynamic properties are a boiling point somewhat below the target temperature, a high heat of vaporization, a moderate density in liquid form, a relatively high density in gaseous form, and a high critical temperature. Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by appropriate choice of operating pressures

	Refrigerant used	Boiling point	Freezing point
1.	R-134a (tetrafloroIthene) C2H2F4	-26ºC	-96ºC
2.	R-11 (trichloromonofloromethene) CCl3F	-59.33ºC	-111ºC
3.	R- 12 (diclorodifloro methane) CCl2F2	-30ºC	-111ºC
4.	R-22 (momocholorodifloro methane) CClF2	-40ºC	-160ºC

R-134a chemical properties:-Now a days R-134a is preferred due its certain chemical properties as follows-

1. Non inflammable

2. Non corrosive

3. Non toxic

4. Color less

5. Non explosive

6. No irritating

7. Low boiling point

8. Low freezing point                                                                                   

9. High latent heat value

10. Heavy than water

11. Environmental friendly and not hazardous for ozone layer

4. REFRIGERATION CYCLE AND ITS PROCESS:-

The refrigeration cycle works on the principal of heat transfer in which the heat is transferred from high temperature side to low temperature side. It is reverse heat transfer cycle which transfer the heat to atmosphere for cooling of area by using by suitable refrigerant for it.

The cycle we studied is using the refrigerant R-134a in chiller machines.

The process of refrigeration is based on the four steps of refrigeration:-

1 .Compression.

2 .Condensation.

3 .Expansion.

4 .Evaporation.

1 .Compression:-

The refrigerant in a form of gas is taken to the inlet of compressor in which the refrigerant gas is compressed to high pressure and its temperature also get increases.

2. Condensation:-

The condensation process is used to decrease the temperature of the refrigerant at constant pressure. In this process the refrigerant heat is transferred to cold water coming from cooling tower. The state of refrigerant is changed at this stage from gas to liquid but pressure is constant.

3. Expansion:-

The expansion process is used for decreasing the pressure and temperature of the refrigerant. The temperature of refrigerant is decrease about to -16ºC.

4. Evaporation:-

The evaporation process is used to decrease the temperature of water coming from the user AHU. The heat is transferred from water to refrigerant. The refrigerant state is converted to gaseous state due to increase in temperature of refrigerant. Then the refrigerant is send toSthe compressor to repeat the further process. This process is repeat continuously.

Pressure – Enthalpy graph of refrigeration cycle

Ton of refrigeration:-

This term is used to indicate the capacity of the refrigeration and air conditioning system and amount of heat required o melt one ton of ice at 0°C ice to 0°C water within 24 hours, that is a heat removal rate of

1 ton of ice = 2000lbs

Latent heat of Fusion of ice is equal to 144 Btu

=

=12000 Btu / hour

So = 3024 kcal / hr or 3.52 kilo-watt (kW)

TR CALCULATIONS:-

FPS 

TR = 3024 K Cal / hr          (1GPM = 8.33 Ipm)

     = 72576 K Cal / hr        (MKS:-1US GPM=3.78 LPM1)

Coefficient of performance (cop)

Cop = Refrigeration effect ÷ work done

1 TR = 3.5167 kW

MKS:-

1US GPM=3.78 LPM1

TR = 3024 K Cal / hr

= 72576 K Cal / hr

Coefficient of performance (cop):-

Cop = Refrigeration effect ÷ work done

1 TR = 3.4 KW

5. COMPRESSORS:-

The compressor are used to compress the refrigerant gases or air to increase its pressure and temperature. The compression of the suction vapor from the evaporator to the condenser pressure can be achieved by mechanical compression, ejector compression or by a process combination of absorption of vapor, pumping, and desorption.

The compressors are of following types:-

A. positive displacement compressors

• Reciprocating compressors
• Rotary compressors
• Scroll compressors
• Screw compressors

B. non-positive displacement compressors

• Centrifugal compressors

In HBNI Chiller Plant we have studied about the single-screw compressor which installed by the BLUE STAR PVT. LTD.

SINGLE-SCREW COMPRESSORS

 The screw single-rotor compressor represents a cylindrical member with spiral grooves.Mating screw in the two plane asterisks on both sides of the screw, rotating in opposite directions from each other.

These stars wheels rotating in the plane of the center of the screw shaft. Gas-tight housing embodies the screw and stars, the screw rotates with a small gap in the cylindrical fireplace that is a part of the body.

These stars wheels rotating in the plane of the center of the screw shaft. Gas-tight housing embodies the screw and stars and the screw rotates with a small gap in the cylindrical fireplace that is a part of the body.

Mantel contains two slots in which the wheels star run. Only the screw is controlled from the outside, and the screw, then drives two stars. Capacity management is using a variable return port is controlled sliding vane, which regulates the position in which the compression begins.

Compression occurs simultaneously in the upper and lower halves of the compressor.

The results of this joint action in negligible net radial loads on the bearings of the screw. The only loads on the bearings in a machine other than the weight of parts, small loads on the wheel of stars of shafts high pressure operating on one side of each tooth in the process of creating the grid.t

Machine and two-screw compressor has few moving parts one screw and two star wheels. Manufacturers seek to extend favorable compression efficiency to a lesser extent than now, suitable for two-screw compressor. In the development of single-screw compressors one of the difficulties was the disclosure of the materials for the wheel of stars that prevent wear. Currently, manufacturers of single-screw compressors seem to prefer a composite of steel and glass-fiber reinforced plastic.

When viewing the screw compressor package, for example, an oil separator is the large size of the component. Were some of the concepts developed in order to exclude this component package size may be reduced. One of such methods is to seal the gaps between the star wheels and a rotor with the help of liquid refrigerant same refrigerant compressor pumps. Oil is still need for lubrication, but none is entered for sealing. 

Compressors are designed for sealing liquid refrigerant is constructed with small gaps between the star rotor wheels and what is the truth, compressors, sealed with oil. This concept can be applied for Halocarbon refrigerants such as R-134a and R-22, and air-conditioning, where the pressure ratio is moderate. The use of liquid refrigerant seals so far not been successful in ammonia compressors, nor for industrial refrigeration application.

Components of screw compressors:-

S no.	Components	S no.	Components
1.	Compressor casing	15.	Male rotor
2.	Motor casing	16.	Suction bearings
3.	Oil separator	17.	Suction bearings inner/outer spacer ring
4.	Motor rotor assembly	18.	Oil guiding ring
5.	Motor stator assembly	19.	Suction filter
6.	Motor rotor washer	20.	Suction flange
7.	Motor rotor spacer ring	21.	Cable box
8.	Piston	22.	Power bolt
9.	Piston spring	23.	Thermostat terminals
10.	Piston rod	24.	Motor cable cover plate
11.	Bearing seat’s cover plate	25.	Baffles
12.	Modulation solenoid valve	26.	Refrigerant lubricant
13.	Modulation slide valve	27.	PTC discharge temperature sensor
14.	Slide valve key	28.	Discharge connect flange

6.OIL SEPARATOR:-

An external oil separator is installed in the compressor discharge line to separate oil from the refrigerant. This is specially designed for low velocity of refrigerant and has demister pads of effective oil separation. This has integral oil reservoir at the bottom. Oil level switch is incorporated for the safe operation of compressor in case of fail in oil level below acceptable limit. The oil flow back to the compressor is due to differential pressure. A solenoid valve provided in the oil return line energies along with compressor start. The oil flow switch provided in the line as an additional safety trips the compressor in case of stoppage of oil return. Majority of the oil is recovered back where as minute quality of oil can travel along with refrigerant further to the system. There are two or three baffle plates are used to separate the oil and the compressed refrigerant. Oil is set at the bottom of the vessel and again re-send to the compression process by its pipe line.

7. CONDENSERS:-

The vapor at discharge from the compressor is of high temperature. Reducing the temperature of refrigerant vapor takes place in the discharge line and in the first few coils of condenser. In some condensers sub-cooling also takes place near the bottom where there is only liquid. The heat is transferred from water to the refrigerant for cooling of water to provide chilled water to the user.

The condensers are generally characterized by the cooling medium:-

1.    Air cooled condenser

2.    Water cooled condensers

3.    Evaporative condenser

Water cooled condenser:-                     

Water cooling condensers can be of three types, i.e (shell & tube, shell & coil, and double tube). In HBNI plant we studied about the shell & tube type water cooled condenser. The shell & tube type, with water flowing through passes inside tubes and the refrigerant condensing in the shell is most commonly used condensers.

8. Drier:-

A filter-drier in a refrigeration or air conditioning system has two essential functions: one, to adsorb system contaminants, such as water, which can create acids, and two, to provide physical filtration. Evaluation of each factor is necessary to ensure proper and economical drier design.

