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Heat and Work: Part 2

Heat and Work: Part 2. Conservation of Energy Heat Engines Second Law of Thermodynamics Energy Efficiency OTEC. Energy in the News. Possible solutions to Energy Problems 1) Smart Buildings and Machines 2) Superconductive Cables 3) Fewer Phantom Loads 4) Distributed Generation

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Heat and Work: Part 2

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  1. Heat and Work: Part 2 • Conservation of Energy • Heat Engines • Second Law of Thermodynamics • Energy Efficiency • OTEC

  2. 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

  3. Equilibrium of Heat Loss

  4. 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?

  5. Heat Engines

  6. Two basic types of heat engines • What are they?

  7. Vapor or Rankine Cycle • Steam engines • Heat pumps

  8. Gas Cycle • Automobiles (Internal Combustion) • Jet Engines (External Combustion) • Where is the fuel burned? • What does the force from burning move?

  9. Ocean Thermal Energy Conversion

  10. 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?

  11. 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

  12. Ideal Case • A completely reversible process • Do common heat engines use reversible processes, why or why not?

  13. Heat Pumps-How They Cool

  14. Why Pump from Ground Rather Than Air?

  15. Heat Pump in Winter

  16. Why Do Animals Burrow ?

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