Heat transmission through a glass window with a curved venetian blind installed

摘要

This article reports a study on the effect of installing a curved venetian blind to a glass window on the solar heat transmission into the space. The mathematical model of the combined glass window and venetian blind is developed. Predicted results from the developed mathematical model are compared with the previous experimental ones to verify their accuracy. The variation of the solar heat gain coefficient (SHGC) with the related blind parameters (optical properties of venetian blind, slat spacing, distance between the blind and glass window, slat angle and solar profile angle) are studied. The variation of the SHGC in the shortwave part (ShW SHGC) and in the long-wave part (LoW SHGC) with the related blind parameters are also studied. The understanding of their variation will provide the important information for the study of the thermal comfort for a person who stays near the glass window with blind. The SHGC can be further classified as the SHGC for direct solar radiation (SHGC(D)) and the SHGC for diffuse solar radiation (SHGC(d)). From the study it is found that installing a curved venetian blind to the glass window causes a significant reduction in solar heat gain compared to the plain glass window. The SHGC(D), ShW SHGC(D) and LoW SHGC(D) are all dependent on the slat angle and solar profile angle. The slat reflectance of the venetian blind has direct effect on the ShW SHGC(D). The slat absorptance of the venetian blind has direct effect on the LoW SHGC(D). The glass window and blind with high slat reflectance gives a lower value of SHGC(D) compared to the glass window and blind with low slat reflectance. The slat curvature also affects the SHGC(D) of the fenestration system (glass window with blind installed). The slat with more curvature (lower value of slat radius of curvature) causes more reduction in the value of SHGC(D) compared to the slat with less curvature. The blind with lower slat spacing yields a lower value of SHGC(D) compared to the blind with higher slat spacing. The effects of slat emittance and distance between the blind and the glass window on the SHGC(D) of the fenestration system are only appeared on the LoW SHGC(D) and such effects are quite small. (C) 2014 Elsevier Ltd. All rights reserved.