| In recent years, district heating system developed rapidly in china, heating region extended from north to south, the scale of system has been expanding, and the heating pipeline has become increasingly complex. However, the proportion of old buildings in the system still higher, at the same time, because the operation management and control technology of the district heating system developed relatively slow, which results in the energy consumption of the system becoming higher, and the energy efficiency becoming lower. The buildings’ energy consumption accounts for about 40% of the total energy consumption of society in our country, in the aspect of production and consumption, the proportion of coal accounts for 65%, and thermal efficiency of the coal-fired boiler is about 60%. Therefore, in addition to improving the efficiency of heat source, the research of improving the operational efficiency is quite important.Firstly, this paper to the "2012-2013 the actual operation of a central heating system data" for the research background, the annual operating data obtained were analyzed by installments operating characteristics of the system, and proposed the measured data problems and system needs aspects to improve, and then used the measured data as well as to compensate for the simulation to guide the operation of the system deficiencies.Secondly, this article takes an indirect district heating system as the model, selecting the two heat exchange station and three communities as the research object. Based on mass and energy conservation principles, a set of dynamic model was developed for an indirect district heating system, not only including the thermal models such as boiler, pipeline, heat exchanger and radiator,but also including control valves and circulating pump model,this improved the integrity and practicability of the heating model. Applying the dynamic model, based on the practical operational data, mainly simulating the influence of the pipeline heat loss, make-up water, extra area of intermediate heat exchangers and radiators,solar radiation and indoor heat gains on the system and indoor temperature,and the transient simulations were conducted to obtain the dynamic responses of the system under the ideal and actual conditionswhen system started. Then, researching the time attaining stable conditionat the design outdoor conditions to the change the fuel consumption, the primary pipeline flow rate and the triple valve openings respectively, and the influence of three factors above on system and indoor temperature. When outdoor temperature changed, transient simulations were conducted to obtain the dynamic responses of the system when no adjusting or solely and jointly adjusting the fuel consumption, the flow rate of the primary pipeline and radiators, and the set value of the boiler supply temperature and secondary pipeline supply temperature could be determined, which provided the basis for the control analysis under variable operation. Considering the effect of hydraulic loss, we could analyze the system dynamic responses and its characteristics vividly, and it provided new method of the operational management and control mode for optimizing the heating pipeline and provided the tools of energy consumption.Finally, the heating control system was established. With the development Internet technology, computer application in the district heating has gradually from the simple design and drawing to intelligent direction. Therefore, making reasonable control strategies to solve the problems reflected by the fact data is necessary. In order to ensure thermal comfort of users and reduce energy consumption, the system operational states were simulated and the energy consumptions were analyzedforthe scenarios of different configurations of the control systembased on MATLAB software, such as the fuel flow rate controller, the primary pipeline flow rate controller and the indoor temperature controller, when one-week actual meteorological parameters were applied. Results indicate that the most steady indoor temperature can be achieved by using the strategy of jointly controlling the fuel,the primary pipeline and the radiator circulating water flow rate. However, the least amount of energy was consumed by using the strategy of jointly controlling the fuel consumption in terms of the boiler supply temperature,primary pipeline water flow ratein terms ofindoor temperature, but the secondary pipeline supply and return temperature fluctuated obviously. And the power consumption would be greatly reduced if variable frequency circulating pump were used in the primary pipeline. Therefore, after the simulation of control strategies, not only improve the indoor temperature sensitivity and accuracy, and improve the whole efficiency of the system, achieved the purpose of energy saving at the same time. |
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