First Law of ThermodynamicsObjective· First Law of Thermodynamics Energy Forms and Energy Transfer..Work, Heat and Mass· Energy Balance for Closed System·EnergyBalance forOpen System· Energy Balance for Steady-Flow System
First Law of Thermodynamics Objective • First Law of Thermodynamics • Energy Forms and Energy Transfer .Work, Heat and Mass • Energy Balance for Closed System • Energy Balance for Open System • Energy Balance for Steady-Flow System
First Law of ThermodynamicsConservationof Energy PrincipleEnergy can be neither created nordestroyed ;lt can only change formsEnergy can change many forms, but its totalvalue keeps constant.The perpetual-motion machine of the first kindcan never be made
First Law of Thermodynamics Conservation of Energy Principle • Energy can be neither created nor destroyed ;It can only change forms. • Energy can change many forms, but its total value keeps constant. • The perpetual-motion machine of the first kind can never be made
亨内考的“魔轮”（13世纪）达.芬奇的“永动机”（15世纪）斯特尔的“永动机”（16世纪）浮力“永动机
First Law of ThermodynamicsIn 1843, at the age of 25, JamesPrescott Joule did a series ofcareful experiments to provetheClEnguinequivalence of heat and work
First Law of Thermodynamics In 1843, at the age of 25, James Prescott Joule did a series of careful experiments to prove the equivalence of heat and work
Forms of Energy Transfer(EnergyEnteringCV}-(EnergyLeavingCV)={EnergyAccumulatinginCV)There are three forms of energy transfer:Work:caused by a force acting through a distancevolume work: moving boundary work.Heat: caused by temperature difference between thesystemandsurroundings?Mass flow: mass flow in or out of the system serves as anenergy transfer
Forms of Energy Transfer There are three forms of energy transfer: •Work:caused by a force acting through a distance volume work: moving boundary work •Heat: caused by temperature difference between the system and surroundings. •Mass flow: mass flow in or out of the system serves as an energy transfer. {Energy Entering CV } － {Energy Leaving CV} ={Energy Accumulating in CV}