Abstract
A new device for inserting an absorber plate to divide a flat-plate channel into two subchannels to conduct double-pass wire mesh packed operations was developed. The proposed wire mesh packed device improves the heat transfer efficiency substantially as compared that to flat-plate single-pass and double-pass operations using the same working dimensions, and the improvement of device performance was investigated experimentally and theoretically. Good agreement between the theoretical prediction and the measured values from the experimental results was achieved. Considerable heat transfer improvement was obtained employing wire mesh packed double-pass operations under the absorber plate with external recycle. The influences of recycle ratio on the heat transfer efficiency and the power consumption increase were also discussed.
Highlights
Low temperature energy technology solar collectors are a special kind of heat exchanger that transforms solar radiation energy into internal energy of the working fluids flowing through the heat exchanger devices
The collector efficiency improvement increases with increasing recycle ratio and air mass flow rate in a more remarkable extent due to the convective heat-transfer coefficient enhancement by enlarging the fluid velocity
This study provides an alternative design for wire mesh packed solar air heaters with recycling operations
Summary
Low temperature energy technology solar collectors are a special kind of heat exchanger that transforms solar radiation energy into internal energy of the working fluids flowing through the heat exchanger devices. Solar radiation collection by solar collectors has attracted a great deal of interest in Energies 2014, 7 recent years, and these devices are widely used, mostly for heating both water and air fluids. In addition to the effects of forced convection [6] and free convection [7,8], a considerable improvement on collector performance is achievable by increasing the heat-transfer area and creating air turbulence inside the flow ducts by using extended heat-transfer areas [9], air turbulence [10] and packing materials [11,12]. The higher convective heat-transfer coefficient and higher thermal energy efficiency are achieved in the solar collector of the present recycling device as the wire mesh is inserted in the lower channel under the absorber plate. Experimental and theoretical researches are undergoing simultaneously to design and modify the augmentation of double-pass solar air heaters [13,14,15]
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