System for testing heat conductivity coefficient of pipeline thermal insulation material under engineering meteorological environment condition

Abstract

The invention relates to the technical field of heat preservation and energy conservation, and particularly discloses a system for testing the heat conductivity coefficient of a pipeline heat preservation material under an engineering meteorological environment condition, which comprises a straight pipe test piece with calibration ends fixedly mounted at two ends, and a heat preservation covering material wrapped on the outer wall of the straight pipe test piece to form a pipe fitting to be tested; the ventilation hood is positioned in the sealed space; air pipes at the output end of the air conditioning system are all located in the sealed space, and air outlets of the air conditioning system directly face the ventilation hood. By simulating multi-parameter coupling working conditions such as in-pipe medium temperature gradient, external temperature and humidity / wind speed circulation and mechanical vibration, the heat conductivity coefficient of the material is dynamically corrected, whether the heat conductivity performance of each layer of material meets the standard specification or not is verified, and the rationality of the composite structure is quantitatively evaluated based on a thermal resistance network model. Data support is provided for optimizing the heat preservation layer combination mode and thickness design, and the problem of design deviation caused by the fact that a traditional method cannot reflect actual engineering working conditions is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline heat insulation and energy conservation, and particularly relates to a test system for the thermal conductivity of pipeline heat insulation materials under engineering meteorological environmental conditions. Background Art

[0002] In view of the heat insulation requirements of high-temperature medium transportation pipelines, existing test methods have significant limitations. Pipeline heat insulation not only needs to reduce heat dissipation losses and ensure transportation safety, but also needs to address issues such as medium temperature drop, energy waste, and environmental safety. Current mainstream standards (such as GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Guarded Hot Plate Method" and GB / T10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method", etc.) adopt the single-layer planar material test method at room temperature, which cannot reflect the true thermal conductivity of multi-layer composite structures under the coupled action of dynamic temperature, humidity, wind speed and other meteorological conditions and medium parameters in actual engineering. Although patents such as the detection device and evaluation method for the performance of pipeline heat insulation materials disclosed in the publication number CN113804722A attempt to improve, their test devices rely on operating pipelines, are limited by the on-site environment and medium working conditions, are difficult to stably simulate specific engineering meteorological conditions, and are still limited to single material evaluation.

[0003] In actual engineering, the performance of the heat insulation structure is affected by three core factors: One is the dynamic changes in the temperature and flow rate of the medium inside the pipe; The second is the periodic fluctuations of the external meteorological environment (such as day-night temperature difference, precipitation, wind speed); The third is the combination method of multi-layer heat insulation materials and the interfacial thermal resistance effect.

[0004] Especially for the application of new high-performance materials (such as aerogels, nanoporous materials), performance synergy needs to be achieved through structural optimization, rather than simply replacing traditional materials. However, the current methods have not established a quantitative model between the thermal conductivity of materials and the above-mentioned multiple factors, resulting in a conservative or insufficient design of the heat insulation thickness, causing economic waste or safety hazards. Summary of the Invention

[0005] The purpose of the present invention is to provide a test system for the thermal conductivity of pipeline heat insulation materials under engineering meteorological environmental conditions to solve the above problems.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A test system for the thermal conductivity of pipeline heat insulation materials under engineering meteorological environmental conditions, comprising: A straight pipe specimen with calibration ends fixedly installed at both ends, and its outer wall is wrapped with a heat insulation covering material to form a pipe fitting to be tested; A ventilation hood in a sealed space; An air conditioning system, the air ducts at its output end are all located within the sealed space, and the air outlets face the ventilation hood; A spray water pipeline and a ventilation system, their output ends are arranged within the ventilation hood, and are distributed directly above the test piece to be measured which is centrally arranged within the ventilation hood; The said simulation test system (thermal conductivity coefficients of each layer of thermal insulation material in the composite thermal insulation structure) includes the following steps: S01. Through a dynamic simulation model to coordinate the air conditioning system, the spray water pipeline, the ventilation system and the heating system arranged within the test piece to be measured, so as to simulate the engineering meteorological environment within the closed test space, wherein: The heating system is heated to a steady-state heat transfer state during the detection; S02. Collect the electric heating power data, temperature data and environmental parameter data of the calibration end and the straight pipe test piece under the steady-state heat transfer state to verify the effectiveness of the data; S03. Based on the heat dissipation heat flux of the calibration end, correct the total heat dissipation heat flux of the test piece to be measured, and calculate the linear heat flux density of the test piece to be measured; S04. According to the linear heat flux density and the inner and outer side temperatures of each layer of thermal insulation material collected, calculate the actual thermal conductivity coefficient of the thermal insulation material layer by layer, and generate an excel report.

[0007] Preferably, the simulation of the engineering meteorological environment in S01 includes: S11. Regulate the temperature of the closed test space through the air conditioning system, and its refrigeration load QL is calculated by the following formula: QL = QL1 + QL2 + QL3 + QL4, where QL1 is the heat transfer from the outdoor environment, QL2 is the heat generated by the air conditioner and the ventilation fan, QL3 is the heat generated by the test piece, QL4 is the heat released by the spray water for cooling, and a 3% - 5% margin is reserved for the refrigeration capacity of the air conditioning system; S12. Simulate the environmental wind speed through the ventilation system, and the calculation formula for the air volume Q is: Q=(S 通风罩 - S 试件 )×wt×3600, where Q represents the air volume, the unit is m 3 / h, S 通风罩 represents the internal cross-sectional area of the ventilation hood, the unit is m 2 , S 试件 represents the cross-sectional area of the test piece to be measured, the unit is m 2 , wt represents the test wind speed, the unit is m / s, and the ventilation system adopts the parallel ventilation combined with the impact angle correction method, and the impact angle correction formula is: , where, is the impact angle, referring to the angle between the wind direction and the axis direction of the test piece to be measured; S13. Simulate the rain state through the spray water pipeline, with the temperature difference between the spray water and the ambient temperature not exceeding 2°C, and the spray water flow rate such that a complete water film is formed on the pipe fitting to be tested.

[0008] Preferably, the verification of the validity of the data in step S02 includes: S21. Determine that the steady-state heat transfer condition is that the temperature deviation at the same measurement point does not exceed 2% of the reference value, and the change after an interval of 5 minutes does not exceed 0.1°C and there are two-way fluctuations; S22. Record each set of data three times, with an interval of 30 minutes each time. When the deviation between the three data and the average value is less than 1%, the data is determined to be valid; S23. The principle for rejecting abnormal data is: If the single measurement value deviates from the average value by more than ±5%, then retest.

