A thermal conductivity testing system for pipeline insulation materials under engineering meteorological conditions

Abstract

The present invention relates to the field of thermal insulation and energy-saving technology, and specifically discloses a thermal conductivity test system for pipeline insulation materials under engineering meteorological environment conditions, comprising: a straight pipe test piece with calibration ends fixedly installed at both ends, the outer wall of which is wrapped with thermal insulation covering material to form a pipe to be tested; a ventilation hood in a sealed space; an air conditioning system, the air ducts at its output end are all located in the sealed space, and the air outlet is facing the ventilation hood. This invention dynamically corrects the thermal conductivity of the material by simulating multi-parameter coupling conditions such as the temperature gradient of the medium in the pipe, the external temperature and humidity / wind speed cycle, and mechanical vibration, verifies whether the thermal conductivity of each layer of material meets the standard specifications, and quantitatively evaluates the rationality of the composite structure based on the thermal resistance network model, providing data support for optimizing the combination of insulation materials and thickness design, and solving the design deviation problem caused by the inability of traditional methods to reflect the actual working conditions of the project.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline thermal insulation and energy saving, and in particular to a thermal conductivity testing system for pipeline thermal insulation materials under engineering meteorological environment conditions. Background Art

[0002] Existing testing methods for the insulation of high-temperature media pipelines have significant limitations. Pipeline insulation not only needs to reduce heat loss and ensure safe transportation, but also address issues such as medium temperature drop, energy waste, and environmental safety. Current mainstream standards (such as GB / T10294-2008, "Thermal Insulation Materials - Determination of Steady-State Thermal Resistance and Related Properties - Guarded Hot Plate Method" and GB / T10295-2008, "Thermal Insulation Materials - Determination of Steady-State Thermal Resistance and Related Properties - Heat Flow Meter Method") utilize single-layer, flat material testing at room temperature. This method fails to reflect the actual thermal conductivity of multi-layer composite structures in real-world projects under the coupled effects of dynamic meteorological conditions such as temperature, humidity, and wind speed, and medium parameters. While patents such as Publication No. CN113804722A, which discloses a device and method for testing the performance of pipeline insulation materials, attempt improvements, these testing devices rely on operating pipelines, are limited by the on-site environment and medium conditions, and lack the ability to reliably simulate specific project meteorological conditions. Furthermore, they remain limited to evaluating a single material.

[0003] In actual engineering, the performance of thermal insulation structure is affected by three core factors:

[0004] One is the dynamic changes of the temperature and flow rate of the medium in the pipe;

[0005] The second is the periodic fluctuation of the external meteorological environment (such as the temperature difference between day and night, precipitation, and wind speed);

[0006] The third is the combination of multi-layer insulation materials and the interface thermal resistance effect.

[0007] In particular, the application of new high-performance materials (such as aerogels and nanoporous materials) requires achieving synergistic performance through structural optimization rather than simply replacing traditional materials. However, current methods fail to establish a quantitative model linking material thermal conductivity with these multiple factors, resulting in conservative or insufficient insulation thickness designs, leading to economic waste and safety risks. Summary of the Invention

[0008] The purpose of the present invention is to provide a thermal conductivity testing system for pipeline insulation materials under engineering meteorological environment conditions to solve the above problems.

[0009] In order to achieve the above object, the present invention provides the following technical solution: a system for testing the thermal conductivity of pipeline insulation materials under engineering meteorological conditions, comprising:

[0010] A straight pipe test piece with calibration terminals fixedly mounted on both ends and its outer wall wrapped with thermal insulation covering material to form the pipe to be tested;

[0011] Ventilation hoods in enclosed spaces;

[0012] The air ducts at the output end of the air conditioning system are all located in the sealed space, and the air outlets face the ventilation hood;

[0013] The output end of the spray water pipe and ventilation system is arranged in the ventilation hood and is located directly above the pipe to be tested that is centrally arranged in the ventilation hood;

[0014] The simulation test system (thermal conductivity of each layer of insulation material in a composite insulation structure) includes the following steps:

[0015] S01. Coordinate the air conditioning system, the sprinkler water pipe, the ventilation system, and the heating system disposed within the pipe to be tested using a dynamic simulation model to simulate an engineering meteorological environment within a closed test space, wherein:

[0016] The heating system is heated to a steady-state heat transfer state during the testing period;

[0017] S02, collecting electric heating power data, temperature data, and environmental parameter data of the calibration end and the straight tube specimen under the steady-state heat transfer state to verify the validity of the data;

[0018] S03, correcting the total heat dissipation flow of the pipe to be tested based on the heat dissipation flow of the calibration end, and calculating the linear heat flux density of the pipe to be tested;

[0019] 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.

[0020] Preferably, the simulated engineering meteorological environment in S01 includes:

[0021] S11. The temperature of the enclosed test space is regulated by the air conditioning system. The cooling load QL is calculated using 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 conditioning and ventilation fans, QL3 is the heat generated by the test piece, and QL4 is the heat released by the spray water cooling. A 3% to 5% margin is reserved for the cooling capacity of the air conditioning system.

[0022] S12, the ventilation system simulates the ambient wind speed, and the air volume Q is calculated as follows: Q=(S 通风罩 -S 试件 )×wt×3600, where Q represents the air volume in m 3 / h,S通风罩 Indicates the internal cross-sectional area of ​​the ventilation hood, in m 2 , S 试件 Indicates the cross-sectional area of ​​the pipe to be tested, in m 2 , wt represents the test wind speed in m / s, and the ventilation system adopts parallel ventilation combined with impact angle correction. The impact angle correction formula is: ,in, The impact angle refers to the angle between the wind direction and the axis of the pipe to be tested;

[0023] S13, simulating a rainy state through the spray water pipe, 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.

