For applications of solar thermal energy, solar water heaters (SWHs) are becoming common. In this study, the effect of a crosswind on the aerodynamic characteristics of residential (an inclined flat plate with a horizontal cylinder) and large-scale SWHs (an inclined flat plate only) is experimentally investigated. The tests are conducted in a low speed wind tunnel and the relative wind direction with respect to the test model, , ranges from 0 to 135 deg. Measurements of the mean and fluctuating pressures are presented. These results demonstrate that higher suction and fluctuating pressure are observed near the upwind corner, particularly for the test case of = 30 deg.

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The internal flowfield including shock reflections structure inside a 2-D half inlet model was examined by a double exposure: holographic interferometry using a Qswitched pulse laser. The interferograms give detailed flow visualization pictures. The structures of regular reflection, lambda reflection and Mach reflection in the inlet channel were observed. From the analysis of fringe patterns, the quantitative distribations of flow density, pressure and Mach number of the internal flowfield have been reconstructed. The boundary layer thickening and separation in the case of lambda reflection and the Mach stem in the case of Mach reflection were clearly demonstrated in the holographic fringe patterns. The results show that the shock interacitons with the ramp and the wall introduce a complicated flow structure which could strongly affect the efficiency of the inlet.

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Solar water heaters (SWHs) can provide hot water at temperatures ranging from 40 to 80 o C for domestic or industrial use. With the subsidy programs (1986-1991 and 2000-present) offered by the Bureau of Energy, Ministry of Economic Affairs and some municipal governments, the accumulated area of solar collectors installed at the end of 2012 reached 2.25 million square meters. The well-orchestrated and concerted efforts put forward by the government of Taiwan, particularly with the Renewable Energy Development Bill promulgated in 2010, have played a significant role in the increased dissemination of SWHs. Further, the long-duration national subsidy programs might constitute one of the main driving forces for local market expansion. The mass media should be more aggressively utilized to enhance public awareness and promote utilization of SWHs. Organizations also need to consider the interests of society by being accountable for their businesses practices and by being responsible for the impact of their activities on the environment. This paper reports the current status and perspectives of SWHs in Taiwan, according to the desk and field surveys.