[0009] Preferably, the calculation formula for the linear heat flux density of the pipe fitting to be tested in step S03 is: q l直管 =(Q t直管 -Q 端头) ×(1 - percentage of power line loss) / L 直管 , where Q 端头 is the separate heat dissipation power of the calibration end, Q t直管 is the separate heat dissipation power of the straight pipe specimen, and L 直管 is the heat preservation measurement length of the straight pipe specimen; The heat dissipation heat flux Q 端头 of the calibration end is determined through the following steps: S31. The calibration end is composed of two hollow cylindrical end caps and a calibration steel pipe. A 50-mm heat preservation gap is reserved at the joint where the end cap and the steel pipe are joined together, and the joint is filled with heat-insulating material; S32. Calculate the instantaneous average value P 1端头 of the electric heating power of the calibration end under steady-state heat transfer conditions; S33. According to the total power consumption Q I端头 of the calibration end during the test period and the test duration t 端头 , calculate the average input power P 2端头 =Q I端头 / t 端头 ; S34. Take the arithmetic mean of P 1端头 and P 2端头 as the heat flux value Q 端头 of the outer surface heat dissipation of the calibration end under the test conditions, Q 1端头 =(P 2端头 ) / 2; The heat dissipation heat flux Q I直管 of the straight pipe specimen is determined through the following steps: S35. Calculate the arithmetic mean value P of the recorded input power of the electric heater inside the specimen under the steady-state heat transfer condition of the test working condition. 1直管 ; S36. Calculate the average heating power P of it through the power consumption Q during the local pipe fitting test under the steady-state heat transfer condition I直管 and the test duration t 直管 , and the calculation formula is: 2直管 P = Q I直管 / t 直管 ; S37. Take the arithmetic mean value of P 1直管 and P 2直管 as the total external surface heat flux Q of the straight pipe section specimen t直管 =(P 1直管 +P 2直管 ) / 2.

[0010] Preferably, the calculation formula for the thermal conductivity of each layer of thermal insulation material described in S04 is as follows: , In the formula: is the thermal conductivity of the i-th layer of composite thermal insulation material, with the unit of W / (m ·K); q l is the linear heat flux density of the thermal insulation pipe specimen, that is, the heat flux per unit length of the thermal insulation pipe specimen, with the unit of W / m; d i is the inner diameter of the i-th layer of thermal insulation material, and d i+1 is the outer diameter of the i-th layer of thermal insulation material, and at the same time, it is also the inner diameter of the (i + 1)-th layer of thermal insulation material, and the units are all m; t1 is the temperature of the outer wall of the steel pipe, that is, the inner temperature of the first layer of thermal insulation layer from the inside to the outside, t2 is the outer temperature of the first layer of thermal insulation layer from the inside to the outside, and so on, t i is the inner temperature of the i-th layer of thermal insulation material, and t i+1 is the outer temperature of the i-th layer of thermal insulation material, and at the same time, it is also the inner temperature of the (i + 1)-th layer of thermal insulation layer, and the units are all °C.

[0011] Preferably, the heating system described in S01 includes a plurality of inner ring heating rods, middle ring stepless adjustable heating rods and a plurality of outer ring heating rods distributed in a circumferential array on the metal disc bracket, and its control includes the following steps: S61. During the heating-up stage, use the fixed power of the outer ring heating rods to heat up quickly, and automatically cut off the power when the temperature of the heating rods exceeds the safety threshold; S62. During the steady-state stage, use the inner ring heating rods and the middle ring stepless adjustable heating rods, and adjust the power through the thyristor voltage regulation module to keep the inner wall temperature of the specimen stable within the range of the set value ±0.5 °C; On S63, a temperature measuring element is provided on the surface of the heating rod to monitor the temperature in real time and feedback control through the DCS system.

[0012] Preferably, the temperature measurement methods for the straight pipe section specimen and the calibration end head include: S100. Arrange 32 temperature measurement points at 150 mm from the end face and the middle section of the straight pipe section specimen, covering the 0, 3, 6, and 9 o'clock directions; S101. The temperature measuring elements of the calibration end head are arranged in a spiral at every 90°, and temperature measurement points are additionally arranged at the end cap head; S102. The temperature measuring elements are fixed by threads through stainless steel wall components or embedded inside the thermal insulation layer, and an adiabatic layer with an emissivity ≥ 0.8 is covered outside.

[0013] Preferably, the environmental monitoring method for the closed test space includes: S200. Arrange 8 WS series temperature and humidity sensors at the four corners of the space to monitor the temperature distribution at the top and middle heights; S201. Arrange 6 integrated intelligent anemometers at the front, middle, and rear sections of the ventilation hood to monitor the wind speed uniformity; S202. All data is transmitted to the operator station in the monitoring room in real time through the data acquisition terminal, and a trend chart and an alarm log are generated.

[0014] In the above technical solution, a thermal conductivity test system for pipeline thermal insulation materials under engineering meteorological environmental conditions provided by the present invention has the following beneficial effects: 1. According to the thermal insulation structure form and installation combination conditions of the actual project, test the thermal conductivity of each layer of pipeline thermal insulation materials under various possible working conditions (mainly referring to four parameters: inner wall temperature of the pipe, ambient temperature, ambient wind speed, and rain condition). The test results are close to the actual project conditions, which has more guiding significance and reference value for engineering construction.

[0015] 2. The test is carried out in a closed space, without being interfered by external meteorological environmental conditions, which improves the convenience and stability of the test. At the same time, it is also beneficial to ensure the accuracy of the test results.

[0016] 3. The specimen uses the heating and temperature rising method of an internal electric heater, without relying on external media to enter the pipe for heating and temperature rising, and is not interfered by external media parameters and transportation working conditions, with strong autonomy and independence.

[0017] 4. The electric heating system is equipped with a pipe wall temperature and heating rod temperature monitoring system to monitor and interlock the temperature of the heating rod itself. At the same time, an intelligent heating power control system is set up. Different power control circuits and control methods are used in the heating stage and the steady-state heat transfer stage to realize intelligent adjustment of the power of different heating rods as heating elements, ensuring the safety, stability and efficiency of the specimen heating process.

[0018] 5. The ambient wind speed is simulated by combining parallel ventilation with the test piece with impact angle correction, which effectively reduces the test cost while ensuring the simulation effect and improves the economy of the test work.

[0019] 6. The test and data recording work are carried out when the specimen is in steady-state heat transfer conditions, and the instantaneous power and cumulative power consumption and steady-state heating time of the electric heating rod under steady-state heat transfer conditions are measured at the same time. The arithmetic mean of the instantaneous power record mean and the average heating power is used as the calculated value of the heating power to reduce the test error rate and improve data reliability.

[0020] 7. Compared with the single-layer plane test method under room temperature, the technology of the present invention obtains the heat flow value of the heat loss of the straight pipe section and the temperature values of the inside and outside of each layer of insulation material through testing, and calculates the actual thermal conductivity coefficient of each layer of insulation material under the test conditions and the overall insulation structure through an algorithm. The results obtained are more in line with reality and have more guiding significance and reference value for the engineering application of insulation materials.

