An Experimental Study for Heat Transfer Enhancement by Laminar Forced Convection from Horizontal and Inclined Tube Heated with Constant Heat Flux, Using Two Types of Porous Media
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Abstract
An experimental forced laminar study was presented in this research for an air flowing through a circular channel for different angles ( ), the channel was heated at constant heat flux , the channel also was packed with steel and glass spheres respectively . The tests were done for three values of Peclets number (2111.71,3945.42,4575.47) with changing the heat flux for each case and five times for each number. The results showed that the dimensionless temperature distribution will decrease with increasing the dimensionless channel length for all cases with changing Peclet number, heat flux and inclination angles, and its lowest value will be for glass spheres at highest flux, while at lower flux for
, and the decreasing in dimensionless temperature was closed for both types of packed at other inclination angles. The study declared that the local Nusselt number decreases with increasing the dimensionless length of the channel for both packeds and for different applied heat flux, also through this study it was declared that the average Nusselt increases as Peclet number increases for both packed. Its value for the glass spheres is greater than the steel spheres with percentage (98.3%) at small Peclet, and percentage (97.2%) at large Peclet number for the horizontal tube, and (98.3%) at small Peclet number and (97.8%) at large Peclet number at θ=
. Through this study its was found that average Nusselt number increases along the channel as the heat flux increases, because the bulk temperature will increase as the flow proceeds toward the end of the channel , so the heat transfer coefficient will increase. It was declared from this study that in the case of the steel packed the heat transfer will occur mainly by conduction, while in the case of glass packed the heat transfer will occur mainly by laminar forced convection, where the lowest Nusselt number (Nu=3.8) was found when the pipe is horizontal and lowest heat flux and lowest Peclet number.
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