Refrigeration and Airconditioning Miscellaneous
 A vapour absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of 100 W is required at 250 K when the heat source available is at 400 K. Heat rejection occurs at 300 K. The minimum value of heat

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From question, since refrigeration effect of 100 W is required
So, 100 = 250 Work obtained 300 – 250
Work obtained = = 100 × 50 = 20 W 250
Now for this amount of work, heat is absorbed from reservoir 3 and rejected to sink 2.∴ η = W = 1  300 = 1 Q_{3} 400 4
⇒ Q_{3} = 4W = 4 × 20 W = 80 WCorrect Option: C
From question, since refrigeration effect of 100 W is required
So, 100 = 250 Work obtained 300 – 250
Work obtained = = 100 × 50 = 20 W 250
Now for this amount of work, heat is absorbed from reservoir 3 and rejected to sink 2.∴ η = W = 1  300 = 1 Q_{3} 400 4
⇒ Q_{3} = 4W = 4 × 20 W = 80 W
 An industrial heat pump operates between the temperatures of 27°C and 13°C. The rates of heat addition and heat rejection are 750 W and 1000 W, respectively. The COP for the heat pump is

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Heat addition, Q_{2} = 750 W
Heat rejected, Q_{1} = 1000 W[C.O.P]_{H.P} = Q_{1} = Q_{1} W Q_{1}  Q_{2} = 1000 = 1000 = 4 1000  750 250
T_{1} = 273 + 27º = 300ºK
T_{2} = 273 – 13 = 260K[C.O.P]_{H.P} = Q_{1} Q_{1}  Q_{2}
for actual heat pump= 1000 = 1000 = 4 1000  750 250 Correct Option: C
Heat addition, Q_{2} = 750 W
Heat rejected, Q_{1} = 1000 W[C.O.P]_{H.P} = Q_{1} = Q_{1} W Q_{1}  Q_{2} = 1000 = 1000 = 4 1000  750 250
T_{1} = 273 + 27º = 300ºK
T_{2} = 273 – 13 = 260K[C.O.P]_{H.P} = Q_{1} Q_{1}  Q_{2}
for actual heat pump= 1000 = 1000 = 4 1000  750 250
 ListI
A. Liquid to suction heat exchange
B. Constant volume heat addition
C. Normal shock
D. Ammoniawater
ListII
1. Vapour absorption refrigeration
2. Vapour compression refrigeration
3. Diesel cycle
4. Otto cycle
5. Converging nozzle
6. Converging diverging nozzle

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A – 2, B – 4, C – 6, D – 1
Correct Option: A
A – 2, B – 4, C – 6, D – 1
 Clearance volume of a reciprocating compressor is 100 ml, and the volume of the cylinder at bottom dead centre is 1.0 litre. The clearance ratio of the compressor is

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Clearance ratio = Clearance volume Swept volume = 100 = 1 1000  100 9 Correct Option: C
Clearance ratio = Clearance volume Swept volume = 100 = 1 1000  100 9
 A refrigerator uses R134a as its refrigerant and operates on a ideal vapourcompression refrigeration cycle between 0.14 MPa and 0.8 MPa. If the mass flow rate of the refrigerant is 0.05 kg/s, the rate of heat rejection to the environment is _______ kW.
Given data:
At P = 0.14 MPa, h = 236.04 kJ/kg , s = 0.9322 kJ/kgK
At P = 0.8 MPa, h = 272.05 kJ/kg (superheated vapour)
At P = 0.8 MPa, h = 93.42 kJ/kg (saturated liquid)

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h_{1} = 236.04 kJ/kg
h_{2} = 272.05 kJ/kg
h_{3} = 93.42 kJ/kg
s_{1} = 0.9322 kJ/kg
ṁ = 0.05 kg/s
Heat Rejection = ṁ(h_{2} – h_{3}) = 0.05(272.05 – 93.42)
Heat Rejection = 8.931 kWCorrect Option: A
h_{1} = 236.04 kJ/kg
h_{2} = 272.05 kJ/kg
h_{3} = 93.42 kJ/kg
s_{1} = 0.9322 kJ/kg
ṁ = 0.05 kg/s
Heat Rejection = ṁ(h_{2} – h_{3}) = 0.05(272.05 – 93.42)
Heat Rejection = 8.931 kW