| At present,the operation and adjustment of the secondary network of most central heating systems in the cold areas of our country is lagging behind quite.In some heat exchange stations,there even exists observational adjustment,or extensive adjustment only in the early,middle and late heating.That makes the heating buildings have room temperature on the high side phenomenon,and excessive heating loss even accounted for about 14% of the total heating volume.Due to the complex nonlinear and large time delay of central heating system,the temperature of heating room is affected by many factors such as outdoor meteorological conditions,thermal inertia of building envelope and contents,so it is difficult to predict the room temperature of heating room.Based on the energy-saving design standards for buildings in cold and cold areas,this thesis selects central heating buildings in Shijiazhuang area(cold B zone)as the research object to study the change rule between indoor temperature and heating time when the heat dissipation of terminal heating equipment changes during the heating period.As indoor temperature changes are affected by many factors,this thesis will study the thermal inertia of building envelope and the regulation of heating end.(1)Mathematical models of outdoor temperature and solar radiation are established.Based on the analysis of solar radiation intensity,ground reflection and night radiation,the external disturbance factors affecting indoor temperature were integrated into outdoor temperature.Based on this,the thermal inertness of the outer envelope was studied,and a function relation between the comprehensive outdoor air temperature and time was established.(2)The thermal inertness of the enclosure structure was characterized by the thermal inertness index,delay time and attenuation multiple.The heat storage property of the enclosure structure is analyzed,and the heat transfer model of the wall is established according to the heat balance relationship.The temperature distribution of the inner and outer surfaces of different walls is calculated by the finite difference method.The temperature of the inner and outer surfaces of the walls shows obvious hysteresis and attenuation,and the heat storage property of the walls is obvious.The correctness of the model is verified by comparing the existing data.(3)The heat balance subsystem equation between the inner surface of the wall and indoor air was established.Under the condition of no internal heat source,the indoor temperature change model was established,and the temperature change rule of the inner surface of the wall under four different outer envelope structures was obtained through calculation.A functional relationship between the inner surface of the envelope structure and time was established,so as to establish the connection with the comprehensive temperature of outdoor air.The correctness of the model is verified by actual measurement.(4)The opening delay and closing delay of terminal equipment were used to represent the thermal inertia of building heating.The influence of the average temperature of different terminal equipment on the thermal inertia of heating was analyzed,and the indoor temperature change model with internal heat source was established.Through numerical calculation,the room temperature variation under radiator heating and low temperature floor radiant heating mode is obtained and analyzed.Through the simulation study of the thermal inertia of the enclosure structure and the regulation of the heating terminal,the prediction model of the indoor temperature changing with time was obtained.The research results of this project have certain reference and engineering application value for central heating control system. |
