In the present work, transient liquid crystal thermography (LCT) has been used for capturing the temperature field as well as the local heat transfer distribution inside a rectangular duct. Experiments have been carried out in an open loop airflow system at a Reynolds number (based on the channel hydraulic diameter) of 58850 and for rib height to channel hydraulic diameter ratio of 0.125. This investigation emphases headed for assessing the potential impact of design parameters such as chamfering angle and rib pitch to height ratio of the trapezium ribbed rectangular duct on the thermo-hydraulic performances, which forms the basis of analysis while using response surface methodology (RSM). The chamfering angle has been varied from 0 to 20° in a step of 5°, while the rib pitch to height ratio is varied from 8 to 12 in a step of 2. The quadratic model generated by RSM is used to predict the optimal performance parameters. The results show that different geometrical parameters have to be considered simultaneously in order to improve the performance of ribbed-duct. Eventually, based on this analysis, the optimum levels of design parameters for trapezium rib corresponding to the highest augmentation Nusselt number, the lowest friction factor, and the highest thermo-hydraulic performance have been determined. Finally, the desired correlations for all performance parameters have been developed using RSM. The comparison of predicted values with the experimental values has been carried out, which is found to be in harmony with the experimental values in the uncertainty range of ±5%., which are found to predict the performance parameters with reasonably good accuracy.

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