Heat Transfer Enhancement of Solar Air Heaters Using Artificial Roughness

Mechanical

In this study, a conventional solar air heater (SAH) was redesigned by introducing transverse wire ribs with different gap configurations to enhance its thermal performance. Experiments were carried out under real outdoor conditions in Jagdalpur, India. The design parameters were kept fixed for most variables’ relative roughness height (e/D = 0.043), relative roughness pitch (p/e = 10), rib roughness diameter (e = 2 mm), and gap width (g = 4 mm) while the number of gaps (Ng) was varied from 1 to 4. The system was tested across a Reynolds number range of 2000–16000. The results show that using two gaps (Ng = 2) provides the best balance between heat transfer and friction factor when compared with other gap configurations, as well as with continuous and smooth duct designs. At these conditions, the heat transfer and friction factor were enhanced by factors of 3.04 and 3.03, respectively, over smooth ducts. The optimal configuration was identified as p/e = 10, e/D = 0.043, e = 2 mm, g = 4 mm, and Ng = 2. Overall, this configuration achieved superior heat transfer improvements compared to similar solar air heater studies, particularly because of the use of multiple gaps in the rib setup.

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