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Heat Flow in homogeneous multi-phase fluid flow


(1) (\rho \,c_{pt})_m \frac{\partial T}{\partial t}   - \ \sum_{a = \{w,o,g \}} \rho_\alpha \ c_{p \alpha} \ \eta_{s \alpha} \ \frac{\partial p_\alpha}{\partial t}   + \bigg( \sum_{a = \{w,o,g \}} \rho_\alpha \ c_{p \alpha} \ \mathbf{u}_\alpha \bigg) \ \nabla T   - \nabla (\lambda_t \nabla T) = \frac{\delta E_H}{ \delta V \delta t}


T(t, {\bf r})

fluid temperature as function of time  t and space location  {\bf r} \in \mathbb{R^3}

{\bf u}(t, {\bf r})

fluid velocity as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\frac{\delta Q}{ \delta V \delta t}

amount of heat  \delta Q generated (or consumed) per unit volume per unit time as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\rho

fluid density

c_p

isobaric specific heat capacity

\lambda

thermal conductivity

Heat Flow in single-phase fluid flow


(2) \rho \, c_p \, \frac{\partial T}{\partial t} - {\bf \nabla}\, \left( \lambda \, {\bf \nabla} T \right) + \rho \, c_p \, {\bf u} \, {\bf \nabla} T - \rho \ c_p \ \eta_s \ \frac{\partial p}{\partial t} = \frac{\delta E_H}{ \delta V \delta t}


T(t, {\bf r})

fluid temperature as function of time  t and space location  {\bf r} \in \mathbb{R^3}

{\bf u}(t, {\bf r})

fluid velocity as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\frac{\delta Q}{ \delta V \delta t}

amount of heat  \delta Q generated (or consumed) per unit volume per unit time as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\rho

fluid density

c_p

isobaric specific heat capacity

\lambda

thermal conductivity

Heat Flow in stabilised single-phase fluid flow


(3) \rho \, c_p \, \frac{\partial T}{\partial t} - {\bf \nabla}\, \left( \lambda \, {\bf \nabla} T \right) + \rho \, c_p \, {\bf u} \, {\bf \nabla} T = \frac{\delta Q}{ \delta V \delta t}



T(t, {\bf r})

fluid temperature as function of time  t and space location  {\bf r} \in \mathbb{R^3}

{\bf u}(t, {\bf r})

fluid velocity as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\frac{\delta Q}{ \delta V \delta t}

amount of heat  \delta Q generated (or consumed) per unit volume per unit time as function of time  t and space location  {\bf r} \in \mathbb{R^3}

\rho

fluid density

c_p

isobaric specific heat capacity

\lambda

thermal conductivity


The heat flow in a restricted volume is also influenced by the heat exchange with other fluids or solids at the contact surface:

(4) j_q |_1 = j_q |_2

where  j_q |_1 and j_q |_2 are a heat flux at contacting surfaces.

See also


Physics / Thermodynamics / Heat Transfer / Heat flow

Heat Flux ]

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