[0021] 8. Compared with the traditional method of testing the thermal conductivity of insulation materials, which tests each insulation material separately, the technology of the present invention tests the thermal conductivity of multiple different insulation materials in the same pipeline insulation structure at the same time, with high testing efficiency, which is conducive to reducing testing costs and improving the economy of testing work. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0023] Figure 1 A diagram illustrating the layout of a closed test space for a thermal insulation property testing device for an insulated pipe according to an embodiment of the present invention; Figure 2 An air flow map of a ventilation system provided by an embodiment of the present invention; Figure 3 A schematic diagram of the arrangement of the spray water pipeline provided in an embodiment of the present invention; Figure 4 A distribution diagram of ambient temperature and wind speed measuring instruments provided by an embodiment of the present invention; Figure 5 Schematic diagram of the installation positions of the metal disc bracket and the electric heating rod provided by the embodiment of the present invention; Figure 6 Simplified diagram of the principle of the calibration end structure provided by the embodiment of the present invention; Figure 7 Schematic diagram of the calibration end structure and assembly provided by the embodiment of the present invention; Figure 8 Schematic diagram of the straight pipe section specimen structure provided by the embodiment of the present invention; Figure 9 Arrangement diagram of the temperature measuring elements of the straight pipe section specimen provided by the embodiment of the present invention.

[0024] Explanation of the reference numerals: 1, straight pipe specimen; 2, calibration end; 4, air conditioning system; 5, spray water pipe; 6, ventilation system; 8, ventilation hood. Specific implementation manners

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] As Figures 1-8 shown, a test system for the thermal conductivity of pipeline insulation materials under engineering meteorological environmental conditions includes: Embodiment 1:

[0027] Combined with Figure 1 and Figure 2 shown, the application to the above simulation test system (the simulation test system mainly performs the test of the thermal conductivity of each layer of insulation material in the composite insulation structure) includes the following components: 1. A straight pipe specimen 1 with calibration ends 2 fixedly installed at both ends, and its outer wall is wrapped with a heat preservation covering material to form a pipe fitting to be measured; 2. A ventilation hood 8 in a sealed space; 3. An air conditioning system 4, the air ducts at its output end are all located in the sealed space, and the air outlets face the ventilation hood 8; 4. A spray water pipe 5 and a ventilation system 6, the output ends of which are arranged in the ventilation hood 8 and are distributed directly above the pipe fitting to be measured arranged in the middle of the ventilation hood 8.

[0028] Specifically, the overall structural layout diagram of the closed test space of the insulation pipeline adiabatic property test device is shown in the appendix Figure 1As shown in the figure, the testing work is mainly completed within this enclosed space. The surrounding of the enclosed space adopts a heat-insulating enclosure structure. Windows are not provided, and only a door is set on one of the narrow walls for transporting and accessing specimens and various devices. On the outside of the opposite narrow wall is a monitoring room for placing various measurement and control equipment and cabinets. The monitoring room is independent of the enclosed testing space and not connected.

[0029] An air-conditioning system 4, a ventilation system 6, and a spray water pipe 5 are provided in the enclosed testing space for simulating different ambient temperatures, ambient wind speeds, and the rain state of the heat-insulating pipes within the space.

[0030] The air-conditioning system 4 is used to control the air temperature in the enclosed testing space and consists of independent refrigeration units. Each set of units is composed of a refrigeration main unit (i.e., the outdoor unit, including a compressor and a condenser) and an indoor unit (including an evaporator). The layout of the refrigeration system is as shown in the appendix Figure 1 As shown, the refrigeration main units are arranged on the ground on one side outside the enclosed testing space, and the indoor units are arranged against the wall within the enclosed testing space. They are installed at a high position near the top of the enclosed testing space with brackets, and a diversion air duct is set at the air outlet of the indoor unit to increase the range of the cold air blown out from the air outlet of the indoor unit, so that the cold air at the outlet forms an air circulation around the ventilation hood 8.

[0031] The ventilation system 6 is used to simulate the ambient wind speed at the project location. Since the space required for vertical ventilation is too large, it is difficult to ensure uniform air flow and the cost is relatively high. Therefore, from the perspective of ensuring uniform air flow and taking into account the cost of the testing device, the ventilation system 6 adopts the method of parallel ventilation combined with impact angle correction, mainly including a ventilation hood 8 and a fan. Its layout is as shown in the appendix Figure 1 As shown. The ventilation hood 8 is set outside the specimen. On the one hand, it can reduce the ventilation area, which is beneficial to controlling the wind speed around the specimen. On the other hand, it can prevent the interference of external airflows (such as the blowing of the indoor unit of the air conditioner). The material of the ventilation hood 8 is selected as metal steel plate, and pulleys are provided at the bottom for easy movement. The layout boundary of the testing device is marked on the ground inside the ventilation hood 8 to ensure that the specimen is located at a place with relatively uniform temperature and directly facing the fan outlet. The clear distance between both sides of the ventilation hood 8 and the wall of the enclosed testing space is not less than 1.5 m. A fan is set at the end of the ventilation hood 8 on the side without a door of the enclosed testing space, and the other end of the ventilation hood 8 is open for accessing the specimen. After the air flows through the space between the ventilation hood 8 and the specimen from the fan outlet, it returns to the fan inlet outside the ventilation hood 8 to form an air flow circulation. The air flow during ventilation is as shown in the appendix Figure 2 As shown.

[0032] A spray water pipe 5 is set in the testing room. Mainly, a spray pipe is installed at the top inside the ventilation hood 8, directly above the specimen axially, as shown in the appendix Figure 3As shown in the figure. The spray pipe is made of porous galvanized steel pipe with DN15, the hole diameter is 5mm, the hole spacing is 100mm, and the holes face downwards. The spray pipe is supplied with water by a DN25 tap water pipe (galvanized steel pipe) in front, and a regulating valve is installed between the spray pipe and the water supply pipe. The ground of the enclosed test space has a certain slope to facilitate drainage. A drainage ditch is set on the east side of the enclosure structure. The drainage ditch is buried with a DN40 sleeve through the enclosure structure section for external drainage. When not draining, the sleeve is blocked with heat insulation material. Since the convective heat transfer between rainwater and the pipe surface is generally stronger than that of air under the same conditions, rain shower will enhance the surface heat dissipation. However, when the rainfall is large enough to completely cover the pipe surface with a water film, the change in rainfall only affects the thickness of the water film and has little effect on convective heat transfer. Therefore, the design of the rain shower system only needs to ensure that the pipe surface is completely covered by the water film, regardless of the size of the water flow. On-site, by adjusting the valve opening, the water flow covers the surface of the specimen. Since the temperature of rainwater is generally close to the ambient temperature when it rains outdoors, the temperature of the spray water is generally also controlled to be close to the ambient temperature during the test. For example, when the simulated engineering ambient temperature is 5°C, the temperature of the spray water is also controlled at about 5°C, and the difference between the temperature of the spray water and the ambient temperature in the enclosed test space is required to be no more than 2°C.

[0033] To ensure that the simulated environmental parameters in the test meet the engineering meteorological environmental conditions, it is necessary to monitor the environmental temperature and environmental wind speed in the enclosed test space. The distribution of measuring instruments is as Figure 3 shown, where "T" represents a thermometer and "S" represents an anemometer. After the output data of each environmental parameter measuring instrument are collected by the data acquisition terminal in the enclosed test space, they are transmitted to the operator station located in the monitoring room through the network.

