Exam Question
(a) Describe how air in the refrigeration plant is purged out (6)
(b) Describe how lube oil is added in the refer compressor (5)
(c) Describe how the lube oil filter of a reefer compressor is cleaned (5)
Class 4 (4th Engineer)
MEP
📅 Mar 2023
Reference Answer
(a) Describe how air in the refrigeration plant is purged out (6)
**1. Purpose of Purging:**
To remove non-condensable gases (primarily air) that have ingressed into the system. The presence of air is detrimental because:
* **Dalton's Law of Partial Pressures:** Air does not condense at the operating pressures and temperatures of the refrigerant. Its presence adds its partial pressure to the refrigerant's condensing pressure, resulting in an abnormally high total discharge pressure.
**1. Purpose of Purging:**
To remove non-condensable gases (primarily air) that have ingressed into the system. The presence of air is detrimental because:
* **Dalton's Law of Partial Pressures:** Air does not condense at the operating pressures and temperatures of the refrigerant. Its presence adds its partial pressure to the refrigerant's condensing pressure, resulting in an abnormally high total discharge pressure.
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