Extended Abstract (132K)4.3
Experimental Study on the Measurement of Sensible Heat Flux at the Roof Surface Coated by High Reflectivity Paints
Masakazu Moriyama, Kobe University, Kobe, Japan; and H. Takebayashi and S. Nogami
1.Introduction: Various roof finish, such as high reflectivity paints, green roofs, are proposed as a countermeasure of urban thermal environment for the reduction of cooling load and the mitigation of heat island effect in summer season. The roof surfaces coated by high reflectivity paints are able to reduce sensible heat flux from roof surface and to prevent heat storage caused by solar radiation. In this study, three kind of paints, white A, white B and grey, were used for estimating sensible heat flux through the result of surface heat budget. The measurement was conducted on the roof surface on the roof experimental installation of university building, floor area 17,500‡u, 8 floor building, in the summer of 2003. The each experimental size is 0.94mx‚Pm. 2.Results of Temperature Measurement The surface temperature, the temperature of two points in the slab and the surface temperature of backside under the slab were measured using thermo couple at the one minute interval. The space under the slab is not covered and has no temperature control. The analysis period are fine three days, and the solar radiation was about 900‚v/‡u at the maximum in daytime. The results show the surface temperature and the inside temperature (10cm from the surface) of concrete and grey were relatively high almost at the same level. The surface temperature of white B surface was about 8 degree lower than concrete and grey. 3.Measurement Results of surface heat budget The values of Albedo were concluded 34.6% for concrete, 57.5% for white A, 76.6% for white B and 36.2% for grey surface. The conductive heat flux was estimated using the method of differential equation based on one dimensional unsteady conductive equation. The influence of evaporative flux was not considered because of any rain during the experimental period. Finally, the sensible heat flux was estimated by the residue method. The results show that the concrete surface and grey were the almost same value and white A and B surfaces were about 70 W/‡u at the maximum. The comparison with green surface and the various conditions such as the constant temperature of backside were planned in future.
Session 4, Mitigation of Urban Heat Islands (parallel with session 3)
Monday, 23 August 2004, 1:30 PM-4:30 PM
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