Heat Transfer on Liquid Laminar Free Convection
The new similarity analysis method is used to transform the governing partial differential equations of laminar free convection of liquid into the corresponding governing dimensionless system, which are identical to the corresponding governing dimensionless system of gas laminar free convection, except different treatment of variable physical properties. Due to the different variable physical properties from gases, the polynomial approach is suggested for treatment of temperature-dependent physical properties of liquid. Taking water as an example, the polynomial approach is applied for expressions of temperature-dependent density, thermal conductivity, and viscous. These expressions are reliable because they are based on the typical experimental values of the physical properties. By means of the equations of the physical property factors coupled with the governing ordinary differential equations of liquid laminar free convection created by the new similarity analysis method, the non-linear governing equations with corresponding boundary conditions are simultaneously solved numerically. The effect of variable physical properties on water laminar free convection along an isothermal vertical plate is investigated. It is found that the wall temperature gradient is the only one no-given condition for prediction of heat transfer. Compared with wall temperature, the bulk temperature dominates heat transfer of laminar free convection. By means of the curve-fitting equation on the wall temperature gradient, the heat transfer analysis equations based on the new similarity analysis model become those with the practical application value for heat transfer prediction.
KeywordsHeat Transfer Free Convection Average Nusselt Number Bulk Temperature Heat Transfer Analysis
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