THE CFD ANALYSIS OF THE EFFECT OF INTERNAL PEAK ANGLE AND MASS-FLOW RATES ON THE THERMAL PERFORMANCE OF SOLAR AIR HEATER WITH TRIANGLE CROSS-SECTION

A new design of solar air heater with triangle cross-section is numerically studied. The thermal performance of solar air heater is studied at various mass-flow rates, inlet air temperatures, and solar irradiation intensities. The CFD model is developed using the software ANSYS FLUENT to study the fluid-flow and heat transfer in the solar air heater. The 3-D discretization is applied to study the thermal performance of solar collector with triangle cross-section. Mesh independence is performed in order to choose the adequate mesh. The discrete ordinate radiation model and the RNG k-epsilon turbulence model are used to study the radiative heat transfer and the turbulent flow inside the solar air heater. Particularly, effects of different internal peak angles (145 degrees,126 degrees, 100 degrees, 80 degrees, and 67.5 degrees) under different solar irradiation intensities (from 620-1081 W/m2) are studied to improve the thermal performance of the solar air heater. The results show a good agreement between the numerical model and the experimental data with an average error of 6%. The maximum outlet air temperature of the solar air heater reached 72 degrees C for the geometries with 12 and 16 channels (internal peak angles of 80 degrees and 67.5 degrees, respectively) under mass-flow rate of 0.0264 kg/s. The thermal performances of the solar air heater with 16 and 12 channels are 24.2% higher than standard gewith internal peak angle of 80 degrees and 12 channels is selected as the optimal with a thermal efficiency of 79%, a low pressure drops compared to geometry with 16 channels and lower costs.