What is the primary cause of frost or ice buildup on the evaporator of a vapor-cycle cooling system?

The primary cause of frost or ice buildup on the evaporator of a vapor-cycle cooling system is inadequate airflow. This issue typically arises when the airflow over the evaporator coil is insufficient to facilitate the evaporation of refrigerant properly. When airflow is restricted, the refrigerant does not absorb the necessary amount of heat, leading to lower temperatures at the evaporator coil surfaces. As a result, moisture from the surrounding air can freeze on these cold surfaces, resulting in frost or ice accumulation.

Factors contributing to inadequate airflow can include dirty filters, blocked ducts, malfunctioning fans, or design issues within the airflow system. These restrictions hinder the effective heat exchange process that is crucial for proper system operation. Without sufficient airflow, the evaporator cannot perform efficiently, leading to the unintended consequence of frost formation.

While excessive refrigerant, a faulty compressor, or high outside temperatures can affect overall system performance, they do not directly lead to frost buildup as inadequate airflow does, making airflow the primary cause in this scenario.