The constant pressure expansion valve is known as ______

The automatic expansion valve maintains a constant pressure in the evaporator. The constant pressure characteristics of the valve results from the interaction of two opposing forces, the evaporator pressure and the spring pressure.

The evaporator pressure, exerted on one side of the bellows or diaphragm acts to move the valve in a closing direction, whereas the spring pressure, acting on the opposite side of the bellows or diaphragm acts to move the valve in an opening direction. When the compressor is running, the valve functions to maintain the evaporator pressure in equilibrium with the spring pressure.