An hourly simulation method for outdoor thermal environment evaluation

A comfortable outdoor thermal environment is very important for pedestrian’s health and safety. Many specific design scenarios were well documented in previous studies. However, simulation studies about microclimate for one month/season are still lacking. In this paper, an hourly simulation system for outdoor thermal environment was developed to study more about the impact of time dependent parameters on outdoor microclimate. To evaluate pedestrians’ thermal comfort condition, thermal indexes for hourly evaluation were proposed. A comfortable outdoor environment was defined as an environment in which pedestrians can reach comfort by adjusting their clothes insulation. A simple case of a 100 m × 100 m block with six 16-floor buildings was studied and results of different time durations were analyzed. From simulation results of each season, it can be concluded that both the radiation and ventilation conditions are the main aspects of outdoor thermal environment design. Simulation results of two typical summer hours and the “average temperature day” differ from that of one month. If only one hour or one day is considered, the designers will be misled by the simulation. In this case, simulation system for hourly evaluation is more informative. Results of statistical sampling method were compared with hourly simulation. The comparison shows that designers can reduce the calculation time by only simulating the sampled hours at the preliminary design stage.