Refrigeration Cycle

Refrigeration cycle produces hot part and cold part (compare to ambient temperature). It needs at least four components, they are compressor, condenser, expansion device, and evaporator. Work fluid (refrigerant) goes around from one component to other component again and again, so we call it cycle. Refrigerant experiences all process in components

Figure 1. Refrigeration cycle schema

Figure 1 show schema of refrigeration cycle which consist of four main components and connected pipes (showed by line), and also the flow direction of refrigerant is showed at that figure. At the figure, there are two types of line, red and blue. The red one shows that the pressure is high and the blue shows the pressure of refrigerant is low.  As known, pressure is proportion by temperature, then the color of line also show the temperature condition of refrigerant.

1 to 2, Compression process. Output from evaporator, refrigerant is gas phase. Then compressor sucks it from evaporator and discharge it to condenser.  Before through the compressor the refrigerant pressure  is low and after through compressor refrigerant pressure is high. This process also makes the refrigerant temperature increase.

2 to 3, Condensation process. Output from compressor, refrigerant phase is still gas. As its name condenser is a component to make refrigerant phase change  from gas into liquid. This process needs to release heat. Usually condenser is put outside, because the temperature of ambient outside is lower than temperature of refrigerant in condenser, then heat transfer can occur from refrigerant to outdoor air temperature.

3 to 4, Expansion Process. Output from condenser, refrigerant phase  is already liquid and has  high pressure and temperature. Expansion device makes pressure of refrigerant drop into low pressure, this process also is followed by drop temperature. Most of refrigerant phase after through expansion valve is still liquid and a few gas.

4 to 1, Evaporation Process. As its name, the function of this component is to make refrigerant phase changes from liquid into gas. This process need heat, and heat is got from the objects which want to be cooled. The temperature of refrigerant in evaporator is lower than the objects, then heat transfer will occur from objects to refrigerant, then heat is used for evaporate refrigerant. After the refrigerant is already in gas phase, refrigerant  will experience the process from number   1 again. It happen repeat and repeat again.