Refrigeration and Liquefaction Principles

Heat absorption at the refrigerating temperature takes place in several ways. If a low-temperature liquid is actually formed in the process, then heat 

For a Carnot cycle with two isothermal and two isentropic processes one can readily show that the coefficient of performance is simply given by 

Since the coefficient of performance in Eq. (4.2) was developed for a Carnot refrigerator with two isothermal and two isentropic processes, it is unrealistic to use that expression for comparing cold-gas refrigerators in which the energy is absorbed at a varying temperature instead of at a constant 

Noting that ( 3 — 4) = ( 2 — iX th entropy change for a constant pressure process is 

Substituting these values back into Eq. (4.3) results in an expression for the coefficient of performance that is based on only the three temperatures shown for the cycle in Fig. 4.2  

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