Central heating system plays a very important role in urban production and life. With the deepening of people's awareness of energy conservation and environmental protection, the optimal design of heating system has become a hot issue of general concern to all sectors of society. In the process of optimizing heating system, the optimization of heating pipe network is particularly important, which is of great significance for saving construction cost, controlling heat loss and protecting urban environment.
1 Significance of optimal design of urban central heating pipe network
1. 1 Improve heating quality and serve residents conveniently.
The urban central heating pipe network system can automatically set the temperature timing through the system, without interference from the outside room temperature, and can automatically stop heating when it reaches the temperature set by the system, fully ensuring the residents' good indoor constant temperature. The optimized pipe network system runs intermittently, which can fully save energy and reduce the running noise of heating equipment. Because the equipment in the heating base is far away from residential areas, it will not interfere with the daily rest and life of residents, and fully implement the people-oriented concept.
1.2 improving environmental protection behavior
After optimization, the urban heating pipe network system is centralized, which effectively reduces the pollution to the environment and saves resources. Among them, the specific measure to reduce environmental pollution is to adopt the design concept of orderly chimney. Because of the large content of fuel equipment in central heating, the power generation rate is further improved, thus fully reducing energy consumption. The concept of environmental protection is deeply rooted in people's hearts. Therefore, as the infrastructure of buildings, builders should put this concept into practice and allocate the utilization rate of resources scientifically and reasonably.
1.3 fully automated.
At present, automatic control is widely used in urban central heating pipe network system, which can reduce the work of workers? According to the scientific configuration, the indoor temperature is adjusted by feeling the outdoor temperature, and central heating equipment is adopted to improve the reliability of equipment operation, reduce the failure rate and improve the heating quality. Central heating system is another important measure to save resources and protect the environment, and it also adapts to the trend and tide of urban modernization [1].
2. Influencing factors of pipeline insulation
The analysis of urban central heating pipe network shows that its actual thermal effect will be affected by many factors, mainly including the following points:
(1) Outside diameter of pipeline. When the water temperature is constant, the heat loss is proportional to the pipe diameter.
(2) Water delivery temperature. When the water temperature is low, the heat loss of each pipe diameter will not be too different, but when the water temperature is high, the heat loss of each pipe diameter will be quite different.
(3) Thermal conductivity of the pipeline. When the pipe diameter is constant, the heat loss of the pipeline is directly proportional to the thermal conductivity.
(4) Thermal conductivity of soil. When the pipe diameter is fixed, the heat loss is directly proportional to the thermal conductivity of soil.
(5) Insulation layer thickness. Heat loss is inversely proportional to the thickness of insulation layer [2].
3 Optimal design method of central heating pipe network
3. Optimization of1pipe diameter
The optimization of central heating pipe network mainly involves three parts, one is pipe diameter design, the other is pipe network layout, and the third is pipe network operation. Among them, pipe diameter design (or optimization) is a key to the optimization of central heating pipe network. Generally speaking, the pipe diameters involved in engineering are discrete, so the essence of pipe diameter optimization is how to do a large-scale combinatorial optimization problem. When there are differences in pipe network layout, usually pipe diameter optimization will also present different and targeted combinations. Therefore, in the process of pipe diameter optimization, the maximum pipe diameter should be determined according to the specific requirements of the project, that is, the value and determination of pipe diameter should be completed within a relatively scientific range. In the process of pipe network design, the diameter of each pipe section is finally calculated according to the corresponding flow rate and specific friction, and the flow rate depends on the actual heat load. Therefore, before determining the specific pipe diameter, it is necessary to reasonably calculate the heat load to be borne by each pipe section, and at the same time scientifically predict the future expansion range. With the continuous reduction of pipe diameter, the transportation resistance will increase, and the corresponding power consumption and cost will also increase; With the continuous increase of pipe diameter, the transmission resistance will decrease, and the corresponding power consumption and cost will also decrease, but there are disadvantages of increasing infrastructure investment. Therefore, under the condition that the layout of heating pipe network is determined, we should devote ourselves to the calculation and determination of the optimal (or most economical) pipe diameter, considering not only the capital investment, but also the power consumption and its cost, so as to minimize the sum of the two. In a word, in the process of optimizing pipe diameter, on the one hand, we must meet the corresponding technical conditions, on the other hand, we must conform to the principle of optimal economy.
