Refrigeration: coefficient of performance and Carnot limit

Why does a larger temperature difference make refrigeration more demanding?

An experiment from Cyril Voyant’s course, running in your browser. Full course and slides (French) · Choose another experiment.

The relationship to understand

COPCarnot=Tcold/(Thot−Tcold), with absolute temperatures in kelvins; refrigeration COP=useful heat extracted/work supplied.

Try it and interpret

Cold reservoir at −10 °C and hot reservoir at +40 °C: maximum COP=263.15/(313.15−263.15)≈5.26. Between −40 °C and +10 °C it is 233.15/50≈4.66. The −40 to +10 °C axis range controls only the cold-side setting. The bound is a theoretical maximum of heat extracted per work supplied, not a temperature bound or a percentage efficiency.

Assumptions and limitations

Reversible cyclic refrigerator between two reservoirs: a bound, not the actual COP of equipment. Do not confuse reservoir temperatures with detailed refrigerant temperatures; fans and actual losses are not modeled.

Go further with the course

This page focuses on one concept. The full chapter (French) contains the reasoning, further examples, slides and FAQ. Demonstration values are computed or constructed within the stated model; they are not new research findings.