In a refrigeration system, what effect does an increase in load on the evaporator have?

An increase in load on the evaporator in a refrigeration system means that there is a higher demand for cooling. As more heat is absorbed by the evaporator, the refrigerant inside it evaporates more rapidly to handle this increased demand. This causes the evaporator to create a greater cooling effect to maintain the desired temperature within the space being cooled.

In response to the increase in cooling load, the suction pressure, which is the pressure at the inlet of the compressor, will generally rise due to the higher quantity of refrigerant vapor entering the compressor. This indicates that more refrigerant is evaporating due to the higher heat absorption.

Concurrently, the high side pressure (HP), or condensing pressure, tends to decrease or stabilize during moderate increases in load because the mechanical systems and expansion devices adjust to the demand. However, at some point, if the load continues to rise significantly, the HP may eventually rise again.

Choosing the option where suction pressure increases while HP decreases reflects the initial response of the system to higher loads effectively, making it the correct choice. This response captures the balance between the evaporator's increased absorption of heat and how the compressor reacts to that increase.