The mass of an engine is negligible. Find the maximum possible efficiency for the following cycle, in which the engine accepts 1800 kJ of heat from reservoir 1 at 1200 K rejects an as yet unspecified amount of heat to reservoir 2 at 300 K ● rejects 300 kJ heat to a finite, 1-kg-mass of water, thereby raising its temperature from 300 K to 371.4 K. The specific heat capacity of water is 4.2 kJ kg-¹ K-¹. Draw a block diagram of the engine plus reservoirs, including all information given above and an adiabatic system boundary. Find the entropy loss in (constant temperature) reservoir 1 and the entropy gain in the 1-kg-mass of water. State why the change in engine entropy may be neglected. What is the minimum entropy gain in (constant temperature) reservoir 2? (Hint, in a thermally isolated system the sum of all entropy changes is equal to or greater than). Estimate the maximum possible cycle efficiency. (Note, for the purposes of simplicity this question is contrived. The "water mass" counts as a part of the radiator water, contained within a moving boundary. At the very end of the cycle it is replaced by another 1-kg-mass at 300 K and the step change in temperature returns all parts of the system to their start-of-cycle condition.)

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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The mass of an engine is negligible. Find the maximum possible efficiency for the following cycle, in
which the engine
accepts 1800 kJ of heat from reservoir 1 at 1200 K
rejects an as yet unspecified amount of heat to reservoir 2 at 300 K
●
rejects 300 kJ heat to a finite, 1-kg-mass of water, thereby raising its temperature from 300 K to
371.4 K. The specific heat capacity of water is 4.2 kJ kg-¹ K-¹.
Draw a block diagram of the engine plus reservoirs, including all information given above and an
adiabatic system boundary. Find the entropy loss in (constant temperature) reservoir 1 and the
entropy gain in the 1-kg-mass of water. State why the change in engine entropy may be neglected.
What is the minimum entropy gain in (constant temperature) reservoir 2? (Hint, in a thermally
isolated system the sum of all entropy changes is equal to or greater than). Estimate the maximum
possible cycle efficiency.
(Note, for the purposes of simplicity this question is contrived. The "water mass" counts as a part of
the radiator water, contained within a moving boundary. At the very end of the cycle it is replaced by
another 1-kg-mass at 300 K and the step change in temperature returns all parts of the system to
their start-of-cycle condition.)
Transcribed Image Text:The mass of an engine is negligible. Find the maximum possible efficiency for the following cycle, in which the engine accepts 1800 kJ of heat from reservoir 1 at 1200 K rejects an as yet unspecified amount of heat to reservoir 2 at 300 K ● rejects 300 kJ heat to a finite, 1-kg-mass of water, thereby raising its temperature from 300 K to 371.4 K. The specific heat capacity of water is 4.2 kJ kg-¹ K-¹. Draw a block diagram of the engine plus reservoirs, including all information given above and an adiabatic system boundary. Find the entropy loss in (constant temperature) reservoir 1 and the entropy gain in the 1-kg-mass of water. State why the change in engine entropy may be neglected. What is the minimum entropy gain in (constant temperature) reservoir 2? (Hint, in a thermally isolated system the sum of all entropy changes is equal to or greater than). Estimate the maximum possible cycle efficiency. (Note, for the purposes of simplicity this question is contrived. The "water mass" counts as a part of the radiator water, contained within a moving boundary. At the very end of the cycle it is replaced by another 1-kg-mass at 300 K and the step change in temperature returns all parts of the system to their start-of-cycle condition.)
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