| The heating scale in China is huge,and the actual operating conditions often do not match the design conditions in the actual heating process.One of the important factors comes from the existence of a certain heat exchange equipment margin,that is,the heat exchange area of the heat exchange equipment in the indirect connection system.The existence of a heat exchange area in the heat exchanger has resulted in a lower supply water temperature of the heating system,which is lower than the design value.In this paper,the effects of excess heat transfer area of plate heat exchangers and radiator on thermal conditions are investigated in different heating modes of the heating system.Firstly,the formula for the heat transfer coefficient of the plate heat exchanger was deduced.For the relevant thermal calculation of the plate heat exchanger,the commonly used Shakhrov-derived approximate formula for the shell-and-tube heat exchanger is no longer used.The numerical equations are used to start the calculation and the formula for the heat transfer coefficient considering the temperature variation of the heating medium on both sides of the plate is deduced.Convenient for subsequent thermal calculations.Taking the Harbin area as an example,the appropriate design values are selected to calculate Impact on thermal conditions of the different heat exchangers’ surplus areas in the three adjustment modes: the primary net in quality regulation,the quality regulation of flow adjustment in stages,and the equal temperature difference adjustment when the secondary net is in quality regulation.It is divided into two schemes.The first solution is to maintain the temperature of the primary water supply and change the flow rate of the primary network to compare the degree of declining of return temperature of the primary network.The second solution is to maintain a constant network flow and compare the decrease in the temperature of the supply water and the return water.Finally,through the regulation curve diagram,the influence of the size of the heat exchange area of the heat exchanger on the temperature of the supply and return water was analyzed.Taking a student apartment in a university in Harbin as the research object,a model was built using De ST-h software to calculate the heating residual heat generated by building energy-saving renovation and human behavior energy saving,and the excess heat transfer area of plate heat exchangers was calculated by calculating the heating waste heat of existing buildings.Among them,the building energy-saving renovation includes the transformation of the building envelope and the change of meteorological parameters.According to the design specifications of different periods,the parameters of the enclosure material of different specifications are input into the software for calculation.The study on the energy-saving part of the behavior was based on a onemonth survey of student dormitory occupants.The research included the students’ stay in the dormitory,the opening of computer equipment,and the opening of lighting equipment.Each hour is counted,and the statistical results are input into the software to calculate the heating residual heat and the excess capacity of the heat dissipation equipment due to free heat.Calculate and analyze the influence of the excess heat exchange area of the heat dissipation equipment on the temperature of the secondary net water supply and return water,and calculate the effect of the heat exchanger surplus on the heat conditions based on the allowance for the heat dissipation equipment,and consider only the heat exchange,the thermal conditions of the excess capacity are compared.An appropriate X factor is selected,and the secondary network is under the quality and quantity adjustment methods of X=0.3 、 0.5.When comparing the secondary network under the same conditions in quality regulation,the effect of the heat exchanger margin on thermal conditions.A comparison is made between the three conditions under the new condition of considering only the allowance of the heat exchanger,only the allowance of the radiator,taking into account the surplus of the heat exchanger and the radiator,and the secondary net with X=0.5,and comparing the correlation between the power consumption and the excess heat exchanger area under different conditions. |
