Performance enhancement of a double pass solar air heater by using curved reflector: Experimental investigation

• Published in: Applied thermal engineering 2022-02, Vol.202, p.117867, Article 117867
• Main Authors: El-Said, Emad M.S., Gohar, Mohammed A., Ali, Aml, Abdelaziz, Gamal B.
• Format: Article
• Language: English
• Subjects: Air flow; Attitude (inclination); Corrugated plates; Double pass; Exergy; External curved reflector; Heat transfer; Heaters; Mass flow rate; Minimum cost; Parameters; Performance enhancement; Production costs; Solar air heater; Solar energy; Temperature; Temperature gradients; Thermo-hydraulic efficiency; Water heaters
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2021.117867

•A solar air heater with double side energy input was studied experimentally.•Maximum effectiveness was 0.74 with 26.5 ˚C average temperature differences.•Maximum thermal and thermo-hydraulic efficiency were about 34.28% and 34.15% respectively.•Maximum cost of heat unit was estimated by about 0.0047 $ with 93.11% reduction.•The optimum values of the performance parameters were at air mass flow rate and tilt angle are 25 l/s and 20°. In this research, a double pass solar air heater with a corrugated absorber plate and built-in external reflector is adopted to improve its thermo-hydraulic performance. The proposed solar air heater is tested with five tilt angles: 0°, 5°, 10°, 15° and 20°. Data obtained from the proposed heater are compared with the conventional design without reflector under a typical seven air flow rates 11, 13, 15, 17, 20 and 25 l/s. The measured results are reported based on some parameters such as thermal, exergy, thermo-hydraulic efficiencies, cost heat unit and temperature differences. The heater with external reflector improves the performance parameters when compared with the conventional heater. Also, the air flow rate has a strong effect on enhancement of the thermal and thermo-hydraulic efficiencies and production cost. The energy input configuration has been shown to be the superior effect on the enhancement of heater performance than the others effects. The maximum effectiveness and achieved average temperature differences for proposed heater were 0.74 and 26.5 °C, respectively. The maximum improvements in average thermal and thermo-hydraulic efficiencies for proposed heater were 19.33% and 19.84% respectively. The maximum value and enhancement ratio of average exergy efficiency for proposed heater was 1.14% and 27.01% respectively. The minimum cost heat unit is achieved using proposed heater estimated by about 0.0047 $ and maximum 93.11% reduction. The optimum values of the performance parameters of the proposed heater under study are obtained when the mass flow rate of flowing air and tilt angle are 25 l/s and 20° respectively. The current study is considered as an attempt to open the research way to new design depends on maximize utilization of the available solar energy.