Refrigeration and Air Conditioning
In a vapour compression refrigeration system, a throttle valve is used in place of an expander because

It leads to significant cost reduction
It improves the C.O.P., as the condenser is small
It considerably reduces mass of the system
The positive work in isentropic expansion of liquid is very small

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Refrigeration and Air Conditioning
Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since

These react with oxygen and cause its depletion
These react with water vapour and cause acid rain
These react with ozone layer
These react with plants and cause greenhouse effect

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