Reducing interior temperature resulting from solar energy using three-dimensional surface patterns

Abstract

Excessive solar energy can significantly increase interior temperatures and yield great energy demands for air conditioning. Whereas reducing energy consumptions is very crucial today, this article employs patterned glass technology which incorporates linear patterns throughout the exterior surface of glass to attenuate the solar effect on the interior thermal field based on theoretical and experimental studies. By periodically imposing linearly three-dimensional patterns over the outer surface of window glass, the analytical results indicate that the interior solar heat is able to be reduced, as the surface patterns increase the incident angle and/or decrease the solar energy loading on the patterned glass material. Moreover, the interior solar heat can be strongly affected by the pattern design. According to thermally measured results, the trapezoidal patterned glass having 3-mm-top-edged patterned members yields lower temperature on the interior surface of glass comparing with that for the trapezoidal patterns having 6-mm-top edges. Therefore, making the least non-sloped feature or flat plane appearing on the patterned glass helps decrease the interior temperature resulting from solar energy.

Attenuation of glazing energy using linear patterns on the glass surface

“…However, as the dimensions of patterned space increases from 11 mm to 26 and 41 mm, the radiation heat flux over the glass interior surface will raise to 160 and 163 W/m 2 , respectively. Therefore, based on results provided in Figure 4, enlarging the patterned space will yield the increase in the radiation heat flux on the glass surface, and this analytical result is supported by experimental measurements given by Lin et al 1 Furthermore, the variation of CFD-determined results based on different mesh/ grid dimensions is analyzed. For the roof trapezoidal patterned glass of Figure 3 having 45°-patterned angle and 11-mm-patterned spacing, the CFD model meshed by sizes of 3.5, 3, and 2.5 mm gives the radiation heat fluxes on the inner face of glass equal to 154, 156, and 155.84 W/m 2 , respectively.…”

“…Reducing glazing energy of the solar-loaded glass material helps attenuate the interior thermal energy resulting from solar radiation. The governing equation of glazing energy written in equation (1) indicates that the glazing energy q due to solar radiation is associated with the direct normal solar irradiation E DN , the cosine function of incident angle u, and the glazing solar heat gain coefficient (SHGC) of the glass material…”

“…Based on Lin et al's analytical results, as the linearly patterned glass is applied on the roof and vertically solar loaded, the interior thermal energy due to solar radiation can be reduced. Based on the theoretical incident angle of the patterned glass given by Lin et al's work, 1 the solar orientation at noon yields the incident angle of the roof linearly patterned glass equal to the patterned angle. For the traditional flat glass applied on the roof, since the flat glass is vertically loaded by solar radiation, the incident angle of the flat glass equals zero which is always smaller than the incident angle of the roof linearly patterned glass under solar radiation at noon.…”

“…Since the glazing energy is related to cosine function of the incident angle, 3 the patterned glass applied on the roof window and loaded by solar radiation at noon will always result in the less glazing energy compared with that of the traditional flat glass. Moreover, Lin et al 1 found that the incident angle of the patterned or traditional flat glass can be dependent on the direction of the incident solar beam and the orientation of the glass (i.e. the tilted angle of glass).…”

“…As the glass material is subjected to patterns over the exterior surface, the pattern member is able to locally vary the incident angle and yield the change in glazing energy due to solar radiation. Lin et al 1 employed the theoretical approach to investigate the incident angle of linearly patterned glass and demonstrated that the linearly patterned glass is able to give the reduction in the interior solar heat based on thermal measurements. Due to difficulties of fabricating patterned glass specimens, Lin et al's work concentrated on analyzing the linearly patterned glass having trapezoidal-shaped patterns under solar energy loaded, and the relation between the thermal performance of linearly patterned glass and the patterned design was investigated based on varying the dimension of top edge of the trapezoidal pattern only.…”