Study On Thermal Environment Control And Energy-saving Strategies Based On The Operative Temperature

Modern public buildings often adopt a glass curtain wall or a large window-wall ratio of the outer envelope structure.In high temperature or cold weather,the surface temperature of the outer envelope structure will change correspondingly,resulting in changes in the average radiant temperature,and have a certain impact on the surrounding indoor thermal environment,so that the thermal comfort of personnel under the same indoor air temperature will be different.The existing air conditioning system mostly takes indoor air temperature as the control signal,and does not fully consider the influence of average radiation temperature on thermal comfort,which is difficult to ensure the thermal comfort of some building areas.Operative temperature comprehensively considers the influence of average radiation temperature and air temperature on thermal comfort,so using operative temperature to control the thermal environment in the room will be more scientific than using air temperature as the control signal.In this regard,this paper studies the changes of indoor thermal environment and energy consumption when air temperature and operative temperature are used as control signals,and proposes optimization control methods and strategies based on the analysis.This paper takes an actual public building library in Qingdao(cold area)as an example to study its typical space reading rooms.The building model is established by Designbuilder,and the energy use condition is simulated according to the actual building structure,air conditioning system and meteorological parameters,and the accuracy of the model was verified by the measured data.Based on the condition that the air temperature in different areas is not exactly the same as the operative temperature,different control methods are proposed by zoning.Based on simulation,this paper analyzes the thermal comfort in reading room and its influence on energy use under different control modes.Further considering the influence factors of different floors,orientation,window-wall ratio and climate zone,relevant simulation studies are carried out to analyze the influence of different factors on indoor thermal environment and energy use,and put forward reasonable control strategies that meets the requirements of thermal comfort and takes into account energy saving.The main research results are as follows:The distribution of thermal environment space inside the reading room is uneven,and the thermal comfort of each area is different.Based on PMV-PPD index and related standard requirements,the evaluation basis of thermal environment comfort is determined that the time proportion of the comprehensive dissatisfaction rate is less than 5% when the overall dissatisfaction rate is more than 27%.The existing control mode of the existing air conditioning system cannot meet the needs.The indoor area is divided according to the spatial distribution of operative temperature,and different control methods based on the operative temperature and air temperature in each area are proposed.The simulation shows that under the same setting value,the thermal comfort is better than the air temperature control when the operative temperature of each area is controlled separately,and the energy use of the air-conditioning system will increase accordingly.Considering the influence of outdoor temperature change on operative temperature,combined with the analysis of comprehensive dissatisfaction rate index,the outdoor temperature(switching boundary temperature)during switching between control modes are determined.When switching boundary temperature control,the air temperature and operative temperature sensor based on the indoor partition can be used to determine the partition temperature control signal input by the air conditioning system according to the outdoor temperature.On the basis of meeting the comfort requirements,this control mode has the lowest energy use.In addition,considering the actual number and type of temperature sensors in the actual buildings are limited,a simplified control mode of air temperature control in the inner area and operative temperature in the outer area is proposed.In this mode,the increase of energy use is relatively small on the basis of ensuring comfort.Aiming at the influencing factors such as floor,orientation and window-wall ratio,the influence on thermal environment and related control is analyzed by simulation.It is found that under different factors,the energy consumption of air conditioning system is the highest when operative temperature control in the most unfavorable area,but the indoor comfort is the best.The energy consumption of the air conditioning system is the least when the air temperature is controlled in the inner zone,but the indoor comfort is the worst.Compared with the middle floor,the top floor room is affected by the roof,and the switching boundary temperature increases in winter and decreases in summer.Through the simulation of rooms with different orients in the building,it is found that compared with the east and west orients,the south and north orients have a greater impact on the indoor thermal environment.The increase of window-wall ratio has little effect on the indoor thermal comfort in the south-facing heating season,but decreases in the cooling season.The indoor thermal comfort of the north room decreases with the increase of window wall ratio in both winter and summer.The simulation analysis of the heating season in cold area and the cooling season in hot summer and warm winter area shows that the influence of zone operative temperature and air temperature control on thermal comfort and energy consumption is basically the same as that in cold area.The comprehensive analysis shows that the air conditioning system needs to be combined with the operative temperature control in the heating season to meet the comfort requirements,while the air temperature control can meet the requirements in the cooling season.Compared with the cold area,the corresponding switching boundary temperature of the heating season in the cold area is 4.1 ℃ lower,while the corresponding switching boundary temperature of the cold season in the hot summer and warm winter area is 6.5 ℃ higher.Based on the above analysis,for building spaces with large glass curtain walls or exterior windows,it is suggested that the control mode combining operative temperature and air temperature should be taken into account in the internal thermal environment.This study provides relevant data for thermal comfort characteristics of building environment based on operative temperature control and its impact on energy use,and can provide relevant theoretical and technical guidance for engineering applications.