Heat and Work: Part 2 Conservation of Energy Heat Engines Second Law of Thermodynamics Energy...
-
date post
20-Dec-2015 -
Category
Documents
-
view
217 -
download
1
Transcript of Heat and Work: Part 2 Conservation of Energy Heat Engines Second Law of Thermodynamics Energy...
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
• A) Solar Cells
• B) Wind
• C) Diesel Generators
• D) Microturbines
• E) Fuel Cells
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?
Gas Cycle
• Automobiles (Internal Combustion)
• Jet Engines (External Combustion)
• Where is the fuel burned?
• What does the force from burning move?
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?
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
Ideal Case
• A completely reversible process
• Do common heat engines use reversible processes, why or why not?