Page 467 - Mechanical Engineers' Handbook (Volume 4)

456 Refrigeration

Figure 17 Typical baffled-shell evaporator. 3

often consists of a vapor or liquid that is the same substance as the refrigerant used in the
system. The response of the TXV and the superheat setting can be adjusted by varying the
type of charge in the capillary tube and bulb.
The operation of a TXV is straightforward. Liquid enters the TXV and expands to a
mixture of liquid and vapor at pressure P . The refrigerant evaporates as it travels through
2
the evaporator and reaches the outlet where it is superheated. If the load on the evaporator

Figure 18 Cross section of a thermal expansion valve. (Reprinted by permission from 2002 ASHRAE
Handbook of Refrigeration. American Society of Heating, Refrigerating, and Air-Conditioning Engi-
neers, Inc., www.ashrae.org.)