1-Absorbing moisture, preventing acids.

2-The ability to remove water from a refrigeration system is the most important function of a drier.

3-Water can come from many sources, such as trapped air from improper evacuation, system leaks, and motor windings, to name a few.

Another source is due to improper handling of polyolester (POE) lubricants, which are hygroscopic; that is, they readily absorb moisture. POEs can pick up more moisture from their surroundings and hold it much tighter than the previously used mineral oils. This water can cause freeze-ups and corrosion of metallic components.

Water in the system can also cause a reaction with POEs called hydrolysis, forming organic acids.

To prevent the formation of these acids, the water within the system must be minimized. This is accomplished by the use of desiccants within the filter-drier. The three most commonly used desiccants are molecular sieve, activated alumina, and silica gel.

Each of these cavities or pores are uniform in size. This uniformity eliminates the co-adsorption of molecules varying in size. This permits molecules, such as water, to be adsorbed, while allowing other larger molecules, such as the refrigerant, lubricant, and organic acids, to pass by.

Activated alumina is formed from aluminum oxide (Al2O3) and is not a highly crystalline material. Both alumina and silica gel show a wide range of pore sizes and neither exhibit any selectivity based on molecular size. Due to the varying pore sizes, they can co-adsorb the much larger refrigerant, lubricant, and organic acid molecules, eliminating the surface area available to adsorb water.

Alumina can also aid in the hydrolysis of the POE lubricants creating organic acids since both water and lubricant are adsorbed into the pore openings of the alumina.

Types:-

1-Spun copper driers(Used in Blue-Star Chillers)

2-Steel liquid-line driers

3-Steel bi-flow driers

9. EXPANSION VALVE:-

This is the basic component of refrigeration system that must reduce the pressure and temperature of the liquid refrigerant coming from the condenser and control the flow of refrigerant on the evaporator.

Description:-

Flow control, or metering, of the refrigerant is accomplished by use of a temperature sensing bulb, filled with a similar gas as in the system that causes the valve to open against the spring pressure in the valve body as the temperature on the bulb increases. As the suction line temperature decreases, so does the pressure in the bulb and therefore on the spring causing the valve to close. An air conditioning system with a valve is often more efficient than other designs that do not use one.

A expansion valve is a key element to a heat pump; the cycle that makes air conditioning, or air cooling, possible. A basic refrigeration cycle consists of four major elements, a compressor, a condenser, a metering device and an evaporator. As a refrigerant passes through a circuit containing these four elements, air conditioning occurs. The cycle starts when refrigerant enters the compressor in a low-pressure, moderate-temperature, gaseous form.

Types:-

There are two main types of thermal expansion valves: internally or externally equalized.

The difference between externally and internally equalized valves is how the evaporator pressure affects the position of the needle. In internally equalized valves, the evaporator pressure against the diaphragm is the pressure at the inlet of the evaporator, whereas in externally equalized valves, the evaporator pressure against the diaphragm is the pressure at the outlet of the evaporator. Externally equalized thermostatic expansion valves compensate for any pressure drop through the evaporator.

Internally equalized valves can be used on single circuit evaporator coils having low pressure drop. Externally equalized valves must be used on multi-circuited evaporators with refrigerant distributors. Externally equalized expansion valves can be used on all applications; however, an externally equalized expansion valve cannot be replaced with an internally equalized expansion valve and high-temperature gaseous state. The high-pressure and high-temperature gas then enters the condenser. The condenser converts the high-pressure and high-temperature gas to a high-pressure liquid by transferring heat to a lower temperature medium, usually ambient air.

The high pressure liquid then enters the expansion valve where the expansion valve allows a portion of the refrigerant to enter the evaporator. In order for the higher temperature fluid to cool, the flow must be limited into the evaporator to keep the pressure low and allow expansion back into the gas phase.

The expansion valve has sensing bulbs connected to the suction line of the refrigerant piping. The gas pressure in the sensing bulbs provides the force to open the expansion valve therefore adjusting the flow of refrigerant and the superheat.

Function of expansion valve in refrigeration cycle:-

Expansion valves are flow-restricting devices that cause a pressure drop of the working fluid. The valve needle remains open during steady state operation. The size of the opening or the position of the needle is related to the pressure and temperature of the evaporator.

There are main parts of the expansion valve that regulate the position of the needle. A sensor bulb, at the end of the evaporator, monitors the temperature change of the evaporator.

10. EVAPORATOR:-

An evaporator is a device used to turn the liquid form of a chemical into its gaseous form. The liquid is evaporated, or vaporized, into a gas.

Uses:-

An evaporator is used in an air-conditioning system to allow a compressed cooling chemical, such as R-134a, R-22 (Freon) or R-410A, to evaporate from liquid to gas while absorbing heat in the process. It can also be used to remove water or other liquids from mixtures.

Working of evaporator:-

The solution containing the desired product is fed into the evaporator and passes across a heat source. The applied heat converts the water in the solution into vapor. The vapor is removed from the rest of the solution and is condensed while the now-concentrated solution is either fed into a second evaporator or is removed. The evaporator, as a machine, generally consists of four sections. The heating section contains the heating medium, which can vary. Steam is fed into this section. The most common medium consists of parallel tubes but others have plates or coils typically made from copper or aluminum. The concentrating and separating section removes the vapor being produced from the solution. The condenser condenses the separated vapor, then the vacuum or pump provides pressure to increase circulation.

Type of evaporator

1. Natural/forced circulation evaporator

2. Rising film (Long Tube Vertical) evaporator

3. Climbing and falling-film plate evaporator

4. Multiple-effect evaporators

5. Agitated thin film evaporators

Flooded Type Evaporator:-

Here flooded evaporators are used. Flooded evaporators, which are sometimes called wet evaporators, are divided into forced-flow evaporators and thermosiphon evaporators. Forced-flow evaporators use a pump or an ejector as the driving force, while the density difference between liquid and gaseous refrigerant drives thermosiphon systems.

An important difference between a flooded evaporator and a direct expansion (DX) evaporator is that the flooded evaporator operates in conjunction with a low-pressure receiver. The receiver acts as a separator of gaseous and liquid refrigerant after the expansion valve and ensures a feed of 100% liquid refrigerant to the evaporator. Unlike in a direct expansion (DX) evaporator, the refrigerant is not fully evaporated and superheated at the flooded evaporator outlet. The leaving refrigerant flow is a two-phase mixture with typically 50-80% gas.

Cycle system:-

In addition to the basic equipment in a direct expansion refrigeration circuit, i.e. evaporator, compressor, condenser and expansion valve, the flooded system needs a receiver to separate the two phase mixture after the expansion valve. The refrigerant leaving the bottom of the receiver is 100% liquid.

The refrigerant from the receiver enters the evaporator and evaporates due to the heat transferred from the secondary side. The refrigerant at the evaporator inlet is slightly sub-cooled due to the pressure increase from the receiver to the evaporator. After the evaporator, the two-phase refrigerant mixture again enters the receiver, where liquid and gas are separated. The gas then enters the compressor, while the remaining liquid is re-circulated through the evaporator.

The gas is compressed in the compressor and condensed in the condenser in the same way as in the basic compression cycle. The force driving the refrigerant through the evaporator depends on the density difference between gaseous and liquid refrigerant. When refrigerant is evaporated inside the BPHE, the lower density of the vapor allows more liquid refrigerant to flow inside the evaporator. Please note that the expansion valve needs no regulating action, because the flooded evaporator is self-regulating. The spontaneous vaporization in the receiver ensures that no liquid enters the compressor.

The forced-flow compression cycle:-

A forced-flow flooded system is identical to a thermosiphon system, except that a pump is installed before the evaporator to serve as a driving force for the refrigerant.

If the installation site does not offer the minimum necessary height difference between the receiver and evaporator to allow density circulation, a forced-flow system may be preferable over a thermosiphon. The higher cost of a pump can still be more economical than elevating the roof of the installation room. Forced-flow systems often have a larger circulation number than thermosiphon systems due to the higher mass flow created by the pump.

Larger static head, i.e. a larger height difference between receiver and evaporator, increases the sub-cooling of the refrigerant. The preheating in the beginning of the evaporator is then increased, which may lead to the requirement of a larger evaporator, because much more heat transfer area is needed to preheat liquid instead of producing gas.

If the lubricating oil is insoluble in and heavier than the refrigerant, oil drainage can be installed before the pump. Oil droplets on the heat transfer surface may decrease the heat transfer dramatically.

