In a refrigeration system containing refrigerant at a dew point condition of -25 degrees, what is desired for the outlet of the evaporator?

In a refrigeration system, the outlet temperature of the evaporator is crucial for ensuring efficient operation. When the refrigerant is at a dew point condition of -25 degrees, it means that this is the temperature at which it would condense into a liquid. To maintain a proper temperature difference and ensure that the evaporator can absorb heat effectively from the environment or the medium being cooled, the outlet temperature should typically be lower than the dew point.

Setting the outlet of the evaporator around -20 degrees allows for sufficient heat exchange while keeping the refrigerant in a gaseous state as it exits the evaporator. This is important because if the temperature were set too close to the dew point, like -25 degrees, there is a risk of flooding or not achieving optimal cooling performance, as the refrigerant wouldn't be able to absorb heat efficiently. Furthermore, going too low, such as -30 degrees, could lead to excessive freezing or lower efficiency.

Therefore, having the outlet temperature of the evaporator around -20 degrees strikes a balance that ensures effective cooling while preventing issues associated with reaching the dew point temperature.