Class 2 (2nd Engineer) MEKG 📅 Nov 2023

Exam Question

With respect to the refrigeration system on board vessels, answer the following. (16)

(a) Why are some TEVs fitted with an external equalizing connection?

(b) What is the purpose of a back pressure valve. what will the effect if it leaks?

Reference Answer

### (a) Thermostatic Expansion Valve (TEV) with External Equalizing Connection
An externally equalized Thermostatic Expansion Valve (TEV) is required on refrigeration systems where there is a significant pressure drop across the evaporator coil. This is common in large capacity evaporators or those using a refrigerant distributor with multiple small-bore tubes.
**1. Principle of a Standard (Internal Equalizer) TEV:**
A standard TEV operates by balancing three pressures to maintain a constant superheat at the evaporator outlet:

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