The Carnot Cycle of Refrigeration

According to Knight (chapter 21), the definition of the carnot cycle and a carnot engine is "any Carnot engine operating between TH  and TC must have exactly the same efficiency as any other carnot engine operating between the same two energy reservoirs."

Tests have been done to understand the refrigeration and cycle, as given by Coker.

Detailed in the cycle, the system starts with an isothermal compression from the compressor, while energy is released. The next step, from the compressor to the condenser, the refrigerant is expanded adiabatically to the "cooler" temperature. Afterwards, energy from the deposit (cold) area is transferred to the refrigerant and is compressed adiabatically back to the disposal (hot) reservoir.


(Coker, pg.625, figure 17-3)

Not only can we find how this cycle reacts under perfect conditions, but the effect of different environments on this system's heat transfer efficiency.

As Patil et al explains in their article, this cylce is affected under conditions, such as frosting, defrosting, and dry/wet operations. With atmospheric pressure and humidity being significant factors in the formation of water droplets in the unit,  heat recovery can be drastically changed with slight modifications.

Shown below is the distribution of  heat (and mass) transfer under different phase transitions of fluid and the humidity percentage of air returning to the unit, and the efficiency of heat exchange under different humidity levels (in winter conditions).

(figure 5, Patil et al, pg.1077)
(figure 4, Patil et al, pg. 1076)

The Processes References