What pressure difference operates the thermostatic expansion valve?

The thermostatic expansion valve (TXV) operates based on the pressure difference between the low side and high side of the refrigeration system. Specifically, it uses the pressure from the low side, which is typically found after the evaporator, to regulate the flow of refrigerant into the evaporator coil.

As the refrigerant evaporates in the evaporator, it creates a low-pressure condition. The TXV senses this low-side pressure through a sensing bulb attached to the evaporator. The valve adjusts the flow of refrigerant to maintain the desired superheat level, ensuring the evaporator is neither starved of refrigerant nor flooded with too much refrigerant.

This pressure difference is crucial because it allows the TXV to effectively control and optimize the system's performance, ensuring efficient cooling and energy use. Other options do not accurately reflect the operational principle of the TXV regarding the pressure it uses to function properly.