[0024] Preferably, the verification of the validity of the data in step S02 includes:

[0025] 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;

[0026] 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%;

[0027] 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.

[0028] Preferably, the calculation formula of the heat flux density of the pipe to be tested in step S03 is: 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 flux of the calibration end, Q t直管 is the heat dissipation flux of the straight tube specimen, L 直管 It is the insulation measurement length of the straight pipe specimen;

[0029] The heat dissipation flux Q of the calibration terminal 端头 Determine this by following these steps:

[0030] S31. The calibration end is composed 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;

[0031] S32. Calculate the instantaneous average value P of the electric heating power of the calibration end under steady-state heat transfer conditions 1端头 ;

[0032] S33, according to the total power consumption Q during the test of the calibration terminal I端头 And test duration t 端头 , calculate the average input power P 2端头 =Q I端头 / t 端头 ;

[0033] S34, P 1端头 With P 2端头 The arithmetic mean value is taken as the heat flux value Q of the outer surface heat dissipation of the calibration end under the test condition 端头 =(P 1端头 +P 2端头 ) / 2;

[0034] The heat dissipation flux Qt of the straight tube specimen 直管 Determine this by following these steps:

[0035] S35. Calculate the arithmetic mean P of the recorded input power of the electric heater inside the straight tube specimen under the steady-state heat transfer condition of the test condition. 1直管 ;

[0036] S36, power consumption Q during the straight tube test under steady-state heat transfer conditions I直管 and test duration t 直管 , calculate the average heating power P 2直管 =Q I直管 / t 直管 ;

[0037] S37, P 1直管 With P 2直管 The arithmetic mean of the total external surface heat flux Q of the straight tube specimen is t直管 =(P 1直管 +P 2直管 ) / 2.

[0038] As an example, the thermal conductivity coefficient of each layer of insulation material in S04 is λ i The calculation formula is:

[0039] ,

[0040] Where: i is the thermal conductivity of the insulation material of the i-th layer of composite insulation, in W / (m·K);

[0041] q l is the linear heat flux density of the pipe to be tested, that is, the heat flow rate per unit length of the pipe to be tested, in W / m;

[0042] d i is the inner diameter of the i-th layer of insulation material, d i+1is the outer diameter of the insulation material of the i-th layer, and is also the inner diameter of the insulation material of the i+1-th layer, both in meters;

[0043] t1 is the outer wall temperature of the straight tube specimen, that is, the inner temperature of the first layer of insulation material from the inside to the outside, t2 is the outer temperature of the first layer of insulation material from the inside to the outside, and so on. i is the temperature inside the i-th layer of insulation material, t i+1 is the outside temperature of the i-th layer of insulation material, and is also the inside temperature of the i+1-th layer of insulation material, both in °C.

[0044] Preferably, the heating system in S01 comprises 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 comprises the following steps:

[0045] S61, during the heating stage, the outer ring heating rod is used to heat rapidly with a fixed power heating rod, and the power is automatically cut off when the temperature of the heating rod exceeds a safety threshold;

[0046] S62, in the steady-state stage, the inner ring heating rod and the middle ring steplessly adjustable heating rod are used to adjust the power through the thyristor voltage regulator module so that the inner wall temperature of the specimen is stabilized within the range of ±0.5°C of the set value;

[0047] S63. A temperature measuring element is set on the surface of the heating rod to monitor the temperature in real time and provide feedback control through the DCS system.

[0048] Preferably, the temperature measurement method of the straight tube specimen and the calibration end head includes:

[0049] S100, arranging 32 temperature measuring points at 150 mm from the end face and the middle section of the straight tube specimen, covering the 0, 3, 6, and 9 o'clock directions;

[0050] S101, the temperature measuring elements of the calibration end are arranged along the spiral line every 90 degrees, and a temperature measuring point is added at the end cap;

[0051] S102. The temperature measuring element is fixed by threads on a stainless steel wall component or embedded in the interior of the thermal insulation material, and is covered on the outside with an insulation layer having an emissivity ≥ 0.8.

[0052] Preferably, the method for environmental monitoring of the closed test space includes:

[0053] 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;

[0054] S201, arranging six integrated intelligent wind speed measuring instruments at the front, middle, and rear sections of the ventilation hood to monitor wind speed uniformity;

[0055] 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.

[0056] In the above technical solution, the present invention provides a system for testing the thermal conductivity of pipeline insulation materials under engineering meteorological conditions, which has the following beneficial effects:

[0057] 1. According to the insulation structure and installation combination conditions of the actual project, the thermal conductivity of each layer of insulation material of the pipeline is tested under a variety of possible working conditions (mainly referring to the four parameters of pipe inner wall temperature, ambient temperature, ambient wind speed, and rain conditions). The test results are close to the actual project conditions and have more guiding significance and reference value for engineering construction.

[0058] 2. The test is carried out in a closed space and is not affected by external meteorological conditions, which improves the convenience and stability of the test and is also conducive to ensuring the accuracy of the test results.

[0059] 3. The test piece adopts the heating and temperature raising method of internal electric heater, which does not rely on external medium to enter the pipe for heating and temperature raising. It is not affected by external medium parameters and transportation working conditions, and has strong autonomy and independence.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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

[0065] 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.

