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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: .7582 on October 01, 2011, 06:16:57 AM

Title: thermodynamic conceptual question
Post by: .7582 on October 01, 2011, 06:16:57 AM
Problem:
You received an unsolicited proposal from a self declared inventor who is seeking investors for the development of his latest idea: a device that uses heat extracted from the ground by a heat pump to boil water into steam that is used to heat a home and to power a steam engine that drives the heap pump. This procedure is potentially very lucrative because, after an initial extraction of energy from the ground, no fossil fuels would be required to keep the device running indefinitely. Would you invest in this idea? state your conclusion and present detailed arguments to support it.

im having trouble with this question as well as our professor when he was discussing it, i just remembered his answer was no and then explained it with a diagram but he stated that he was not quite sure about it. can someone help me with this? thanks in advance.
Title: Re: thermodynamic conceptual question
Post by: jusy1 on October 02, 2011, 05:11:53 PM
Hi,

I think it is impossible too. Here it's what I've done:

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg713.imageshack.us%2Fimg713%2F8025%2Fpumpsp.jpg&hash=acc0dba0e344812fd09786353a1002be) (http://imageshack.us/photo/my-images/713/pumpsp.jpg/)

We know that Wpump < Wsteam because some work will be lost as heat.

So, Qpump = Wpump = Wsteam + Qhome which is impossible.

I've admitted that all the work given to the heat pump will be used to heat the water.