An ideal refrigerator or ideal heat pump is equivalent to a Carnot engine running in reverse. That is, energy | Q c | is taken in from a cold reservoir and energy | Q h | is rejected to a hot reservoir. (a) Show that the work that must he supplied to run the refrigerator or heat pump is W = T h − T c T c | Q c | (b) Show that the coefficient of performance (COP) of the ideal refrigerator is COP = T c T h − T c
An ideal refrigerator or ideal heat pump is equivalent to a Carnot engine running in reverse. That is, energy | Q c | is taken in from a cold reservoir and energy | Q h | is rejected to a hot reservoir. (a) Show that the work that must he supplied to run the refrigerator or heat pump is W = T h − T c T c | Q c | (b) Show that the coefficient of performance (COP) of the ideal refrigerator is COP = T c T h − T c
Solution Summary: The author explains how the work supplied to run the refrigerator is cWleft|Q_hright
An ideal refrigerator or ideal heat pump is equivalent to a Carnot engine running in reverse. That is, energy |Qc| is taken in from a cold reservoir and energy |Qh| is rejected to a hot reservoir. (a) Show that the work that must he supplied to run the refrigerator or heat pump is
W
=
T
h
−
T
c
T
c
|
Q
c
|
(b) Show that the coefficient of performance (COP) of the ideal refrigerator is
An ideal refrigerator or ideal heat pump is equivalent to a
Carnot engine running in reverse. That is, energy |Q] is
taken in from a cold reservoir and energy |Q,| is rejected
to a hot reservoir. (a) Show that the work that must be sup-
plied to run the refrigerator or heat pump is
Т, — т.
-
W =
T.
(b) Show that the coefficient of performance (COP) of the
ideal refrigerator is
T.
СОР
T- T.
It has been proposed to use the thermal gradient of the ocean to drive a heat engine. Suppose that at a certain location the water temperature is 22° C at the ocean surface and 40 C at the ocean floor.
(a) What is the maximum possible efficiency of an engine operating between these two temperatures? (b) If the engine is to produce 1 GW of electrical power, what minimum volume of water must be processed (to suck out the heat) in every second?
(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 50.0ºC and a cold reservoir temperature of −20.0ºC ?
(b) How much heat transfer occurs into the warm environment if 3.60×107J of work ( 10.0kW ⋅ h ) is put into it? (c) If the cost of this work input is 10.0 cents/kW ⋅ h , how does its cost compare with the direct heat transfer achieved by burning natural gas at a cost of 85.0 cents per therm. (A therm is a common unit of energy for natural gas and equals 1.055×108J .)
Chapter 22 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
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The Second Law of Thermodynamics: Heat Flow, Entropy, and Microstates; Author: Professor Dave Explains;https://www.youtube.com/watch?v=MrwW4w2nAMc;License: Standard YouTube License, CC-BY