[0066] 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;

[0067] Figure 2 A schematic diagram of the arrangement of the spray water pipeline provided in an embodiment of the present invention;

[0068] Figure 3 An air flow map of a ventilation system provided by an embodiment of the present invention;

[0069] Figure 4 A distribution diagram of ambient temperature and wind speed measuring instruments provided by an embodiment of the present invention;

[0070] Figure 5 A schematic diagram of the installation position of the metal disc bracket and the electric heating rod provided in an embodiment of the present invention;

[0071] Figure 6 A schematic diagram of the calibration terminal structure provided in an embodiment of the present invention;

[0072] Figure 7 A schematic diagram of the calibration terminal structure and assembly provided in an embodiment of the present invention;

[0073] Figure 8 A schematic diagram of the straight tube test piece structure provided by an embodiment of the present invention;

[0074] Figure 9 This is a diagram showing the arrangement of temperature measuring elements for a straight tube specimen provided in an embodiment of the present invention.

[0075] Description of reference numerals:

[0076] 1. Straight pipe test piece; 2. Calibration end; 4. Air conditioning system; 5. Sprinkler water pipe; 6. Ventilation system; 8. Ventilation hood. DETAILED DESCRIPTION

[0077] 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.

[0078] like Figure 1-8 As shown, a thermal conductivity test system for pipeline insulation materials under engineering meteorological environment conditions includes:

[0079] Example 1:

[0080] Combine Figure 1 and Figure 2 As shown, the simulation test system used in the above (the simulation test system mainly performs the test of the thermal conductivity coefficient of each layer of insulation material in the composite insulation structure) includes the following components:

[0081] 1. A straight pipe test piece 1 with calibration terminals 2 fixedly mounted on both ends, and its outer wall wrapped with thermal insulation covering material, constitutes the pipe to be tested;

[0082] 2. A ventilation hood 8 in a sealed space;

[0083] 3. The air ducts at the output end of the air conditioning system 4 are all located in a sealed space, and the air outlet faces the ventilation hood 8;

[0084] 4. The output ends of the spray water pipe 5 and the ventilation system 6 are arranged in the ventilation hood 8 and are located directly above the pipe to be tested that is centrally arranged in the ventilation hood 8.

[0085] Specifically, the overall structural layout of the closed test space of the insulation pipe insulation characteristics test device is as shown in the attached Figure 1 As shown, testing is primarily conducted within this enclosed space. The enclosed space is surrounded by an insulated enclosure and lacks windows. A door is located on one narrow wall, allowing for the transport and entry of test specimens and various devices. The opposite narrow wall houses a monitoring room, housing various measurement and control equipment and cabinets. The monitoring room is independent of the enclosed test space and is not connected.

[0086] An air conditioning system 4, a ventilation system 6 and a spray water pipe 5 are provided in the closed test space to simulate different ambient temperatures, ambient wind speeds and rain conditions of the insulation pipe in the space.

[0087] The air conditioning system 4 is used to control the air temperature in the closed test space. It is composed of independent refrigeration units. Each unit consists of a refrigeration host (i.e., outdoor unit, including compressor and condenser) and an indoor unit (including evaporator). The layout of the refrigeration system is shown in the attached figure. Figure 1As shown, the refrigeration main unit is arranged on the ground on one side outside the closed test space, and the indoor unit is arranged against the wall in the closed test space and installed at a high place near the top of the closed test space with a bracket. A guide air duct is set at the air outlet of the indoor unit to increase the range of the cold air blown out of the air outlet of the indoor unit, so that the outlet cold air forms an air circulation around the ventilation hood 8.

[0088] The ventilation system 6 is used to simulate the wind speed in the environment where the project is located. Since vertical ventilation requires too much space, it is difficult to ensure uniform air flow and the cost is high. Therefore, from the perspective of ensuring uniform air flow and taking into account the cost of the test device, the ventilation system 6 adopts parallel ventilation combined with impact angle correction. It mainly includes a ventilation hood 8 and a fan. Its layout is shown in the attached figure. Figure 1 As shown. A ventilation hood 8 is set outside the specimen. On the one hand, it can reduce the ventilation area, which is beneficial to control the wind speed around the specimen, and on the other hand, it can prevent interference from external airflow (such as air blowing from the indoor unit of the air conditioner). The ventilation hood 8 is made of metal steel plate and has a pulley 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 specimen is located at a place with relatively uniform temperature and facing the fan outlet. The net distance between the two sides of the ventilation hood 8 and the wall of the closed test space is not less than 1.5m. A fan is set at the end of the ventilation hood 8 on the side of the wall without a door. The other end of the ventilation hood 8 is open for entering and exiting the specimen. After the air flows from the fan outlet through the space between the ventilation hood 8 and the specimen, it returns to the fan inlet outside the ventilation hood 8 to form an air flow cycle. During ventilation, the air flows as shown in the attached figure. Figure 2 shown.

[0089] The test room is equipped with a spray water pipe 5, which is mainly installed on the top of the ventilation hood 8, just above the axial direction of the test piece. Figure 3 As shown. The sprinkler pipe utilizes a DN15 porous galvanized steel pipe with 5mm diameter holes and 100mm spacing, facing downward. A DN25 tap water pipe (galvanized steel pipe) supplies water to the sprinkler pipe, with a regulating valve installed between the pipe and the sprinkler pipe. The floor of the enclosed test space has a slope to facilitate drainage. A drainage ditch is installed on the east side of the retaining structure, running through the retaining structure and burying a DN40 casing to drain water outward. The casing is sealed with insulating material when not draining. Because convective heat transfer between rainwater and the pipe surface is generally stronger than air under the same conditions, rain intensifies surface heat dissipation. However, once rainfall is heavy enough to completely cover the pipe surface with a water film, changes in rainfall only affect the film thickness and have little impact on convective heat transfer. Therefore, the design of the sprinkler system only needs to ensure complete water coverage of the pipe surface, regardless of the water flow rate. The valve opening is adjusted on-site to ensure that the water flow covers the test specimen surface. Since the temperature of rainwater is generally close to the ambient temperature when it rains outdoors, the temperature of the spray water during the test is generally also controlled to be close to the ambient temperature. For example, when the simulated engineering ambient temperature is 5°C, the spray water temperature is also controlled at around 5°C. 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.

