Evaluation Of Thermal Environment And Thermal Comfort On Block Scale In Guang Zhou

The rapid urbanization is accompanied by a variety of thermal environmental problems. It becomes increasingly significant. In recent years, thermal environmental problems are gradually been recognized and close attentions are paid to them, one of the most well-known is the urban heat island effect. The city is composed of urban blocks. As important component unit, the evaluation of thermal environment and thermal comfort on block scale effects people’s wellbeing. It’s a complex interdisciplinary issue. Current studies on block-scale thermal environment have some shortcomings: First, these studies are mostly from the perspective of a single discipline, much less for a comprehensive interdisciplinary research in various disciplines; Second, computational models for numerical simulation of the block-scale thermal environment are complex, They are difficult to be applied in practical project; Third, there is no systematic evaluation methods on block-scale thermal environment. Conclusion of field measurement and numerical simulation can’t be applied in urban block designing.This study combined building environment with urban climatology and urban planning. In consideration of climate conditions, urban blocks and architectural features of Guangzhou, research on block-scale thermal environment and thermal comfort issues is carried out. This study aims at combining the numerical simulation with field measurement, and summarizing the impact of detailed planning factors on thermal environment in Guangzhou. And to sum up a practical evaluation index system on thermal environment and thermal comfort on block scale, establish a thermal environment and thermal comfort evaluation simple model for district thermal environmental analysis, the thermal environment to provide guidance for planning and design of urban block. This paper focuses on the following aspects:(1) The influence factors of block thermal environment are summarized, including factors on architectural forms, layout, orientation, types of underlying, thermo physical properties and shade structures, etc. A thermal environment and thermal comfort evaluation index system is established, the target level combines the evaluation index with the thermal environment parameters, the index level includes microclimate condition, building layout, building materials, properties of underlying and anthropogenic heat index.(2) On the basis of existing urban regional thermal climate prediction model(UDC) of our research group, the original model is improved and extended. Field measurement of thermal environment is carried out in a district of Guangzhou. The measurement last for a week. Simulation of thermal environment of the district is carried out with the improved model. By comparing simulation results and experimental data, the improved model is verified.(3) According to the theory of one-parameter analysis numerical experiments are designed. Numerical simulation is carried out to obtain variation laws of thermal environment under different combinations of the factors. The main conclusions are as follows: the impact of building density and floor area ratio on thermal environment is non-linear, non-monotonic, when the building density and volume rate change, the response curve of the ambient temperature and the comfort index’s performance for the similar functional form concave conic. Although increasing the reflectivity of hard surface and outer surface of a building, has benefit for the thermal environment, but too much reflect will increase the mean radiant temperature, or even cause light pollution, causing human discomfort. A moderate reflectivity material would be a better choice. Construction of piloti, green space and landscaping, permeable pavement, water and other underlying surface and shade structures can improve the thermal environment.(4) On the basis of a large number of numerical experiments, considering the interaction between the thermal-environment factors, these factors are reintegrated for regression. Thereby evaluation model of targets on thermal environment and thermal comfort is obtained. The model is programmed into the urban thermal environment evaluation software for regulatory detailed planning in Guangzhou. Parameter uncertainty and sensitivity analysis is carried out with global sensitivity analysis. The main conclusions are as follows:(1) Building density and floor number are most sensitive factors for thermal environment valuation indexes,(2) Construction of piloti are third-sensitive factor for WBGT, and for SET and UHII, third-sensitive factor is the ratio of green space,(3) The overall sensitive index considerate interactions between factors, it’s more comprehensive and accurate for sensitivity analysis.