Difference between Heat Engine Heat Pump and Refrigerator

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Difference between Heat Engine

Heat Pump

and

Refrigerator

In this article we are going to have detailed study of difference between Heat Engine Heat Pump and Refrigerator.

Heat Engine:

Heat engine is a device which converts heat energy into mechanical work. In heat engine how much work is extracted from a given amount of heat is an important quantity.

Difference between Heat Engine Heat Pump and Refrigerator - Heat Engine - Curio Physics    Q1=W+Q2    ⇒     W=Q1-Q2

Efficiency \displaystyle (\eta )=\frac{W}{{{Q}_{1}}}=\frac{{{Q}_{1}}-{{Q}_{2}}}{{{Q}_{1}}}

or              \displaystyle \eta =\frac{{{T}_{H}}-{{T}_{L}}}{{{T}_{H}}}=1-\frac{{{T}_{L}}}{{{T}_{H}}}

For Heat Engine,  W < Q1  ⇒  η < 1

 

Heat PUmp:

Heat pump is a device that transfers heat from a colder area to a hotter area by using mechanical/electrical energy, as in a refrigerator. Heat pumps may be used either to heat or cool. In heat pump how much heat is rejected at higher temperature is an important quantity.

Example: Room Heater

Difference between Heat Engine Heat Pump and Refrigerator - Heat Pump - Curio Physics    Q1=W+Q2    ⇒     W=Q1-Q2

Efficiency(Coefficient of Performance) \displaystyle (\eta )=\frac{{{Q}_{1}}}{W}=\frac{{{Q}_{1}}}{{{Q}_{1}}-{{Q}_{2}}}

or     \displaystyle \eta =\frac{{{T}_{H}}}{{{T}_{H}}-{{T}_{L}}}

For Heat Pump,  Q1 > W ⇒  η > 1

 

Refrigerator:

refrigerator is a device which is designed to remove heat from a space that is at lower temperature than its surroundings. In refrigerator heat extracted from lower temperature is an important quantity.

Difference between Heat Engine Heat Pump and Refrigerator - Refrigerator - Curio Physics    Q1=W+Q2    ⇒     W=Q1-Q2

Efficiency(Coefficient of Performance) \displaystyle (\beta )=\frac{{{Q}_{2}}}{W}=\frac{{{Q}_{2}}}{{{Q}_{1}}-{{Q}_{2}}}

or  \displaystyle \beta =\frac{{{T}_{L}}}{{{T}_{H}}-{{T}_{L}}}

Important: For refrigerator  TH > TL

⇒ β >1 , if T≤  2TL

for TH>2TL , let TL=5°C=278K, So 2TL = 556K=283°C  , which is not possible.

Generally TH and TL difference is less than TL, so β is always greater than 1 for refrigerator.]

[Example:-  let TL=5°C=278K and TH=25°C=300K , So TH-TL=300-278=22K<TL(278K) ]

 

video lecture for Difference between Heat Engine Heat Pump and Refrigerator :-

 

 

About the author

Manoj Kumar Verma

Hi, I'm Manoj Kumar Verma, a physics faculty having 7 years of teaching experience. I have done B.Tech (E.E.). I am also a YouTuber and Blogger. This blog is dedicated to help students learn the physics concepts easily.

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