[0090] In order to ensure that the simulated environmental parameters in the test meet the engineering meteorological environmental conditions, it is necessary to monitor the ambient temperature and ambient wind speed in the closed test space. The measuring instruments are distributed as follows: Figure 3 As shown in the figure, "T" represents a thermometer and "S" represents a speedometer. The output data of each environmental parameter measuring instrument is collected by a data acquisition terminal in the closed test space and transmitted via the network to the operator station in the monitoring room.

[0091] Example 2:

[0092] like Figure 3 and Figure 4 As shown, this embodiment aims to provide a simulation test system for the thermal conductivity of each layer of insulation material in a composite insulation structure implemented under the conditions of Example 1, including the following steps:

[0093] S01. A dynamic simulation model is used to 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 to simulate the engineering meteorological environment in a closed test space, wherein:

[0094] The heating system is heated to a steady-state heat transfer condition during the test period.

[0095] Specifically, the steps of simulating the engineering meteorological environment in the above embodiment include:

[0096] S11. The temperature of the enclosed test space is regulated by air conditioning system 4. The cooling load QL is calculated using the following formula: QL = QL1 + QL2 + QL3 + QL4, where QL1 is the heat transferred 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 spray water cooling. A 3% to 5% margin is reserved for the cooling capacity of air conditioning system 4.

[0097] S12, simulate the ambient wind speed through the ventilation system 6, and the calculation formula of the air volume Q is: Q=(S 通风罩 -S 试件 )×wt×3600, where Q represents the air volume in m 3 / h,S 通风罩 Indicates the internal cross-sectional area of ​​the ventilation hood 8, in m 2 , S 试件 Indicates the cross-sectional area of ​​the pipe to be tested, in m 2 , wt represents the test wind speed in m / s, and the ventilation system 6 adopts parallel ventilation combined with impact angle correction. The impact angle correction formula is: ,in, The impact angle refers to the angle between the wind direction and the axis of the pipe to be tested;

[0098] 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.

[0099] The above-mentioned heating system includes a plurality of inner ring heating rods, a middle ring steplessly adjustable heating rod and a plurality of outer ring heating rods arranged in a circular array and mounted on a metal disc support. The control thereof includes the following steps:

[0100] S61, during the heating stage, the outer ring heating rod is used for fast heating with a fixed power heating rod, and the power is automatically cut off when the temperature of the heating rod exceeds the safety threshold;

[0101] In the steady-state stage, the inner and middle ring heating rods are used to adjust the power through the thyristor voltage regulator module to stabilize the inner wall temperature of the specimen within the set value ±0.5°C.

[0102] S63. A temperature measuring element is set on the surface of the heating rod to monitor the temperature in real time and provide feedback control through the DCS system.

[0103] The above embodiment secures the electric heating rods by placing a metal disc bracket inside the test tube. The bracket length is adjustable based on the test tube's needs. The outer straight rod has a fixed power rating and is primarily used for rapid heating during the temperature rise phase. The inner straight rod and the middle ring rod are infinitely adjustable and primarily used for heating during the steady-state heat transfer phase, maintaining a stable temperature on the inner wall of the test tube.

[0104] Heating power supply and power control:

[0105] The electric heating rod is powered by a three-phase AC power supply, which is controlled by the switch cabinet in the monitoring room. The heating power supply is divided into two states: the heating stage and the steady state stage, with different power supply circuits configured.

[0106] Heating stage: The rated voltage is applied directly to the heating rods, and the heating speed is adjusted by changing the number of working heating rods. The power automatic adjustment module is not connected.

[0107] Steady-state phase: During this phase, heating power must be adjusted based on temperature, utilizing a thyristor (SCR) module. Calculated power is based on windless, dry conditions. As test conditions adjust, the required power will vary, ranging from 0.8 to 1.5 times the calculated power. Assuming sufficient regulation capability, the power allocation during the steady-state heat transfer phase should be no less than twice the calculated power. A thyristor (SCR) voltage regulator module is used to adjust the output voltage to regulate the heating rod power, which in turn adjusts the power supply for stepless temperature control, stabilizing the pipe inner wall temperature at the set value.

[0108] If the heating power of a heater rod exceeds its heat transfer rate during use, the rod temperature may rise above the safe operating temperature, potentially damaging the rod. Therefore, a temperature sensor is installed on all heater rods to monitor the rod temperature. If the rod temperature exceeds the safe operating temperature, the heater is powered off.

[0109] Heating power metering:

[0110] During steady-state heat transfer, the electric heating power and heat dissipation flow of the test pipe are balanced, and the two values ​​are equal. The technology of the present invention is equipped with a high-precision electricity meter to measure the power supply power and active electric energy of the electric heating rod, and the measurement accuracy is not less than 0.5 levels. In order to further improve the measurement accuracy, the technology of the present invention simultaneously measures the instantaneous electric heating power and the cumulative electric heating power 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 power by the cumulative heating time. When the deviation between the instantaneous electric heating power and the average power is less than 0.01kW, the average value of the two is taken as the electric heating power during steady-state heat transfer, that is, the heat dissipation flow of the test pipe during steady-state heat transfer. The line power loss of the power supply line, electricity meter, and power regulation module of the test device of the present invention is calculated as 1.5% in total.

