Question

In a vapour compression refrigeration cycle using R134a, the enthalpies are (i) 240 kJ/kg at the beginning of compression, (ii) 275 kJ/kg at the end of compression, (iii) 96 kJ/kg at the beginning of throttling. Then the coefficient of performance (COP) of the cycle is ____________ (rounded off to one decimal place).

Hint:

COP improves when refrigerating effect increases or compressor work decreases.

Answer 1

Correct Answer: 4

Cooling effect: \[ q_L = h_1 - h_4 = 240 - 96 = 144\ \text{kJ/kg} \] Compressor work: \[ w_c = h_2 - h_1 = 275 - 240 = 35\ \text{kJ/kg} \] Coefficient of performance: \[ COP = \frac{q_L}{w_c} = \frac{144}{35} = 4.11 \] Thus the answer lies within: \[ \boxed{4.0\ \text{to}\ 4.2} \]
Final Answer: 4.1