Which factor can lead to excessive superheat in a refrigeration system?

Excessive superheat in a refrigeration system occurs when the refrigerant leaves the evaporator in a gaseous state that is much hotter than the saturation temperature corresponding to its pressure. A malfunctioning thermal expansion valve (TXV) can significantly contribute to this condition. The TXV is responsible for regulating the flow of refrigerant into the evaporator based on the cooling demand and the heat absorbed by the refrigerant. If the TXV fails to open sufficiently, it restricts the flow of refrigerant entering the evaporator. As a result, less refrigerant is available to absorb heat, leading to an increase in superheat, as the existing refrigerant absorbs heat beyond its saturation point before reaching the compressor.

This situation can cause operational issues such as increased compressor temperature, reduced efficiency, and potential damage to the compressor from overheating. Understanding the role of the TXV in regulating refrigerant flow helps diagnose issues related to superheat and ensures optimal system performance.