The green machine.

ISSUE 3 | 2016 Reciprocating compressors use a piston and cylinder, similar to an internal combustion engine, to move heat from a refrigerator’s interior to the exterior. While an internal combustion engine burns fuel in the cylinder to move the piston and turn a crankshaft, a reciprocating compressor uses an electric motor to turn a crankshaft that moves the piston to compress refrigerant in the cylinder. In an internal combustion engine, valves that open to deliver fuel to the cylinder and allow exhaust gases to escape are mechanically driven by a camshaft. Reciprocating compressors, on the other hand, typically use reed valves whose open/close movements are driven by fluid flowing through the compressor. Much of a typical compressor’s losses occur around these valves, so the compressor’s energy efficiency and noise levels largely depend on their design and operation, as well as on the suction muffler (suction side) and shock–loop system (discharge side), which are used to attenuate noise. As a general rule, restricting flow reduces a compressor’s efficiency while making it quieter. In the past, designing a new reciprocating compressor was largely by trial and MACHINE AND FUEL EFFICIENCY