Tuesday, April 24, 2007
HW #6, P4 - Effect of Source and Sink Temperatures on HE Efficiency - 6 pts
A heat engine operates between a source at TH and a sink at TC. Heat is supplied to the heat engine at a steady rate of 1200 kJ/min. Study the effects of TH and TC on the maximum power produced and the maximum cycle efficiency. For TC = 25oC, let TH vary from 300oC to 1000oC. Create plots of Wcycle and ηth as functions of TH. For TH = 550oC, let TC vary from 0oC to 50oC. Create plots of Wcycle and ηth as functions of TC. Discuss the results.
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6 comments:
Is this a reversible HE, and if not, how do we relate temperature to COP and efficiency?
The problem asks for the maximum power and efficiency. Reversible heat engines have the max power and efficiency. So, yes, please consider the heat engine to be reversible.
would like to double check if the answers are correct. when i plot by power and efficiency cycles, i obtained an increasing function with increasing Thot. shouldn't max power and efficiency then occur at 1000 instead of 300 degrees? similarly, i obtained a decreasing power and efficiency function with increasing Tcold, which means max power and efficiency should occur at 0 degrees? i'm unsure how did 25 degrees came about. are my functions wrong? pls advice. thanks
y:
The answers that I gave are representative values so you can check and compare your results at 300 degC and 25 degC. I did not mean toimply that the values I provided are the maximum values.
maybe you've mentioned this in class already, but is this something you are expecting us to do in excel or more like a sketch?
Anon:
I suggest you do this in Excel. It is faster and better. But the choice is yours.
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