THERMODYNAMICS EML 3100
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This 6 page Class Notes was uploaded by Aric Jast MD on Thursday September 17, 2015. The Class Notes belongs to EML 3100 at Florida State University taught by Leonard Van Dommelen in Fall. Since its upload, it has received 69 views. For similar materials see /class/205479/eml-3100-florida-state-university in Engineering Mechanical at Florida State University.
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Date Created: 09/17/15
Statements of the Second Law of Thermodynamics Clausius Statement Application Refrigerators and Heat Pumps It is impossible for any system to operate in such a way that the sole result would be an energy transfer by heat from a cooler to a hotter body High Temperature Reservoir TH QH QL NOT POSSIBLE QL Low Temperature Reservoir TL I High Temperature Reservoir TH l I High Temperature Reservoir TH l QH QL QH POSSIBLE W QH 39 QL QL QL Low Temperature Reservoir TL l l LOW Temperature ReserVOiL TL KelvinPlank Statement Application Heat Engines It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of work to its surroundings while receiving energy by heat transfer from a single thermal reservoir High Temperature Reservoir TH QH WZQH NOT POSSIBLE Low Temperature Reservoir TL High Temperature Reservoir TH l QH W QH QL POSSIBLE QL Low Temperature Reservoir TL The Clausius and the KelvinPlank statements are equivalent The equivalence is demonstrated by showing that the Violation of one statement implies the Violation of the other Second Law Corollaries It is impossible to construct an engine operating between two given thermal reservoirs that is more ef cient than a reversible engine operating between the same two reservoirs High Temperature Reservoir TH Any Reversible Engine Engine I R V Low Temperature Reservoir TL Proof 1 Let any heat engine I and a reversible engine R operate between the high and low temperature reservoirs TH and TL 2 Assume the statement above is false ie assume TlI gt UK 3 Operate the engines such that QIH QRH QH 4 By definition QH Wnet and Qm Th QH a T R by assumption 2 E gt T11 QH T R QH 2 hence WI gt WR 5 Reverse the reversible engine High Temperature Reservoir TH T QHR Reversible Engine R QLR Low Temperature Reservoir TL 6 Since WI gt WR take part of WI and supply WR High Temperature Reservoir TH T QHR Any Reversible Engine Engine R QLR W1 WR Low Temperature Reservoir TL 7 Use QHR to supply QHI note that QHI QHR QH I High Temperature Reservoir TH Reversible Engine R QLR Low Temperature Reservoir TL 8 Take the two engines as a single system High Temperature Reservoir TH QHI QHR QH T WR Reversible Engine QLI V W1 WR QLR Low Temperature Reservoir TL 9 Note that now we now have a single engine system which exchanges heat with a single reservoir TL and produces net work W1 WR This is a direct violation of the second law of thermodynamics WIWR QL QLR QLI Low Temperature Reservoir TL 10 CONCLUSION It is impossible to construct an engine that operates between two given reservoirs and is more efficient than a reversible engine operating between the same two reservoirs ie
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