Final answer:
When evaporator pressure drops, spring pressure and atmospheric pressure will cause the Automatic Expansion Valve (AXV) valves to close. This action helps regulate the refrigerant flow and maintains the efficiency of the refrigeration or air conditioning system.
Step-by-step explanation:
When evaporator pressure drops, spring pressure and atmospheric pressure will cause the valves to close. This occurrence is part of the functionality of the Automatic Expansion Valve (AXV) in refrigeration and air conditioning systems. The AXV regulates the flow of the refrigerant based on the evaporator pressure. When the pressure in the evaporator coils drops, it indicates that less refrigerant is evaporating, which could be due to a lower heat load. The spring and atmospheric pressures push against the valve, causing it to move towards a closed position to restrict the flow of refrigerant. This action prevents the evaporator coils from becoming too cold, which would otherwise lead to a decrease in efficiency or freezing of the coils. Conversely, if the evaporator pressure increases, indicating a higher heat load or more refrigerant evaporation, the valve is pushed open to allow more refrigerant to flow to absorb the additional heat.