[0034] Embodiment 2:

[0035] As Figure 3 and Figure 4 shown, the present embodiment aims to provide a simulation test system for the thermal conductivity of each layer of thermal insulation material in a composite thermal insulation structure implemented under the conditions of Embodiment 1, including the following steps: S01. Through a dynamic simulation model, coordinate the air conditioning system 4, the spray water pipe 5, the ventilation system 6, and the heating system arranged in the pipe to be tested, so as to simulate the engineering meteorological environment in the enclosed test space, where: The heating system is heated to a steady-state heat transfer state during the detection period.

[0036] Specifically, the steps of simulating the engineering meteorological environment in the above embodiment include: S11. Regulate the temperature of the enclosed test space through the air-conditioning system 4. Its refrigeration load QL is calculated by the following formula: QL = QL1 + QL2 + QL3 + QL4, where QL1 is the heat transfer from the outdoor environment, QL2 is the heat generated by the air conditioner and ventilation fan, QL3 is the heat generated by the specimen, QL4 is the heat released by the cooling of the spray water, and a 3% - 5% margin is reserved for the refrigeration capacity of the air-conditioning system 4; S12. Simulate the ambient wind speed through the ventilation system 6. The calculation formula for the air volume Q is: Q=(S 通风罩 -S 试件 )×wt×3600, where Q represents the air volume, with the unit of m 3 / h, S 通风罩 represents the internal cross-sectional area of the ventilation hood 8, with the unit of m 2 , S 试件 represents the cross-sectional area of the pipe fitting to be tested, with the unit of m 2 , wt represents the test wind speed, with the unit of m / s, and the ventilation system 6 adopts the parallel ventilation combined with the impact angle correction method. The impact angle correction formula is: , where is the impact angle, which refers to the angle between the wind direction and the axis direction of the pipe fitting to be tested; S13. Simulate the rain shower state through the spray water pipe 5. The temperature difference between the spray water and the ambient temperature does not exceed 2°C, and the spray water flow rate is such that a complete water film is formed on the pipe fitting to be tested.

[0037] And the above-mentioned heating system includes a plurality of inner ring heating rods, middle ring steplessly adjustable heating rods and a plurality of outer ring heating rods arranged in a circular array on the metal disc bracket. Its control includes the following steps: S61. In the heating-up stage, use the outer ring heating rods with fixed power to quickly heat, and automatically cut off the power when the temperature of the heating rods exceeds the safety threshold; S62. In the steady state stage, use the inner ring heating rods and the middle ring steplessly adjustable heating rods, and adjust the power through the thyristor voltage regulation module to keep the inner wall temperature of the specimen stable within the range of the set value ±0.5°C; S63. Temperature measuring elements are arranged on the surface of the heating rods to monitor the temperature in real time and feedback control through the DCS system.

[0038] In the above embodiment, the electric heating rods are fixed by arranging a metal disc bracket inside the test pipe fitting, and the length of the bracket is adjusted according to the needs of the test pipe fitting. The outer straight rods have fixed power and are non-adjustable, mainly used for quickly heating in the heating-up stage. The inner straight rods and the middle ring rods are steplessly adjustable, mainly used for heating in the steady state heat transfer stage to keep the inner wall temperature of the specimen pipe stable.

[0039] Heating power supply and power control: The electric heating rod is powered by a three-phase AC power supply and its on / off is controlled by a switch cabinet in the monitoring room. The power supply of the heating power is configured with different power supply circuits in two states: the heating-up stage and the steady-state stage.

[0040] Heating-up stage: The rated voltage is directly applied to the heating rod, and the heating-up speed is adjusted by changing the number of working heating rods. The power automatic adjustment module is not connected.

[0041] Steady-state stage: In the steady-state stage, the heating power needs to be adjusted according to the temperature, and a thyristor module is used. The calculated power is calculated under the conditions of no wind and dryness. With the adjustment of the test conditions, the required power is adjusted and is between 0.8 and 1.5 times the calculated power. On the premise of sufficient adjustment ability, the configured power in the steady-state heat transfer stage is considered to be not less than 2 times the calculated power. A thyristor voltage regulation module is used to adjust the output voltage to achieve the power adjustment of the heating rod, and then the power supply power is adjusted to achieve stepless temperature regulation, so that the inner wall temperature of the pipe fitting is stabilized at the set value.

[0042] If the heating power of the heating rod is greater than the heat transfer speed during use, the temperature of the heating rod may rise to exceed the safe use temperature, resulting in damage to the heating rod. Therefore, temperature measuring elements are fixed on all heating rods to monitor the temperature of the heating rods. When the temperature of the heating rod exceeds the safe use temperature, the power supply of the heating rod is stopped.

[0043] Heating power measurement: During steady-state heat transfer, the electric heating power of the test pipe fitting and the heat dissipation power reach equilibrium, and the two values are equal. The technology of the present invention measures the power supply power and active electric energy of the electric heating rod through a high-precision electric meter, and the measurement accuracy is not less than 0.5 level. And in order to further improve the measurement accuracy, the technology of the present invention measures the instantaneous electric heating power and the cumulative electric heating quantity during steady-state heat transfer (the cumulative heating time is not less than 30 minutes), and calculates the average power of the electric heating by dividing the cumulative heating quantity by the cumulative heating time. When the deviation between the instantaneous electric heating power and the average power is less than 0.01 kW, the average value of the two is taken as the electric heating power during steady-state heat transfer, that is, the heat dissipation power of the test pipe fitting during steady-state heat transfer. For the line power loss of the power supply line, electric meter, and power adjustment module of the test device of the present invention, the total is calculated at 1.5%.

[0044] S02. Collect the electric heating power data, temperature data, and environmental parameter data of the calibration end 2 and the straight pipe specimen 1 under the steady-state heat transfer state to verify the validity of the data; Specifically, the verification of the validity of the above data includes: S21. Determine that the steady-state heat transfer condition is that the temperature deviation at the same measuring point does not exceed 2% of the reference value, and the change after an interval of 5 minutes does not exceed 0.1 °C and there are two-way fluctuations; S22. Record each set of data three times, with an interval of 30 minutes between each time. The data is considered valid when the deviation between the three data and the average value is less than 1%; S23. The principle of data elimination is: if a single measurement value deviates from the average value by more than ±5%, the test should be repeated.

[0045] Furthermore, the temperature measurement method of the straight pipe section specimen 1 and the calibration end head 2 in the embodiment includes: S100, 32 temperature measurement points were arranged at 150 mm from the end face and the middle section of the straight pipe specimen 1, covering the 0, 3, 6, and 9 o'clock directions; S101, calibrate the temperature measuring elements of terminal 2 by arranging them in a circle every 90° along the spiral line, and add a temperature measuring point at the end cap; S102. The temperature measuring element is fixed by threads on the stainless steel wall component or embedded in the insulation layer, and the outside is covered with an insulation layer with an emissivity of ≥0.8.

