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Chapter 20: Problem 20

Is it a violation of the Second Law of Thermodynamics to capture all the exhaust heat from a steam engine and funnel it back into the system to do work? Why or why not?

Short Answer

Expert verified
Answer: Yes, it is a violation of the Second Law of Thermodynamics to capture all the exhaust heat from a steam engine and funnel it back into the system to do work. This would imply a total conversion of heat into work with no increase in entropy, which is not possible according to the Second Law. There will always be some loss of energy in the form of waste heat that cannot be converted into work, making 100% heat engine efficiency unattainable.

Step by step solution

01

Understand the Second Law of Thermodynamics

The Second Law of Thermodynamics states that the total entropy of an isolated system can never decrease over time; it can only remain constant or increase. In other words, natural processes tend to move towards a state of greater disorder (entropy). This means that it is impossible to convert heat completely into work without any increase in entropy.
02

Analyze the steam engine system

A steam engine operates initially by adding heat to water to generate steam. Next, the steam is used to perform work (e.g., turning a wheel or piston). After performing work, the steam's temperature drops, and it then needs to be cooled down to form water again before being reused.
03

Consider the heat recovery process

If we were to capture all the exhaust heat from the steam engine and funnel it back into the system, we would essentially be trying to create a 100% efficient heat engine. This would mean converting all the heat from the steam back into work without losing any energy in the form of waste heat.
04

Apply the Second Law of Thermodynamics to this scenario

According to the Second Law of Thermodynamics, it is impossible to convert heat completely into work with no increase in entropy. The attempt to capture all exhaust heat implies that no entropy increase would occur, but this contradicts the Second Law.
05

Determine if this is a violation of the Second Law of Thermodynamics

Yes, it is a violation of the Second Law of Thermodynamics to capture all the exhaust heat from a steam engine and funnel it back into the system to do work. Such a process would imply total conversion of heat into work with no increase in entropy, which is not possible according to the Second Law of Thermodynamics. There will always be some loss of energy in the form of waste heat that cannot be converted into work, which explains why 100% heat engine efficiency is unattainable.

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Most popular questions from this chapter

Consider a Carnot engine that works between thermal reservoirs with temperatures of \(1000.0 \mathrm{~K}\) and \(300.0 \mathrm{~K}\). The average power of the engine is \(1.00 \mathrm{~kJ}\) per cycle. a) What is the efficiency of this engine? b) How much energy is extracted from the warmer reservoir per cycle? c) How much energy is delivered to the cooler reservoir?

What is the magnitude of the change in entropy when \(6.00 \mathrm{~g}\) of steam at \(100{ }^{\circ} \mathrm{C}\) is condensed to water at \(100{ }^{\circ} \mathrm{C} ?\) a) \(46.6 \mathrm{~J} / \mathrm{K}\) c) \(36.3 \mathrm{~J} / \mathrm{K}\) b) \(52.4 \mathrm{~J} / \mathrm{K}\) d) \(34.2 \mathrm{~J} / \mathrm{K}\)

An ideal gas undergoes an isothermal expansion. What will happen to its entropy? a) It will increase. c) It's impossible to determine. b) It will decrease. d) It will remain unchanged.

If liquid nitrogen is boiled slowly-that is, reversiblyto transform it into nitrogen gas at a pressure \(P=100.0 \mathrm{kPa}\), its entropy increases by \(\Delta S=72.1 \mathrm{~J} /(\mathrm{mol} \mathrm{K}) .\) The latent heat of vaporization of nitrogen at its boiling temperature at this pressure is \(L_{\text {vap }}=5.568 \mathrm{~kJ} / \mathrm{mol}\). Using these data, calculate the boiling temperature of nitrogen at this pressure.

20.9a) The maximum efficiency of a Carnot engine is \(100 \%\) since the Carnot cycle is an ideal process. b) The Carnot cycle consists of two isothermal processes and two adiabatic processes. c) The Carnot cycle consists of two isothermal processes and two isentropic processes (constant entropy). d) The efficiency of the Carnot cycle depends solely on the temperatures of the two thermal reservoirs.
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