[0111] S02. Collecting electric heating power data, temperature data, and environmental parameter data of the calibration end 2 and the straight tube specimen 1 under a steady-state heat transfer state to verify the validity of the data;

[0112] Specifically, the verification of the validity of the above data includes:

[0113] 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;

[0114] 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%;

[0115] 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.

[0116] Furthermore, the temperature measurement method of the straight tube specimen 1 and the calibration end head 2 in the embodiment includes:

[0117] S100, arrange 32 temperature measurement points at 150 mm from the end face and the middle section of straight tube specimen 1, covering the 0, 3, 6, and 9 o'clock directions;

[0118] 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;

[0119] S102. The temperature measuring element is fixed by threads on the stainless steel wall component or embedded in the insulation material, and is covered with an insulation layer with an emissivity of ≥0.8 on the outside.

[0120] Secondly, environmental monitoring methods for closed test spaces include:

[0121] 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;

[0122] 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;

[0123] 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.

[0124] To analyze the actual thermal conductivity of each insulation layer, the straight pipe specimen also requires measuring the temperature between each insulation layer. Because the insulation section near the end face is affected by the interface, heat dissipation increases, while the center of the pipe provides the best insulation. Therefore, the temperature distributions at two sections, 150 mm from the end face and the center of the pipe, are 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.

[0125] Temperature measuring elements are set on the inner wall of the straight tube specimen 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.

[0126] 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.

[0127] Thermal resistor temperature measurement locations include the inner wall of a straight tube specimen, between layers of insulation material, and on the outer surface of the insulation material. The inner wall of a straight tube specimen is essentially the same temperature as the hot air inside the tube, so it is less affected by conduction and convection, and may only be affected by radiation, resulting in errors. The thermal resistors and wires between layers of insulation material are completely encased in the insulation, so errors caused by installation are minimal. The outer surface of the insulation material is directly affected by the external environment, and due to the lower ambient temperature, conduction, convection, and radiation heat transfer may affect the temperature measuring element, so this is a key consideration.

[0128] In order to expand the contact area with the test piece, a stainless steel wall component with a size of 20mm×40mm is set at the end. It can be directly welded to the metal surface to be tested or fixed with self-tapping screws. During installation, the thermal resistance probe is inserted into the internal threaded hole of the wall component and fixed with a threaded connection, which can effectively increase the thermal contact area.

[0129] The thermal resistors between each layer of insulation material are pre-buried by the manufacturer when making the insulation test piece, and the temperature measuring element and the adjacent inner layer of insulation material are fixed together by binding and winding with iron wire.

[0130] Because the temperature measuring elements on the outer surface of the insulation material are directly affected by the external environment and the ambient temperature is relatively low, to reduce heat transfer losses through conduction, convection, and radiation, the wires at the RTD installation site must maintain at least 10mm of contact with the surface. After installation, the RTD must also be covered with a layer of insulation material. To minimize internal radiative heat transfer, the inner surface emissivity of this insulation layer must be greater than 0.8. The other side of the RTD is connected to the terminal junction boxes on both sides of the test specimen via temperature measuring wires. From these terminal junction boxes, multi-core cables are connected to the measurement and control system. The insulation material and other environmental information measurement points are connected to the measurement and control system via their own cables.

[0131] S03, correcting the total heat dissipation flow of the pipe to be tested based on the heat dissipation flow of the calibration end 2, and calculating the linear heat flux density of the pipe to be tested;

[0132] Specifically, the calculation formula for the linear heat flux density of the pipe to be tested in the above embodiment is: l直管 =(Q t直管 -Q 端头) ×(1-power line loss percentage) / L 直管 , where Q 端头 To calibrate the heat dissipation flow of terminal 2, Q t直管 is the heat dissipation flux of straight tube specimen 1, L 直管 The insulation measurement length of the straight tube specimen 1;

[0133] Calibrate the heat dissipation flow Q of terminal 2 端头 Determine this by following these steps:

[0134] S31, 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 calibration steel pipe, and the gap is filled with insulation material;

[0135] 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 ;

[0136] S33, according to the total power consumption Q during the test of the calibration terminal 2 I端头 And test duration t 端头 , calculate the average input power P 2端头 =Q I端头 / t 端头 ;

[0137] S34, P 1端头 With P2端头 The arithmetic mean value is used as the heat flow value Q for the heat dissipation of the outer surface of the calibration end 2 under the test condition. 端头 =(P 1端头 +P 2端头 ) / 2;

[0138] Heat dissipation flux Qt of straight tube specimen 1 直管 Determine this by following these steps:

[0139] S35. Calculate the arithmetic mean P of the recorded input power of the electric heater inside the straight tube specimen under the steady-state heat transfer condition of the test condition. 1直管 ;

[0140] S36, power consumption Q during the straight tube test under steady-state heat transfer conditions I直管 and test duration t 直管 , calculate the average heating power P 2直管 =Q I直管 / t 直管 ;

[0141] S37, P 1直管 With P 2直管 The arithmetic mean of the heat flux of the straight tube specimen 1 is taken as the heat flux value, Q t直管 =(P 1直管 +P 2直管 ) / 2.

[0142] To ensure that the cooling capacity of the air conditioning system 4 meets the requirements, the cooling load within the test enclosed space needs to be calculated. This includes 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 cooling.

[0143] 1) Air conditioning system 4

[0144] ① Outdoor environment heat transfer Q L1 , according to the surface area A of the test room maintenance structure and the heat transfer coefficient K, the maximum outdoor temperature T out , minimum indoor temperature T in , calculate the outdoor environment heat transfer Q through the enclosure structure under the most unfavorable working conditions L1 , that is, Q L1 =K×A×(T out -T in ).

