National Chinese Children's Heart Journal reasonably selects steam pipe insulation material Jin Qiqi (Hangzhou Urban Construction Design and Research Institute Co., Ltd., Hangzhou 310002, China) The technical performance parameters of the commonly used thermal insulation materials in steam pipelines are reasonable for the selection and calculation of specific steam passage insulation materials. The selection of steam pipe insulation materials is of great significance for reducing heat loss, saving energy and reducing engineering cost.
Key solid: steam pipe insulation material performance parameters heat loss energy saving 0 Foreword In the goal of the overall energy saving of the building specified by the Ministry of Construction of more than 50%, the heat transfer efficiency of the urban heating project should be more than 90%. Insulation of the steam pipe can reduce heat loss and save energy. However, what kind of insulation materials are used best, and how low heat loss should be calculated is often not taken seriously by people. In particular, the insulation of low and medium pressure parameters steam pipes is large, and there are two kinds of situations in the field. A large number of high-efficiency insulation materials are used in places with low requirements to cause great resources and waste of funds for the country. Many places with high insulation requirements only use low-efficiency insulation materials or the thickness of the insulation layer is not enough to meet the insulation requirements and cause energy waste. Therefore, it is of great significance to reasonably select the insulation material of the steam pipeline to reduce the heat loss of the heat network, save energy and reduce the project cost.
1 Selection of thermal insulation materials 11 National standards and specifications for steam pipe insulation materials selection in accordance with the relevant provisions of GB5026497 industrial equipment and pipeline insulation engineering design specifications in operation, when the average temperature is lower than 350C, the thermal insulation system of thermal insulation materials shall not exceed 0.12 The density of W(mK) culvert insulation material shall not exceed 300kg/m3; the density of soft materials and semi-rigid products shall not exceed 200kg/m3; the compressive strength of hard materials used for heat preservation shall not be less than 0.4MPa, and the water content of thermal insulation materials shall not exceed The rate shall not be greater than 7.5%. According to the provisions of 7.930 of the Heating Ventilation and Air Conditioning Design Code of GB500192003, equipment and pipeline insulation materials shall be selected with preference for small thermal conductivity, large temperature resistance factor, low water absorption, low density and comprehensive economy. High-efficiency materials; insulation materials should be non-combustible or non-combustible materials; the thickness of the insulation layer of the pipeline is determined by the economic thickness in the GB817 equipment and pipeline insulation design guidelines when heating.
12 Factors affecting the thermal insulation effect of steam pipelines Many factors affecting the thermal insulation effect of pipelines are mainly the thermal conductivity of thermal insulation material X, the heat release coefficient of insulation layer a, the annual average temperature of pipeline environment and the average annual wind speed V, height coefficient, insulation Layer thickness 5 and construction quality. In general, in the case of the same heat loss, the thermal conductivity X and the surface heat release coefficient a of the insulating layer are larger, and the thickness of the insulating layer 5 is thicker. The lower the average annual temperature in the environment, the higher the average annual wind speed, and the higher the thickness of the insulation layer required for the outdoor pipe rack. Under certain conditions, the annual temperature, average wind speed and height coefficient of the region are fixed values. The thermal insulation effect is mainly due to the thermal conductivity X of the thermal insulation material and the thickness of the thermal insulation layer. These two items directly affect the material selection and insulation costs. For the specific insulation material, the best insulation thickness can be achieved to save energy and reduce investment.
13 Performance parameters of several common steam pipe insulation materials China's current materials suitable for steam pipe insulation are mainly porous calcium silicate products, aluminum silicate products, rock wool, ultra-fine glass wool, etc. Their performance and price are shown in Table 1. Table 1 Performance and price of several steam pipe insulation materials Thermal conductivity / density price Microporous calcium silicate products Aluminum silicate products Rock wool superfine glass wool Note: m is the average temperature of the inner and outer surface temperature of insulation materials Main market information of East China Price 2003) does not include transportation costs.
Whether the selection of insulation materials is reasonable or not can be measured mainly from the heat loss, the required thickness of the insulation materials and the economy. Under the same conditions of heat loss, it is necessary to minimize the insulation cost of the pipeline. Generally, to reduce heat loss, it is necessary to increase the thickness or use a material with a smaller heat conduction system. The cost is related to the thickness of the material, the thermal conductivity, etc. In addition, construction, material sources, maintenance, brackets, labor protection, etc. must be considered. According to GB50264-Industrial equipment and pipeline insulation engineering design specifications, according to China's current energy prices, policies and energy consumption, the general heat loss should be controlled within the scope of Table 2, which is more reasonable, and the energy waste is too small. The payback period is long.
