Novel experimental-numerical study on inverse heat transfer by free convection and conduction for diamond-arranged tubes in a hot box

The present research utilizes an inverse 3D CFD technique, coupled with the least squares approach and laboratory temperature readings, to predict the suitable turbulence flow model and unknown heat transfer rates within a cubic hot box. This enclosure features four cylindrical horizontal tubes arranged in a diamond configuration, functioning as heaters to generate heat within the space. Furthermore, the heat dissipation from each tube, flow field and temperature contours are also established. The energy equation for tubes and the governing equations for air are solved by coupling. The present estimates are obtained assuming a constant heat transfer rate. The range of the Rayleigh number is from 60,294 to 76,824. Testing various turbulence models revealed that the zero-equation turbulence model reduces the root mean square discrepancy between the simulated thermal behavior and laboratory outcomes compared to other methodologies. To verify the chosen flow model's accuracy, the Nusselt numbers and flow field distributions aress compared with existing correlations and interferometer photographs. The maximum errors between the estimates of heat loss and heat transfer rate and the corresponding values from previous studies are 44 and 28% for St = 0.036, 34 and 3% for St = 0.045, and 37 and 18% for St = 0.054. To assess the impact of tube surface and spacing on the flow field model, calculation results are compared with those from four square-arranged tubes, revealing a lack of existing studies on this specific investigation.