Final answer:
To increase evaporator pressure in an automatic expansion valve, the adjusting screw on top should be turned clockwise, leading to more refrigerant flow and a rise in pressure.
Step-by-step explanation:
To increase the evaporator pressure in an automatic expansion valve (AEV), the adjustment required often involves turning a screw located on the top of the valve. This adjustment is carried out to control the amount of refrigerant flowing into the evaporator. By turning the adjusting screw clockwise, you compress the spring inside the valve, which applies more force on the diaphragm or sensing bulb. This action will cause the valve to open more, allowing for an increase in the flow of refrigerant and consequently raising the evaporator pressure. The reverse, turning the screw counter-clockwise, reduces the spring tension and decreases the amount of refrigerant, leading to a drop in evaporator pressure. These adjustments are crucial in refrigeration systems such as an autoclave, where maintaining a specific pressure allows the steam to achieve temperatures above the normal boiling point of water, vital for sterilization processes.