Characteristics of flooded systems:-

An advantage of flooded evaporators is that the potential problem of poor refrigerant distribution in the evaporator is reduced. The refrigerant is 100% liquid, and a liquid stream is much better distributed between the channels compared with the two-phase mixture of DX systems. Thus, when selecting a flooded evaporator, a SWEP B-model should be used for flooded evaporators, in contrast to DX systems where BPHEs with refrigerant distribution device are the better choice.

The receiver separates the refrigerant vapor before feeding it to the compressor, so there is no need for superheating the refrigerant in a flooded evaporator. A larger portion of the total heat surface area will thus be used for evaporation compared with a DX evaporator, where 10-30% of the total heat surface area may be dedicated to superheating.

In the pipe that connects the receiver and the flooded evaporator, the evaporator inlet liquid is sub-cooled.

The pressure gain in the receiver-evaporator pipe is actually approximately 5-50 k Pa (0.05-0.5 bar), while the pressure lift over the compressor is roughly 12-17 bar. Because there is no need for superheating in a flooded evaporator, the evaporation temperature can be a few degrees higher than in a DX evaporator.

Due to the higher evaporation temperature in a flooded evaporator, the pressure lift between the evaporator and condenser sides is smaller.

The advantage is that less compressor work (W) is needed. Perhaps the largest advantage of flooded evaporators is that they use all the latent energy of the refrigerant in the phase transition between liquid and gas to cool a fluid.

11. Load calculations

The basic load calculation, called a block load, is used only to find the required unit size. It looks at the home as a whole and gives a total load. Several factors affect this such as:

1. The type of foundation

2. Type and color of roof

3. Insulation values in walls, floors, and ceilings.

4. Window type, location, and quantity.

5. Type, location, and quantity of exterior doors

6. Desired temperature

7. The area in which you live.

8. Size of home

The basic load calculation is only recommended for a single level home and only as a guide in replacing a unit with existing ductwork or checking to make sure the existing unit is big enough. A more advanced version of load calculation requires more information such as individual room measurements. This is called a room by room calculation. This not only gives you the equipment size but also designs the duct system based on the needs of each room. It is important to know what proportion of conditioned air is required in each room.

NOTE:- In many cases, the required proportion will change between the heating and cooling seasons.

Once you know how much air is required in each room, dampers in the duct system can be adjusted to get the proper airflow through each register. This process is commonly called air balancing and it helps to eliminate large temperature differences from room to room in the home. It results in a higher level of comfort.

12. Human Comfort:-

Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation (ANSI/ASHRAE Standard .Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC (heating, ventilation, and air conditioning) design engineers.

Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. The main factors that influence thermal comfort are those that determine heat gain and loss, namely metabolic rate, clothing insulation, air temperature, mean radiant temperature, air speed and relative humidity. Psychological parameters, such as individual expectations, also affect thermal comfort.

The Predicted Mean Vote (PMV) model stands among the most recognized thermal comfort models. It was developed using principles of heat balance and experimental data collected in a controlled climate chamber under steady state conditions. Occupants control their thermal environment by means of clothing, operable windows, fans, personal heaters, and sun shades.

Influencing factors

Since there are large variations from person to person in terms of physiological and psychological satisfaction, it is hard to find an optimal temperature for everyone in a given space.

People have different metabolic rates that can fluctuate due to activity level and environmental conditions. Standard defines metabolic rate as the level of transformation of chemical energy into heat and mechanical work by metabolic activities within an organism, usually expressed in terms of unit area of the total body surface.

Metabolic rate is expressed in met units, which are defined as follows:-

1 met = 58.2 W/m² (18.4 Btu/h·ft²), which is equal to the energy produced per unit surface area of an average person seated at rest. The surface area of an average person is 1.8 m² (19 ft²).

1.    Clothing insulation

2.    Air temperature

3.    Mean radiant temperature

4.    Air speed

5.    Relative humidity

6.    Skin wetted ness

13. Cooling Tower:-

A cooling tower is a heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature.

In HBNI a/c plant the cooling tower capacity is 500 TR of each. There are three cooling tower for three chillers, two for Blue Star chillers and one for Diakine chiller.

An HVAC (heating, ventilating, and air conditioning) cooling tower is used to dispose of ("reject") unwanted heat from a chiller. Water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat rejection to tower water at or near wet-bulb temperatures. Air-cooled chillers must reject heat at the higher dry-bulb temperature, and thus have a lower average reverse-Carnot cycle effectiveness. In areas with a hot climate, large office buildings, hospitals, and schools typically use one or more cooling towers as part of their air conditioning systems. Generally, industrial cooling towers are much larger than HVAC towers.

HVAC use of a cooling tower pairs the cooling tower with a water-cooled chiller or water-cooled condenser. Cooling towers are also used in HVAC systems that have multiple water source heat pumps that share a common piping water loop. In this type of system, the water circulating inside the water loop removes heat from the condenser of the heat pumps whenever the heat pumps are working in the cooling mode, then the externally mounted cooling tower is used to remove heat from the water loop and reject it to the atmosphere.

Fans are used for flashing air cool the water droplets. The cooled water droplets gets cooled in the sump and they are again polled through the condenser for the cooling the refrigerant than cycle in the repeated for continues removing heat from the refrigerant system.

Cooling Tower Range=

Cooling tower inlet temp - Cooling tower outlet temp.

Cooling Tower Approach=

Cooling tower outlet temp - Wet bulb temp.

Cooling Tower Efficiency=

Cooling tower range/ (Cooling tower inlet temp - wet bulb temp)

There Are Two Types Of Cooling Tower:-

(1) Natural Draft Cooling Tower

(2) Mechanical Draft Cooling Tower

(a) Forced draft cooling tower

(b) Induced draft cooling tower                                                    

(1)Natural Draft Cooling Tower:-

NDCT isthat device in which hot water condenser is sprayed from the top of the tower and is cooled by the movement's natural air through it.

(2)Mechanical Draft Cooling Tower:-

(a)Forced Draft Cooling Tower:-

The water from the condenser is sprayed at the top of the tower and air is forced by the fan from the bottom of the tower the air velocity of 120m/min is recommended with a flow of 100 to 130cu m per min per ton of refrigeration capacity.

(b) Induced Draft Cooling Tower:-

The induced tower has the fans located at the top of the tower sucking air induced an air movement up the tower.

Differences b/w Forced & Induced Draft Cooling

Forced Draft Cooling Tower	Induced Draft Cooling Tower
1) lower power consumption 2)Low cost 3)Less corrosion 4)Normal cooling range 5)Air short cycling possible 6)Low efficiency	1) High power consumption 2)High cost & easy maintenance 3)High corrosion 4)High cooling range 5)No air short cycling possible 6)High efficiency

TECHNICAL DATA OF COOLING TOWER

S no.	DESCRIPTION	DETAILS
1.	Make	MIHIR ENGINEERING LTD
2.	Motor	CM20
3.	Motor HP	15
4.	Motor RPM	600
5.	Year	2007 SEP

14. Circuit (piping) flow of chiller in HBNI plant:-

Ø  Air from ambient flow in the compressor. Compressor gear need to be cooled so oil is supplied.

Ø  Refrigerant with oil is harmful so it cannot be use and it can be dangerous.

Ø  Oil separator is provided which separate the oil and refrigerant.

Ø  Oil circulate back in the compressor for cooling.

Ø  Refrigerant then goes in condenser and extract heat from water.

Ø  Vapor refrigerant convert into liquid in condenser.

Ø  Water of condenser then go for cooling in cooling tower.

Ø  Refrigerant then go through the expansion valve in which high pressure high temperature refrigerant get converted into low pressure and low temperature refrigerant.

Ø  Refrigerant then pass through the drier where it get dried.

Specification	Detail
Motor type	2phase permanent magnet, 2 coil bipolar
Supply voltage	12v dc, -5% +10%  measured at valve leads
Connections	4 leads,18AWG,pvc insulated
Phase resistance	75 ohms per winding ±10%
Current range	0.131 to 0.215amps/winding 0.262 to 0.439 amps with two winding
Maximum power	4 watts
Inductance per winding	62±10mH
Required step rate	200 step per second
No of step	6386
Resolution	0.000783 inches/step (.2mm/step)
Total stroke	0.50 inches (12.7)
Maximum allowable	Less than cc/min at psi internal leakage Estimated
Maximum allowable	Less than .10oz/year(.20gr/year at 300psig external leakage

Ø  In evaporator water inlet is from user and also outlet of chilled water to user.

Ø  Liquid refrigerant absorb heat of water in evaporator and get converted into vapor.

Chilled Water Cycle

Return header:-

The chilled water from various user reaches the return by following pipe line.

1-HRDD AHU

2- Convention Center

The return header received used water chilled water having a temperature 10 to 12°C & pressure 20 psi to 30 psi and again moves to the pump.

