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GATE 2020: Thermodynamics Quiz 7
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Question 1
In the working of a vapour-compression refrigeration plant, the following enthalpies are recorded at salient points in the cycle:
1) Enthalpy at inlet to compressor (saturated vapour),
2) Enthalpy at outlet of compressor (after isentropic compression),
3) Enthalpy at exit of condenser (saturated liquid),
What is the COP of the plant?
1) Enthalpy at inlet to compressor (saturated vapour),
2) Enthalpy at outlet of compressor (after isentropic compression),
3) Enthalpy at exit of condenser (saturated liquid),
What is the COP of the plant?
Question 2
Refrigerant vapor enters into the compressor of a standard vapor compression cycle at - 10 °C (h= 402 kJ/kg) and leaves the compressor at 50 °C (h= 432 kJ/kg). It leaves the condenser at 30 °C (h= 237 kJ/kg). The COP of the cycle is ________
Question 3
The working temperatures in the evaporator and condenser coils of a refrigerator are -30 °C and 32 °C respectively. If the actual refrigerator has a COP of 0.85 of the maximum, the required power input for a refrigerating effect of 5 kW is nearly,
Question 4
Saturated ammonia at 0.2365 MPa enters a single acting compressor and liquid ammonia at 21 °C enters the expansion valve of a
refrigerating plant.
If head pressure is 1.1638 MPa, then the COP of the refrigerating cycle is:
Given: CP (Liquid NH3) = 4.6 kJ/kgK; CP (Vapour NH3) = 2.75 kJ/kgK
refrigerating plant.
If head pressure is 1.1638 MPa, then the COP of the refrigerating cycle is:
Given: CP (Liquid NH3) = 4.6 kJ/kgK; CP (Vapour NH3) = 2.75 kJ/kgK
Question 5
A freezing plant requires 50 tons of refrigeration. The freezing temperature is – 33 °C and ambient temperature is 27 °C. If the performance of the plant is one-third of the theoretical reversed Carnot cycle working between the same temperature limits, the power input (in kW) required for the plant is
Question 6
Consider the following statements in respect of a vapour-absorption refrigration cycle :
1) The absorption refrigeration cycle is generally used when waste heat is avilable from an existing source or when free energy like solar energy is to be used.
2) There are no moving parts in the absorption refrigeration plant except a small liquid pump.
3) The value of the coefficient of performance is nearly the same in both vapour-absorption and vapour- compression refrigeration plants.
Which of the above statements are correct?
1) The absorption refrigeration cycle is generally used when waste heat is avilable from an existing source or when free energy like solar energy is to be used.
2) There are no moving parts in the absorption refrigeration plant except a small liquid pump.
3) The value of the coefficient of performance is nearly the same in both vapour-absorption and vapour- compression refrigeration plants.
Which of the above statements are correct?
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