Study On Differentiated Thermal Requirements In Temporal And Spatial Dimensions And The Optimization Of Heating System In Rural Residential Buildings In Northwest China

With the improvement of the overall economic level in western China,the living conditions and living standards of rural residents have been significantly improved,resulting in higher requirements for indoor thermal environment in winter.However,the continuous indifference district heating mode of the existing cities is difficult to be directly applied to rural residentials due to the poor thermal performance of the building envelope,the obsolete heating facilities,the imperfect heating system and the high heating energy consumption.Based on the activity trajectory of the northwest rural residents in the main functional rooms,such as the main bedroom,second bedroom,and the differentiation state of activity and sleep in the day and night,the time and spatial partition heating mode is adopted in the northwest rural buildings to reduce the heating energy consumption.Therefore,it is of great significance to study heating modes from the extensive type to the refined time and spatial partition mode.In this paper,the refined time and spatial partition heating mode was developed by field study,theoretical analysis,experimental test and numerical simulation to study the thermal requirements and the heating system optimization design of the time and spatial partition heating mode in the northwest rural.The research content and conclusions are as follows:(1)Thermal requirements and heating modes of indoor time and spatial partition of the northwest rural buildings were obtained.Current situation of indoor thermal environment in northwest rural buildings,resident activity track and thermal environment assessment had been extensively tested and investigated.The situations,including the indoor activity status,dressing situation,heating measures,indoor thermal environment and dissatisfaction rate of the residents in the northwest rural buildings were mastered.Through the analysis of the subjective evaluation of residents' indoor thermal sensation,the linear relationship between the room temperature and the average thermal sensation of the residents under the condition of activity and sleep in villages and towns of the five northwest provinces was obtained.The results showed that the recommended values of the indoor comfortable temperature range under the activity and sleep states are 16~18°C and 11~13°C,respectively.The Markov chain model was introduced to characterize the indoor activity trajectory of residents in winter.The probability of presence of personnel in each room was calculated,and the corresponding relationship between heating space and time in rural buildings was determined.Then the thermal requirements of time and spatial partition including the double-period(day and night)as well as the double-space(function room-bed room)were formed,and the time and spatial partition heating mode suitable for the northwest rural buildings was proposed.(2)The thermal environment construction and heat dissipation characteristics of the combined heating terminal under different operating modes were mastered.A novel combined terminal form(Kang and floor heating)was proposed based on the heating requirement characteristics in the master bedroom,which presented differences between day and night and between bed and room,and this form could remedy the regret of that single heating terminal cannot satisfy the temporal and spatial dimensions of heating requirement.An experiment on the thermal performance of Kangfloor combined heating terminal was built,and the indoor thermal environment construction,the terminal heat dissipation characteristics and the heating energy consumption are investigated under the modes of separate operation,joint operation and alternative operation.The dynamic changes of indoor air temperature,ground surface and Kang surface temperature are mastered,and the characteristics of indoor thermal environment affected from the combined heating terminal were discussed under different operating modes.The experimental results showed that the alternative operation of the combined heating terminal has obvious advantages to meet the thermal requirements of time and spatial partition.The feasibility of the Kang-floor combined heating terminal in meeting the complex thermal requirements characteristics of the master bedroom was demonstrated.(3)The theoretical analysis models for the coupling thermal process of building and time and spatial partition heating terminal were established.Based on the experiment results that the alternative operation of the combined heating terminal has obvious advantages to meet the thermal requirements of time and spatial partition heating in the main bedroom,the dynamic thermal process analysis models of the alternative operation of the combined heating terminal with the time and spatial partition heating was developed.The interaction of heat storage/dissipation performances of the Kang and floor combined heating terminal under the double space comfort temperature requirements of the indoor environment and the bedding environment was expounded,which provided a theoretical basis for the heat dissipation performance analysis and optimal design of combined heating terminal.(4)The optimization design strategy of time and spatial partition combined heating terminal of the northwest rural buildings was proposed.By changing the combined terminal design parameters(coil spacing and filling thickness),operation parameters(pipe inlet temperature and flow)and operation strategies(opening and closing time)in northwest rural buildings,the dynamic variation characteristics of indoor air temperature,bedding temperature and ground temperature were simulated and analyzed,and the influences of various factors on the response speed,temperature and coincidence degree of the thermal environment was revealed.Based on the time and spatial partition thermal requirements,the optimization sequence from design parameters to operation parameters and operation strategies were defined,and the optimization design strategy of Kang and floor combined heating terminal was formed.The indoor design parameters,heat dissipation characteristics,optimal design methods and operation strategies of combined heating terminal of time and spatial partition heating obtained in this study had provided the foundations for refined heating of northwest rural buildings to meet the actual indoor thermal requirements of residents in winter,improve the living quality of residents and reduce the heating energy consumption.It is of positive significance for speeding up the construction of the western region and implementing policies such as saving energy and reducing emission.