[0046] Secondly, environmental monitoring methods for closed test spaces include: S200, 8 WS series temperature and humidity sensors are arranged at the four corners of the space to monitor the temperature distribution at the top and middle heights; S201. Arrange six integrated intelligent wind speed measuring instruments at the front, middle, and rear sections of the ventilation hood 8 to monitor wind speed uniformity; S202. All data are transmitted to the operator station in the monitoring room in real time through the data acquisition terminal, and trend charts and alarm logs are generated.

[0047] To analyze the actual thermal conductivity of each insulation layer, the temperature between each insulation layer must also be measured for the straight pipe section. Because heat dissipation increases near the end faces due to the influence of the interface, while the center of the pipe provides the best insulation, the temperature distribution at two sections, 150 mm from the end face and the center of the pipe, is compared to analyze the influence of the interfaces at both ends. The average temperature of each insulation layer is then used to calculate the thermal conductivity of the material.

[0048] Temperature measuring elements are set on the inner wall of the steel pipe and the inner and outer surfaces of each layer of insulation material along the radial direction of the two sections, covering the four positions of 0 o'clock, 3 o'clock, 6 o'clock and 9 o'clock, totaling 2×4×4=32. The specific positions are as follows Figure 9 As shown, for clarity of the diagram, only the temperature measuring element outside the protective layer is shown in the figure.

[0049] It should be noted that, in order to ensure the test accuracy, the above embodiment uses a high-precision platinum thermal resistor as the temperature measuring element.

[0050] The thermoresistance temperature measurement positions include three cases: the inner wall of the steel pipe, between the insulation layers, and the outer surface of the insulation layer. Among them, the inner wall of the steel pipe is basically consistent with the temperature of the hot air inside the pipe, and the influence of heat conduction and convective heat transfer is small. Only errors may be caused by radiation; the thermoresistance and wires between the insulation layers are completely wrapped by the insulation materials, so the installation error is small; the outer surface of the insulation layer is directly affected by the external environment, and due to the low ambient temperature, heat conduction, convection, and radiation heat transfer may all affect the temperature measurement element, which should be focused on.

[0051] To increase the contact area with the specimen, a stainless-steel wall component is set at the end, with dimensions of 20mm×40mm. It can be directly welded to the surface of the metal to be measured or fixed with self-tapping screws. When installing, the thermoresistance probe is inserted into the internal threaded hole of the wall component and fixed by threaded connection, which can effectively increase the heat conduction contact area.

[0052] The thermoresistance between the insulation layers is pre-buried by the manufacturer when making the insulation specimen, and the temperature measurement element is fixed to the adjacent inner insulation layer by means of wire bundling and winding.

[0053] Since the temperature measurement element at the outer surface of the insulation layer is directly affected by the external environment and the ambient temperature is low, to reduce heat transfer losses such as heat conduction, convection, and radiation, the wire at the thermoresistance installation location is ensured to have a length of at least 10mm in contact with the surface. After the thermoresistance is installed, an adiabatic material layer needs to be covered outside. In order not to reduce the internal radiation heat transfer, the emissivity of the inner surface of the covered adiabatic layer is greater than 0.8. The other side of the thermoresistance is connected to the terminal junction box on both sides of the specimen through the temperature measurement wire, and is connected to the measurement control system through a multi-core cable from the terminal junction box. The insulation layer and other environmental information measuring points are connected to the measurement control system through their respective cables.

[0054] S03. Correct the total heat dissipation heat flow of the pipe fitting to be measured based on the heat dissipation heat flow of the calibration end 2, and calculate the linear heat flux density of the pipe fitting to be measured; Specifically, the calculation formula for the linear heat flux density of the pipe fitting to be measured in the above embodiment is: q l直管 =(Q t直管 -Q 端头) ×(1 - power line loss percentage) / L 直管 , where Q 端头 is the heat dissipation power of the calibration end 2 alone, Q t直管 is the heat dissipation power of the straight pipe specimen 1 alone, and L 直管 is the insulation measurement length of the straight pipe specimen 1; The heat dissipation heat flow Q 端头 of the calibration end 2 is determined through the following steps: S31. The calibration end 2 consists of two hollow cylindrical end caps and a calibration steel pipe. A 50-mm thermal insulation gap is reserved at the joint where the end cap and the steel pipe are joined together, and the joint is filled with heat-insulating material. S32. Calculate the instantaneous average value P of the electric heating power of the calibration end 2 under steady-state heat transfer conditions. 1端头 ; S33. According to the total power consumption Q of the calibration end 2 during the test I端头 and the test duration t 端头 , calculate the average input power P 2端头 = Q I端头 / t 端头 ; S34. Take the arithmetic mean of P 1端头 and P 2端头 as the heat flux value Q of the outer surface heat dissipation of the calibration end 2 under the test conditions 端头 = (P 1端头 + P 2端头 ) / 2; The heat flux Q of the straight pipe specimen 1 is determined through the following steps: I直管 S35. Calculate the arithmetic mean P of the recorded values of the input power of the electric heater inside the specimen under steady-state heat transfer conditions of the test conditions. 1直管 ; S36. Through the power consumption Q during the test of local pipe fittings under steady-state heat transfer conditions I直管 and the test duration t 直管 , calculate its average heating power P 2直管 = Q I直管 / t 直管 ; S37. Take the arithmetic mean of P 1直管 and P 2直管 as the total outer surface heat flux Q of the straight pipe section specimen 1 t直管 = (P 1直管 + P 2直管 ) / 2.

[0055] As described above, to ensure that the cooling capacity of the air-conditioning system 4 meets the requirements, it is necessary to calculate the cooling load in the test enclosed space, including four parts: the heat transfer from the outdoor environment, the heat generated by the air-conditioning and ventilation system 6, the heat generated by the test piece, and the heat released by the spray water for cooling: 1) The air-conditioning system 4 ① The heat transfer Q from the outdoor environment L1 , according to the surface area A of the maintenance structure of the test room, the heat transfer coefficient K, the highest outdoor temperature T out , and the lowest indoor temperature T in , calculate the heat transfer Q from the outdoor environment through the maintenance structure under the most unfavorable conditions L1 , that is, Q L1=K×A×(T out -T in ).

[0056] ② The heat production Q of the air conditioner and the ventilation fan L2 = The power of the indoor unit of the air conditioning system 4 + the power of the fan of the ventilation system 6.

[0057] ③ The heat production Q of the test piece L3 : It is determined according to the theoretical heat dissipation on the surface of the test piece during steady-state heat transfer. Calculate the heat dissipation of the straight pipe test piece 1 (including the calibration end 2), calculate according to the straight pipe test piece 1 with the largest heat dissipation, and additionally consider a 100% margin coefficient when calculating the heat dissipation.

[0058] ④ The heat Q released by the spray water for cooling L4 : According to the spray water flow rate Mp l , unit kg / s, the maximum temperature drop of the spray water t pl , unit in °C, and t pl =t pl -t amin , where, t pl is the initial temperature of the spray water in the pipe, unit in °C, which can be approximately considered equal to the outdoor ambient temperature, t amin is the lowest indoor ambient temperature, that is, the lowest ambient temperature simulated by the test, unit in °C, the specific heat of water is taken as 4.2 kJ / kg °C, the calculation formula for the heat dissipation of the spray water is: Q L4 =4.2×M pl × t pl .

