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Class 2 (2nd Engineer) MEKG 📅 Oct 2022

Exam Question

(a) Explain with a sketch the operation of an automatic expansion valve as fitted in the direct expansion refrigeration plants. How is this valve adjusted?

(b) Explain how critical temperature restricts plant operation and how these limitations can be overcome?

(c) Explain how this system maintains the provision rooms at different temperatures?

Exam question diagram

Reference Answer

### (a) Automatic Expansion Valve (AEV)
An Automatic Expansion Valve (AEV), also known as a constant pressure expansion valve, is a refrigerant control device that maintains a constant pressure in the evaporator, regardless of the cooling load. Its primary function is to meter the flow of liquid refrigerant into the evaporator at a rate that matches the compressor's pumping capacity at the desired evaporator pressure.
#### Construction & Operation
The valve consists of the following main components:

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