DIELECTRIC HEATING OF LIQUID IN THE REGIME OF TEMPERATURE STRATIFICATION AT A VERTICAL SURFACE UNDER THE CONDITIONS OF NON-STATIONARY RADIATION-CONVECTIVE HEAT TRANSFER
Keywords:
dielectric heating, nonstationary heat transfer, convectionAbstract
A class of nonlinear problems of liquid dielectric heating in the regime of natural convection near a vertical surface under the conditions of non-stationary radiation-convective heat transfer at microwave influence with a small depth of penetration is studied. These problems are solved using highly effective asymptotic procedures at the successive stages of non-stationary and stationary radiation-convective heat transfer. The non-stationary and stationary parts of solutions are joined by the “vertical coordinate-time”
characteristic. The solutions, derived on these principles, are in good agreement with the exact limiting solutions. The error is within the limits of 7%. With a distance from the lower edge of the vertical surface, convective heat transfer changes from the values characteristic of the boundary condition of the second kind to the values characteristic of the boundary condition of the first kind. The rate of this transition depends significantly on the complex parameter of microwave and thermal radiation. An important advantage of solutions to this class of external problems is the fact that even before complex calculations it is possible to perform an exhaustive analysis of the features of the studied processes. Moreover, despite a number of initial simplifications, the latter do not significantly affect the accuracy of results, guaranteeing reliable quantitative information. The developed method can be also extended to the regimes of natural convection with linear dependence of physical properties on temperature, using the Dorodnitsyn transformation. To confirm the adequacy of the constructed mathematical model, an experimental study of stationary radiation-convective heat transfer carried out. Comparison of theoretical and experimental data shows that they are in a good agreement. This again confirms the effectiveness of the developed method for constructing theoretical solutions to the nonlinear problems of natural convection using the asymptotic procedures.
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