Class 4 (4th Engineer) MEP 📅 Apr 2024

Exam Question

(a) Sketch, describe and explain the operation of the domestic refrigeration system of a ship using one of the HFC as refrigerant. What kind of maintenance is essential for the system. (8)

(b) Describe the causes for the following in the domestic refrigeration system: (8)

(i) Frequent cut-in and cut-out of the compressor

(ii) Low oil pressure cut out of the compressor

(iii) High low pressure cut out of the compressor

(iv) Frosting on the compressor suction side

Reference Answer

### (a) Domestic Refrigeration System: Sketch, Operation, and Maintenance
#### Description and Operation
A ship's domestic refrigeration system operates on the vapor-compression refrigeration cycle. It is designed to transfer heat from the refrigerated spaces (e.g., galley stores for meat, fish, vegetables) to a heat sink, typically the ship's central cooling water system. The refrigerant used in modern systems is a Hydrofluorocarbon (HFC) such as R-134a or R-404A, replacing older ozone-depleting substances like R-22 (an HCFC) in compliance with MARPOL Annex VI regulations. The fundamental cycle remains the same regardless of the specific refrigerant.
The system consists of four main components: Compressor, Condenser, Expansion Valve, and Evaporator, along with essential ancillary equipment.

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