Table 2 The maximum allowable heat loss on the outer surface of the insulation structure is the heat loss of the medium temperature!
Media temperature heat loss!
Perennial running season running year-round running season operation 1.4 selection of insulation materials Due to China's vast territory, climatic conditions vary greatly, and the sources and prices of insulation materials vary from place to place. Therefore, when selecting the insulation material, the heat loss of the insulation material and the economic insulation thickness of the pipeline should be calculated in combination with the actual project, but it cannot be directly selected according to the data in the relevant specification manual.
An example of the selection of insulation materials for steam pipes is now given. For example, the outdoor steaming temperature of DN150 steam pipe is 300C. The average annual temperature ta of the area is 16.2C, and the average wind speed V is 2.3m/s. The microporous calcium silicate product is used for heat preservation.
The heat release coefficient a of the outer surface of the outdoor pipe insulation structure is related to the radiation heat transfer coefficient a of the heat preservation material and the convective heat transfer coefficient a. That is, a is related to factors such as wind speed, insulation material and color. The heat release coefficient a of the outer surface of the outdoor pipe insulation structure can be calculated as follows: Calculate the thermal conductivity from the thermal conductivity of the microporous calcium silicate in Table 1. Calculate the thermal insulation thickness 5 firstly perform the heat dissipation loss on the surface of the outer thermal insulation layer of the pipe. The loss meets the requirements of Table 2: t-taD-pipe outer diameter; pipe insulation layer outer diameter; t pipe outer surface temperature, C. calculation heat preservation cost yuan / m pipe insulation structure outer surface temperature ts can be calculated as follows: using the above method The insulation cost and heat loss of each insulation material can be calculated. If the heat loss is greater than the heat loss shown in Table 2, the outer surface temperature of the pipeline can be appropriately reduced or the material with smaller thermal conductivity can be used until the heat loss is controlled in Table 2. In the range. Check other data. According to the above data and materials, transportation costs, maintenance and other factors, consider the best insulation materials. Generally speaking, high-temperature pipelines use better insulation materials, and low-temperature pipelines use low-temperature insulation materials. It is imperative to use materials blindly to achieve less cost and more energy. Table 4 lists the costs required to keep the pipes warm with different materials with substantially the same heat loss. a=a+a Table 3 Protective layer material blackness e Table 4 Pipes use different insulation materials heat loss and cost items Maximum use temperature / c insulation thickness / mm outer surface temperature / c heat loss / (yuan / m) micro Porous calcium silicate product 6508029.2917655.0 aluminum silicate products 1 2007528.9417364.2 rock wool 6006528.8617619.5 ultra-fine glass wool 4007528.8117152.4 Note Each fee is only included in the main material fee does not include surface protection and other auxiliary materials and labor. Calculate material name Surface state blackness e Material name Surface state blackness e è¾› é“ é“ æœ‰ 有 有 æ°´æ³¥ æ°´æ³¥ æ°´æ³¥ æ°´æ³¥ æ°´æ³¥ å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² å·² 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑 黑The same is listed.
Here, we need to pay attention to the values ​​of t and V2 key coefficients, because the temperature and wind speed will directly affect the accuracy of material selection calculation.
According to the previous calculation results, it can be seen that if microporous calcium silicate insulation is used in the case of the same heat loss, the cost is 55.0 yuan/m. If the rock wool insulation cost is only 19.5 yuan/m, the cost is only micropores. 35.5% of calcium silicate. When the new 11 materializes the national Chinese children's heart protection hot box method, the heat is transferred into or out of the wall through the radiant heat exchange between the test piece and other surfaces in the box and the convection on the surface of the test piece. Heated. The amount of radiant heat transfer depends on the average radiant temperature of the baffle surface parallel to the test piece; convective heat transfer depends on the temperature of the air in the flow guide cavity. Therefore, the heat flow through the test piece is affected by the radiant temperature and the air convection temperature of either side of the hot and cold sides.
However, in actual projects, some actual materials and labor costs should be added. The actual total price is larger than that calculated in Table 4. By comparing some common insulation occasions, it is possible to select insulation materials with convenient materials and low prices. For insulation parts with special requirements, materials with the same performance requirements should be used for heat preservation.
2 Conclusions (1) The selection of thermal insulation materials in pipeline insulation should meet the national requirements for energy conservation in terms of technical performance. It is energy-saving and economical to control the heat loss of steam pipelines within the allowable range according to economic thickness requirements.
(2) The choice of insulation materials cannot be generalized in different regions and different occasions. According to the climate, use occasions, performance of thermal insulation materials, price and other factors, comprehensive consideration should be given to the selection of thermal insulation materials for steam pipes by calculation.
(Finish)
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