Differential formulation of governing equations

From Thermal-FluidsPedia

The microscopic (differential) formulations to be presented here include conservation equations and jump conditions. The former apply within a particular phase, and the latter are valid at the interface that separates two phases. The phase equations for a particular phase should be the same as those for a single-phase system. Most textbooks (e.g., White, 1991; Incropera and DeWitt, 2001; Bejan, 2004; Kays et al., 2004) obtain the governing equations for a single-phase system by performing mass, momentum, and energy balances for a microscopic control volume. We will obtain the conservation equations by using the integral equations for a finite control volume that includes only one phase. Jump conditions at the interface will be obtained by applying the conservation laws at the interfaces.

1 Continuity Equation
2 Momentum Equation
3 Energy Equation
4 Entropy Equation
5 Conservation of mass species equation
6 References
7 Further Reading
8 External Links

Continuity Equation

$\frac{{D\rho }}{{Dt}} + \rho \nabla \cdot {{\mathbf{V}}_{rel}} = 0$

See Main Article Continuity equation

Momentum Equation

$\rho \frac{{D{{\mathbf{V}}_{rel}}}}{{Dt}} = \sum\limits_{i = 1}^N {{\rho _i}{{\mathbf{X}}_i}} - \nabla p + \nabla \cdot (\mu \nabla {{\mathbf{V}}_{rel}})$

See Main Article Momentum equation

Energy Equation

$\rho {c_p}\frac{{DT}}{{Dt}} = \nabla \cdot (k\nabla T) + T\beta \frac{{Dp}}{{Dt}} + q''' + \nabla {{\mathbf{V}}_{rel}}:{{\mathbf{\tau }}_{rel}}$

See Main Article Energy equation

Entropy Equation

For a multicomponent system without internal heat generation ( $q''' = 0$ ), the entropy flux vector and the entropy generation are

${\mathbf{s''}} = \frac{1}{T}\left( {{\mathbf{q''}} - \sum\limits_{i = 1}^N {{h_i}{{\mathbf{J}}_i}} } \right)$ $T{\dot s'''_{gen}} = - \left( {{\mathbf{q''}} - \sum\limits_{i = 1}^N {{h_i}{{\mathbf{J}}_i}} } \right) \cdot \nabla \ln T - \sum\limits_{i = 1}^N {\left( {{{\mathbf{J}}_i} \cdot \frac{{c{R_u}T}}{{{\rho _i}}}{{\mathbf{d}}_i}} \right)} - {\mathbf{\tau }}:\nabla {\mathbf{V}} - \sum\limits_{i = 1}^N {\frac{{{{\bar g}_i}}}{{{M_i}}}{{\dot m'''}_i}}$

See Main Article Entropy equation

Conservation of mass species equation

$\rho \frac{{D{\omega _i}}}{{Dt}} = - \nabla \cdot {{\mathbf{J}}_i} + {\dot m'''_i}$

See Main Article Conservation of Mass Species

References

Bejan, A., 2004, Convection Heat Transfer, 3^rd ed., John Wiley & Sons, New York.

Faghri, A., and Zhang, Y., 2006, Transport Phenomena in Multiphase Systems, Elsevier, Burlington, MA

Faghri, A., Zhang, Y., and Howell, J. R., 2010, Advanced Heat and Mass Transfer, Global Digital Press, Columbia, MO.

Incropera, F.P., and DeWitt, D.P., 2001, Fundamentals of Heat and Mass Transfer, 5^th ed., John Wiley & Sons, New York.

Kays, W.M., Crawford, M.E., and Weigand, B., 2004, Convective Heat Transfer, 4^th ed., McGraw-Hill, New York, NY.

White, F.M., 1991, Viscous Fluid Flow, 2^nd ed., McGraw-Hill, New York.

External Links

Retrieved from "http://thermalfluidscentral.org/encyclopedia/index.php/Differential_formulation_of_governing_equations"

Differential formulation of governing equations

From Thermal-FluidsPedia

Contents

Continuity Equation

Momentum Equation

Energy Equation

Entropy Equation

Conservation of mass species equation

References

Further Reading

External Links

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