                              

Pump:-

The chilled water is pumped to the floating header pump section pressure 2kg/cm^² & discharge pressure is 5 kg/cm^² pump type is split casing double suction & single discharge.

Floating header:-

Floating header water turns to the refrigeration machine inlet. Floating header is used as common header for any chiller machine & chiller pump can be utilized.

Refrigeration machine:-

Refrigeration machine receiving used chilled water having a temperature 10°C to 12°C & pressure 40 psi to 45 psi & chiller machine outlet chilled water temperature 7°C to 9°C & pressure 35 psi to 40 psi.

Refrigeration machine is absorbed of heat of used chilled water then chiller machine chilled water is sent to the supply header.

Supply header:-

The chilled water comes to common supply header the chilled water is than supplied to various following header.

1-HRDD AHU

2-Convention Center

Then used chilled water again comes back to return header & the cycle continues.

BLOCK DIAGRAM OF CHILLED WATER SUPPLY TO USER

15. Pumps:-

A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.

"The pump is powered by an electric motor that drives an impeller, or centrifugal pump. The impeller moves water, called drive water, from the well through a narrow orifice, or jet, mounted in the housing in front of the impeller. Its function is to slow down the water and increase the pressure". Pumps operate by some mechanism (typically reciprocating or rotary), and consume energy to perform mechanical work by moving the fluids

Single stage pump-

 When in a casing only one impeller is revolving then it is called single stage pump.

Double/multi-stage pump –

When in a casing two or more than two impellers are revolving then it is called double/multi-stage pump.

Types of Pumps:-

1-Reciprocating pumps - piston, plunger and diaphragm.

2-Power pumps.

3-Steam pumps.

4-Rotary pumps - gear, lobe, screw, vane, regenerative (peripheral) and progressive cavity.

Centrifugal Pumps:-

Here we use centrifugal pumps for move the water for different purposes.

The cut view of centrifugal pump is shown in below color diagram.

Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbo machinery. Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing).

A centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure.

Efficiency factor

η =

Where:-

P = is the mechanics input power required (W)

ρ = is the fluid density (kg/m3)

g = is the standard acceleration of gravity (9.80665 m/s2)

H = is the energy Head added to the flow (m)

Q = is the flow rate (m3/s)

η = is the efficiency of the pump plant as a decimal.

16. TROUBLE SHOOTING

The table below shows some problem that might encounter in the job sight during commissioning or upon operation of compressor. This table will only serve as a guide for the Engineer to understand the situation once the problem occurred in the site.

PROBLEMS	PROBABILITY	REMEDY/ CORRECTIVE ACTION
Sudden trip of motor thermistor/ sensor	Low suction pressure cause low refrigeration	Check compressor working unloaded for a long period
	Refrigerant shortage	Charge refrigerant
	Suction filter clogged	Clean filter
	High suction temperature	Check refrigerant liquid level
	High suction superheat	Adjust the superheat less than 10ᵒK
	Unstable electricity system or failure	Check electricity power supply
	Motor overload	Check and rectify
	Bad motor coil causing temperature rising rapidly	Check and rectify
Compressor unable to load	Low ambient temperature or high oil viscosity	Turn on the oil heater before compressor start
	Capillary clogged	Clean or replace capillary
	Modulation solenoid valve clogged or solenoid valve coil burnt	Clean / purge check the oil level  solenoid valve core or replace the solenoid valve coil
	Internal built-in oil line clogged	Check and clean the compressor oil circuit
	Piston stuck-up	Change piston or piston ring
	Oil filter cartridge clogged	Clean oil filter (replace if needed)
	Too small the high-low pressure differential.	Minimum pressure differential is 4 bar. Consider to install an oil pump
Compressor unable to unload	Modulation solenoid valve clogged or burnt	Clean or replace the solenoid valve
	Piston ring worn off or broken, or cylinder damaged resulting leakage	Change piston (if cylinder damaged severely, change the cylinder)
	Lubrication oil insufficient	Check the oil level of the compressor if enough, add some oil if necessary
	Leakage at internal discharge cover plate end side	Check or replace the gasket and tighten the bolts.
	solenoid valve voltage misused	Check the control voltage
	Piston stuck-up	Change the piston set, and check the cylinder and slide valve
Poor installation of motor	Capacity control logic unstable. 1. Bad compressor motor coil. 2. Motor power terminal or bolt wet or frosty. 3. Motor power terminal or bolt bad or dusty. 4. Bad installation of magnetic contactors. 5. Acidified internal refrigeration system. 6. Motor coil running long time continuously under high temperature. 7.Compressor restart counts too many times	Check the coil or change the motor stator
Compressor starting failure or Y-∆ starter shifting failure	Slide valve piston unable to go back to its lowest % original position.	Check if the unloading SV is energized once the compressor shut down. Unload the compressor before shut down
	Voltage incorrect	Check the power supply
	Voltage drop too big when starting the compressor or magnetic contactor failure or phase failure.	Check the power supply and the contactor
	Motor broken down.	Change the motor
	Motor thermistor sensor trip	See “sudden trip of motor sensor” above
	Incorrect supply power connection	Check and re-connect
	Y-∆ timer failure	Check or replace
	Discharge or suction stop valve closed.	Open the stop valve
	Improper connection between node terminal of Y-∆ wiring	Check and re-connect the wiring
	Rotor locked	Check and repair
	Earth fault	Check and repair
	Protection device trip	Check
Abnormal vibration and noise of compressor	Damaged bearing.	Change bearing
	Phenomenon of liquid compression	Adjust proper suction superheat
	Friction between rotor or between rotor and compression chamber	Change the screw rotor or/and compression chamber.
	Insufficient lubrication oil	Check the oil level of the compressor if enough, add some oil if necessary.
	Loosen internal part	Dismantle the compressor and change the damage parts
	Electromagnetic sound of the solenoid valve	Check and repair / replace
	System harmonic vibration caused by improper piping system	Check the system piping and if possible improve it using copper pipe.
	External debris fallen into the compressor.	Dismantle the compressor and check the extent or the damage.
	Friction between slide valve and rotors.	Dismantle the compressor and change the damaged parts.
	Motor rotor rotates imbalance	Check and repair
Compressor does not run	Motor line open	Check
	Tripped overload	Check the electrical connection
	Screw rotor seized	Replace screw rotor, bearing etc.
	Motor broken	Change motor
High discharge temperature	Insufficient refrigerant	Check for leak. Charge additional refrigerant and adjust suction superheat less than 10ᵒK.
	Condenser problem of bad heat exchange.	Check and clean condenser.
	Refrigerant overcharge	Reduce the refrigerant charge.
	Air / moisture in the refrigerant system	Recover and purify refrigerant and vacuum system
	Improper expansion valve.	Check and adjust proper suction super heat
	Insufficient lubrication oil.	Check the oil level and add oil
	Damaged bearing	Stop the compressor and change the bearing and other damaged part.
	Improper Vi valve.	Change the slide valve
	No system additional cooling (liquid injection or oil cooler)	Install additional system(liquid injection or oil cooling or both base on working condition limitation)
Compressor losses oil	Lack of refrigerant	Check for leaks. Charge additional refrigerant.
	Improper system piping
	Refrigerant fills back	Maintain suitable suction super heat at compressor
Low suction pressure	Lack of refrigerant	Check for leaks. Charge additional refrigerant
	Evaporator dirty or iced	Defrost or clean coil
	Clogged liquid line filter drier	Replace the cartridge
	Clogged suction line or compressor suction strainer	Clean or change suction strainer
	Expansion valve malfunctioning	Check and recheck for proper superheat
	Condensing temperature too low	Check means for regulating condensing temperature
High suction pressure	Cooler water flow rate is higher than the rated flow rate	Maintain the rated flow rate
	Cooler water inlet temperature is higher than rated	Supply the rated temperature cooling water at cooler inlet
	System is over changed	Remove the excess refrigerant
High suction temperature	High water inlet temperature	Ensure that correct water temperature is available
	System ids under charged	Charge refrigerant
	Expansion valve man-functioning	Check & rectify

17. AIR HANDLING UNIT:-

An air handler, or air handling unit (often abbreviated to AHU), is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal box containing a blower, heating or cooling elements, filter, racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a duct work ventilation system that distributes the conditioned air through the building and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork.

Small air handlers, for local use, are called terminal units, and may only include an air filter, coil, and blower; these simple terminal units are called blower coil or FCU. A larger air handler that conditions 100% outside air, and no recirculated air, is known as a makeup air unit (MAU). An air handler designed for outdoor use, typically on roofs, is known as a packaged unit (PU) or rooftop unit (RTU).

