https://orcid.org/0000-0002-6620-7747
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ABSTRACT
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.
Nomenclature
| f | = | Friction factor |
| T | = | Temperature (°C) |
| m˙ | = | Mass flow rate (kg/s) |
| k | = | Fluid thermal conductivity, W/m.K |
| CP | = | Specific heat of air (kj/kg. K) |
| W˙ | = | Work rate or power (kw) |
| Ex˙ | = | Exergy rate (kw) |
| R | = | Universal gas constant (J/kg K) |
| I | = | Solar radiation (W/m2) |
| AC | = | Surface area of the collector (m2) |
| P | = | Fluid pressure (Pa) |
| h | = | Enthalpy (kj/kg) |
| QS | = | Incident energy in the collector area (kw) |
| S | = | Entropy (kj/kg K) |
| Re | = | Reynolds number |
| Nu | = | Nusselt number |
| Dh | = | Hydraulic diameter, m |
| SAH | = | Solar air heater |
| Δp | = | Pressure drop, Pa |
| Δp | = | Pressure drop, Pa |
| Greek letters | = | |
| α | = | Emissivity |
| τ | = | Transmissivity |
| ψ | = | Specific exergy (kj/kg) |
| η | = | Efficiency (%) |
| ρ | = | Air density (kg/m3) |
| Subscripts | = | |
| p | = | Plate |
| in | = | Inlet |
| out | = | Outlet |
| dest | = | Destruction |
| a | = | Air |
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Notes on contributors
S.A. Marzouk
S.A. Marzouk is an Assistant lecturer in the Department of Mechanical Engineering at Kafrelsheikh University. He obtained his master’s in mechanical engineering from Kafrelsheikh University. His research interests include heat transfer enhancement, heat exchangers, energy applications, fuel cells, solar and renewable energy, and computational fluid dynamics.
Maisa A. Sharaf
Maisa A. Sharaf is an assistant professor of mechanical engineering at Damanhour University, Egypt. She received her Ph.D. from Tanta University. Her research interests include different techniques in two-phase and single-phase convective heat transfer.
Ahmad Aljabr
Ahmad Aljabr is an assistant professor of mechanical engineering at Majmaah University, Department of Mechanical and Industrial Engineering. He received his Ph.D. from University of Dayton. He is a member of International Ground Source Heat Pump Association. His research interests include renewable energy systems, energy efficiency, enhanced heat exchangers, thermal energy storage systems, and machine learning.
Emad M.S. El-Said
Emad M.S. El-Said received his Ph.D. in Mechanical Power Engineering (Energy Engineering) at Tanta University and is associate professor in Mechanical Engineering Department, Faculty of Engineering, Damietta University. His research interests include desalination, heat exchangers, energy applications, thermal, and hydraulic engineering, solar and renewable energy.