Test your level of competency for GATE Mechanical Engineering and UPSC ESE Mechanical Engineering exam for the topic of Vapour compression and Air refrigeration cycle.
Q1) A reversed Brayton cycle is used to maintain a body at -250C. Temperature at the end of isobaric cooling is 27oC and rise in the temperature of air in the refrigerator is 48oC. Determine the net work of compression.
Q2) In a VCC refrigeration plant, the refrigerant leaves the evaporator at 240 kJ/kg and the condenser at 60 kJ.kg. Determine the rate of cooling per kg of the refrigerant.
Q3) The enthalpies at the beginning of compression, at the end of compression and at the end of condensation are 180 kJ/kg and 80 kJ/kg respectively. Determine the COP of the VC refrigeration system.
Common statement for Q4 and Q5.
A refrigerator based on ideal VCC operates between the temperature limits of -20oC and 40oC. The refrigerant enters the condenser as saturated vapour and leaves as saturated values for saturated liquid and vapour at these temperatures is given in the table below:
Q4) If refrigerant circulation rate is 0.025 kg/s, the refrigeration effect is equal to __________.
Q5) The COP of the refrigerator is _______.
Q6) In a closed cycle air refrigeration system, air is drawn from cold chamber at -5oC and 1 bar and compressed to 6 bar. The air is cooled to 20oC and then expanded to 1 bar to produce 10TR. Determine
- mass flow rate of air
- Power requirement of the compressor
Q7) COP of a refrigerator working between two fixed temperature limits T1 and T2 (T1 > T2) will have
- COP increased when the working substance has high specific heat
- COP increases with the increase in latent heat of vaporization during heat absorption process at T2
- Cannot be predicted
- Fixed COP
Q8) A Carnot refrigerator requires 1.5 kW of work for 6 kW of RE. If it absorbs heat at 240 K then the temperature of heat reservoir at which the heat is rejected equal to
- 320 K
- 300 K
- 400 K
- 280 K
Q9) A Carnot refrigerator has COP = 5. The ratio of higher temperature T1 to lower temperature T2 is
Q10) The mass flow rate of refrigerant to compressor is 2 kg/s/TR having volumetric efficiency 0.8 and specific volume of refrigerant as 0.1 m3/kg, the volume of refrrigerant to be handled by compressor per TR is ____.