[0145] ②Heat generation Q of air conditioner and ventilation fan L2 = Air conditioning system 4 indoor unit power + ventilation system 6 fan power.

[0146] ③Heat generation of specimen Q L3: Determined based on the theoretical heat dissipation of the test piece surface during steady-state heat transfer. Calculate the heat dissipation of straight tube specimen 1 (including calibration tip 2) based on straight tube specimen 1, which has the highest heat dissipation, and consider an additional 100% margin factor when calculating the heat dissipation.

[0147] ④The heat Q released by spraying water cooling L4 : According to the spray water flow Mp l , unit kg / s, maximum temperature drop of spray water ∆t pl , in °C, and ∆t pl =t pl -t amin , where t pl is the initial temperature of the spray water in the pipe, in °C, which can be approximately considered to be equal to the outdoor ambient temperature, t amin The lowest temperature of the indoor environment, that is, the lowest ambient temperature simulated by the test, is in °C. The specific heat of water is 4.2 kJ / kg·°C. The heat dissipation of the spray water is calculated as follows: Q L4 =4.2×M pl ×∆t pl .

[0148] In summary, the total cooling load of the closed test space is Q L =Q L1 +Q L2 +Q L3 +Q L4 The cooling capacity of the air-conditioning system 4 should at least meet the cooling capacity requirement, and leave an appropriate margin of 3~5%.

[0149] 2) Ventilation system 6

[0150] The ventilation system 6 is used to simulate the wind speed in the environment where the project is located. Since vertical ventilation requires too much space, it is difficult to ensure uniform air flow and the cost is high. Therefore, from the perspective of ensuring uniform air flow and taking into account the cost of the test device, the ventilation system 6 adopts parallel ventilation combined with impact angle correction. It mainly includes a ventilation hood 8 and a fan. Its layout is shown in the attached figure. Figure 1 As shown. A ventilation hood 8 is set outside the specimen. On the one hand, it can reduce the ventilation area, which is beneficial to control the wind speed around the specimen, and on the other hand, it can prevent interference from external airflow (such as air blowing from the indoor unit of the air conditioner). The ventilation hood 8 is made of metal steel plate and has a pulley 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 specimen is located at a place with relatively uniform temperature and facing the fan outlet. The net distance between the two sides of the ventilation hood 8 and the wall of the closed test space is not less than 1.5m. A fan is set at the end of the ventilation hood 8 on the side of the wall without a door. The other end of the ventilation hood 8 is open for entering and exiting the specimen. After the air flows from the fan outlet through the space between the ventilation hood 8 and the specimen, it returns to the fan inlet outside the ventilation hood 8 to form an air flow cycle. During ventilation, the air flows as shown in the attached figure. Figure 2shown.

[0151] The fan is selected mainly based on the air volume required for the test. You can choose a multi-speed constant speed axial flow fan or a centrifugal fan. The air volume calculation method is: Q=(S 通风罩 -S 试件 )×wt×3600, where Q represents the air volume in m 3 / h,S 通风罩 Indicates the internal cross-sectional area of ​​the ventilation hood 8, in m 2 , S 试件 Indicates the cross-sectional area of ​​the specimen, in m 2 , wt represents the test wind speed, the unit is m / s.

[0152] In actual projects, different wind directions’ impact angles on the pipes will affect the surface convection heat transfer. The impact angle of the forced convection heat transfer of the single-tube can be corrected according to actual needs. The correction formula is: ,in The impact angle refers to the angle between the wind direction and the pipeline axis.

[0153] 3) Spray water pipe 5

[0154] In order to simulate the working condition of pipeline being exposed to rain, a spray water pipe 5 is set up in the test room. The main thing is to install a spray pipe on the top of the ventilation hood 8, which is located directly above the axial direction of the test piece. Figure 3 As shown. The sprinkler pipe utilizes a DN15 porous galvanized steel pipe with 5mm diameter holes and 100mm spacing, facing downward. A DN25 tap water pipe (galvanized steel pipe) supplies water to the sprinkler pipe, with a regulating valve installed between the pipe and the sprinkler pipe. The floor of the enclosed test space has a slope to facilitate drainage. A drainage ditch is installed on the east side of the retaining structure, running through the retaining structure and burying a DN40 casing to drain water outward. The casing is sealed with insulating material when not draining. Because convective heat transfer between rainwater and the pipe surface is generally stronger than air under the same conditions, rain intensifies surface heat dissipation. However, once rainfall is heavy enough to completely cover the pipe surface with a water film, changes in rainfall only affect the film thickness and have little impact on convective heat transfer. Therefore, the design of the sprinkler system only needs to ensure complete water coverage of the pipe surface, regardless of the water flow rate. The valve opening is adjusted on-site to ensure that the water flow covers the test specimen surface. Since the temperature of rainwater is generally close to the ambient temperature when it rains outdoors, the temperature of the spray water during the test is generally also controlled to be close to the ambient temperature. For example, when the simulated engineering ambient temperature is 5°C, the spray water temperature is also controlled at around 5°C. 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.

[0155] S04. Based on the linear heat flux density and the collected internal and external temperatures of each layer of insulation material, the actual thermal conductivity of the insulation material is calculated layer by layer and an Excel report is generated.

