Heat transfer measurement in rectangular channel with detach ribs by liquid crystal thermography

This paper deals with the study of heat transfer in solar air heater consisting of Winglet shaped roughness on the absorber plate using liquid crystal thermography technique. The winglet type roughness element was placed on the absorber surface of a rectangular channel solar air heater having an aspect ratio of 4. The absorber surface was heated uniformly by a constant heat flux of 800 W/m2. The non-dimensional roughness parameter considered as relative roughness pitch i.e., P/e, and its values range between 5-12 with Reynolds number (Re) range between 6500 - 22000. The value of angle of attack i.e., alpha and relative roughness width i.e. (W/w) were kept constant, and the relative roughness pitch was varied to measure the heat transfer coefficient. The enhancement in heat transfer has been compared and it is observed that at P/e of 8 for the angle of attack (α) of 60 degrees resulting it's optimum value. The enhancement of heat transfer with the increase in Reynolds number is also noted.

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Heat Transfer Augmentation of a Solar Air Heater Using a Twisted V-Shaped Staggered Rib Over the Absorber Plate

Kumar

Layek

2022

Journal of Solar Energy Engineering

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An effort is made to study the performance of a solar air heater having the absorber surface roughened by providing staggered, twisted V-shaped ribs roughness. Liquid crystal thermography technique is applied to get the Nu distribution over the surface. Experimentation is done for Reynolds number ranges from 3000 to 21000, relative roughness to pitch ratio (P/e) from 7 to 11 and relative staggered distance (d/e) of 2 to 6, for fixed angle of attack (a), relative twist length (y/e), relative roughness length (S/e). It is found that maximum Nusselt number and friction factor augmentation is of 3.43 and 2.57 times than that of smooth duct. The maximum thermo-hydraulic performance (THP) value obtained is of 2.69 for the P/e of 9 and d/e of 4. It can be inferred that staggered twisted V-shaped rib roughness helps to get the enhanced Nu with minimum friction penalty.

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Heat transfer measurement in rectangular channel with detach ribs by liquid crystal thermography

Cited by 3 publications

References 6 publications

Application of liquid crystal thermography for temperature measurement of the absorber plate of solar air heater

Application of liquid crystal thermography for temperature measurement of the absorber plate of solar air heater

Heat Transfer Measurement in a Rectangular Channel of Solar Air Heater With Winglet-Type Ribs Using Liquid Crystal Thermography

Heat Transfer Augmentation of a Solar Air Heater Using a Twisted V-Shaped Staggered Rib Over the Absorber Plate

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