The enlargement valve holds again the refrigerant and maintains the high stress with the condenser. In the expansion valve, a little orifice will allow a restricted number of refrigerant to continue to flow. Since it flows by means of this restriction it reaches the lower stress side in the valve. https://www.penmann.co.uk/penmann-delivers-permanent-glycol-chiller-solution-for-ambrosia-creamery-in-lifton/