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Chapter 21: Q. 9 (page 594)

Do the energy-transfer diagrams inFIGUREQ21.9represent possible refrigerators? If not, what is wrong?

Short Answer

Expert verified

a. The figure is not refrigerator ,because this engine dumps heat in the cold reservoir which is not a refrigerator does.

b. In figure K<Kc,so it is refrigerator engine.

c. In figure K>Kc,so it is not refrigerator engine.

Step by step solution

01

Possible of refrigerators for part a

a.

WorkWinis used to compress a coolant and raise its temperature over that of the surrounding environment.

Win=QH−QC

Consider the figure of part a,

20=(10-10)

20≠0

02

Possible of refrigerators for part b

b.

Consider the part b of figure,


The efficiency of normal refrigerator engine is,

K=QCWin

K=10/20=0.5

The efficiency of carnot refrigerator engine is,

Kc=T1T2-T1

Kc=300/300=1

So it's a possibility.

03

 Possible of refrigerators for part c

c.

Consider the figure,


The efficiency of normal refrigerator engine is,

K=QCWin

K=20/10=2

The efficiency of carnot refrigerator engine is,

Kc=T1T2-T1

Kc=300/300=1

So it's a possibility.

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Most popular questions from this chapter

A nuclear power plant generates 3000MWof heat energy from nuclear reactions in the reactor’s core. This energy is used to boil water and produce high-pressure steam at 300°C. The steam spins a turbine, which produces 1000MWof electric power, then the steam is condensed and the water is cooled to 25°Cbefore starting the cycle again.

a. What is the maximum possible thermal efficiency of the power plant?

b. What is the plant’s actual efficiency?

c. Cooling water from a river flows through the condenser (the low-temperature heat exchanger) at the rate of 1.2*108L/h ( ≈30 million gallons per hour). If the river water enters the condenser at 18°C, what is its exit temperature?

What are (a) the thermal efficiency and (b) the heat extracted from the hot reservoir for the heat engine shown in FIGUREEX21.15?

FIGURE Q21.4 shows the pV diagram of a heat engine. During which stage or stages is (a) heat added to the gas,(b) heat removed from the gas, (c) work done on the gas, and (d) work done by the gas?

A car’s internal combustion engine can be modeled as a heat engine operating between a combustion temperature of 1500oC and an air temperature of 20oC with 30% of the Carnot efficiency. The heat of combustion of gasoline is 47kJ/g. What mass of gasoline is burned to accelerate a 1500kgcar from rest to a speed of 30 m/s?

In Problems 65through 68you are given the equation(s) used to solve a problem. For each of these, you are to

a. Write a realistic problem for which this is the correct equation(s).

b. Finish the solution of the problem.

0.20=1-QC/QH

Wout=QH-QC=20J
See all solutions

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