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Heat and Work: Part 2 Conservation of Energy Heat Engines Second Law of Thermodynamics Energy Efficiency OTEC
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Energy in the News Possible solutions to Energy Problems –1) Smart Buildings and Machines –2) Superconductive Cables –3) Fewer Phantom Loads –4) Distributed Generation A) Solar Cells B) Wind C) Diesel Generators D) Microturbines E) Fuel Cells
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Equilibrium of Heat Loss
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Heat Loss Hypothermia-what causes it? Basic physics Lakes-ice and summer warmth. Why retained? Space blankets-very thin-what do they do? Why cold when standing near a window in winter? Why warm near a fire?
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Heat Engines
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Two basic types of heat engines What are they?
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Vapor or Rankine Cycle Steam engines Heat pumps
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Gas Cycle Automobiles (Internal Combustion) Jet Engines (External Combustion) Where is the fuel burned? What does the force from burning move?
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Ocean Thermal Energy Conversion
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Practicalities of OTEC Maximum Efficiency (Carnot efficiency) =100% * ( Thigh-Tlow)/Thigh T in degrees Kelvin What is more efficient? Thermal engines with large or small temperature differences? When will it be 100% efficient?
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Second Law of Thermodynamics Entropy (Disorder) always increases Unless energy is added Examples: Kids room Spontaneous heat flow (Hot to Cold yes, never cold to hot) Waste Heat is always present
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Ideal Case A completely reversible process Do common heat engines use reversible processes, why or why not?
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Heat Pumps-How They Cool
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Why Pump from Ground Rather Than Air?
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Heat Pump in Winter
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Why Do Animals Burrow ?
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