Artificial enhancer for small-scale solar air heater—A comprehensive review

• Published in: Cleaner Energy Systems Vol. 4; p. 100046
• Main Authors: Markam, Bhupendra, Maiti, Subarna
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2023
• Subjects: Artificial roughness (rib); Exergy analysis; Rib design; Solar air heater (SAH); Sustainability Index; Thermal performance factor (TPF); Artificial roughness (rib); Thermal performance factor (TPF); Solar air heater (SAH); Exergy analysis; Sustainability Index; Rib design
• ISSN: 2772-7831; 2772-7831
• DOI: 10.1016/j.cles.2022.100046

•Various type of artificial enhancers in small scale-solar air heater discussed.•Shape and pattern of incorporation given most significance for thermal performance.•Rib shape, thermo-hydraulic performance, Nusselt number and friction factor correlated.•Discussion on exergy analysis and sustainability of solar air heaters.•CFD turbulence model has been discussed for solar air heaters.•Comparative study shows best thermal performance factor for dimple-shaped enhancers with the transverse arrangement. The solar air heater (SAH), a device to harness solar thermal energy, is widely used in agriculture process drying, space and water heating in domestic and commercial settings, refrigeration, and steam generation. The typically used air heaters have a low heat transfer coefficient due to the development of a viscous thermal boundary layer near the wall, and this causes a reduction in the efficiency of the device. Improved heat transfer efficiency can be suitably brought about by passive methods involving artificial enhancers like fin, rib, and groove on the surface near the wall. This paper critically reviews various artificial enhancers and their effects on heat transfer. The shape and pattern of incorporation classify the enhancers. V shape, arc, S-type, W- rib, and their placement arrangements, like transverse, inclined and longitudinal, are discussed in this review. Light is thrown on their impact on parameters like Nusselt number and friction factor. It is observed that the dimple shape and V staggered rib gave significant enhancement on the thermal performance factor (TPF). It is seen that most research focuses on forced convection to compensate for the friction factor and enhance the Nusselt number, and less is reported for natural convection. Studies also show that along with experimental work, the CFD-based approach with proper selection of turbulence model for heat and momentum transfer characterization improves thermal energy transfer in the heaters. Exergy analysis and sustainability index parameters are also discussed in this review of artificial enhancers. The methodologies can pave the way for higher heat transfer efficiencies for future directions of efficient SAH design on the small-scale, thus aiding the broader application of the heaters. Graphical Abstract. [Display omitted] .