eml 3100 lecture on efficiencies

# eml 3100 lecture on efficiencies - 1 Thermodynamics First...

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Unformatted text preview: 1 Thermodynamics First Law Efficiencies Efficiency(Performance) = " " )" ( " for pay you What useful Get You What 2 Thermodynamics out in net Q Q W or- = in netout Q W / = η Note for an heat engine: Q in W net out Q out in out net Q Q W = + in out Q Q Qin Qout Qin- =- = 1 η 3 Thermodynamics in netout Q W / = η Q in W net out Q out 400,000 btu/h 70 kW (238,840 btu/h) η = 238,840/400,00 Example: Q out = Q in – W net out Qout = 400,000 – 238,840 = 161,160 btu/h 4 Thermodynamics Q in W net out Q out We may be able to convert some of Q out to additional work if the quality (temperature) of the energy is high enough. Q out W net out Called “Bottoming Cycle” on a power plant. 5 Thermodynamics net in R W Q input quired effect Useful COP = = _ Re _ in out in R Q Q Q COP - = in W Let’s Talk Refrigeration Cycle (yes, Ingley likes air conditioning stuff) Q’ in or Not a typical efficiency!! Can be greater than 1. More on refrigeration cycles later....
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eml 3100 lecture on efficiencies - 1 Thermodynamics First...

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