ICC Commercial Mechanical Practice Exam

The main purpose of thermal expansion valves in refrigeration systems is to regulate the flow of refrigerant based on cooling demand. These valves adjust the amount of refrigerant that enters the evaporator coil, which is crucial for maintaining the desired temperature and efficiency in the cooling process. By sensing the temperature of the evaporator outlet or the superheat in the system, the thermal expansion valve modulates the flow of refrigerant to ensure that it matches the load requirements. This responsive control allows the refrigeration system to operate efficiently, preventing both overfeeding and underfeeding of refrigerant, which can lead to performance issues and potential system damage.

Other options, while related to refrigeration systems, do not accurately describe the primary function of thermal expansion valves. For instance, decreasing refrigerant pressure is typically achieved in the evaporator portion of the system, and enhancing condenser efficiency generally refers to maximizing heat exchange without directly involving the flow control of refrigerant. Separating refrigerant phases is not a function of the thermal expansion valve; rather, it occurs within the system through other means, such as evaporators and condensers.