Thermodynamics: An Engineering Approach 8th Edition

Published by McGraw-Hill Education
ISBN 10: 0-07339-817-9
ISBN 13: 978-0-07339-817-4

Chapter 11 - Refrigeration Cycles - Problems - Page 648: 11-105

Answer

$\dot{Q}_{\text {cooling }}=51,840 \text{ kJ/h}$

Work Step by Step

The COP of the heat pump is given to be 3.4. Then the COP of the air-conditioning system becomes $$ \mathrm{COP}_{\text {air-cond }}=\mathrm{COP}_{\text {heat pump }}-1=3.4-1=2.4 $$ Then the rate of cooling (heat absorption from the air) becomes $$ \dot{Q}_{\text {cooling }}=\mathrm{COP}_{\text {air-cond }} \dot{W}_{\text {in }}=(3.4)(6 \mathrm{~kW})=20.4 \mathrm{~kW}=51,840 \mathrm{~kJ} / \mathrm{h} $$ Since $1 \mathrm{~kW}=3600 \mathrm{~kJ} / \mathrm{h}$. We conclude that this heat pump can meet the cooling needs of the room since its cooling rate is greater than the rate of heat gain of the room.
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