MSC. EASY5 GD Library Overview Governing equations for fluid flow are represented as ordinary differential equations rather than partial differential equations Fluid flow is considered one-dimensional; but this is still a rigorous treatment that includes: Transient energy effects Fluid compressibility No flow or flow reversal possibilities Transient momentum effects in pipes Consideration of moisture condensation - important for ECS applications Gas laws-ideal, Lee-Kestler(built into the library)and user-defined Modeling and Simulation of Gas Systems with MSCEASY5 -Chart 11 MSC XSOFTWARE
MSC.EASY5 Modeling and Simulation of Gas Systems with MSC.EASY5 - Chart 11 GD Library Overview • Governing equations for fluid flow are represented as ordinary differential equations rather than partial differential equations. • Fluid flow is considered one-dimensional; but this is still a rigorous treatment that includes: – Transient energy effects – Fluid compressibility – No flow or flow reversal possibilities – Transient momentum effects in pipes – Consideration of moisture condensation- important for ECS applications – Gas laws- ideal, Lee-Kestler (built into the library) and user-defined
MSC. EASY5 Governing Equations · Conservation of mass Conservation of Energy Conservation of momentum Flow/Pressure Drop Correlations for Pipes and Orifices Pipe Friction Factors as a Function of Reynolds Number Modeling and Simulation of Gas Systems with MSC EASY5 - Chart 12 MSC XSOFTWARE
MSC.EASY5 Modeling and Simulation of Gas Systems with MSC.EASY5 - Chart 12 Governing Equations • Conservation of Mass • Conservation of Energy • Conservation of Momentum • Flow/Pressure Drop Correlations for Pipes and Orifices • Pipe Friction Factors as a Function of Reynolds Number
MSC. EASY5 Conservation of mass d(P)= d(;) dt , out or dt Density in terms of temperature and (species partial) pressures P +∑ P d(r)分aP For an ideal gas, this term Fluid Properties is zero if i≠j Modeling and Simulation of Gas Systems with MSC EASY5 - Chart 13 MSC XSOFTWARE
MSC.EASY5 Modeling and Simulation of Gas Systems with MSC.EASY5 - Chart 13 Conservation of Mass i in i out i w w dt d V , , ( ) or w w V dt d V i in i out i i , , ( ) • Density in terms of temperature and (species partial) pressures: j j j i i i P P T dt T d Fluid Properties For an ideal gas, this term is zero if i j
MSC. EASY5 Conservation of Energy Energy balance written in terms of enthalpies, temperature and pressure rates mc.T p(ar/P=w mvv+Awcond +i 22 Net enthalpy Later Heat 〔 includes work Net kinetic heat transfer on fluid by energy net pressure force) Species mass balances energy balance form a system of equations that must be solved simultaneously for Pi and T Modeling and Simulation of Gas Systems with MSC EASY5 - Chart 14 MSC XSOFTWARE
MSC.EASY5 Modeling and Simulation of Gas Systems with MSC.EASY5 - Chart 14 Conservation of Energy • Species mass balances + energy balance form a system of equations that must be solved simultaneously for and . • Energy balance written in terms of enthalpies, temperature and pressure rates: Pi T mvv w q v v P w h h w T VT mC T cond in in in in P p 2 2 2 2 Net enthalpy (includes work on fluid by net pressure force) Net kinetic energy Latent heat Heat transfer
MSC. EASY5 Conservation of Momentum. Transient Form Transient Momentum balance: plv=(Pin-Pex)Acs-f* 2 wall In In ressure force shear force convective momentum flux Fluid velocity state =v f∫ Friction factor =f( Re D Exit flow =w2=paCs Modeling and Simulation of Gas Systems with MSC EASY5 - Chart 15 MSC XSOFTWARE
MSC.EASY5 Modeling and Simulation of Gas Systems with MSC.EASY5 - Chart 15 Conservation of Momentum, Transient Form • Transient Momentum Balance: Fluid velocity state = v Friction factor = f (Re,D) Exit flow = w2 = vAcs v in v in w wall A v v c f Pex A s in Vv P 2 ( ) pressure force shear force convective momentum flux