Construction:-

The air handler is normally constructed around a framing system with metal infill panels as required to suit the configuration of the components. In its simplest form the frame may be made from metal channels or sections, with single skin metal infill panels. The metalwork is normally galvanized for long term protection. For outdoor units some form of weatherproof lid and additional sealing around joints is provided.

Larger air handlers will be manufactured from a square section steel framing system with double skinned and insulated infill panels. Such constructions reduce heat loss or heat gain from the air handler, as well as providing acoustic attenuation. Larger air handlers may be several meters long and are manufactured in a sectional manner and therefore, for strength and rigidity, steel section base rails are provided under the unit. Where supply and extract air is required in equal proportions for a balanced ventilation system, it is common for the supply and extract air handlers to be joined together, either in a side-by-side or a stacked configuration.

Components:-

The major types of components are described here in approximate order, from the return duct (input to the AHU), through the unit, to the supply duct (AHU output).

Filters:-

Air filtration is almost always present in order to provide clean dust-free air to the building occupants. This order to keep all the downstream components clean. Depending upon the grade of filtration required, typically filters will be arranged in two (or more) successive banks with a coarse-grade panel filter provided in front of a fine-grade bag filter, or other "final" filtration medium. The panel filter is cheaper to replace and maintain, and thus protects the more expensive bag filters.

The life of a filter may be assessed by monitoring the pressure drop through the filter medium at design air volume flow rate. This may be done by means of a visual display using a pressure gauge, or by a pressure switch linked to an alarm point on the building control system. Failure to replace a filter may eventually lead to its collapse, as the forces exerted upon it by the fan overcome its inherent strength, resulting in collapse and thus contamination of the air handler and downstream ductwork. 

Heating or cooling elements:-

Air handlers may need to provide heating, cooling, or both to change the supply air temperature, and humidity level depending on the location and the application. Such conditioning is provided by heat exchanger coil(s) within the air handling unit air stream, such coils may be direct or indirect in relation to the medium providing the heating or cooling effect.

Direct heat exchangers include those for gas-fired fuel-burning heaters or a refrigeration evaporator placed directly in the air stream. Electric resistance heaters and heat pump can be used as well. Evaporative cooling is possible in dry climates.

Indirect coils use hot water or steam for heating, and chilled water for cooling (prime energy for heating and cooling is provided by central plant elsewhere in the building). Coils are typically manufactured from copper for the tubes, with copper or aluminum fins to aid heat transfer. Cooling coils will also employ eliminator plates to remove and drain condensate. The hot water or steam is provided by a central boiler, and the chilled water is provided by a central chiller. Downstream temperature sensors are typically used to monitor and control "off coil" temperatures, in conjunction with an appropriate motorized control valve prior to the coil.

If dehumidification is required, then the cooling coil is employed to over cool so that the dew point is reached and condensation occurs. A heater coil placed after the cooling coil re-heats the air (therefore known as a re-heating coil) to the desired supply temperature. This has the effect of reducing the relative humidity level of the supply air.

In colder climates, where winter temperatures regularly drop below freezing, then frost coil or re-heating coil are often employed as a first stage of air treatment to ensure that downstream filters or chilled water coils are protected against freezing. The control of the frost coil is such that if a certain off-coil air temperature is not reached then the entire air handler is shut down for protection.

Humidifier:-

Humidification is often necessary in colder climates where continuous heating will make the air drier, resulting in uncomfortable air quality and increased static ventilation. Various types of humidification may be used:

·         Evaporative: dry air blown over a reservoir will evaporate some of the water. The rate of evaporation can be increased by spraying the water onto baffles in the air stream.

·         Vaporizer: steam or vapor from a boiler is blown directly into the air stream.

·         Spray mist: water is diffused either by a nozzle or other mechanical means into fine droplets and carried by the air.

•      Ultrasonic: A tray of fresh water in the airstream is excited by and ultrasonic device forming a fog or water mist.

·         Wetted medium: A fine fibrous medium in the airstream is kept moist with fresh water from a header pipe with a series of small outlets. As the air passes through the medium it entrains the water in fine droplets. This type of humidifier can quickly clog if the primary air filtration is not maintained in good order.

Mixing chamber:-

In order to maintain indoor air quality, air handlers commonly have provisions to allow the introduction of outside air into, and the exhausting of air from the building. In temperate climates, mixing the right amount of cooler outside air with warmer return air can be used to approach the desired supply air temperature. A mixing chamber is therefore used which having damper controlling the ratio between the return, outside, and exhaust air.

Blower/fan:-

Air handlers typically employ a large square cage barrel driven by an AC induction electric motor to move the air. The blower may operate at a singles speed, offer a variety of set speeds, or be driven by a variable frequency. Drive to allow a wide range of air flow rates. Flow rate may also be controlled by inlet vanes or outlet dampers on the fan.

Some problem:- Air circulation is greatly reduced at the vents (as wobble is lost energy), efficiency is compromised, and noise is increased. Another major problem in fans that are not balanced is longevity of the bearings (attached to the fan and shaft) is compromised. This can cause failure to occur long before the bearings life expectancy.

Heat recovery device

A heat recovery device heat exchanger of many types, may be fitted to the air handler between supply and extract airstreams for energy savings and increasing capacity. These types more commonly include for:

·         Plate Heat exchanger: A sandwich of plastic or metal plates with interlaced air paths. Heat is transferred between airstreams from one side of the plate to the other. The plates are typically spaced at 4 to 6mm apart. Can also be used to recover coolant temperature. Heat recovery efficiency up to 70%.

·         Rotary heat exchanger: A slowly rotating matrix of finely corrugated metal, operating in both opposing airstreams. When the air handling unit is in heating mode, heat is absorbed as air passes through the matrix in the exhaust airstream, during one half rotation, and released during the second half rotation into the supply airstream in a continuous process. When the air handling unit is in cooling mode, heat is released as air passes through the matrix in the exhaust airstream, during one half rotation, and absorbed during the second half rotation into the supply airstream. Heat recovery efficiency up to 85%. Wheels are also available with a hygroscopic coating to provide latent heat transfer and also the drying or humidification of airstreams.

·         Run around coil: Two air to liquid heat exchanger coils, in opposing airstreams, piped together with a circulating pump and using water or a brine as the heat transfer medium. This device, although not very efficient, allows heat recovery between remote and sometimes multiple supply and exhaust airstreams. Heat recovery efficiency up to 50%.

·         Heat pipe: Operating in both opposing air paths, using a confined refrigerant as a heat transfer medium. The heat pipe uses multiple sealed pipes mounted in a coil configuration with fins to increase heat transfer. Heat is absorbed on one side of the pipe, by evaporation of the refrigerant, and released at the other side, by condensation of the refrigerant. Condensed refrigerant flows by gravity to the first side of the pipe to repeat the process. Heat recovery efficiency up to 65%.

Controls

Controls are necessary to regulate every aspect of an air handler, such as: flow rate supply air temperature, mixed air temperature, humidity, air quality.

Common control components include temperature sensors, humidity sensors, sail switches, actuators, motors, and controllers.

Vibration isolators

The blowers in an air handler can create substantial vibration and the large area of the duct system would transmit this noise and vibration to the occupants of the building.

To avoid this, vibration isolators (flexible sections) are normally inserted into the duct immediately before and after the air handler and often also between the fan compartment and the rest of the AHU.

The rubberized canvas-like material of these sections allows the air handler components to vibrate without transmitting this motion to the attached ducts.

The fan compartment can be further isolated by placing it on a spring suspension, which will mitigate the transfer of vibration through the floor.

AHU Details:-

In HRDD- HBNI building,there are total 9 AHU on the 1st and 2nd floor. Among them 5th and 6th AHUs having the cooling capacity of 60 TR, remaining AHUs, 1,2,3,4,7,8,9 having the capacity of 30 TR.

AHU No- 1,2,3,4

AHU details	Motor Details
Make –Nutech Sr. No - 9/2007 Model No - DAH-9 Fan Cap - 20400 CMH Fan S.P. - 50MM WG Motor HP - 15 Fan RPM - 593 Fan Type - DIDW/FC Belt No - A54	Make - Kirloskar Type - 3 phase induction motor kW- 5.5 Hz- 50 Voltage- 415 RPM- 1440 A°C- 1P55 M/c No - F622103-801 Duty -S1 Amp - 11.0 Efficiency - 84%

AHU No- 5-6

AHU details	Motor Details
Make - Nutech Model - UHF-12 Fan Cap - 1200 CFM	Make - Bharat Bijlee Type - 3phase Pre. Gauge - 0-10kg kW/HP - 5-50/7.50 RPM - 1445 Duty - S1 Amp. - 10.40 Voltage - 415

18. Fan Coil Unit (FCU):-

A Fan Coil Unit(FCU) is a simple device consisting of a heating and/or cooling heat exchanger or 'coil' and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. A fan coil unit is a diverse device sometimes using duct work, and is used to control the temperature in the space where it is installed, or serve multiple spaces. It is controlled either by a manual on/off switch or by a thermostat, which controls the through put of water to the heat exchanger using a control valve and/or the fan speed.

