Experimental study of wind effects on unglazed transpired collectors

High wind velocity affects the performance of unglazed transpired collectors (UTC); indeed, wind flow on the collector’s surface reduces useful heat transferred to the collector fluid by effectuating convection losses and suction in the pores and thereby outflow from the plenum. Wind does not impinge uniformly on all points on a large area; the velocity distribution depends on wind direction and surroundings of the concerned area. The paper describes an experimental and analytical parametric study to assess the effect of wind on UTCs. Velocity measurements obtained using wind-tunnel experiments were applied to analytical models of UTC performance evaluation and were found to influence UTC performance. The assumption that a reference wind speed acts uniformly throughout the UTC area, as opposed to the more realistic non-uniform distribution, resulted in the overestimation of heat exchange effectiveness up to 50% and underestimation of convective heat transfer coefficients up to 20%. The importance of using actual velocity distribution, as opposed to an assumed uniform velocity distribution in building simulation, has been discussed.

[1]  Charles F. Kutscher,et al.  Wind Heat Loss From Corrugated, Transpired Solar Collectors , 2001 .

[2]  N. Ito,et al.  Field experiment study on the convective heat transfer coefficient on exterior surface of a building , 1972 .

[3]  Craig Christensen,et al.  Unglazed transpired solar collectors: Heat loss theory , 1993 .

[4]  C. F. Kutscher,et al.  Heat Exchange Effectiveness and Pressure Drop for Air Flow Through Perforated Plates With and Without Crosswind , 1994 .

[5]  K.G.T. Hollands,et al.  Effect of wind on flow distribution in unglazed transpired-plate collectors , 2002 .

[6]  Mglc Marcel Loomans,et al.  Comparing internal and external run-time coupling of CFD and building energy simulation software , 2004 .

[7]  Dominique Derome,et al.  High-resolution CFD simulations for forced convective heat transfer coefficients at the facade of a low-rise building , 2009 .

[8]  Suzelle Barrington,et al.  Performance of unglazed solar ventilation air pre-heaters for broiler barns , 2011 .

[9]  Chuck Kutscher,et al.  Development of a flow distribution and design model for transpired solar collectors , 1997 .

[10]  Andreas K. Athienitis,et al.  A prototype photovoltaic/thermal system integrated with transpired collector , 2011 .

[11]  William H. Melbourne,et al.  Wind loading of structures , 1998 .

[12]  Jianing Zhao,et al.  Field Measurement of the Convective Heat Transfer Coefficient on Vertical External Building Surfaces Using Naphthalene Sublimation Method , 2010 .

[13]  Douglas John Harris,et al.  Full-scale measurements of convective coefficient on external surface of a low-rise building in sheltered conditions , 2007 .

[14]  Bje Bert Blocken,et al.  Validation of external BES-CFD coupling by inter-model comparison , 2008 .

[15]  James Bambara,et al.  Experimental Study of a Façade-integrated Photovoltaic/thermal System with Unglazed Transpired Collector , 2012 .

[16]  Walter Jürges.  Der Wärmeübergang an einer ebenen Wand , 1924 .

[17]  Linda Kaye.  Buildings and Structures , 1988 .

[18]  Brian A. Fleck,et al.  A field study of the wind effects on the performance of an unglazed transpired solar collector , 2002 .

[19]  Steve Sharples,et al.  Full-scale measurements of convective energy losses from exterior building surfaces , 1984 .

[20]  K.G.T. Hollands,et al.  Heat-exchange relations for unglazed transpired solar collectors with circular holes on a square or triangular pitch , 2001 .

[21]  T. Stathopoulos,et al.  Wind Tunnel Assessment of the Wind Velocity Distribution on Vertical Façades , 2012 .