Final answer:
On a TXV, the high side pressure exerts a closing influence on the valve, regulating refrigerant flow by balancing against the bulb pressure and evaporator pressure.
Step-by-step explanation:
On a TXV (Thermostatic Expansion Valve), the high side pressure exerts a closing influence on the valve. The purpose of a TXV is to regulate the flow of refrigerant to the evaporator in air conditioning systems. It maintains the superheat at the evaporator outlet by balancing three pressures: the bulb pressure (which tends to open the valve), the spring pressure (which tends to close the valve), and the evaporator pressure (which also tends to close the valve). The high side pressure mentioned in the question refers to the condenser pressure, part of which is transmitted to the top of the TXV diaphragm, working against the opening force of the bulb pressure and thus having a closing effect on the valve.
As an additional reference, gas moves from an area of high pressure to an area of low pressure, which is a fundamental principle in thermodynamics and fluid dynamics. Also, the volume of a gas is directly proportional to temperature when the pressure of the gas is constant, according to Charles's Law.