> Heat transfer is the science which seeks to predict the energytransferwhich may take place between material bodies due to temperaturedifference.Driving force:temperature differenceThermalEquilibrium> Thermal equilibrium:two systems are said to be inthermalequilibrium when their temperatures are equal.Ineguilibrium,therearenoheatflows.> The steady state: In steady state, temperatures do not changewithtime
Thermal Equilibrium ➢ Thermal equilibrium: two systems are said to be in thermal equilibrium when their temperatures are equal. In equilibrium, there are no heat flows. ➢ The steady state: In steady state, temperatures do not change with time. ➢ Heat transfer is the science which seeks to predict the energy transfer which may take place between material bodies due to temperature difference. ➢ Driving force: temperature difference
Thermal EnergyEnergyconservationInOutGenRate ofRate ofRate ofRateof+EnergyInEnergyOutEnergyGenerationEnergy StorageThefirstlaw of thermodynamics: energy is conserved> Total energy of the system plus surroundings remain constant.> Different forms of energy can inter-convert but their sumremains constant
Energy conservation The first law of thermodynamics: energy is conserved ➢ Total energy of the system plus surroundings remain constant. ➢ Different forms of energy can inter-convert but their sum remains constant. Thermal Energy
Thermal EnergyEnergy conservation5g-10℃Q = mc4T2.1 J/g°℃m: massc: specific heat capacity△T: temperature difference5g10°℃4.2J/g°CEnergy Inm1Cp(Ti -0)=0EnergyOut=0EnergyGeneration=ChangeinEnergy Storage(m1Cpl +m2Cp2)(T -0) -m2Cp2(T2 - 0)finalinitial
Energy conservation m: mass c: specific heat capacity 𝛥𝑇: temperature difference 𝑄 = 𝑚𝑐𝛥𝑇 Thermal Energy oC oC
Thermal EnergySpecific heat capacity (c)> The quantity of heat required to raise the temperature of a substanceper gram by one degree Celsius is called the specific heat capacity ofthe substance.Unit: J/(g°C) or J/(gK)食用油c: water is 4.18 J/(g°C)oil is 1.97 J/(gC)
➢ The quantity of heat required to raise the temperature of a substance per gram by one degree Celsius is called the specific heat capacity of the substance. Unit: J/(g oC) or J/(gK) c: water is 4.18 J/(g oC) oil is 1.97 J/(g oC) Specific heat capacity (c) Thermal Energy
Thermal EnergyRate ofRateofRate ofRateof+EnergyOutEnergyGenerationEnergyStorageEnergyIn5g-10℃2.1J/gm1Cpl(Ti-0)=(m1Cpl+m2Cp2)(T-0)-m2Cp2(T2-0)5g10℃4.2 J/g5(2.1)(-10- 0) = (5(2.1) + 5(4.2))(T - 0) -5(4.2)(10 - 0)The final temperature T = 3.33°C.Thus, using energy conservation, we can find the final orequilibrium temperature or the final state of the system
The final temperature T = 3.33℃. Thus, using energy conservation, we can find the final or equilibrium temperature or the final state of the system. Thermal Energy