Heat-transfer enhancement of double-pass solar air heaters with external recycle

Abstract The effects of double-pass and external-recycle operations on the collector efficiency in solar air heaters have been investigated theoretically. It is found that considerable improvement in collector efficiency is obtainable if the operation is carried out with an external recycle, where the desirable effect of increasing fluid velocity to decrease the heat transfer resistance compensates for the undesirable effect of decreasing the driving force (temperature difference) of heat transfer, due to the remixing at the inlet by recycle operation. The enhancement increases with increasing reflux ratio, especially for operating at lower air flow rate. Moreover, performance of double-pass solar air heater with recycling device is better in comparison to single-pass solar air heater of the same size.

[1]  H. P. Garg,et al.  Evaluation of a matrix solar air heater , 1990 .

[2]  Paisarn Naphon,et al.  On the performance and entropy generation of the double-pass solar air heater with longitudinal fins , 2005 .

[3]  F. K. Forson,et al.  Experimental and simulation studies on a single pass, double duct solar air heater , 2003 .

[4]  Ho-Ming Yeh,et al.  Effects of free convection on collector efficiencies of solar air heaters , 1986 .

[5]  H. Yeh.  Effects of reflux and reflux-barrier location on solvent extraction through cross-flow flat-plate membrane modules with internal reflux , 2006 .

[6]  Pekka Oinas,et al.  Hydrodynamics and mass transfer in an airlift reactor , 1999 .

[7]  V. Lazarova,et al.  Holdup and Liquid Circulation Velocity in a Rectangular Air-Lift Bioreactor , 1999 .

[8]  Ho-Ming Yeh,et al.  The influence of recycle on double-pass heat and mass transfer through a parallel-plate device , 1999 .

[9]  Chii-Dong Ho,et al.  Effect of collector aspect ratio on the collector efficiency of upward type baffled solar air heaters , 2000 .

[10]  H. Yeh,et al.  Effect of recycle-barrier location on membrane extraction in a parallel-flow rectangular module with internal reflux , 2005 .

[11]  H. Yeh,et al.  The effect of collector aspect ratio on the collector efficiency of flat-plate solar air heaters , 1995 .

[12]  P. Iengo,et al.  Mass transfer and kinetics in ehtoxylation spray tower loop reactors , 1999 .

[13]  Ho-Ming Yeh,et al.  A study of separation efficiency in thermal diffusion columns with a permeable vertical barrier , 1986 .

[14]  Ho-Ming Yeh,et al.  Recycle effects on heat and mass transfer through a parallel‐plate channel , 1987 .

[15]  Soteris A. Kalogirou,et al.  Solar thermal collectors and applications , 2004 .

[16]  H. Yeh,et al.  Influence of channel-width ratio on solvent extraction through a double-pass parallel-plate membrane module , 2004 .

[17]  Ho-Ming Yeh,et al.  Solar air heaters with external recycle , 2009 .

[18]  G. Ward,et al.  Performance of flat-plate solar heat collector , 1955 .

[19]  S. Klein.  Calculation of Flat-Plate Collector Loss Coefficients , 1975, Renewable Energy.

[20]  Ho-Ming Yeh,et al.  An analytical study of heat and mass transfer through a parallel-plate channel with recycle , 1998 .