This simulation illustrates how to calculate the coefficient of performance (COP) of an ideal
mechanical refrigeration system using a pressure–enthalpy diagram. Use the sliders to set the
enthalpies of the refrigerant at the four principal points in the cycle. The COP value is displayed
above a schematic drawing of the mechanical refrigeration system that shows where energy enters and
leaves and the refrigerant’s flow direction. A plot of pressure versus enthalpy for the selected
cycle is shown below the drawing. The cold side of the cycle is shown in blue and the hot side in red.
The coefficient of performance (COP) is calculated from the enthalpies of the refrigerant at the
four principal points A, B, C, and D of the cycle:
COP =
hA − hD
hB − hA
where
COP = coefficient of performance (dimensionless)
hA = enthalpy of the refrigerant leaving the evaporator and entering the compressor (kJ/kg)
hB = enthalpy leaving the compressor and entering the condenser (kJ/kg)
hC = enthalpy leaving the condenser and entering the expansion valve (kJ/kg)
hD = enthalpy leaving the expansion valve and entering the evaporator (kJ/kg); hD = hC because expansion across the valve is isenthalpic
The numerator (
hA −
hD) is the heat absorbed by the
refrigerant in the evaporator (the useful cooling), and the denominator (
hB −
hA) is the work supplied to the compressor. The pressure does not enter into the
calculation and is presented on an arbitrary scale.
This simulation was created in the
Department of Chemical and Biological Engineering
at University of Colorado Boulder for
LearnChemE.com
by John L. Falconer using Claude AI. It is a JavaScript/HTML5 implementation of a
Mathematica simulation
by Mark D. Normand and Micha Peleg. It was prepared with financial support from the National Science
Foundation (DUE 2336987 and 2336988) in collaboration with Washington State University. Address any
questions or comments to LearnChemE@gmail.com.