This simulator draws the vapor-compression cycle that cools most buildings, on a pressure-enthalpy diagram. Four numbered points mark compressor suction, compressor discharge, condenser liquid and the point after the expansion device. Move the evaporating and condensing saturation temperatures or the superheat and subcooling, and the cycle reshapes while the tiles recompute refrigeration effect, compressor work, COP and EER.
• A pressure-enthalpy diagram with a dashed saturation dome, a closed cycle 1 → 2 → 3 → 4 and a dot that travels around it to show flow direction. • Four sliders: evaporator saturation, condenser saturation, superheat and subcooling, with an Imperial/SI toggle. • Readout tiles for refrigeration effect, compressor work, COP and EER, plus a list of enthalpy at each state point. • Expandable notes on each process, formulas and a worked COP example.
Compression (1 → 2) raises low-pressure vapor to condenser pressure and adds work. Condensation (2 → 3) rejects heat and turns the vapor to liquid, with subcooling lowering the liquid's enthalpy. Expansion (3 → 4) drops the pressure at constant enthalpy, so no heat is exchanged. Evaporation (4 → 1) absorbs heat from the space, and superheat ensures only vapor returns to the compressor. The refrigeration effect is h₁ − h₄ and the compressor work is h₂ − h₁.
COP is refrigeration effect divided by compressor work, and EER is COP × 3.412. Raising the condensing temperature or lowering the evaporating temperature increases the pressure lift, so work grows and COP falls; more subcooling increases the refrigeration effect. The enthalpy values use a simplified linear R-410A approximation for teaching and are not refrigerant property tables, so use the trends rather than the decimals.
Pressure is plotted against specific enthalpy. The refrigeration cycle appears as a closed loop: compression moves right and up, condensation moves left at high pressure, expansion drops straight down at constant enthalpy, and evaporation moves right at low pressure.
COP equals the refrigeration effect (h₁ − h₄) divided by the compressor work (h₂ − h₁). With the default settings the effect is about 75 BTU/lb and the work about 25.4 BTU/lb, giving a COP near 2.95. EER is COP multiplied by 3.412.
Superheat keeps liquid refrigerant from reaching the compressor, and subcooling keeps liquid from flashing before the expansion device. Subcooling also lowers the liquid enthalpy, which increases the refrigeration effect per unit of refrigerant.
They are a simplified linear approximation for teaching, not data from refrigerant property tables. The diagram and readouts show correct trends, but they should not be used for equipment selection or charge calculations.