What happens to the efficiency of the evaporator if the load increases?

In a refrigeration or air conditioning system, the evaporator's efficiency is tied to its ability to absorb heat from the environment and transfer it to the refrigerant. As the load on the system increases—meaning there is more heat to be absorbed—certain factors come into play that can lead to a decrease in efficiency.

When the load increases, the evaporator must work harder to remove this additional heat. If the system is not adequately designed to handle the increase in load, or if it runs outside its optimal operating conditions, the refrigerant may not flow efficiently or may not be able to absorb heat effectively. This inefficiency can be exacerbated if the temperature difference between the refrigerant and the medium it is absorbing from becomes too small, which can further lead to a reduction in the overall effectiveness of the heat exchange process.

Additionally, at higher loads, the evaporator can become prone to issues such as flooding or increased pressure drop, which contribute to a decline in performance and efficiency. Therefore, with an increased load on the evaporator, the efficiency typically decreases, resulting in the correct choice.