Study On The Calculation Method Of Intermittent Heating Load And The Effect Of Heat Transfer On The Interior Wall Of Residential Buildings

Hot summer and cold winter area one of the five climate zones in China,mainly refer to the middle and lower reaches of the Yangtze River and its surrounding areas.The average temperature range of the coldest month is 0-10℃.This area is not a central heating area in history.With the economic raiseing in rocket and the improvement of living standards,people’s pursuit of indoor thermal environment comfort is increasing,so there is a demand for indoor heating in winter.At the same time,with the South expansion of the heating area,the newly added heating areas are mostly located in hot summer and cold winter areas.Different from the central heating mode in cold areas.The heating time in hot summer and cold winter areas is relatively short in winter.In order to improve the poor indoor low temperature environment in winter,residents adopt diversified decentralized heating mode to solve the problem by themselves,and the heating mode is mostly partial space and intermittent function.Therefore,when the heating system of existing residential buildings is added and the that of new buildings is designed,there are many problems such as inaccurate calculation of heating load,too large or too small selection of equipment and so on.The heat transfer and heating load calculation of local heating room and non heating adjacent room are still worth discussing.Taking residential buildings in Chengdu as an example,this paper uses software of De ST-H simulating the natural room temperature and heating load of buildings in winter under the intermittent heating mode of split air conditioning,and compares the calculation results with those obtained by traditional heating load calculation methods,and puts forward a method that conforms to the characteristics of intermittent heating load in local space,and considers the heat transfer between internal enclosure structures The calculation method of the influence of the thermal performance of the peripheral protection structure and the starting load of the system on the intermittent heating load of the local space.The additional coefficient of heat load for intermittent heating in the whole room of buildings with different exterior envelope structures₁ is calculated.Additional coefficient of heat load of buildings with different external envelope structures under local intermittent heating of a single room₂.At last,the formula of=·（1+₁）·（1+₂）is obtained,which is suitable for residential buildings in Chengdu area under the mode of split air conditioning heating.A new idea of energy saving and consumption reduction based on the improvement of the thermal performance of the inner enclosure is proposed.On the basis of De ST-H simulation results,aiming at the heat transfer problem of internal enclosure structure when different heating ends are used for intermittent heating of local rooms,this paper uses CFD numerical simulation software to further simulate the temperature change characteristics of indoor working area,the change of internal wall surface temperature and heat flow density,and the total heat transfer of internal enclosure structure,and discusses and analyzes the simulation results.The simulation results show that:（1）by comparing the start-up load of the same room and the minimum design temperature time of the indoor working area between CFD simulation and De ST-H simulation,the start-up load and the heat transfer load of the internal enclosure must be considered simultaneously when calculating the intermittent heating load of the local room.（2）Through the analysis of the temperature change of the inner wall,we can know that the heat transfer of floor radiant heating through the inner wall is the most,while the heat transfer of radiator is the least.At the same time,the temperature of the adjacent part of the inner wall and the outer wall,the connecting part of the inner wall and the beam and column is lower than that of the other parts of the inner wall.Therefore,in addition to the overall insulation of the internal wall,the adjacent parts of the internal wall and the external wall,and the connecting parts of the internal wall and the beams and columns can also be partially insulated.（3）The heat flux density of the inner wall is affected by both the wall temperature and the time when the wall reaches the peak heat flux.（4）In CFD simulation,the ratio of the total heat dissipation of the main bedroom to the total heat load of the main bedroom of the type III building in De ST-H simulation is 0.245 under the split air conditioning heating mode,which is compared with the average daily additional rate of the local space intermittent heating of the main bedroom of the type III building in De ST-H simulation on January 5,Compared with1)₂=0.254,the error is less than 5%.