air temperature

Increasing roof reflectance reduces absorption of solar radiation, roof surface temperatures, and heat flux in the building interior. At the building level this leads to savings in air-conditioning energy consumption and increase in indoor comfort. At the macro level it helps in mitigating Urban Heat Island effect and reduces net solar radiation absorbed by the earth, lowering local air temperature and pollutant formation, and reducing global warming. Various studies have demonstrated energy savings in buildings using cool roofs.

We have developed a new evaluation method of “thermal radiative power” (TRP) for investigating the impact of building surface material albedo on urban environment. The simulation system ENVI-met is used. This system is a 3D computer model which analyzes micro-scale thermal interactions within urban environments. It simulates urban-scale environmental conditions such as roofs, exterior wall, and ground surface temperatures. Focuses of this research are on the climate change in urban and community scale in cold climates.

In this study the instantaneous temperatures and velocities close to a diffuser for displacement ventilation have been recorded by using whole-field measuring techniques. The air temperatures were measured indirectly by the use of a low thermal mass screen in conjunction with infrared thermography. The measuring screen was mounted parallel to the airflow, acting as a target screen. By using the thermal images the size of the near zone was also calculated. To determine air movements a whole field method called particle streak velocimetry (PSV) was used.

After a literature review about zonal models, we have developed a simplified approach to simulate buoyancy-driven flow in rooms. With two different simple models we have computed the Annex-20 test case d using the procedure prescribed by Lemaire (Annex 20 report, R.I. 1.15). The two simplified methods employ a two-zone and five-zone model. The simulation results of test case d are submitted for comparison with experimental data of heat fluxes and air temperature profiles. The two-zone and five-zone models are also compared with each other.