| With the further implementation of air pollution control,energy saving and emission reduction,cogeneration has been widely used in large district heating projects.At present,most thermal power plants use large heat storage tanks for flexible peak adjustment.When the power plant runs over the limit,the excess electricity will be heated into the heat storage tank through the electric boiler for heat storage,and when the power plant runs under the limit,the heat stored will be released.The heat storage of long distance heating pipe network uses the excess heat of thermal power plant to store heat in the pipe network,which not only realizes the diurnal shift of heat load of heating pipe network,reduces the capacity of peak-regulating heat source,but also shorts the working time of heat source.As one of the main components of the heating system,the heating pipe network mainly undertakes the task of conveying high temperature media,so the pipe network is more flexible in heat storage.The main factors affecting the heat storage capacity of heating pipe network are the water capacity of pipe network and the water supply and return temperature of pipe network.For large pipe networks,indirect connection is mostly used for heating.The heating pipe network is divided into primary pipe network from heat source to heat exchange station and secondary pipe network from heat exchange station to user.The pipe diameter,length and water capacity of the primary pipe network are generally higher than that of the secondary pipe network,so the primary pipe network is taken as the main research object.This topic takes a long distance heating pipe network of zunhua district heating as the research object,and collects heat source,supply and return water temperature of different connection points and outdoor temperature through experimental method.Through the experimental study,it can be seen that the heat storage mode of heating pipe network with temperature rise and increasing flow can not only increase the flexibility of heat source,but also have higher economy.Further,the modeling of longdistance heating network is studied by numerical simulation,and different heat storage modes are discussed to study the better operating parameters of long-distance heating network under heat storage conditions.The results show that the main factors affecting the heat storage capacity of pipe network are outdoor temperature and water supply and return temperature,and the temperature-rising heat storage mode has a significant effect on the heat storage capacity of pipe network.The increased flow heat storage mode has an effect on the heat storage capacity of the pipe network,but the effect is less than that of the temperature rise heat storage mode.In the flow-temperature-rise heat storage mode,the increase of heating parameters has great influence on the heat storage capacity of pipe network,while the change of total circulation has little influence on the thermodynamic parameters of pipe network heat storage.When the outdoor temperature of the long distance heating pipe network was between-4 ℃ and 4℃,and the water supply temperature of the pipe network was between 70 ℃ and 90℃,the pipe network had a strong heat storage capacity in the heat storage mode.Exergic efficiency of the pipe network was about 90%,thermal efficiency was 97.5%,and thermodynamic perfection was good.When the outdoor temperature ranges from-16 ° C to-10 ° C,the heat storage capacity of the pipe network is poor.However,the heat storage capacity of the pipe network in this mode increases with the increase of pipe circulation capacity.When the outdoor temperature is between 10 ° C and 16 ° C,the heat storage capacity of the pipe network is strong,but the user needs less heat.In the temperature range of-10℃～-4℃ and 4℃～10℃,the mode of current-temperature-rising heat storage is adopted.When the water supply temperature is 70℃～95℃ and 65～70℃ respectively,the exergic efficiency and thermal efficiency are about 85% and 95%. |
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