3.2 Optimization of pipe network layout
The analysis of heating system construction shows that the investment of heating pipe network accounts for the highest proportion, and its construction is also the most complicated and arduous. We should pay attention to and choose the form of heating pipe network, which is not only related to the reliability of heating, but also related to the operability, convenience of operation and economy of the pipe network. In the process of heating pipe network layout, it should not conflict with the overall planning of urban construction. Under the guidance of the latter, the heat load distribution, the specific location of heat source, the relationship with other pipelines or structures, hydrological characteristics, geological conditions and other factors are comprehensively considered.
In the process of heating pipe network layout, the following basic principles should be effectively implemented:
(1) is economical and reasonable. The trunk line should be as straight as possible, not only that, but also try to choose the area with the most concentrated heat load;
(2) The technology is reliable. In the process of laying lines, we should choose ideal areas, such as areas with small fluctuation, good soil quality and low groundwater level, and avoid those areas with large fluctuation, loose soil quality and relatively high groundwater level as much as possible;
(3) The pipeline shall be worn as little as possible or not. Usually, the pipeline should be parallel to the road center line, and should also be set outside the roadway as far as possible. Generally speaking, pipelines are only laid on one side of the road. Laying pipelines on the ground should be avoided as far as possible, because doing so will destroy the overall beauty of the urban environment on the one hand and hinder the normal operation of roads on the other. In the process of laying heating pipes, we should keep enough distance from other pipes or structures to ensure the efficiency of later construction, safe operation and convenient maintenance.
3.3 Optimization of pipe network operation
The investigation of central heating pipe network in some cities in China shows that there are many problems in its normal operation, especially the serious waste of energy, which makes its economy unsatisfactory. At present, with the emergence and application of various types of heating systems, it has become an urgent problem to optimize the operation of pipe network scientifically. It is worth mentioning that in the actual operation of heating network, the problem of uneven cooling and heating is widespread and has brought a series of adverse effects. The hydraulic imbalance of heating network is the main factor leading to this problem. Therefore, it is urgent to effectively control the hydraulic power of heating network to make it tend to balance, which will have a direct and important impact on the normal and efficient operation of heating network. The corresponding number and power of dynamic regulating devices should be selected and installed to effectively control the hydraulic power of each loop and reduce or avoid the occurrence of imbalance. In the process of some users adjusting their own heat consumption, dynamic adjustment equipment will play a very positive role in adjustment. In addition, in the process of adjustment, it will not adversely affect the actual heat consumption of adjacent circuits, and it also has the advantage of no noise. But it should be noted that for dynamic systems, there is the possibility of steady-state imbalance, so we should pay attention to this problem and take corresponding preventive measures. In a word, when the hydraulic power is out of balance, the related heat users will face the problem of over-cooling or over-heating, which is the most important concern of heating operation enterprises. In order to alleviate or solve this problem, we should comprehensively consider technology and economy, continuously and rationally optimize the operation scheme of pipe network, effectively alleviate or avoid the adverse effects caused by hydraulic imbalance, so as to ensure the working quality of heating network and finally realize the overall goal of continuous and reliable operation of heating system.
4 conclusion
China's urban population density is high, which requires high performance of heating pipe network. Therefore, it is a relatively complex and arduous project to ensure the continuity and reliability of urban central heating pipe network. In the process of optimizing the design of urban central heating pipe network, we should not only consider its safety and stability, but also consider its economy and science. On this basis, the pipe diameter, pipe network layout and pipe network operation should be optimized to promote the optimization of the whole city heating pipe network system. Y. With the increasing demand of urban central heating pipe network system, its design technology and level are constantly improved, and the performance of heating pipe network is obviously improved, showing good application potential and development potential.
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