The GATE Grind

GATE 2019 ME (ME1) – Question 22

Thermal Engineering Applications · Refrigeration and heat pump cycles · 1 mark · Multiple choice

An ideal vapour-compression refrigerator replaces throttling by isentropic expansion with all other processes unchanged. Which is true?

  1. COP is higher than in the original cycle.
  2. COP is lower than in the original cycle.
  3. COP is unchanged.
  4. Refrigerating effect is lower than in the original cycle.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) COP is higher than in the original cycle.

Explanation

An isentropic expander lowers evaporator-inlet enthalpy below its throttled value and recovers work. Refrigerating effect increases, while net required work decreases if recovered work is credited. Both effects raise **COP, A**. Throttling instead keeps enthalpy constant and destroys available work.