[0059] In summary, the total cooling load of the closed test space is Q L =Q L1 +Q L2 +Q L3 +Q L4 , the refrigeration capacity of the air conditioning system 4 should at least meet this refrigeration requirement, and a proper margin of 3 - 5% should be reserved.

[0060] 2) Ventilation system 6 The ventilation system 6 is used to simulate the environmental wind speed at the project location. Since the space required for vertical ventilation is too large, it is difficult to ensure uniform air flow and the cost is relatively high. Therefore, from the perspective of ensuring uniform air flow and considering the cost of the test device, the ventilation system 6 adopts the method of parallel ventilation combined with impact angle correction, mainly including the ventilation hood 8 and the fan, and its layout is as attached Figure 1As shown in the figure. A ventilation hood 8 is arranged outside the test piece. On the one hand, it can reduce the ventilation area, which is beneficial to controlling the wind speed around the test piece. On the other hand, it can prevent the interference of external airflows (such as the blowing of the indoor unit of an air conditioner). The material of the ventilation hood 8 is selected as metal steel plate, and pulleys are provided at the bottom for easy movement. The layout boundary of the test device is marked on the ground inside the ventilation hood 8 to ensure that the test piece is located at a place with relatively uniform temperature and directly facing the outlet of the fan. The net distance between both sides of the ventilation hood 8 and the wall of the enclosed test space is not less than 1.5 m. A fan is arranged at the end of the ventilation hood 8 on the side without a door wall. The other end of the ventilation hood 8 is open for the test piece to enter and exit. After the air flows through the space between the ventilation hood 8 and the test piece from the outlet of the fan, it returns to the inlet of the fan outside the ventilation hood 8 to form an air circulation. When ventilating, the air flow is as shown in the appendix Figure 2 As shown.

[0061] The fan is mainly selected according to the required air volume for testing. A multi-speed constant-speed axial flow fan can be selected, or a centrifugal fan can also be selected. The calculation method for the selected air volume is: Q = (S 通风罩 -S 试件 ) × wt × 3600, where Q represents the air volume, with the unit of m 3 / h, S 通风罩 represents the internal cross-sectional area of the ventilation hood 8, with the unit of m 2 , S 试件 represents the cross-sectional area of the test piece, with the unit of m 2 , and wt represents the test wind speed, with the unit of m / s.

[0062] In actual engineering, different impact angles of the wind direction on the pipeline will affect the convective heat transfer on the outer surface. According to actual needs, the impact angle of forced convection heat transfer of a single tube in cross-flow can be corrected. The correction formula is: , where, is the impact angle, which refers to the angle between the wind direction and the axis direction of the pipeline.

[0063] 3) Spraying water pipeline 5 In order to simulate the working condition of the pipeline being rained on, a spraying water pipeline 5 is set in the test room. Specifically, a spray pipe is installed at the top inside the ventilation hood 8, directly above the axis of the test piece, as shown in the appendix Figure 3As shown in the figure. The spray pipe is made of perforated galvanized steel pipe with DN15, the hole diameter is 5mm, the hole spacing is 100mm, and the holes face down. The spray pipe is supplied with water by a DN25 tap water pipe (galvanized steel pipe) in front, and a regulating valve is installed between the spray pipe and the water supply pipe. The ground of the closed test space has a certain slope for easy drainage. A drainage ditch is set on the east side of the enclosure structure. The drainage ditch is buried with a DN40 sleeve through the enclosure structure section for external drainage. When not draining, the sleeve is blocked with heat insulation material. Since the convective heat transfer between rainwater and the pipe surface is generally stronger than that of air under the same conditions, rain will enhance the surface heat dissipation. However, when the rainfall is large enough to completely cover the pipe surface with a water film, the change in rainfall only affects the thickness of the water film and has little effect on convective heat transfer. Therefore, the design of the rain shower system only needs to ensure that the pipe surface is completely covered with a water film, regardless of the size of the water flow. On-site, the water flow is adjusted by adjusting the valve opening to cover the surface of the test piece. Since the temperature of rainwater is generally close to the ambient temperature when it rains outdoors, the temperature of the spray water is generally also controlled to be close to the ambient temperature during the test. For example, when the simulated engineering ambient temperature is 5°C, the spray water temperature is also controlled at about 5°C, and the difference between the spray water temperature and the ambient temperature in the closed test space is required to be no more than 2°C.

[0064] S04. According to the linear heat flux density and the inner and outer side temperatures of each layer of thermal insulation material collected, calculate the actual thermal conductivity of the thermal insulation material layer by layer, and generate an excel report.

[0065] The specific thermal conductivity of each layer of thermal insulation material The calculation formula is: , In the formula: is the thermal conductivity of the i-th layer of composite thermal insulation material, with the unit of W / (m K); q l is the linear heat flux density of the insulated pipe test piece, that is, the heat flow per unit length of the insulated pipe test piece, with the unit of W / m; d i is the inner diameter of the i-th layer of thermal insulation material, d i+1 is the outer diameter of the i-th layer of thermal insulation material, and at the same time, it is also the inner diameter of the (i + 1)-th layer of thermal insulation material, and the units are all m; t1 is the temperature of the outer wall surface of the steel pipe, that is, the inner side temperature of the first layer of thermal insulation layer from the inside to the outside. t2 is the outer side temperature of the first layer of thermal insulation layer from the inside to the outside, and so on. t i is the inner side temperature of the i-th layer of thermal insulation material, t i+1 is the outer side temperature of the i-th layer of thermal insulation material, and at the same time, it is also the inner side temperature of the (i + 1)-th layer of thermal insulation layer, and the units are all °C.

[0066] In the second embodiment described above, the thermal insulation pipeline specimen is tested under simulated engineering meteorological environmental conditions. The radial heat flux density of the thermal insulation pipeline is calculated based on the data collected when the specimen is in a steady-state heat transfer condition, and then the actual thermal conductivity coefficients of each layer of thermal insulation material under the test working conditions and in the overall thermal insulation structure are calculated. Thus, it is verified whether the thermal conductivity coefficients of each layer of thermal insulation material in the pipeline thermal insulation structure meet the relevant standard specifications and specific engineering requirements, and a quantitative analysis is carried out on the combination and layout of each layer of thermal insulation material of the pipeline and the rationality of the thickness setting of each layer of thermal insulation material, providing reliable data support for the further optimization and improvement of the pipeline thermal insulation structure.

