Energy-saving Improvement Of Ultra-long-distance Heating Pipe Network Based On Fluid-solid Coupling

Coal-fired combined heat and power can greatly improve the thermal efficiency of coal conversion.Long-distance centralized heating can effectively eliminate the risk of coal power overcapacity,promote structural reforms on the district heating supply side,it can effectively realize the centralized ultra-low emission of heating pollutants,and improve the quality of urban heating and urban environment.The heat insulation and resistance reduction design of the heat transfer pipe network is the key to the long-distance centralized heating technology.In order to realize the energy-saving optimization design of the ultra-long-distance heating pipe network,the research on the fluid-solid coupling calculation model for the temperature drop and pressure loss of the heating pipe network was carried out,and the design algorithm of temperature drop and pressure drop coupling design of heating pipe network was constructed;The software for visually designing the coupling of the temperature and pressure drop of the heating pipe network was developed.Based on the software,the influence rules of the parameters of the heating pipeline were studied;Numerical experimental research verified that the software design was reliable.And numerically studied the influence of different thermal insulation methods and soil moisture content on the performance of heating pipes;The proposed energy-saving optimization plan for the pipeline network was proposed.Fluid-solid coupling design method for temperature drop and pressure loss of ultra-long distance heating pipe network.The heat dissipation loss models of heating pipes with different laying methods were researched,and the formulas for calculating the thermal insulation layer and heat dissipation amount of pipes with different laying methods were established;Based on the laws of mass conservation,momentum conservation,and energy conservation,the flow continuity equation,flow momentum equation,and kinetic energy equation of the heating pipeline medium were derived;By combining the three major equations of the heating pipeline flow and introducing the state equation and enthalpy equation of the heating pipeline fluid,the coupled calculation model for temperature drop and pressure loss of the heating pipeline network was established;By analyzing the solution algorithm of ordinary differential equations,the calculation algorithm of temperature drop and pressure loss coupling calculation model of heating pipeline was determined.Development of coupling design software for temperature drop and pressure loss of heating pipe network.Constructed the fluid-solid coupling design program flow for the temperature drop and pressure loss of the heating pipe network,and developed a visualmodular design software based on C ++ builder.The software includes water and water vapor property parameter calculation,insulation layer thickness and heat dissipation calculation,pipe Network temperature and pressure loss coupling calculation function module,it can realize long-distance heating pipe network with different laying methods,pipeline structure,pipeline connection,thermal insulation structure,thermal insulation material,soil environment and heat medium for any combination of selection and optimization design;And it can realize long-term Study on the characteristics of temperature drop and pressure loss of distance heating pipe network and its influence law.Study on the influence rule of the temperature drop and pressure loss pipe section parameters of heating pipe network.By using the developed heating pipe network design calculation software,the effects of pipe length,heat medium temperature,heat medium pressure,heat medium flow rate,and pipe network diameter on pipe network cooling temperature drop and flow pressure loss were calculated and studied.The results of the study show that: under other conditions unchanged,with the increase in tube length and initial temperature,the temperature drop and pressure drop of the pipeline continue to increase;while when the initial pressure increases,the temperature drop and pressure drop of the pipeline will decrease;With the increase of flow rate,the temperature drop will become smaller and the pressure drop will increase;when the pipe diameter is too small,the temperature drop and pressure drop will be larger.With the increase of the pipe diameter,the change trend of temperature drop and pressure drop tends to be gentle;And through the calculation and research of the heating pipe network under different working conditions,it can be seen that the temperature drop and pressure drop of the pipe section with a smaller pipe diameter and more resistance components are larger.Research on numerical simulation of heating pipeline.In order to verify the reliability of the development software,numerical simulation was performed on the heat medium pipe insulation system based on the standard k-? turbulence model and the DO radiation model.The results show that the thermal insulation scheme of overhead heating pipes using CNT +glass wool and adding a reflective layer outside each thermal insulation layer can effectively reduce heat loss and have the best thermal insulation effect;Increasing the burial depth for directly buried heating pipes can increase the thermal insulation effect of the pipeline,and the increase in thermal insulation effect when the burying depth is increased from 1.5 m to 2 m is better than 1m to 1.5 m;The effect of soil moisture content on the Morgan heating pipeline is less than that on glass wool;In soil water content of 0-10 %,the effect of water content on directly buried pipelines is greater than the effect of water content of 10 %-20 %;By comparing the simulation results with the calculation results of the heating network design software,the maximum calculation error of the calculated temperature is only 0.0139 °C,which proves the accuracy of the numerical simulation and the calculation software of the network design.The research in this paper has an important role in promoting the development of ultra-long-distance heating pipe network technology.The research results can provide atheoretical basis for the energy-saving design and optimization of heating pipe networks.