Lecture14-08.1-Heat_engines

Lecture14-08.1-Heat_engines - 1 Announcement Monday, Oct....

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Unformatted text preview: 1 Announcement Monday, Oct. 25, in class. Covers Lectures 1-15 Chapters 1-8 Midterm LECTURE 14 Last Time Bose Einstein Condensation Excitations of a Bose Einstein Condensate Superfluidity -- why theyre so stable Fermi Gases: Heat Capacity Application to Electrons in Metals LECTURE 14 2 Today Chapter 8 (part 1) Heat and Work: Heat Engines LECTURE 14 Heat to work conversion Reversible Heat engine Carnot efficiency C Refrigerators and Heat Pumps: Carnot Coefficient C Carnot Cycle Engine Power First steam engine: 1698, Thomas Savery (water pump) An engine to rise water by fire www.mgsteam.btinternet.co.uk/engdev.htm Heat Work Conversion 3 Heat Work Conversion 1 st steam locomotive hauls 20 tons at 5 mph (Richard Trevithick, 1803) http://www.voteview.com/rtopic5_ucsd_1.htm www.tifft.com/steamer.html http://www.nd.edu/~techrev/Archive/Fal 2001/a4.html Energy Conversion in an Engine Heat Work Particles To do work: * Add heat to a system (heat engine) * Add particles (chemical energy conversion) * Use internal energy (what are limitations?) Most important in industry: Internal combustion engine & steam engine dU d pdV dN =- + 4 Heat & Work Differences Heat Work Particles Fundamental differences between heat and work: entropy Heat transfer dU d = dU d = Heat transfer is accompanied by entropy transfer Work: energy transfer by change in external parameters, no entropy transfer! dU pdV = - dU d pdV dN =- + Heat & Work Differences Heat Work Particles Fundamental differences between heat and work: entropy Heat transfer 2. Is total entropy conserved? 1. Is total energy of the two systems in contact conserved? 3. When is entropy transfer between two systems well defined? dU d pdV dN =- + 5 Heat & Work Differences Heat Work Particles Heat transfer Reversible process: & Q d Heat received in the process dU = & Q & W + & W = dU - & Q dU d =- d = 0 : pure work dU = d : pure heat Work on the system Energy conservation: dU d pdV dN =- + * Using & Q instead of dQ since it is an increment, not a derivative of a function Heat & Work Differences Heat Work Particles All types of work are convertible into each other since d = 0 Electrical motor Electrical generator electrical mechanical work conversion Work can be completely converted into heat, but the reverse is not true work heat complete conversion work heat complete conversion Example: work work complete conversion dU d pdV dN =- + 6...
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Lecture14-08.1-Heat_engines - 1 Announcement Monday, Oct....

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