Refrigeration Plant Operator B Practice Test

Which condition in the engine room indicates the evaporator temperature?

1. Discharge pressure

2. Suction pressure

3. Condensing pressure

4. Refrigerant temperature

The correct answer is: Suction pressure

The condition in the engine room that indicates the evaporator temperature is the suction pressure. The evaporator's role in a refrigeration cycle is to absorb heat from the space being cooled, turning the refrigerant from a low-pressure liquid into a low-pressure vapor as it absorbs heat. The temperature of this vapor can be directly derived from the suction pressure due to the thermodynamic properties of the refrigerant being used. In refrigeration systems, there is a relationship between pressure and temperature known as the saturation pressure-temperature relationship. By measuring the suction pressure in the evaporator, operators can determine the corresponding evaporator temperature. This relationship is crucial for maintaining proper system operation and ensuring that the refrigerant is able to adequately absorb heat from the environment. While other factors such as condensing pressure and discharge pressure are significant in the overall refrigeration process, they do not directly indicate the evaporator temperature. These pressures relate to other components of the system, such as the compressor and condenser, and are vital for system efficiency and performance rather than for identifying the evaporator temperature directly.