Due to their simplicity and flexibility, fan coil unitscan be more economical to install than ducted100% fresh air systems (VAV)or central heating systems withair handling unitsorchilled beams. Various unit configurations are available, including horizontal (ceiling mounted) or vertical (floor mounted).

Noise output from FCUs, like any other form of air conditioning, is principally due to the design of the unit and the building materials around it. A correctly selected FCU, like some of those from the UK, can offer noise levels as low as NR25 or NC25.The output from an FCU can be established by looking at the temperature of the air entering the unit and the temperature of the air leaving the unit, coupled with the volume of air being moved through the unit. This is a simplistic statement, and there is further reading on sensible heat ratios and the specific heat capacity of air, both of which have an effect on thermal performance.

Operation and Design:-

Fan Coil Unit design falls principally into two main types: blow through and draw through. As the names suggest, in the first type the fans are fitted such that they blow through the heat exchanger, and in the other type the fans are fitted after the coil such that they draw air through it. Draw through units are considered thermally superior, as ordinarily they make better use of the heat exchanger. However they are more expensive, as they require a chassis to holdthe fans whereas a blow-through unit typically consists of a set of fans bolted straight to a coil.

An exposed fan coil unit may be wall-mounted, freestanding or ceiling mounted, and will typicallyinclude an appropriate enclosure to protect and conceal the fan coil unit itself, with return airgrilleand supply airdiffuserset into that enclosure to distribute the air.

A concealed fan coil unit will typically be installedwithin an accessible ceiling void or services zone. The return air grille and supply air diffuser, typically set flush into the ceiling, will be ducted to and from the fan coil unit and thus allows a great degree of flexibility for locating the grilles tosuit the ceiling layout and/or the partition layout within a space. It is quite common for the return air not to be ducted and to use the ceiling void as a return air plenum.

The coil receives hot or cold water from a central plant, and removes heat from or adds heat to the air throughheat transfer. Traditionally fan coil units can contain their own internalthermostat, or can be wired to operate with a remote thermostat. However, and as is common in most modern buildings with aBuilding Energy Management System(BEMS), the control of the fan coil unit will be by a local digital controller or outstation (along with associated room temperature sensor and control valve actuators) linked to the BEMS via a communication network,and therefore adjustable and controllable from a central point, such as a supervisors head end computer.

Fan coil units circulate hot or cold water through a coil in order to condition a space. The unit gets its hot or cold water from a central plant, ormechanical roomcontaining equipment for removing heat from the central building's closed-loop. The equipment used can consist of machines used to remove heat such as achilleror acooling towerand equipment for adding heat to the building's water such as aboileror a commercial water heater.

Fan coil units are divided into two types: Two-pipe fan coil units or four-pipe fan coil units. Two-pipe fan coil units have one (1) supply and one (1) return pipe. The supply pipe supplies either cold or hot water to the unit depending on the time of year. Four-pipe fan coil units have two(2) supply pipes and two (2) return pipes. This allows either hot or cold water to enter the unit at any given time. Since it is often necessary to heatand cool different areas of a building at the same time, due to differences in internal heat loss or heat gains, the four-pipe fan coil unit is most commonly used here.

Depending upon the selected chilled water temperatures and the relative humidity of the space, it is likely that the cooling coil will dehumidify the entering air stream, and as a product of this process, it will at times produce a condensate which will need to be carried to drain.The fan coil unit will contain a purpose designed drip tray with drain connection for this purpose. The simplest means to drain the condensate from multiple fan coil units will be by a network ofpipework laid to falls to a suitable point. Alternatively a condensate pump may be employed where space for such gravity pipework is limited.

Speed control of the fan motors within a fan coil unit is partly used to control the heating and cooling output desired from the unit. Some manufacturers accomplish speed control by adjusting the taps on an AC transformer supplying the power to the fan motor. A simple speed selector switch (Off-High-Medium-Low) is provided for the local room occupant to control the fan speed. Compared to units with asynchronous 3-speed motors, the fan coil units with brushless motors will reduce the power consumption by 70%.

19. PRECISION AIR CONDITIONERS:-

Precision air conditioning plants are used for cooling of supercomputer system. The precision units have an advantage to control the temperature at precise level. The precision units also remove or maintain the humidity present in the air. The precision unit is of 17 TR each. The temperature is maintained about 17ºC-20ºC.

The refrigerant used in precision unit is R-22 at HBNI.

The refrigeration cycle used in precision unit are depend on refrigerant gas. The following components are used in precision unit:-

·         Filter

·         Cooling coil /Evaporator

·         Humidifier

·         Compressor

·         Dryer

·         Refrigerant R-22

·         Condenser (Air cooled type)

·         Blower / fan unit

The cold air is supplied to the server unit room for cooling the system of supercomputer. The air supplied from downward blow system and return through the return duct connected at the air inlet of precision unit.

Precision air conditioners are used to ensure precise control of temperature, humidity and indoor air conditions thus ensuring optimum working environment in IT centers, apparatus rooms, reference chambers and server rooms. Precision air conditioners hardware implementation may vary widely: from single-module units of 0.3kW power to the modular systems with the cooling capacity of up to 280 kW, which can be used for the wide range of purposes. Blue Star's Precision Air conditioners (generally known as PACs or CRACs) are ideal cooling solutions wherever continuous, round-the-clock, precise control of temperature, humidity and filtered air is desired.

Modular in design, Blue Star's PAC, highly energy-efficient and designed for 24x7 operation, using an open-architecture control protocol, these air conditioners offer very low cost of ownership and subsequent up gradation.

Features of precision unit:-

*.High Energy Efficiency

*.Rapid Dehumidification

*.Ease of Maintenance

*.Low cost of ownership

*.Designed for 24x7 year round operation

*.Option for tropicalized condenser

*.Hot gas reheat

*.Standard up-flow and down-flow models available

.

20. (A) Belt Drive:-

A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. In a two pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the driver if on parallel shafts). As a source of motion, a conveyor belt is one application where the belt is adapted to carry a load continuously between two points.

Power transmission

Belts are the cheapest utility for power transmission between shafts that may not be axially aligned. Power transmission is achieved by specially designed belts and pulleys. The demands on a belt-drive transmission system are large, and this has led to many variations on the theme. They run smoothly and with little noise, and cushion motor and bearings against load changes, albeit with less strength than gears or chains. However, improvements in belt engineering allow use of belts in systems that only formerly allowed chains or gears.

Power transmitted between a belt and a pulley is expressed as the product of difference of tension and belt velocity.

P = (T1-T2)v

Where, T1 and T2 are tensions in the tight side and slack side of the belt respectively. They are related as

Log [T1/T2] = μα

Where, μ is the coefficient of friction, and α is the angle (in radians) subtended by contact surface at the center of the pulley.

The angular-velocity ratio may not be constant or equal to that of the pulley diameters, due to slip and stretch. However, this problem has been largely solved by the use of toothed belts. Working temperatures range from −31 °F (−35 °C) to 185 °F (85 °C). Adjustment of center distance or addition of an idler pulley is crucial to compensate for wear and stretch.

The equation for power is

Power [kW] = (torque [N·m]) × (rotational speed [rev/min]) × (2π radians) / (60 s × 1000 W).

Types of belt:-

The most common types of belt drives include

1-Round belts: Round belts are generally made of rubber.

2-V belts: V belts are arguably the most widely used belts in industry.

3-Flat belts: Flat belts are also used to transmit power from one shaft to another.

4-Timing/toothed belts: tooth are present for efficient power transmission.

Belt Material:-

1. Leather belts

2. Cotton or fabric belts

3. Rubber belt

4. Balata belts

5. Plastic belt.

 (B) BEARING:-

Abearingis a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fix axis, or it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction.

Rotary bearings hold rotating components such as shafts or axles within mechanical systems, and transfer axial and radial loads from the source of the load to the structure supporting it. The simplest form of bearing, theplain bearing consists of a shaft rotating in a hole. Lubrication is often used to reduce friction. In the ball bearing and roller bearing, to prevent sliding friction, rolling elements such as rollers or balls with a circular cross-section are located between the races or journals of the bearing assembly. A wide variety of bearing designs exists to allow the demands of the application to be correctly met for maximum efficiency, reliability, durability and performance.

