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Q&A_-6- 10/20/2005(6) Ji-Sheng Chang

The Advanced Chemical Engineering Thermodynamics Heat(q) and work(w) effects in a process and internal energy(U) and enthalpy(H) at a change of states. Q&A_-6- 10/20/2005(6) Ji-Sheng Chang. Equations of a substance. The ideal gas behavior of a fluid

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Q&A_-6- 10/20/2005(6) Ji-Sheng Chang

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  1. The Advanced Chemical Engineering ThermodynamicsHeat(q) and work(w) effects in a process and internal energy(U) and enthalpy(H) at a change of states Q&A_-6- 10/20/2005(6) Ji-Sheng Chang

  2. Equations of a substance • The ideal gas behavior of a fluid • Volumetric equation: PV=nRT, or PV=RT • Thermal equation: U=U(T), ordU=Cv(T)dT, and ΔU=∫Cv(T)dT;dH=Cp(T)dT, and ΔH=∫Cp(T)dT.

  3. Equations for process calculations • Equations of work, heat, internal energy, and enthalpy for process calculations • 1. The first law of thermodynamics for closed system… dU=dQirr.+dWirr.= dQrev.+dWrev. • 2. Internal energy… dU=CvdT • 3. Enthalpy… dH=CpdT • 4. Work… dWrev.=-PdV • 5. Heat flow… dQrev.=dU+PdV

  4. Heat and work • Equations of work and heat for process calculations • 1. Work … • 2. Heat flow …

  5. Isothermal process • Equations of work, heat, internal energy, and enthalpy for process calculations • ΔT=0; • ΔU=∫Cv dT=0 • ΔH=∫Cp dT=0 • W=-PdV • Q=W

  6. Isobaric process • Equations of work, heat, internal energy, and enthalpy for process calculations • ΔH=∫Cp dT • ΔU=∫Cv dT • Q=ΔH • W=ΔU-Q

  7. Isochoric process • Equations of work, heat, internal energy, and enthalpy for process calculations • ΔH=∫Cp dT • ΔU=∫Cv dT • Q=ΔU • W=0

  8. Adiabatic process • Equations of work, heat, internal energy, and enthalpy for process calculations • Q=0 • dU=W; CvdT=-PdV • for ideal gas: • TVγ-1=constant • TP(1-γ)/γ=constant • PVγ=constant ; γ=Cp/Cv • PV=RT; PV/T= constant

  9. Polytropic process • Equations of work, heat, internal energy, and enthalpy for process calculations • Polytropic process : PVσ=constant • Isothermal process : σ=1 • Isobaric process : σ=0 • Isochoric process : σ=∞ • Adiabatic process : σ=γ

  10. Enthalpy change for a state change • Sensible heat effects of a change of states • ΔH=∫Cp dT • Latent heats of pure substances • Theoretical model • Empirical models

  11. Standard enthalpy change • Standard heat of reaction • ΔH(T0)rexa. • Standard heat of formation • ΔH(T0)form. • Standard heat of combustion • ΔH(T0)comb.

  12. The heat of reaction • Temperature dependence of heat of reaction • ΔH(T)=ΔH(TT0)+ΔH(T0)+ΔH(T0 T) • sensible heat latent heat sensible heat

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