[0067] In summary, according to the thermal insulation structure form and installation combination conditions of the actual project, the thermal conductivity performance of each layer of thermal insulation material of the pipeline is tested under various possible working conditions (mainly referring to four parameters: the temperature of the inner wall of the pipe, the ambient temperature, the ambient wind speed, and the rain condition). The test results are close to the actual project conditions and are more instructive and reference valuable for engineering construction. Moreover, the test is carried out in a closed space, without being interfered by the external meteorological environmental conditions, improving the convenience and stability of the test. At the same time, it is also conducive to ensuring the accuracy of the test results. The specimen uses the heating and temperature-rising method of an internal electric heater, without relying on the external medium to enter the pipe for heating and temperature-rising, and is not interfered by the external medium parameters and the conveying working conditions, with strong autonomy and independence. The electric heating system is equipped with a monitoring system for the wall temperature and the self-temperature of the heating rod, monitoring and providing interlock protection for the self-temperature of the heating rod. At the same time, a smart control system for the heating power is set up, adopting different power control circuits and control methods in the temperature-rising stage and the steady-state heat transfer stage to realize the intelligent adjustment of the power of different heating rods serving as heating elements, ensuring the safety, stability, and high efficiency of the specimen heating and temperature-rising process. The method of combining parallel ventilation of the specimen with impact angle correction is used to simulate the ambient wind speed, effectively reducing the test cost while ensuring the simulation effect and improving the economy of the test work. The test and data recording work are carried out when the specimen is in a steady-state heat transfer condition, and at the same time, the instantaneous power, cumulative power consumption, and steady-state heating time of the electric heating rod under the steady-state heat transfer condition are measured. The arithmetic mean of the instantaneous power recording mean value and the average heating power is used as the heating power calculation value, reducing the test error rate and improving the data reliability. Compared with the single-layer plane test method in the room temperature environment, the technology of the present invention obtains the heat flow value of the heat loss due to heat dissipation from the straight pipe section and the temperature values inside and outside each layer of the thermal insulation material through the test, and calculates the actual thermal conductivity coefficients of each layer of the thermal insulation material under the test working conditions and of the overall thermal insulation structure through an algorithm. The obtained results are more in line with the actual situation and are also more instructive and reference valuable for the engineering application of the thermal insulation material. Compared with the traditional method of separately testing the thermal conductivity performance of each type of thermal insulation material, the technology of the present invention simultaneously tests the thermal conductivity performance of multiple different thermal insulation materials in the same pipeline thermal insulation structure, with high test efficiency, which is conducive to reducing the test cost and improving the economy of the test work.

[0068] Example 3:

[0069] Based on Example 2, this example aims to provide a simulation test system for the thermal conductivity coefficients of each layer of thermal insulation materials in a detailed composite thermal insulation structure for deploying thermal insulation pipes in coastal areas or coastal cities. It includes: Air conditioning system 4 Adopt a two-stage compression refrigeration unit and integrate a rotary wheel dehumidification module to ensure that the temperature (-10°C to 50°C) and relative humidity (30% to 95%) in the enclosed test space are independently adjustable. The refrigerant pipeline and evaporator are made of 316L stainless steel and are coated with a salt spray resistant coating on the surface to prevent corrosion. And a salt spray generator is added to the air supply pipeline of the air conditioner to simulate a salt spray environment by atomizing seawater, with the salt spray concentration adjustable (0.5 to 5 mg / m³). At the same time, a high-efficiency air filter (HEPA) and an activated carbon adsorption layer are configured to quickly remove salt spray residues after testing. It should be noted that the slope of the drainage pipeline is increased to 5%, the inner wall is coated with a hydrophobic material, and a regular pulse flushing function is set to prevent salt crystallization from blocking.

[0070] Ventilation system 6 Adopt a parallel layout of a centrifugal fan and an axial flow fan, and the maximum wind speed is increased to 15 m / s (simulating typhoon conditions), supporting stepless adjustment of the wind speed. The fan impeller and housing are made of titanium alloy, which is resistant to salt spray corrosion. And a rotatable deflector is added inside the ventilation hood 8, and the deflector angle (0° to 180°) is controlled by a servo motor to simulate multi-directional strong winds by the sea. The impact angle correction formula is extended to: , and a conductivity sensor is installed on the inner wall of the ventilation hood 8 to monitor the salt spray deposition amount in real time, and an automatic cleaning program is triggered when the limit is exceeded.

[0071] Spray water pipeline 5 The spray water uses artificial seawater (salinity 3.5%), and heating / cooling coils are installed in the storage tank, with the water temperature control range of 5°C to 35°C (the temperature difference from the environment ≤ 2°C). The spray pipe is upgraded to a DN20 Hastelloy perforated pipe with a pore diameter of 3 mm and a pore spacing of 50 mm, and the spray coverage rate is increased to 98%.

[0072] The spray frequency and water volume are controlled by PLC programming to simulate the tidal cycle (such as 6 hours / cycle), and a three-stage mode of "flood tide - peak - ebb tide" is set. The spray intensities are 5 L / (m² min), 10 L / (m² min), 3 L / (m² min) respectively to imitate the change of air humidity during flood tide - peak - ebb tide.

[0073] The above-mentioned integration of air conditioning, ventilation, and sprinkler modules through the DCS system supports the simulation of multi-parameter coupling conditions of "salt spray - humidity - wind speed - water temperature". Moreover, through precise environmental simulation, corrosion-resistant hardware upgrade, and intelligent control, it can comprehensively reproduce the complex coastal climate conditions, providing high-reliability support for the weather resistance test of insulation materials for coastal engineering pipelines.

[0074] Only some exemplary embodiments of the present invention have been described by way of illustration. Without doubt, for those of ordinary skill in the art, various different ways can be used to modify the described embodiments without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A test system for the thermal conductivity of pipeline insulation materials under engineering meteorological environmental conditions, characterized in that, include: A straight pipe test piece (1) with calibration end pieces (2) fixedly mounted at both ends, the outer wall of which is wrapped with a thermal insulation covering material to form a pipe to be tested; A ventilation hood (8) within the sealed space; An air conditioning system (4), wherein the air ducts at the output end are all located in the sealed space, and the air outlet faces the ventilation hood (8); The spray water pipe (5) and the ventilation system (6) have output ends arranged in the ventilation hood (8) and located directly above the pipe to be tested that is centrally arranged in the ventilation hood (8); The simulation test system comprises the following steps: S01. Coordinating the air conditioning system (4), the spray water pipe (5), the ventilation system (6), and the heating system arranged in the pipe to be tested by a dynamic simulation model to simulate the engineering meteorological environment in a closed test space, wherein: The heating system is heated to a steady-state heat transfer state during the testing period; S02, collecting electric heating power data, temperature data and environmental parameter data of the calibration end head (2) and the straight tube test piece (1) under the steady-state heat transfer state to verify the validity of the data; S03, correcting the total heat dissipation heat flow of the pipe to be tested based on the heat dissipation heat flow of the calibration end head (2), and calculating the linear heat flux density of the pipe to be tested; S04. Calculate the actual thermal conductivity of the insulation material layer by layer based on the linear heat flux and the collected internal and external temperatures of each layer of insulation material, and generate an Excel report.

