The expansion valve is situated in the liquid line between the condenser and the inlet of the evaporator. It operates on the opposite side of the system, relative to the compressor. Whereas the compressor operates to increase the pressure and pump the refrigerant through the system, the expansion device releases the pressure between the high-pressure condensation side and the low-pressure evaporation side.
There are numerous types of expansion valves, depending on the demand for control and the type of evaporator, i.e. flooded or direct expansion. This chapter discusses the characteristics of different expansion techniques and their suitability for BPHE evaporators.