Study On The Evaluation Method Of Indoor Thermal Environment In Naturally Ventilated Buildings With Different Temperature Heat Source

As one of the traditional passive cooling approaches,natural ventilation(NV)technology have the potential to improve indoor air quality and reduce the operation time of HVAC systems to decrease the building energy consumption.All of these advantages contribute to the wide application of natural ventilation technology among civil buildings and industrial buildings.However,the application conditions of natural ventilation in different type of buildings are significantly different,which are regarding the indoor environment characteristics and occupants' s activity as well as environmental demand.Therefore,reasonable evaluation method considering the heat source temperature is one of the essential problems for optimization design of naturally ventilated buildings.This paper has studied the indoor thermal environment characteristics and its evaluation methods for naturally ventilated buildings with typical low temperature heat source and high temperature heat source.In order to provide data to support the establishment of indoor thermal environment evaluation model,classrooms and steel and iron plant were selected as typical naturally ventilated buildings with low temperature heat source and high temperature heat source respectively.Field measurement and questionnaire survey were performed firstly to investigate the indoor thermal environment.The results showed that the air temperature in summer were 23.7~25.4? in classrooms,the mean radiant temperature(MRT)was slightly higher than air temperature,with a difference of 0.4?~0.6?.While in the steel and iron plant,the air temperature were 35.4~37.0?,the MRT was clearly higher than air temperature with a difference of 0.8?~5.3?.In view of the relative large difference on indoor thermal environment characteristics between naturally ventilated buildings with high and low heat source temperature,the effect of difference between MRT and air temperature on human subjective perceptions at different activity level were investigated through laboratory test and subjective questionnaire.The results demonstrated that the threshold WBGT for the subjects at different activity level from psychology aspect was in agree with the threshold WBGT value of ISO 7243 and GB/T 17244 from physical aspects.The subjective perceptions show nonlinearly variations with the difference of MRT and air temperature.For the subjects at low and moderate activity level,inflection appeared when the difference was 0.7? and 1.0?,respectively.In order to evaluate the thermal environment in naturally ventilated buildings with low temperature heat source reasonably and accurately,considering the influence of occupants' expectations and human adaptive functions,evaluation models were developed on the basis of the human heat balanced models,including the extended standard effective temperature(SET)model and adaptive SET model.The results showed that when the indoor air velocity ranged from 0 to 0.2 m/s and from 0.2 to 0.8 m/s,the expectancy factors and the adaptive coefficients for the extended SET model and adaptive SET model were from 1.330 to 1.363 and-0.213 to-0.195.While the difference between the measured thermal sensation and the predicted thermal sensation using modified SET models was approximately less than 25%.The results suggest that the modified SET models are less affected by the air velocity and thus can be recommended to predict human thermal sensation in naturally ventilated buildings with low temperature heat sources.In order to apply the indoor web bulb globe temperature(WBGT)index in the evaluation and design for naturally ventilated industrial buildings with high temperature heat sources conveniently,a prediction model for the indoor WBGT using standard thermal environmental parameters was developed strictly based on the law of analogy for heat and mass transfer.It was demonstrated that the predictions agreed quite well with the measured data for WBGT between 24°C to 30°C in summer,the absolute differences between the predicted and measured WBGT were 1.1°C.The proposed WBGT model was shown to be reseanable and accurate.Finally,the MATLAB and CFD numerical simulation technology was adopted respectively to build the thermal environment predicting lumped parameter model for a typical office building and predict the distribution of environmental parameter for a typical naturally ventilated industrial buildings with high temperature heat sources(plant).The indoor thermal environment comfort or health level at different NV design parameters were evaluated by the SET(or WBGT)index and the difference between MRT and air temperature.It shows that the evaluation method proposed in this paper can provide rational and convenient methods to evaluate indoor thermal environment of naturally ventilated buildings with different temperature heat source,and provide theoretical basis for the design of naturally ventilated buildings.