article · Energy Sources Part A Recovery Utilization and Environmental Effects
This research evaluates the thermal and fluid dynamic performance of different absorber designs within a tubular solar air heater. Five distinct arrangements were tested, comparing standard absorbers using direct flow and swirl flow against swirl flow systems fitted with perforated longitudinal fins, radial fins, and perforated radial fins. Testing took place across Reynolds numbers between 8488 and 25,464. The results show that higher Reynolds numbers increase the Nusselt number, exergy efficiency, and overall performance evaluation criteria, whilst lowering the friction factor. Utilising an air swirl flow at the inlet delivered better performance than conventional direct flow. In particular, the configuration combining swirl flow with perforated radial fins achieved the highest performance, producing the greatest gains in heat transfer and overall efficiency compared to the standard direct flow setup. This improvement is linked to vortex generation and secondary flow behaviour caused by the perforated fins.
Solar air heaters capture renewable solar energy to warm air for heating and drying processes. Improving their internal design allows them to transfer heat much more effectively without suffering severe flow resistance. By identifying fin shapes and inlet flows that generate useful air mixing, this work provides clear guidance on how to make solar thermal collectors more energy-efficient.
This research could inform the design of more efficient tubular solar air heaters for manufacturers of solar thermal equipment, industrial drying systems, and space-heating installations. Because the study relies on comparative fluid dynamic and thermal parameter analysis, it represents early-stage design research that requires full prototyping and operational validation before direct commercial implementation.
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In this study, the effects of various absorber configurations of a tubular solar air heater are investigated. The models such as direct flow with a standard absorber (DF-SA), swirl flow with a standard absorber (SF-SA), swirl flow with perforated longitudinal fins (SF-PLF), swirl flow with radial fins (SF-RF), swirl flow with perforated radial fins (SF-PRF) are studied. Investigation parameters including Nusselt number, exergy efficiency, PEC, and friction factor are examined with Reynolds numbers ranging from 8488 to 25,464. The findings reveal an enhancement in Nusselt number, PEC, and exergy efficiency corresponding to an increase in Reynolds numbers, while the friction factor decreases. Models employing air-swirl flow entrances demonstrate superior effects in improving the performance compared to direct flow inlets. Notably, the SF-PRF shape records the maximum Nu ratio of (102.5–108%). This model has the maximum values of PEC enhancement ratio of (103.9–106.2%) compared to DF-SA, indicating the enhancement obtained by using swirl flow with perforated ring fins. Analysis of streamlines and distributions of temperature, pressure, and velocity elucidates the effects of perforated radial fins on vortex generation and secondary flow, particularly when incorporating air swirl inlets.
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DOI: 10.1080/15567036.2024.2318008
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