Flat Air Collector Research Articles

Design and Thermal Behavior Analysis of a Plan Air Solar Collector

In order to find heat production techniques for drying and heating applications of premises in tropical climates from process characterization studies, a flat air collector with air and forced convection was first designed. A simulation of solar radiation, thermal behavior of the solar collector and an experimental test of the latter were carried for validation. The time profiles of the evolution of solar radiation and the temperatures of the heat transfer fluid at the inlet and outlet of the collector as well as those of the collector components during a day were presented, November 17th, 2019. During this day, for an ambient air temperature at the collector inlet varying between 20°C and 41°C, the experimental temperatures of the absorber and solar collector outlet air temperature are respectively 96°C and 78°C for maximum measured solar irradiation of the order of 900 W/m². For the same interval of variation of ambient air temperature, the simulated temperatures of the absorber and of the solar collector outlet air are respectively of the order of 105°C and 90°C when the simulated maximum solar irradiation attains 880 W/m² of collection at true solar noon. The values of R2 obtained for the data of the solar radiation, collector outlet air temperature and temperatures of the absorber are respectively of the order of 0.960, 0.98 and 0.950, indicating a good correlation between the experimental and predicted data; whereas the root mean square error (RMSE) are respectively around 0.020, 0.013 and 0.011, showing a very good match between experimental and modelled temperatures. The temperature range at the outlet of the present device which is simple and achievable at low cost is important for the drying needs of the various products and heating.

CFD Numerical Investigation of a New Solar Flat Air-Collector Having Different Obstacles with Various Configurations and Arrangements

This work deals with a numerical parametric optimization study of a new Solar Flat Air Collector (SFAC) configuration. The CFD numerical parametric study investigates various SFAC structures inside the air cavity without obstacles and with spherical, cubic, cylindrical, and pyramidal obstacles. The study optimizes the most convenient configuration and arrangement that allow for the increase of the heat-transfer surface and to make the flow homogeneous in order to generate turbulence zones inside the SFAC air cavity. The result shows that the thermal performances of the cubic form are close to those of the spherical obstacles. Another set of simulations was performed to evaluate the performances of the cubic shape baffles for three orientation angles equal to 0°, 22.5°, and 45°, respectively. Each configuration has three forms of arrangement with a relative roughness pitch (b/a) varying between 2, 4, and 6. The results of the simulation study showed that the relative roughness pitch, the Reynolds number, as well as the angle of orientation influence the performance and the operation of the SFAC. The results of the simulations showed that the combination of an orientation of 45° with a roughness pitch of b/a = 2 increases the SFAC thermal performances, which can reach 85%.

Experimental study on the performance of flat air collector with reticulated endothermic body

Because the flat air collector is simple in structure, reliable in operation, and resistant to cold and frost, it is more suitable for applications such as building heating. This paper presents a flat air collector with a mesh heat sink, and analyzes the effects of air flow, temperature difference between inlet and outlet, and wire mesh density on the heat collection efficiency of the collector. The results show that when the pore density is fixed, the heat collection efficiency increases with the increase of air flow rate, which is 10% higher than that of natural convection when the air flow rate is maximum; when the air flow rate is fixed, the heat collection efficiency increases with the increase of the pore density and the temperature difference between the inlet and outlet, which can be increased by 10% -20%.

Method of Efficiency Improvement in District Heating Systems

The article determines application potential of solar energy in conditions of sharply continental climate. It presents an energy-efficient solar energy recovery scheme in district heating systems, allowing to reduce capital costs and maintenance charges and to increase degree of substitution of conventional sources of heat. Versatility of systems using this method results in its multi-zone application: From a cottage-type house to heating of industrial premises and green house complexes. The main principle of the suggested method is in connection of a solar collector via heated medium to an air conduit, which is connected with heated space and antifreeze, circulating in-line: Reservoir-accumulator-solar collector. A method of heat transfer enhancement using dimple-type intensifiers is suggested. The article determines enhancement efficiency via calculation of daily heat-absorption of a flat air collector with and without dimple intensifiers, as well as economic effect from introducing of the suggested method. According to calculations, the adoption of the suggested heating system and heat transfer enhancement on the surface of the collector connecting to it, may give a perceptible economic effect.