| As a place for university teachers and students to study and research,university libraries have the characteristics of large number of people in the room and long use period.At the same time,the library usually adopts the design of large atrium space and large area curtain wall to create a comfortable and open reading environment,which leads to a high level of energy consumption of ventilation and air conditioning to improve the thermal environment of library buildings.Therefore,combined with the use of university libraries and the characteristics of indoor and outdoor building environment,it is of great significance to study how to make full use of natural cold source in transition season to remove indoor load,and put forward reasonable operation control strategy of ventilation and air conditioning system in transition season to reduce the start-up time of refrigerator,ensure the thermal comfort of indoor thermal environment and realize energy-saving operation.Based on theoretical analysis,data measurement and numerical simulation,taking a university library in Chongqing as the research object,this paper analyzed the distribution of indoor temperature and expected adaptive average thermal sensation index(APMV)in the transition season,the influence of outdoor meteorological parameters on the cooling and heating load of the building and the control effect of different ventilation modes on the indoor thermal environment.On this basis,the control strategy of the ventilation and air conditioning system was optimized.The research contents and conclusions are as follows:(1)The thermal environment characteristics of the library were analyzed based on the measured data of the indoor thermal environment in the transition season of the library;The annual hourly load of the library was simulated and studied by using the building environment simulation software De ST,and the load characteristics of the transition season were analyzed.At the same time,based on the basic assumption of BIN method,combined with the theoretical calculation data of indoor load in transition season,the calculation model of indoor load in transition season was established.Based on the evaluation standard of non-artificial cold and heat sources for indoor thermal and humidity environment graphical method and the data of typical meteorological years in Chongqing,the relationship between the upper limit of indoor design temperature and outdoor temperature in transition season was fitted.(2)Numerical simulation of indoor air condition of library on day 1 by Fluent software.The calculated results were compared with the measured data,and the average relative error between the simulated temperature and the measured temperature at each measuring point was determined to be 1.0%.The average relative error between the simulated temperature and the measured temperature at each floor in the reading area was0.68%.The accuracy of the calculation model was high,which proved the reliability of the numerical simulation.(3)Combined with the indoor load calculation model of library in transition season and the heat balance principle,the upper switching temperature,natural ventilation switching temperature and the lower switching temperatures of library ventilation are25.2℃,18.8℃and 9.1℃.The minimum ventilation and air infiltration in cold season are18944m~3/h and 28715m~3/h respectively.According to the characteristics of indoor temperature distribution in the library,combined with the setting of fans in the region,four working conditions using partial mechanical ventilation were proposed,and the indoor thermal environment under each working condition was simulated and analyzed by using Fluent software.It was verified that the temperature and APMV values under each working condition met the II grade evaluation standard of thermal and humidity environment for non-artificial cold and heat sources,and the switching temperatures corresponding to the above four working conditions were 23.9℃,22.6℃,21.2℃and19.5℃.(4)According to the grade II thermal comfort standard and ventilation switching temperature of the long-term residence area,the meteorological envelope map of Chongqing typical meteorological year was divided into five meteorological zones,and the operation scheme of the library annual ventilation and air conditioning system based on the meteorological envelope map was proposed.The analysis shows that the energy saving rate of the operation scheme is about 15.7%. |
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