Viscous dissipation is the conversion from mechanical energy to thermal energy associated
with viscous forces acting in a fluid. It is only important in cases involving
high-speed flow and/or highly viscous fluid. Since so many engineering applications
satisfy one or more of the above four conditions, Equation 1.11e is commonly
used for the analysis of heat transfer in moving fluids. It will be used in Chapter 8 in
the study of convection heat transfer in internal flow.
The mass flow rate of the fluid may be expressed as VAc, where is the
fluid density and Ac is the cross-sectional area of the channel through which the
fluid flows. The volumetric flow rate is simply VAc /.