How to use this calculator

Enter the evaporator and condenser pressures (or their saturation temperatures), the compressor efficiency, and any superheat or subcooling. Give the mass flow or the cooling load to get rates.

Formulas

Throttleh₄ = h₃

Compressorh₂ = h₁ + (h_2s − h₁)/η_c, s_2s = s₁

PerformanceCOP_R = (h₁ − h₄)/(h₂ − h₁)

Worked example

Ideal cycle between 0.14 and 0.8 MPa, 0.05 kg/s of R-134a (the default; Çengel Example 11-1)

h₁ = h_g at 0.14 MPa = 239.2 kJ/kg; s₂ = s₁ at 0.8 MPa gives h₂ = 275.4 kJ/kg.
h₃ = h_f at 0.8 MPa = 95.5 kJ/kg = h₄.
Q̇_L = 0.05(239.2 − 95.5) = 7.18 kW, Ẇ = 0.05(275.4 − 239.2) = 1.81 kW, COP = 3.97.

Frequently asked questions

Why superheat at the compressor inlet?

A few degrees of superheat make sure no liquid droplets reach the compressor. It slightly changes the COP.

What’s the difference between COP_R and COP_HP?

A refrigerator’s useful output is the heat removed, q_L; a heat pump’s is the heat delivered, q_H = q_L + w, so COP_HP = COP_R + 1.