Chapter 5 Principles of Refrigeration 87 Copyright by Goodheart-Willcox Co., Inc. Figure 5-9. This is an older refrigeration system using an expansion valve. Compare the parts used with those in Figure 5-8. (Nissan) High-pressure gas High-pressure liquid Low-pressure liquid Low-pressure gas Compressor Evaporator Blower motor Expansion valve Receiver-drier Condenser D S Outside air Figure 5-10. In the evaporator, refrigerant changes from liquid to gas and absorbs heat. The evaporator is made of a material with good heat transfer characteristics. Most evaporators are made of aluminum and copper. Figure 5-11. Modern refrigeration systems use accumulators to store refrigerant and prevent liquid refrigerant from reach- ing the compressor. Other functions of the accumulator are to trap debris, remove moisture, and ensure that oil returns to the compressor.