Experimental study on the augmented Nusselt number of the endwall through a square-sectioned sharp-turn channel using novel heat exchanger

Aquiring higher thermal efficiency with minimum energy consumption is the continuous pursuit of heat exchanger design. This work aims to demonstrate a novel enhanced heat exchange approach for a two-pass heat exchanger surface using four forms of a novel heat exchanger (nHEX), such as high straight and low curved turbulators, etc. The nHEXs are arranged parallel and equally spaced on the internal endwall. A comparison between current design and conventionally turbulated endwalls of sharp-turn channels is presented. The results indicate that the heat transfer rate is greatly augmented by inserting an array of nHEXs compared to a smooth endwall channel. The strategically placed vortex generators can improve the lowest heat transfer region on the smooth endwall to achieve overall thermal enhancement and temperature uniformity. Among the studied geometries, higher height or straight forms of the nHEXs are prone to enhance endwall heat transfer. The high straight forms of the nHEXs provide the maximum improvement of the normalized Nusselt number and thermal enhancement factor in a sharp-turn channel, which are 32% and 18% higher than the corresponding values of the smooth endwall, respectively. This study proved the potential of an array of parallel nHEXs to provide endwall heat transfer enhancement in a sharp-turn channel with an acceptable pressure drop penalty.