Project ForgeA refrigerator operates between 120 kPa and 800 kPa in an ideal vapor compression cycle with R-134a as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s. Properties: at 120 kPa, hg=237 kJ/kg, sg=0.95 kJ/kg.K; at 800 kPa, hf=95.5 kJ/kg; superheated R-134a at 800 kPa and 40°C has h=276.45 kJ/kg, s=0.95 kJ/kg.K. The rate at which heat is extracted, in kJ/s, from the refrigerated space is
- 28.3
- B42.9
- C34.4
- D14.6
Explanation
State 1 (compressor inlet, saturated vapor at 120 kPa): h1=237 kJ/kg. State 3 (condenser exit, saturated liquid at 800 kPa): h3=95.5 kJ/kg. Throttling to the evaporator is isenthalpic: h4=h3=95.5 kJ/kg. Refrigeration effect = ṁ(h1−h4) = 0.2×(237−95.5) = 0.2×141.5 = 28.3 kJ/s.
Source: GATE ME 2012 (Booklet Code A) (2012)
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