Wet bulb globe temperature(WBGT)is a comprehensive index obtained mainly from three parameters:black globe temperature(Tg),wet bulb temperature(Tw),and dry bulb temperature(Ta).While in field observation and numerical simulation,black globe temperature and wet bulb temperature were not easy to obtain,so WBGT was difficult to measure and calculate directly.In order to solve this problem,air dry bulb temperature,wet bulb temperature,globe temperature,relative humidity,mean air velocity,solar radiation and wet bulb globe temperature were collected during the summer(July)in Guangzhou.Correlation analysis and regression analysis were used to get a simplified method to calculate WBGT.The results showed that dry bulb temperature,relative humidity,solar radiation and WBGT were interrelated to some extent.These three parameters could be used in the simplified method to predict WBGT,and the linear correlation and precision of this model were high.In addition,we used the measured data to verify the simplified method,and the results showed that the error of the calculated value and the measured value was all below 5%,which means the simplified calculating method is feasible and can be used in field observation and simulation research of urban thermal environment.
ZHANG Lei,MENG Qing-lin,ZHAO Li-hua,ZHANG Yu-feng(State Key Laboratory of Subtropical Building Science,South China University of Technology,Guangzhou,Guangdong 510640,China)
In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several layers in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m)and a large area(with a horizontal scale of more than 1 000 m)in Guangzhou in summer were used to validate the proposed model.The calculated results agree well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.
ZHANG Lei,MENG Qing-lin(State Key Laboratory of Subtropical Building Science,South China University of Technology,Guangzhou,Guangdong 510640,China)
Polyvinylchloride(PVC)panel is one of the most favorite decorative materials that has been popularly applied as finishing of ceiling in residential buildings.It is about five years that the people incline to redecorate the ceiling of old buildings with PVC panel in big cities of Iran,such as Mashad.In this study,the influence of ceiling PVC panel on the cooling and heating loads of studied apartment were determined by software DeST-h.In addition,the summer natural ventilation of the mentioned apartment is investigated by determining the wind speed into the apartment through the computational fluid dynamics(CFD)software.The evaluation of environment indoor wind velocity showed that most of the apartment space is a comfortable zone.The results of studied building analyses demonstrated that using PVC panel on the ceiling can decline the energy consumption of the penthouse(fifth level)of the investigated building,which is about 3.7%and 7%for studied methods of without and with air layer,respectively.In addition,although the existence of air layer can decline the cooling and heating loads,the increase in air layer thickness did not show significant decrease on building energy consumption.However,the PVC panel is expensive and is not suitable to be used for ceiling thermal insulation,but adding a thin layer of air between ceiling and PVC panel can be a good step toward sustainable building,when the people are inclined to utilize it as a decorative ceiling.
