Expansion valves

Key Features and Functions:

1. Temperature Sensing Bulb: Expansion valves feature a temperature sensing bulb connected to the valve body or located at the evaporator outlet. The bulb contains a temperature-sensitive fluid (usually a refrigerant) that expands or contracts in response to changes in evaporator temperature.
2. Bulb and Capillary Tube Assembly: The temperature sensing bulb is connected to the valve body via a capillary tube. As the temperature of the refrigerant leaving the evaporator changes, the fluid in the bulb expands or contracts, causing corresponding changes in pressure within the capillary tube.
3. Diaphragm or Bellows: Expansion valves employ a diaphragm or bellows mechanism to convert changes in pressure from the temperature sensing bulb into mechanical motion. This motion adjusts the valve opening, controlling the flow of refrigerant into the evaporator coil.
4. Adjustable Superheat: Many expansion valves feature an adjustable superheat setting, allowing technicians to fine-tune the valve’s operation by adjusting the spring tension or the position of the diaphragm. This adjustment ensures that the refrigerant entering the evaporator coil is fully evaporated, optimizing system performance and efficiency.
5. Valve Body: The valve body contains the internal components responsible for regulating refrigerant flow, including the diaphragm or bellows assembly, the valve seat, and the metering orifice. Expansion valves are available in various configurations, such as thermostatic, electronic, and pressure-actuated valves, to suit different system designs and applications.
6. Metering Orifice: The metering orifice, also known as the valve seat or expansion orifice, controls the rate at which refrigerant flows into the evaporator coil. The size of the orifice determines the amount of refrigerant passing through the valve and influences system performance, capacity, and efficiency.
7. Bi-Flow Capability: Some expansion valves are designed with bi-flow capability, allowing refrigerant to flow in both directions through the valve. Bi-flow valves are commonly used in heat pump systems and reversible refrigeration cycles to accommodate heating and cooling modes of operation.
8. External Equalization Port: Expansion valves may feature an external equalization port that connects to the suction line or evaporator outlet. This port allows the valve to sense the pressure at the outlet of the evaporator coil, compensating for variations in pressure drop across the coil and ensuring accurate control of refrigerant flow.