QUESTION $3$

A standard vapour$-$compression cycle using ammonia as the refrigerant operates between a condensing temperature of $30C,$ and an evaporating temperature of $-20C.$ Assuming that the compressor is isentropic and that the liquid leaving the condenser is saturated,

$3\mathrm{.}1$ draw the T$-$s diagrams and

$3\mathrm{.}2$ compare the coefficient of performance $($COP$)$ of the refrigeration cycle which uses

$($a$)$ dry compression with one that uses

$(6\frac{1}{2})$

$($b$)$ wet compression. In the wet compression the refrigerant enters the compressor in such a condition that it is saturated vapour upon leaving the compressor.

$(7\frac{1}{2})$

$[18]$