2. The thermal conductivity test system for pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, characterized in that, The simulated engineering meteorological environment in S01 includes: S11. The temperature of the closed test space is regulated by the air conditioning system (4). The cooling load QL is calculated by the following formula: QL=QL1+QL2+QL3+QL4, wherein QL1 is the heat transfer from the outdoor environment, QL2 is the heat generated by the air conditioner and ventilation fan, QL3 is the heat generated by the test piece, and QL4 is the heat released by the spray water cooling. The cooling capacity of the air conditioning system (4) is reserved with a margin of 3% to 5%; S12. Simulate the ambient wind speed through the ventilation system (6). The calculation formula for the air volume Q is: Q = (S 通风罩 - S 试件 ) × wt × 3600, where Q represents the air volume, with the unit of m 3 / h, S 通风罩 represents the internal cross-sectional area of the ventilation hood (8), with the unit of m 2 , S 试件 represents the cross-sectional area of the pipe fitting to be measured, with the unit of m 2 , wt represents the test wind speed, with the unit of m / s, and the ventilation system (6) adopts the parallel ventilation combined with the impact angle correction method. The impact angle correction formula is: , where is the impact angle, which refers to the included angle between the wind direction and the axis direction of the pipe fitting to be measured; S13, simulating a rainy state through the spray water pipe (5), the difference between the spray water temperature and the ambient temperature does not exceed 2°C, and the spray water flow rate is such that a water film is completely formed on the pipe to be tested.

3. The thermal conductivity test system for pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, wherein, The verification of the validity of the data in step S02 includes: S21. The steady-state heat transfer condition is that the temperature deviation at the same measuring point does not exceed 2% of the reference value, and the change after a 5-minute interval does not exceed 0.1°C and there is bidirectional fluctuation; S22. Record each set of data three times, with an interval of 30 minutes between each time. The data is considered valid when the deviation between the three data and the average value is less than 1%; S23. The principle of data elimination is: if a single measurement value deviates from the average value by more than ±5%, the test should be repeated.

4. A test system for the thermal conductivity of pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, characterized in that, In the step S03, the calculation formula for the linear heat flux density of the pipe fitting to be measured is: q l直管 =(Q t直管 -Q 端头) ×(1 - percentage of power line loss) / L 直管 , where Q 端头 is the heat dissipation power of the calibration end (2) alone, Q t直管 is the heat dissipation power of the straight pipe specimen (1) alone, and L 直管 is the heat preservation measurement length of the straight pipe specimen (1); The heat dissipation heat flux Q of the calibration end (2) 端头 is determined by the following steps: S31, the calibration end (2) consists of two hollow cylindrical end caps and a calibration steel pipe, a 50mm insulation gap is reserved at the junction of the end cap and the steel pipe, and the gap is filled with insulation material; S32. Calculate the instantaneous average value P of the electric heating power of the calibration end (2) under steady-state heat transfer conditions 1端头 ; S33. Calculate the average input power P according to the total power consumption Q during the test of the calibration end (2) I端头 and the test duration t 端头 , where 2端头 P = Q I端头 / t 端头 ; S34. Take the arithmetic mean of P 1端头 and P 2端头 as the heat flux value Q of the outer surface heat dissipation of the calibration end (2) under the test condition 端头 =(P 1端头 +P 2端头 ) / 2; The heat dissipation heat flux Q of the straight pipe specimen (1) I直管 is determined by the following steps: S35. Calculate the arithmetic mean value P of the recorded input power of the electric heater inside the specimen under the steady-state heat transfer condition of the test working condition 1直管 ; S36. Calculate its average heating power P I直管 through the power consumption Q 直管 during the local pipe fitting test under steady-state heat transfer conditions 2直管 and the test duration t I直管 as P = Q 直管 / t; S37. Take the arithmetic mean of P 1直管 and P 2直管 as the total external surface heat flux Q of the straight pipe section specimen (1) t直管 =(P 1直管 +P 2直管 ) / 2.

5. The thermal conductivity test system for pipeline insulation materials under engineering meteorological environmental conditions according to claim 1, characterized in that, The thermal conductivity of each layer of thermal insulation material described in S04 The calculation formula is as follows: ， Wherein: is the thermal conductivity of the i-th layer of thermal insulation material for composite thermal insulation, with the unit of W / (m K); q l is the linear heat flux density of the insulated pipe specimen, i.e., the heat flux per unit length of the insulated pipe specimen, with the unit of W / m; d i is the inner diameter of the i-th layer of thermal insulation material, d i+1 is the outer diameter of the i-th layer of thermal insulation material and also the inner diameter of the (i + 1)-th layer of thermal insulation material, with the unit of m for both. t1 is the temperature of the outer wall surface of the steel pipe, that is, the inner temperature of the first layer of thermal insulation from the inside to the outside. t2 is the outer temperature of the first layer of thermal insulation from the inside to the outside, and so on. t i is the inner temperature of the i-th layer of thermal insulation material, and t i+1 is the outer temperature of the i-th layer of thermal insulation material, and at the same time, it is also the inner temperature of the (i + 1)-th layer of thermal insulation layer. The unit of all of them is °C.

6. The thermal conductivity testing system for pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, characterized in that, The heating system in S01 includes a plurality of inner ring heating rods, a middle ring steplessly adjustable heating rod, and a plurality of outer ring heating rods distributed in a circular array, which are mounted on a metal disc support. The control thereof includes the following steps: S61. During the heating-up stage, the outer heating rods with fixed power are used for rapid heating, and the power supply will be automatically cut off when the temperature of the heating rods exceeds the safety threshold; S62. During the steady-state stage, the inner heating rods and the middle-ring continuously adjustable heating rods are used. The power is adjusted through the thyristor voltage regulation module to keep the temperature of the inner wall of the specimen stable within the range of the set value ±0.5°C; S63. Temperature measuring elements are arranged on the surface of the heating rods to monitor the temperature in real time and feedback control through the DCS system.

7. A test system for the thermal conductivity of pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, characterized in that, The temperature measurement method for the straight pipe section specimen (1) and the calibration end (2) includes: S100. 32 temperature measurement points are arranged at 150 mm from the end face and the middle section of the straight pipe section specimen (1), covering the 0, 3, 6, and 9 o'clock directions; S101. The temperature measuring elements of the calibration end (2) are arranged in a spiral at every 90°, and additional temperature measurement points are added at the end cap sealing head; S102. The temperature measuring elements are fixed by threads through the stainless steel wall components or embedded inside the insulation layer, and the outside is covered with an adiabatic layer with an emissivity ≥0.

8.

8. The thermal conductivity testing system for pipeline thermal insulation materials under engineering meteorological environmental conditions according to claim 1, wherein The environmental monitoring method for the enclosed test space includes: S200. 8 WS series temperature and humidity sensors are arranged at the four corners of the space to monitor the temperature distribution at the top and middle heights; S201. 6 integrated intelligent anemometers are arranged at the front, middle, and rear sections of the ventilation hood (8) to monitor the wind speed uniformity; S202. All data are transmitted to the operator station in the monitoring room in real time through the data acquisition terminal, and trend charts and alarm logs are generated.

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