8.21. Air-standard power cycles are conventionally displayed on PV diagrams. An

Question

8.21. Air-standard power cycles are conventionally displayed on PV diagrams. An alterna- tive is the PT diagram. Sketch air-standard cycles on PT diagrams for the following: (a) Carnot cycle; (b) Otto cycle: (c) Diesel cycle: (d) Brayton cycle Why would a PT diagram not be helpful for depicting power cycles involving liq- uid/vapor phase changes? 9.1. An easy way to rationalize detinitions of cycle performance is to think of them as: What you get Measure of performance What you pay fo --WQH : for a refrigerator. the coef- . Define a coefficient of performance for a Thus, for an engine, thermal efficiency is rformance is a-QdW pump. What is for a Cunlof heat pump? heat

Explanation / Answer

Answer of 9.21

the coefficient of performace of the heat pump is defined by the given formula as a ratio of heat released to the higher temp to the work performedor given to the pump. i..e QH/W

the coefficient of performance (COP) of heat pump is always greater than the COP of refrigerator

COP(heat pump) = QH/W

= COP(refrigerator) + 1

= QC/W + 1

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