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Abstrakt

Direct solar radiation is the greatest influencing factor of cooling load in hot and humid area in summer. The surface of metallic roof rises up to a high temperature caused by direct solar radiation. The heat flux through roof and ceiling become air-conditioning load. Therefore, it is important to decrease the surface temperature of roof for reducing the cooling load in the building with the metallic roof. The shielding method of direct solar radiation by sunshade sheets is widely used recently. It is thought that a sunshade sheet is effective to decrease the surface temperature of roof, but the reduction effect of sunshade sheets on air-conditioning load is not clarified yet.
The purpose of this study is to clarify the reduction effect on cooling load by strip type sunshade sheets settled over folded-plate roof. The measurement and calculation were conducted on a small house with metallic folded-plate roof in summer. Two conditions were tested; condition without sunshade sheets over roof and condition with sunshade sheets over roof.
We proposed a heat transfer model that predicts the heat flux through roof with sunshade sheets and ceiling. The solar transmittance, reflectance and absorptivity were used as properties of sunshade sheet. To verify the validity of this model, the calculated values were compared with measured values. In general, calculated values are in good agreement with measured values.
It is clarified that using a sunshade sheet can decrease air-conditioning load at daytime in summer from results of measurement and calculation. However, condition with sunshade sheet has slightly a worse hand at nighttime in summer.

Referanser

Azumi, H. Koizumi, K., Kobayakawa, K., Kawatani, S. (2010) Performance Evaluation of Shading Sheet Mount above Roofbased on Thermal Load Calculation, Journal of General Building Research Corporation (in Japanese), October 2010, Volume 35 No. 4, 28-35

Biwole, P.H., Woloszyn, M., Pompeo, C. (2008), Heat transfers in a double-skin roof ventilated by natural convection in summer time, Energy and Buildings, Volume 40, Issue 8, 1487-1497

Lim, E., Yamanaka, T., Kotani, H., Momoi, Y., Sagara, K., Soma, M. (2011) Evaluation of solar Shielding Effect of Sunshade Sheets over Roof (Part 1) Reduction Effect for Cooling Load by Strip Type Sunshade Sheets in Summer, Technical Papers of Annual Meeting of Kinki Branch of The Society of Heating, Air-Conditioning and Sanitary Engineers of Japan (in Japanese), Jun 2011, 85-88

Soma, M., Yamanaka, T., Lim, E., Kotani, H., Momoi Y., Sagara, K. (2011) Evaluation of Solar Shielding Effect of Sunshade Sheets over Roof (Part2) Analysis of Heat Transfer through Roof and Ceiling, Technical Papers of Annual Meeting of Kinki Branch of The Society of Heating, Air-Conditioning and Sanitary Engineers of Japan (in Japanese), Jun 2011, 89-92





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