Where is the sensing bulb located in a thermal expansion valve on a direct expansion system?

The sensing bulb in a thermal expansion valve (TXV) on a direct expansion system is typically located at the outlet of the evaporator. This positioning allows the sensing bulb to accurately monitor the temperature of the refrigerant just as it exits the evaporator coil. The purpose of the sensing bulb is to provide feedback to the valve regarding the refrigerant's temperature and pressure, allowing the valve to modulate the flow of refrigerant into the evaporator based on the cooling needs of the system.

When the bulb senses a higher refrigerant temperature, it indicates that the evaporator is not absorbing enough heat, prompting the TXV to open and allow more refrigerant to flow into the evaporator. Conversely, if the refrigerant is cooler, the TXV can reduce the flow. This feedback mechanism is essential for optimizing the efficiency of the refrigeration cycle and maintaining consistent cooling performance.

Thus, the correct positioning of the sensing bulb at the outlet of the evaporator is vital for the effective operation and regulation of the thermal expansion valve within the system.