What are the three operating pressures of the thermostatic expansion valve?

The operating pressures of a thermostatic expansion valve are indeed best described by the factors of evaporator pressure, spring pressure, and bulb pressure.

The evaporator pressure is vital as it directly relates to the system's ability to absorb heat and evaporate refrigerant within the evaporator coil. This pressure essentially controls how the refrigerant enters the evaporator, determining its effectiveness in cooling.

Spring pressure represents the force exerted by the internal spring within the valve, which helps regulate flow based on the refrigerant's temperature and volume. The thermostatic expansion valve adjusts the flow of refrigerant based on this pressure, allowing for optimal performance across varying load conditions.

Bulb pressure refers to the pressure sensed in the bulb located at the outlet of the evaporator. This bulb is filled with a fluid that expands and contracts based on temperature changes. When the temperature of the evaporator changes, the pressure in the bulb alters, causing the valve to open or close accordingly. This ensures that the valve maintains a steady flow of refrigerant, optimizing system efficiency and preventing issues like flooding or starvation of the evaporator.

Together, these three pressures work cohesively to regulate the flow and distribution of refrigerant in the system, thus maintaining efficient cooling performance.