COMPARISON OF EXPERIMENTS AND HYBRID SIMULATIONS OF TRANSIENT CONJUGATED CONDUCTION-CONVECTION-RADIATION

摘要

Experimental results and hybrid numerical-analytical simulations for transient laminar forced convection over flat plates of non-negligible thickness, subjected to an applied wall heat flux at the fluid-solid wall interface, are critically compared. The conjugated conduction-convection-radiation problem is first simplified through the employment of the Coupled Integral Equations Approach (CIEA) to reformulate the heat conduction problem on the plate by averaging the related energy equation in the transversal direction. A partial differential formulation for the transversally averaged wall temperature is obtained, and the boundary condition for the fluid in the heat balance at the solid-fluid interface is then rewritten. The coupled partial differential equations within the thermal boundary layer are handled by the Generalized Integral Transform Technique (GITT) under its partial transformation mode, combined with the method of lines implemented in the Mathematica 7.0 routine NDSolve. For the experiments, an apparatus was employed involving an air blower and flash lamps that heat a vertical PVC plate of 33 cm in length and 12 mm in thickness, while the temperature at the surface exposed to the cooling air is measured by infrared thermography. Thermocouple measurements are also utilized to provide estimates of heat losses at the back surface of the plate. The transient evolution of the measured surface temperatures along the plate length are critically compared against the simulation results, and the model is then analyzed to illustrate the major effects that require further treatment for a closer agreement with the experimental findings.