Application of transient experimental techniques for developing a heat transfer correlation for mixed convection in porous medium

摘要

An approach based on transient heat transfer experiments combined with numerical optimization procedures is studied to develop a heat transfer correlation for mixed convection heat transfer in a vertical duct filled with metallic porous structures. The heat source of the vertical duct is a near isothermal plate which during cooling is treated as a lumped heat capacity model. The temperature-time history, during the cooling of the plate, is measured using K-type (36AWG) thermocouples connected to a PC-based data acquisition system. A numerically computed temperature-time history of the plate is then compared with the experimentally known temperature-time history to estimate the residual. The minimization of sum of the squares of the residual is done using a hybrid numerical optimization technique, i.e. a combination of Genetic Algorithm and the Levenberg-Marquardt method, in order to obtain the coefficient and the exponents of the pertinent non-dimensional parameters in the Nusselt number correlation. The consistency of the present approach is further substantiated by comparing the Nusselt number values predicted using the proposed correlation and that evaluated from the steady-state experiments.