Class 4 (4th Engineer) MEKG 📅 Oct 2025

Exam Question

With reference to a typical shipboard refrigeration system:

(a) Sketch the arrangement which controls superheat temperature of refrigerant gas leaving the evaporator. (8)

(b) Describe the operation of the arrangement sketched in (a) assuming one of the HFC refrigerant is the working medium. (4)

Reference Answer

### (a) Arrangement for Superheat Control
The arrangement used to control the superheat temperature of refrigerant gas leaving the evaporator is the **Thermostatic Expansion Valve (TEV or TXV)**. The sketch should illustrate the following key components and their relative positions:
1. **Valve Body**: Contains the valve seat and needle/pin, forming an orifice through which the refrigerant flows.
2. **Diaphragm**: A flexible metallic disc that separates the control pressure chamber from the evaporator pressure chamber.

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