Heat pump, engine and refrigeration

Questions on
 Heat Pump, Heat Engine & Refrigeration Effect

1.  Find the COP of a refrigeration system of the work input is 80Kj/Kg and refrigerant effect produced is 160 Kj/Kg of flowing.

2.  A machine working on a Carnot cycle operates between 305K and 260K. Determine the COP when it is operated as
i) a refrigerating machine
ii) a heat pump
iii) Heat Engine

3.  A Carnot refrigeration cycle absorbs heat at 270K and rejects it at 300K.
i) Calculate the COP of this refrigeration cycle
ii) If the cycle is absorbing 1130 Kj/min at 270K. How many KJ of work is required per second
iii) If the Carnot heat pump operates between the same temperature as the above refrigeration what is the COP.
iv) How many KJ/min will heat pump deliver at 300K if it absorbs 1130 KJ/min at 270K.

4.  A cold storage is to be maintained at -5 degree while the surroundings are at 35 degree. The heat leakage from the surroundings into the cold storage into the cold storage is estimated to be 29 KW. The actual COP of the refrigeration plant is one third of an ideal plant working between the same temperatures. Find the power required to drive the plant.

5.  Two refrigerator A and B operate in series. The refrigerator A absorbing energy at the rate of 1 KJ/s from a body at temperature 300K and rejects energy as heat to a body at temperature T. The refrigerator B absorbs the same quantity of energy which is rejected by the refrigerator A from the body at temperature T, and rejects energy as heat to a body at temperature 1000K. If both the refrigerators have the same COP. Calculate-
i) The temperature T of the body
ii) The COP of the refrigerator
iii) the rate at which energy is rejected as heat to the body at 1000K.

6.  A refrigerating system operates on the reversed Carnot cycle. The higher temperature of the refrigerant in the system is 35 degree and the lower temperature is -15degree. The capacity is to be 12TR. Determine-
i) COP
ii) Heat rejected from the system per hour
iii) Power required

7.  1.5KW per ton of refrigeration is required to maintain the temperature of -40degree in the refrigerator. If the refrigeration cycle works on Carnot cycle, determine the following-
i) COP of the cycle
ii) Temperature of the sink
iii) Heat rejected to the sink per ton of refrigeration
iv) Heat supplied and EPR if the cycle is used as a heat pump.

8.  The capacity of a refrigeration is 200TR when working between -6degree and 25degree. Determine the mass of ice produced per day from water at 25degree. Also find the power required to drive the unit. Assume that the cycle operates on reversed Carnot cycle and latent heat of ice is 334 KJ/Kg.

9.  Five hundred Kg of fruits are supplied to a cold storage at 20 degree. The cold storage is maintained at -5degree and the fruits get cooled to the storage temperature in 10 hours. The latent heat of freezing is 105 KJ/Kg and specific heat of fruit is 1.256 KJ/Kg K Find the refrigeration capacity of the plant.

10.                   A cold storage plant is required to store 20Ton of fish. The fish is supplied at a temperature of 30 degree. The specific heat of fish above freezing point is 2.93 KJ/Kg K. The specific heat of fish below freezing point is 1.26 KJ/Kg K. The fish is stored in cold storage which is maintained at -8 degree. The freezing point of fish is -4 degree. The latent heat of fish is 235 KJ/Kg. If the plant requires 75 KW to drive the plant then find-
i) The capacity of the plant
ii) Time taken to achieve cooling
Assume Actual COP of the plant as 0.3 of the Carnot COP.