There are at least 6 common types of bearing, each of which operates on different principles:

1- Plain bearing, consisting of a shaft rotating in a hole. There are several specific styles: bushing, journal bearing, sleeve bearing, rifle bearing and composite bearing.

2- Rolling-element bearing, in which rolling elements placed between the turning and stationary races prevent sliding friction. There are two main types

a- Ball bearing, in which the rolling elements are spherical balls

b- Roller bearing, in which the rolling elements are cylindrical rollers

3- Jewel bearing, a plain bearing in which one of the bearing surfaces is made of an ultra-hard glassy jewel material such as sapphire to reduce friction and wear

4- Fluid bearing, a noncontact bearing in which the load is supported by a gas or liquid,

5- Magnetic bearing, in which the load is supported by a magnetic field

      6- Flexure bearing, in which the motion is supported by a load element which bends.

21. Safety Devices:-

Cut Out For Safety:-

A: Low chiller temperature: 4.5 °C (41°F)

B: Low evaporator pressure: 30 PSIG

C:High Condenser Pressure: 140 PSIG

D: Low oil pressure: 60 PSIG

E: Condenser water suspension: 4.5 PSIG

Compressors in air conditioning and refrigeration plants have to be provided with protective devices and circuits to protect them from damage. The basic protective devices are the high pressure cut out, low pressure cut out, oil low pressure cut out, and oil separator or oil extractors.

1- Compressor Safety

The three common safeties provided are the high pressure trip, the low pressure trip, and the low oil pressure trip among the others. A compressor has to be protected against high pressure that can cause structural failure therefore a high pressure cut out is provided, similarly any deficiency in the oil pressure can damage the bearings and a low oil pressure cut out has to be provided, a lower atmospheric in the pipe line can cause air ingress and therefore must be avoided. In this article we discuss the different safeties one by one.

2- High Pressure Cut Out

High pressure can be caused in a refrigeration plant due to various causes like over charge, loss of cooling water, high ambient temperature, air, or other incompressible gases in the system, and obstruction in the discharge line of the compressor. For protecting the compressor from high pressure and subsequent failure, a high pressure cut out is provided that take a pressure tapping from the discharge line and when it detects an over pressure, it stops the compressor. The HP cut out is not resettable automatically but has to be reset manually by the operator. This is because the high pressure is a serious fault and the cause must be investigated and corrected before the plant is started again.

3- Construction of High Pressure Cut Out

Operation of a High Pressure Cut Out. The high pressure cut out as shown in the diagram is of a simple construction. It has a bellows that is set against a spring. The nut at the end of the spring is used to adjust the cut out pressure. When the high pressure gas enters the bellow, the bellow expands and presses the spring. At the cut off pressure the movement of the bellow against the spring releases the catch and the contact is broken and the compressor cuts off. The switch arm can be pressed and the cut out reset after the cause of the over pressure has been found and rectified. Low Pressure Cut Out to protect the compressor against low pressure in the system and to avoid the ingress of air into the system if a vacuum is generated in the lines a low pressure cut out is provided. Also when the refrigerated compartments are cut off by the solenoids and there is no return gas, the low pressure cut out is activated. When the solenoid of the refrigerated compartments open, the return gas comes in the inlet of the compressor and the suction pressure rises, and then the low pressure switch cuts in the compressor. Unlike the high pressure cut out, the low pressure cut out is self-resettable and does not need to be reset manually.

4- Low Oil Pressure Cut Out

The oil is pumped under pressure by an attached oil pump that supplies oil to the bearings for lubrication. Any problem in the lube oil pressure can jeopardize the bearings and therefore a tapping is taken from the pump outlet and fed to the oil pressure switch. Any fall in the pressure will activate the cut out which will stop the compressor. Oil Separator As oil is miscible with the refrigerant and often goes out of the compressor with it, it can go to the evaporator where it can cause a decrease in heat transfer. To avoid the oil from going to the evaporator where it can form a layer inside or cause obstruction an oil separator is used. It basically consists of baffle plates that separate the oil from the refrigerant and feed it back to the compressor. A float valve is provided so that short circuiting of the refrigerant should not take place.

The refrigeration plant compressor has to be protected against unnatural working conditions by safety devices and controls. The high pressure cut out, the low pressure cut out, and the low oil pressure cut out are some of the basic protective devices provided. In large complex circuits other additional safety devices are provided according to the complexity of the circuit.

22.Pump - Motor Alignment:-

Experience shows that many pump distress events (failures) have their root cause in the misalignment of the pump to motor. Misaligned pumps can even consume up to 15% more energy input than well-aligned pumps. Even small pumps can generate big losses when shaft misalignment imposes reaction forces on shafts, even if the flexible coupling suffers no immediate damage. The inevitable result is premature failure of shaft seals and bearings. Performing precise alignment, therefore, pays back through preventing the costly consequences of poor alignment. Indeed, using precise alignment methods is one of the principal attributes of a reliability focused organization.

Proper alignment has been demonstrated to lead to-

a- Lower energy losses due to friction and vibration.

b- Increased productivity through time savings and repair avoidance.

c- Reduced parts expense and lower inventory requirements.

Further, in order to insure good alignment, the alignment must be checked and correctly set when a pump and drive unit are initially installed (before grouting the baseplate, after grouting the baseplate, after connecting the piping, and after the first run).

*After a unit has been serviced.

*The process operating temperature of the unit has changed.

*Changes have been made to the piping system.

Periodically, as a preventive maintenance check of the alignment, following the plant operating procedures for scheduled checks or maintenance.

Alignment Problem:- Hundreds of technical articles and presentations have elaborated on the serious problems that are caused by incorrect alignment between the pump and driver, such as:

*Coupling overheating and resulting component degradation

*Extreme wear in gear couplings and component fatigue in dry element couplings.

*Pump and driver shaft fatigue failure.Pump and driver bearing overload, leading to failure or short bearing life.

Destructive vibration events.

Harmful machinery vibration is created whenever misalignment exists. Excessive pump vibration can shorten bearing and mechanical seal life. Pump Alignment Basics Pump shafts exist in three-dimensional space and misalignments can exist in any direction. It has been found to be most convenient to break this three-dimensional space up into two planes, the vertical and the horizontal; and to describe the specific amount of offset and angularity that exists in each of these planes simultaneously, at the location of the coupling. Thus, we end up with four specific conditions of misalignment, traditionally called Vertical Offset, Vertical Angularity, Horizontal Offset, and Horizontal Angularity. These conditions are described at the location of the coupling, because it is here that harmful machinery vibration is created whenever misalignment exists

Basic issues that must be taken into account regarding pump alignment are-

1- Alignment equipment sag (with dial indicators)

2- Cold, hot or running alignment.

3- Where to make shimming adjustments (Align the motor to the pump by shimming the motor feet)

4- Soft foot problems.

5- Type of alignment equipment.

Alignment Methods:-

Alignment accuracy is critical to pump and driver longevity as stated above, and generally the better the alignment the longer the pump and driver bearing life. The three most prevalent alignment methods practiced in the industrial, worldwide.

1- Straight Edge and Feeler Gauges.

2- Dial Indicator.

3- Lasers-optic Straight Edge, Feeler Gauge

Dial Indicators:-

There are two basic dial indicator methods. The Single Indicator Method uses a single dial indicator to take both the rim and face reading. You can then calculate shim changes for the motor feet to correctly align the unit. The Reverse Indicator Method uses a dial indicator on the pump shaft to read the motor shaft, and a dial indicator on the motor shaft to read the pump shaft. You can then use mathematical formulas to calculate shim changes to correctly align the unit. Although better then "straight edge and feeler gauge method", the dial indicator method does have a few shortcomings, such as

1- Sagging indicator brackets.

2- Sticking/jumping dial hands.

3- Low resolution rounding losses.

4- Leading errors.

5- Play in mechanical linkages.

