Nusselt number and friction characteristics of solar air heater roughened with novel twisted V-shaped staggered ribs using liquid crystal thermography

Dheeraj Kumar and Apurba Layek

Renewable Energy, 2022, vol. 201, issue P1, 651-666

Abstract: The objective of this study is to investigate the Nusselt number and friction characteristics of rectangular channel solar air heater (SAH) ducts roughened with staggered V-shaped ribs using the liquid crystal thermography technique. Experimentation is performed for Reynolds numbers ranges from 3000 to 21000, relative roughness pitch (P/e) of 7–11, relative roughness length (S/e) of 6.15–10.26, relative staggered distance (d/e) between 2 and 6, and fixed angle of attack (α) and relative twist length (y/e). The change in temperature of the roughened absorber surface that produced the RGB (red, green, blue) colour pattern is acquired by a charge-coupled device and converted into (Hue, Saturation, and Intensity) HSI using MATLAB. For all the varied parameters, results are discussed in terms of Nusselt number, friction factor, thermal enhancement factor, and visualization of fluid flows. Results show that the maximum augmentation ratio in Nusselt number and friction factor is 3.43 and 2.57 times more than that of a smooth duct, respectively. Among the varied roughness parameter, a maximum TEP value of 2.69 is noticed with P/e of 9, d/e of 4, and S/e of 6.15. It is concluded that inclusion of staggered twisted V-shaped ribs helps in enhancing heat transfer with the least amount of friction penalty.

Keywords: Liquid crystal thermography; Secondary flow; Twisted V-shape rib; Thermal enhancement factor; Nusselt number augmentation (search for similar items in EconPapers)
Date: 2022
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Citations: View citations in EconPapers (2)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:201:y:2022:i:p1:p:651-666

DOI: 10.1016/j.renene.2022.11.007

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