[0156] Specific thermal conductivity coefficient λ of each layer of insulation material i The calculation formula is:

[0157] ,

[0158] Where: i is the thermal conductivity of the insulation material of the i-th layer of composite insulation, in W / (m·K);

[0159] q l is the linear heat flux density of the pipe to be tested, that is, the heat flow rate per unit length of the pipe to be tested, in W / m;

[0160] d i is the inner diameter of the i-th layer of insulation material, d i+1 is the outer diameter of the insulation material of the i-th layer, and is also the inner diameter of the insulation material of the i+1-th layer, both in meters;

[0161] t1 is the outer wall temperature of the straight tube specimen (steel tube), that is, the inner temperature of the first layer of insulation material from the inside to the outside, t2 is the outer temperature of the first layer of insulation material from the inside to the outside, and so on. i is the temperature inside the i-th layer of insulation material, t i+1 is the outside temperature of the i-th layer of insulation material, and is also the inside temperature of the i+1-th layer of insulation material, both in °C.

[0162] The above-mentioned embodiment 2 tests the insulated pipe specimen under simulated engineering meteorological environment conditions, and calculates the radial heat flux density of the insulated pipe through the data collected when the specimen is under steady-state heat transfer conditions, and then calculates the actual thermal conductivity of each layer of insulation material under the test conditions and in the overall insulation structure, thereby verifying whether the thermal conductivity of each layer of insulation material in the pipeline insulation structure meets the relevant standards and regulations and specific engineering requirements, and quantitatively analyzes the combination and arrangement of each layer of insulation material in the pipeline and the rationality of the thickness setting of each layer of insulation material, providing reliable data support for further optimization and improvement of the pipeline insulation structure.

[0163] In summary, the thermal conductivity of each layer of pipeline insulation material was tested under a variety of possible operating conditions (primarily focusing on four parameters: inner wall temperature, ambient temperature, wind speed, and rain exposure) based on the actual insulation structure and installation combination of the project. The test results closely reflect actual project conditions, providing valuable guidance and reference for project construction. Furthermore, the tests were conducted in a closed space, unaffected by external meteorological and environmental conditions, enhancing the convenience and stability of the test and ensuring the accuracy of the test results. The specimens utilize internal electric heaters for heating, independent of external media entering the pipe for heating and unaffected by external media parameters or conveying conditions, resulting in strong autonomy and independence. The electric heating system incorporates monitoring systems for both the pipe wall temperature and the heater rod temperature, providing interlocking protection. Furthermore, an intelligent heating power control system utilizes different control circuits and control methods during the heating phase and the steady-state heat transfer phase, enabling intelligent adjustment of the power of the different heater rods, ensuring safe, stable, and efficient heating of the specimens. The ambient wind speed is simulated by using parallel ventilation of the specimen combined with the correction of the impact angle, which effectively reduces the test cost while ensuring the simulation effect, thereby 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 the instantaneous power and cumulative power consumption and steady-state heating time of the electric heating rod under the steady-state heat transfer condition are measured at the same time. The arithmetic mean of the instantaneous power record mean and the average heating power is used as the heating power calculation value to reduce the test error rate and improve data reliability. 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 of each layer of insulation material under the test conditions and the overall insulation structure through an algorithm. The obtained results are more in line with reality and have more guiding significance and reference value for the engineering application of insulation materials. 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. Example

[0164] Based on the second embodiment, this embodiment aims to provide a simulation test system for the thermal conductivity of each layer of insulation material in a composite insulation structure deployed in an insulated pipe located at the seaside or in a coastal city. The system includes:

[0165] Air conditioning system 4

[0166] A two-stage compression refrigeration unit with an integrated rotary dehumidification module ensures independently adjustable temperature (-10°C to 50°C) and relative humidity (30% to 95%) within the enclosed test space. The refrigerant piping and evaporator are constructed of 316L stainless steel, coated with a salt-fog-resistant coating to prevent corrosion. A salt spray generator is installed in the air conditioning duct to simulate a salt spray environment by atomizing seawater. The salt spray concentration is adjustable (0.5 to 5 mg / m³). A high-efficiency particulate air (HEPA) filter and activated carbon adsorption layer are also included to quickly remove residual salt spray after testing. It is important to note that the drainage pipe slope has been increased to 5%, the inner wall is coated with a hydrophobic material, and a regular pulse flushing function is configured to prevent salt crystallization and clogging.

[0167] Ventilation system 6

[0168] The parallel arrangement of centrifugal and axial fans increases the maximum wind speed to 15m / s (simulating typhoon conditions) and supports stepless wind speed adjustment. The fan impeller and housing are made of titanium alloy, which is resistant to salt spray corrosion. In addition, a rotatable deflector is added to the ventilation hood 8, and the deflection angle (0° to 180°) is controlled by a servo motor to simulate strong multi-directional winds at the seaside. The impact angle correction formula is expanded to: , a conductivity sensor is installed on the inner wall of the ventilation hood 8 to monitor the amount of salt mist deposition in real time, and trigger the automatic cleaning program when it exceeds the limit.

[0169] Spray water pipe 5

[0170] Artificial seawater (salinity 3.5%) is used for spraying, and the water storage tank is equipped with a heating / cooling coil. The water temperature is controlled within a range of 5°C to 35°C (≤2°C from ambient temperature). The spray pipe has been upgraded to a DN20 Hastelloy porous pipe with a 3mm pore diameter and 50mm spacing, increasing spray coverage to 98%.

[0171] The spraying frequency and water volume are controlled by PLC programming to simulate the tidal cycle (e.g. 6 hours / cycle). A three-stage mode of "high tide-peak-low tide" is set with spraying intensities of 5L / (m²·min), 10L / (m²·min), and 3L / (m²·min) respectively, to imitate the changes in air humidity during high tide-peak-low tide.

