Study On The Cooling Characteristics And Optimal Control Method Of Night Ventilation In Hot Summer And Cold Winter Area

In the hot summer and cold winter area,the weather in summer is very hot.With the improvement of China's economic development and people's living standard,the requirements of people for indoor thermal comfort are getting higher and higher,which leads to a sharp increase in the energy consumption of the air conditioning system in the area.It has been made an important part of China's electricity peak load.To save the energy consumption of the air conditioning system,outdoor air in low temperature during the night can be used to take away the waste heat of indoor.However,how to effectively design and run the night ventilation system is the question being researched and discussed.Changsha,as a typical representative city of the hot summer and cold winter area,is selected as the research object in this paper,and simulated respectively by DeST.By analyzing the parameters relating to the cooling effect of night ventilation,the cooling characteristics and optimal control method of night ventilation can be gained.The main work is as follows.Firstly,by theoretically analyzing the night ventilation theory and establishing night ventilation heat balance equation of the room,the factors related to the cooling effect of night ventilation can be gained.Secondly,cooling potential of several typical representative cities in the hot summer and cold winter area were analyzed by using weather tool software,the feasibility of night ventilation technology in hot summer and cold winter area can be obtained.And typical representative city in the cold area,hot summer and warm winter zone,temperate regions were analyzed correspondingly?The results show that it is not suitable to use night ventilation technology in the hot summer and warm winter area.Then,taking Changsha as an example,the paper establish the night ventilation building model by DeST and analyze the effect of the factors including thermal storage level of building envelope,internal heat sources,air exchange frequency and outdoor air temperature on the cooling characteristics of night ventilation.The results show that the relationships among ventilation time,air exchange frequency and exhaust temperature is logarithmic under different outdoor weather conditions for different buildings during the night ventilation.Finally,based on the result that the relationships among ventilation time,air exchange frequency and exhaust temperature is logarithmic by DeST,by taking the minimum total energy consumption of fan and air conditioning equipment as the optimization objective,the optimal combination of air exchange frequency and ventilation time can be gained by MATLAB Toolbox.The cooling characteristics and optimal control method of night ventilation in this paper are universal for different buildings in the hot summer and cold winter area.And the method and the results are available to the optimal design and operation of the night ventilation system.