Abstract
Mini-channel solar air heaters (SAHs) are good candidates for implementation in hot air production fields due to their simple design, favourable performance and operational characteristics. In this paper, a numerical investigation of the energetic-exergetic performance of various mini-channel SAH absorber configurations is introduced using 3D CFD (computational fluid dynamics) analysis and under quasi-dynamic conditions. Three glass-covered mini-channel SAH absorber designs were investigated: a flat absorber with rectangular channels (RSAH), a tubular-channel absorber (TSAH) and a V -corrugated triangular channel absorber (VSAH). The performance analysis results are obtained and compared for all absorber configurations, including the simple, single-channel type solar air heater (SSAH). The developed CFD collector model was validated against available experimental data for the tubular mini-channel geometry. Hourly solar radiation values were calculated and meteorological data for Cairo, Egypt were obtained and coupled to the CFD model, based on typical seasonal days of the year. To highlight the absorber configuration of the best thermo-hydraulic performance, an energetic and exergetic performance analysis was performed. The maximum accumulative useful heat energy was achieved by the VSAH collector with average yearly increases of 79.42%, 6.42% and 29.69% as compared to SSAH, RSAH and TSAH, respectively. In addition, the average seasonal daily efficiency range for this type of collectors is 34.10%-41.32% as compared to 19.08%-22.78% for the SSAH type with an average increase of 79.73%. The average seasonal daily exergy efficiency range for this type of collectors is 1.60%-2.25% as compared to 0.49%-0.68% for the SSAH type with an average increase of 229.59%. Among all mini-channel collector configurations, VSAH collectors recorded the maximum collected annual energy of 1183.3 kWh/m(2)/y with an increase of 79.42% as compared to collected annual energy using SSAH collectors.