4.8 - 4 4.8 This problem is not well posed since we do not...

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4.8 This problem is not well posed since we do not know exactly what is happening. There are several possibilities: (1) Water contact is very short so neither stream changes T very much. In this case we have the Carnot efficiency η = = = + == = W Q TT T high low high 22 27 273 22 300 00733 7 33% .. (2) Both warm surface water (27 ° C) and cold deep water (5 ° C) enter work producing device, and they leave at a common temperature. T L T H T O M.B.: dM dt MMM M MM + + = + 0 00 ±±± ± ±± HL bg E.B.: dU dt MH MH W + + + = ± ² ± ² ± ² ± HH LL ² ± ² ² ± ²² ± WM HM HMM H MH H MCT T =− + + +− H L HP H LP L ch a f a f 0 S.B.: dS dt MS + + + 0 ± ² ± ± Q T 0 + S gen 0 ± ² ± ² ² ± ± ± ln ± ln ± ± M M S MS S MS S MC T T T T T T T T T H L 0 0 0 H L H L or −+ −=⇒ + = F H G I K J F H G I K J + 0 1 0 T MMM MMM 0 = ++ HHL LHL ±±± ±±± From this can calculate . Then T 0 ± W MCT T H L af ± L This can be used for any flow rate ratio. (3) Suppose very large amount of surface water is contacted with a small amount of deep water, i.e.,
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This note was uploaded on 01/20/2012 for the course CHE 330 at USC.

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4.8 - 4 4.8 This problem is not well posed since we do not...

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