2. Thermodynamics

Refrigeration Cycles — Quiz

Test your understanding of refrigeration cycles with 5 practice questions.

Practice Questions

Question 1

In a vapor-compression cycle using R-22, the enthalpies at state points are $h_{1}=420\,\mathrm{kJ/kg}$ at the evaporator outlet, $h_{2}=460\,\mathrm{kJ/kg}$ at the compressor outlet, and $h_{3}=240\,\mathrm{kJ/kg}$ at the condenser outlet (with $h_{4}=h_{3}$). What is the coefficient of performance $\mathrm{COP}_{R}$ of this cycle?

Question 2

A single-effect absorption refrigeration system has a refrigeration capacity of $15\,\mathrm{kW}$, requires a generator heat input of $25\,\mathrm{kW}$, and has a solution pump work of $0.5\,\mathrm{kW}$. What is its coefficient of performance $\mathrm{COP}_{\mathrm{abs}}$?

Question 3

How does subcooling the liquid refrigerant by $5\,\mathrm{K}$ before the expansion valve affect the COP of a vapor-compression refrigeration cycle?

Question 4

Which component in an ideal vapor-compression refrigeration cycle contributes the most to thermodynamic irreversibility?

Question 5

Why is the COP of any refrigeration cycle always greater than 1?