[0172] The above-mentioned DCS system integrates air conditioning, ventilation, and sprinkler modules, supports the simulation of multi-parameter coupled working conditions of "salt spray-humidity-wind speed-water temperature", and through precise environmental simulation, corrosion-resistant hardware upgrades and intelligent control, it can fully reproduce the complex climatic conditions at the seaside, providing high-reliability support for the weather resistance testing of coastal engineering pipeline insulation materials.

[0173] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways 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.

Claims

1. A method for testing the thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions, using a thermal conductivity testing system for pipeline insulation materials under engineering meteorological environment conditions, characterized in that: include: The system comprises: A straight pipe test piece (1) with calibration end caps (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, wherein the calibration end caps (2) are composed of two hollow cylindrical end caps and a calibration steel pipe, and a 50mm thermal insulation gap is reserved at the junction of the end caps and the steel pipe, and the gap is filled with thermal insulation material; 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); A spray water pipe (5) and a ventilation system (6), wherein the output end of the spray water pipe (5) is arranged in the ventilation hood (8) and is located directly above the pipe to be tested that is centrally arranged in the ventilation hood (8); The test method 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; The calculation formula of the heat flux density of the pipe to be tested in step S03 is: 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 flux of the calibration end (2), Q t直管 is the heat flux of the straight tube specimen (1), L 直管 is the insulation measurement length of the straight tube specimen (1).

2. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is 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. The ambient wind speed is simulated by the ventilation system (6). The air volume Q is calculated as follows: Q=(S 通风罩 -S 试件 )×wt×3600, where Q represents the air volume in m 3 / h,S 通风罩 Indicates the internal cross-sectional area of ​​the ventilation hood (8), in m 2 , S 试件 Indicates the cross-sectional area of ​​the pipe to be tested, in m 2 , wt represents the test wind speed, in m / s, and the ventilation system (6) adopts parallel ventilation combined with impact angle correction, and the impact angle correction formula is: ,in, The impact angle refers to the angle between the wind direction and the axis of the pipe to be tested; S13, simulating a rainy state through the spray water pipe (5), controlling the difference between the spray water temperature and the ambient temperature to not exceed 2°C, and controlling the spray water flow rate so that a water film is completely formed on the pipe to be tested.

3. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is characterized in that: The verification data validity 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 eliminating abnormal data is: if a single measurement value deviates from the average value by more than ±5%, the test should be repeated.

4. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is characterized in that: The heat dissipation flow Q of the calibration end (2) 端头 Determine this by following these 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, according to the total power consumption Q during the test of the calibration terminal (2) I端头 And test duration t 端头 , calculate the average input power P 2端头 =Q I端头 / t 端头 ; S34, P 1端头 With P 2端头 The arithmetic mean of the heat flux value of the outer surface heat dissipation of the calibration end (2) under the test condition is Q 端头 =(P 1端头 +P 2端头 ) / 2; The heat dissipation flux Qt of the straight tube specimen (1) 直管 Determine this by following these steps: S35. Calculate the arithmetic mean P of the recorded input power of the electric heater inside the straight tube specimen under the steady-state heat transfer condition of the test condition. 1直管 ; S36, power consumption Q during the straight tube test under steady-state heat transfer conditions I直管 and test duration t 直管 , calculate the average heating power P 2直管 =Q I直管 / t 直管 ; S37, P 1直管 With P 2直管 The arithmetic mean of the heat flux of the straight tube specimen (1) is taken as the heat flux value of the outer surface heat dissipation, Q t直管 =(P 1直管 +P 2直管 ) / 2.

5. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is characterized in that: The thermal conductivity coefficient λ of each layer of thermal insulation material in S04 i The calculation formula is: ， Where: i is the thermal conductivity of the insulation material of the i-th layer of composite insulation, in W / (m·℃); q l is the linear heat flux density of the pipe to be tested, that is, the heat flow rate per unit length of the pipe to be tested, in W / m; d i is the inner diameter of the i-th layer of insulation material, d i+1 is the outer diameter of the insulation material of the i-th layer, and is also the inner diameter of the insulation material of the i+1-th layer, both in meters; t1 is the outer wall temperature of the straight tube specimen, that is, the inner temperature of the first layer of insulation material from the inside to the outside, t2 is the outer temperature of the first layer of insulation material from the inside to the outside, and so on. i is the temperature inside the i-th layer of insulation material, t i+1 is the outside temperature of the i-th layer of insulation material, and is also the inside temperature of the i+1-th layer of insulation material, both in °C.

6. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is 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 stage, the outer ring heating rod is used to quickly heat the device at a fixed power, and the power is automatically cut off when the temperature of the heating rod exceeds a safety threshold; S62, in the steady-state stage, the inner ring heating rod and the middle ring steplessly adjustable heating rod are used to adjust the power through the thyristor voltage regulator module so that the inner wall temperature of the specimen is stabilized within the range of ±0.5°C of the set value; S63. A temperature measuring element is set on the surface of the heating rod to monitor the temperature in real time and provide feedback control through the DCS system.

7. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is characterized in that: The temperature measurement method of the straight tube test piece (1) and the calibration end head (2) includes: S100, arranging 32 temperature measuring points at 150 mm from the end face and the middle section of the straight tube 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 circle every 90 degrees along the spiral line, and a temperature measuring point is added at the end cap; S102. The temperature measuring element is fixed by screw threads on a stainless steel wall component or embedded in the interior of the thermal insulation material, and is covered with a thermal insulation layer on the outside.

8. The method for testing thermal conductivity of pipeline insulation materials under engineering meteorological environment conditions according to claim 1 is characterized in that: The environmental monitoring method of the closed 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, arranging a total of 6 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.

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