A refrigerator: A A) converts heat input to an equivalent amount of work B B) converts work to an equivalent amount of heat C) takes heat in, does work, and loses energy heat D) uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir E) uses positive work done on the system to transfer heat from a high temperature reservoir to a low temperature reservoir

A refrigerator: A A) converts heat input to an equivalent amount of work B B) converts work to an equivalent amount of heat C) takes heat in, does work, and loses energy heat D) uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir E) uses positive work done on the system to transfer heat from a high temperature reservoir to a low temperature reservoir

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter18: Heat Engines, Entropy, And The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 22P

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You are working on a summer job at a company that designs non-traditional energy systems. The company is working on a proposed electric power plant that would make use of the temperature gradient in the ocean. The system includes a heat engine that would operate between 20.0C (surface-water temperature) and 5.00C (water temperature at a depth of about 1 km). (a) Your supervisor asks you to determine the maximum efficiency of such a system. (b) In addition, if the electric power output of the plant is 75.0 MW and it operates at the maximum theoretically possible efficiency, you must determine the rate at which energy is taken in from the warm reservoir. (c) From this information, if an electric bill for a typical home shows a use of 950 kWh per month, your supervisor wants to know how many homes can be provided with power from this energy system operating at its maximum efficiency. (d) As energy is drawn from the warm surface water to operate the engine, it is replaced by energy absorbed from sunlight on the surface. If the average intensity absorbed from sunlight is 650 W/m2 for 12 daylight hours on a clear day, you need to find the area of the ocean surface that is necessary for sunlight to replace the energy absorbed into the engine. (e) From this information, you need to determine if there is enough ocean surface on the Earth to use such engines to supply the electrical needs for all the homes associated with the Earths population. Assume the energy use for a home in part (c) is an average over the entire planet. (f) In view of your results in this problem, your supervisor has asked for your conclusion as to whether such a system is worthwhile to pursue. Note that the fuel (sunlight) is free.
A large electrical power station generates 1000 MW of electricity with an efficiency of 35.0%. (a) Calculate the heat transfer to the power station, Qh, in one day. (b) How much heat transfer Qc occurs to the environment in one day? (c) If the heat transfer in the cooling towers is from 35.0C water into the local air mass, which increases in temperature from 18.0C to 20.0C, what is the total increase in entropy due to this heat transfer? (d) How much energy becomes unavailable to do work because of this increase in entropy, assuming an 18.0C lowest temperature? (Part of Qccould be utilized to operate heat engines or far simply heating the surroundings, but it rarely is.)
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A heat pump used for heating shown in Figure P18.25 is essentially an air conditioner installed backward. It extracts energy from colder air outside and deposits it in a warmer room. Suppose the ratio of the actual energy entering the room to the work done by the devices motor is 10.0% of the theoretical maximum ratio. Determine the energy entering the room per joule of work done by the motor given that the inside temperature is 20.0C and the outside temperature is 5.00C. Figure P18.25
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What is the coefficient of performance of an ideal heat pump that has heat transfer from a cold temperature of 5.0C to a hot temperature of 40.0C ?
The first law of thermodynamics and the conservation of energy, as discussed in Conservation of Energy, ale cleanly related. How do they differ in the types of energy considered?
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