6- Tilted dial indicator (offset error) Lasers-optic Devices

23. Readings and Observations:-

AMBIENT TEMPERATURE: DBT/WBT

COMPRESSOR 1	UNITS	READINGS
OIL LEVEL		3/4
OIL PRESSURE	PSIG	155.5
DIFFERENTIAL OIL PRESSURE	PSIG	105
OIL TEMPERATURE	°C/°F	NA
SUCTION TEMPERATURE	°C/°F	51.6
DISCHARGE TEMPERATURE	°C/°F	132.9
DISCHARGE SUPERHEAT	°C/°F	201.1
SLIDE WANTED	%	77.3
FLA	%	84
EXPANSION VALVE OPENING	%	56
LOAD SOLENOID VALVE	ON/OFF
UNLOAD SOLENOID VALVE	ON/OFF
LIQUID INJECTION	ON/OFF
MOTOR VOLT	VOLT
MOTOR AMP (R/Y/B)	AMP	186.3
REFRIGERANT: CHILLER
SUCTION PRESSURE	PSIG	47.3
SUCTION SUPERHEAT	°C/°F	-0.8
SUCTION SET TEMPERATURE	°C/°F	51
REFRIGERANT:CONDENSER
DISCHARGE PRESSURE.	PSIG	158.4
DISCHARGE SET TEMPERATURE	°C/°F	113

AMBIENT TEMPERATUR- DBT/WBT

COMPRESSOR 1	UNITS	READINGS
OIL LEVEL		3/4
OIL PRESSURE	PSIG	155.5
DIFFERENTIAL OIL PRESSURE	PSIG	105
OIL TEMPERATURE	°C/°F	NA
SUCTION TEMPERATURE	°C/°F	51.6
DISCHARGE TEMPERATURE	°C/°F	132.9
DISCHARGE SUPERHEAT	°C/°F	201.1
SLIDE WANTED	%	77.3
FLA	%	84
EXPANSION VALVE OPENING	%	56
LOAD SOLENOID VALVE	ON/OFF
UNLOAD SOLENOID VALVE	ON/OFF
LIQUID INJECTION	ON/OFF
MOTOR VOLT	VOLT
MOTOR AMP (R/Y/B)	AMP	186.3
REFRIGERANT: CHILLER
SUCTION PRESSURE	PSIG	47.3
SUCTION SUPERHEAT	°C/°F	-0.8
SUCTION SET TEMPERATURE	°C/°F	51
REFRIGERANT:CONDENSER
DISCHARGE PRESSURE.	PSIG	158.4
DISCHARGE SET TEMPERATURE	°C/°F	113
CHILLER: WATER
INLET TEMPERATURE	°C/°F	59.8
OUTLET TEMPERATURE	°C/°F	52.5
INLET PRESSURE	PSIG	3.8
OUTLET PRESSURE.	PSIG	2.8
FLOW RATE	M^3/hr	207
CONDENSER: WATER
INLET TEMPERATURE	°C/°F	91.8
OUTLET TEMPERATURE	°C/°F	99.4
INLET PRESSURE	PSIG	2
OUTLET PRESSURE	PSIG	1.2
FLOW RATE	M^3/hr	285

24.Water Softening Plant:-

Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. Water softening is usually achieved using lime softening or ion-exchange resins .The presence of certain metal ions like calcium and magnesium principally as bicarbonates, chlorides, and sulfates in water causes a variety of problems. This is a very vital consideration when the water is send to cooling tower of chiller plant.

Water Softening Method:-

The most common means for removing water hardness rely on ion-exchange resin or reverse osmosis.

Ion-exchange resin device:- Conventional water-softening appliances intended for household use depend on an ion-exchange resin in which "hardness ions" - mainly Ca2+ and Mg2+ - are exchanged for sodium ions. As described by NSF/ANSI Standard 44, ion-exchange devices reduce the hardness by replacing magnesium and calcium (Mg2+ and Ca2+) with sodium or potassium ions (Na+ and K+).

Ion exchange resins are organic polymers containing anionic functional groups to which the divalent cations (Ca++) bind more strongly than monovalent cations (Na+). Inorganic materials called zeolites also exhibit ion-exchange properties. These minerals are widely used in laundry detergents. Resins are also available to remove carbonate, bi-carbonate and sulfate ions which are absorbed and hydroxide ions released from resin.

When all the available Na+ ions have been replaced with calcium or magnesium ions, the resin must be re-charged by eluting the Ca2+ and Mg2+ ions using a solution of sodium chloride or sodium hydroxide depending on the type of resin used. For anionic resins, regeneration typically uses a solution of sodium hydroxide (lye) or potassium hydroxide. The waste waters eluted from the ion-exchange column containing the unwanted calcium and magnesium salts are typically discharged to the sewage system.

Softening Reaction-

Water Treatment:-

Backwash System:-Water treatment filters that can be backwashed include rapid sand filters, pressure filters and granular activated carbon (GAC) filters. Diatomaceous earth filters are backwashed according to the proprietary arrangement of pumps, valves and filters associated with the filtration system. Slow sand filters and self-cleaning screen filters employ mechanisms other than backwashing to remove trapped particles. To keep water treatment filters functional, they have to be cleaned periodically to remove particulates.

V1-RAW WATER INLET

V2-SOFT WATER OUT LINE

V3-BACKWASH INLET

V4-BACKWASH OUTLET

V5-RINSE OUTLET

V6-AIR RELEASE

V7-BRINE SOLUTION

V8-POWER OUTLET

Procedure for Backwash:-

Backwashing of granular media filters involves several steps. First, the filter is taken off line and the water is drained to a level that is above the surface of the filter bed. Next, compressed air is pushed up through the filter material causing the filter bed to expand breaking up the compacted filter bed and forcing the accumulated particles into suspension. After the air scour cycle, clean backwash water is forced upwards through the filter bed continuing the filter bed expansion and carrying the particles in suspension into backwash troughs suspended above the filter surface.

 In some applications, air and water streams are simultaneously pushed upwards through the granular media followed by a rinse water wash. Backwashing continues for a fixed time, or until the turbidity of the backwash water is below an established value. At the end of the backwash cycle, the upward flow of water is terminated and the filter bed settles by gravity into its initial configuration. Water to be filtered is then applied to the filter surface until the filter clogs and the backwash cycle needs to be repeated.

Water Quality In Consideration Of Chiller A/C Plant:-

Sr. No	Test Item	Chilled Water Quality	Cooling Water	Make Up Water
1	PH	7.2-8.2	7.2-8.3	8.0 Quality-8
2	Total hardness CaCO3 PPM	Maximum 80	Less than 200	Max 50
3	Total alkalnity CaCO3 PPM	Less than 100	Less than 100	Less Than 80
4	Chloride Ion PPM	Less than 50	Less than 200	Less than 50
5	Total Ion Fe PPM	Less than 0.3	Less than 1	Less than 0.3

Abnormal Behavior Water:-

"The anomalous properties of water are those where the behavior of liquid water is quite different from what is found with other liquids. No other material is commonly found as solid, liquid and gas. Frozen water (ice) also shows anomalies when compared with other solids."

Water however shows an exceptional behavior below 4 degree C. If we cool water at room temperature we find that it goes on contracting but as the temperature falls below 4 degree C it begins to expand instead of contracting, conversely if water is heated from 0 degree C to 4 degree C instead of expanding it contracts. The phenomena of abnormal behavior of water is an important consideration in chiller plants due to water depending cycle.

25.Ozone Layer Depletion:

The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0. Chlorodifluoro methane (R-22), for example, has an ODP of 0.05. CFC 11, or R-11 has the maximum potential amongst chlorocarbons because of the presence of three chlorine atoms in the molecule.

It was defined as a measure of destructive effects of a substance compared to a reference substance.

Precisely, ODP of a given substance is defined as the ratio of global loss of ozone due to given substance to the global loss of ozone due to CFC-11 of the same mass.

ODP can be estimated from the molecular structure of a given substance. Chlorofluorocarbons have ODPs roughly equal to 1. Brominated substances have usually higher ODPs in range 5 - 15, because of more aggressive bromine reaction with ozone. Hydro chlorofluorocarbons have ODPs mostly in range 0.005 - 0.2 due to the presence of the hydrogen which causes them to react readily in the troposphere, therefore reducing their chance to reach the stratosphere where the ozone layer is present. Hydro fluorocarbons (HFC) have no chlorine content, so their ODP is essentially zero.

ODP is often used in conjunction with a compound's global warming potential (GWP) as a measure of how environmentally detrimental it can be.

26. Conclusion:-

The refrigeration and air conditioning process system is of two types- (1) direct system and (2) indirect system. Here, the indirect system is installed at HBNI,BARC and generally called chiller machine plant.

The indirect refrigeration and air conditioning system is having more advantages over the direct system, like high coefficient of performance, easy maintenance, separate plant, easy control and last but not the least is it can provide air conditioning in large scale as requirement.

I learned the chiller machines system with its air handling unit (AHU) cooling tower system, water softening plant and also studied about Precision Air Conditioning Unit installed for cooling of Super Computers. The chiller machines plant provide air conditioning to HRDD-HBNI & Convention Center.

I got a conclusion about this system and learned the structure of the plant, readings and detailed analysis of machines, working process, AHU & air conditioning supply control system, about cooling towers, water softening plant.

This report is written by me on the basis of I learned and plant studded here.