Heating pipe fluid temperature test correction method and supply and return water temperature difference test correction method

Abstract

A method for correcting fluid temperature in heating pipelines includes the following steps: S0, constructing a CFD three-dimensional simulation geometric model to simulate the transfer of temperature between the outer wall of the pipeline and the fluid temperature; S1, setting the simulation parameters and boundary conditions of the above-mentioned CFD three-dimensional simulation geometric model; S2, performing numerical simulation calculations within the CFD three-dimensional simulation geometric model; S3, obtaining datasets for different combinations of pipeline materials and fluid media; S4, constructing a fluid temperature-outer wall temperature regression model; S5, constructing fluid temperature correction formulas for different combinations of pipeline materials and fluid media; A method for correcting the supply and return water temperature difference in heating pipelines includes the following steps: obtaining measured values ​​of the outer wall temperature of the supply and return water pipelines; calculating the supply water temperature correction value and the return water temperature correction value respectively based on the fluid temperature correction formula obtained by any of the above-mentioned methods for correcting fluid temperature in heating pipelines and corresponding to the current pipeline and medium; and calculating the supply and return water temperature difference correction value.

Description

Technical Field

[0001] This invention relates to the field of building heating testing technology, and in particular to a method for correcting the temperature of fluids in heating pipes and a method for correcting the temperature difference between supply and return water. Background Technology

[0002] Current building energy efficiency testing standards in my country, such as JGJ / T 132-2009 "Standard for Energy Efficiency Testing of Residential Buildings" and JGJ / T 177-2009 "Standard for Energy Efficiency Testing of Public Buildings", stipulate that when testing the heat supply of heating pipes, in order not to damage the pipes or system structure, a non-invasive indirect measurement method is usually used to obtain the difference between the supply water temperature of the supply pipe and the return water temperature of the return pipe, i.e., the supply and return water temperature difference. The aforementioned non-invasive indirect measurement method involves placing wall-mounted temperature sensors on the outer walls of the supply and return water pipes to obtain the outer wall temperatures of both pipes. The supply water temperature is then used to represent the supply water temperature, and the return water temperature is used to represent the return water temperature, thus obtaining the supply and return water temperature difference. However, due to heat transfer errors caused by external factors such as the external environment and pipe material, as well as environmental radiation interference, the above method suffers from significant measurement errors. Current building energy efficiency testing standards, such as JGJ / T 132-2009 "Standard for Energy Efficiency Testing of Residential Buildings" and JGJ / T 177-2009 "Standard for Energy Efficiency Testing of Public Buildings," do not explicitly address this measurement error, resulting in a significant deficiency. This leaves testing personnel facing a lack of clear guidelines in engineering practice. Therefore, a correction method is urgently needed to address the deficiencies in current building testing standards. Summary of the Invention

[0003] In view of this, it is necessary to provide a correction method for testing the fluid temperature of heating pipes and a correction method for testing the temperature difference between supply and return water, so as to make up for the deficiencies in the current building energy efficiency testing standards and provide a correction path that can be applied to the testing personnel in engineering practice.

[0004] According to one aspect of the present invention, a method for correcting the temperature of fluid in a heating pipe is provided, comprising the following steps:

[0005] S0. Construct a CFD three-dimensional simulation geometric model to simulate the temperature transfer between the outer wall of the pipe and the fluid, specifically including:

[0006] A three-dimensional simulation geometric model is established based on the pipe material and specifications, the insulation layer material and thickness, and the fluid medium type.

[0007] S1. Set the simulation parameters and boundary conditions for the above CFD three-dimensional simulation geometric model, specifically including:

[0008] Set simulation parameters, including pipe material and specifications, insulation layer material and thickness, and thermal properties of pipe material, insulation layer material and fluid medium;

[0009] Set boundary conditions, including fluid temperature and medium flow rate, and external air temperature and ambient wind speed;

[0010] S2. Perform numerical simulation calculations within the CFD three-dimensional simulation geometric model, specifically including:

[0011] Coupled heat transfer simulation was performed using the Standard k-epsilon turbulence model, the Standard Wall Function (SWF), and the Rosseland radiation model. Steady-state heat transfer calculations were performed under various combinations of simulation parameters and boundary conditions set in S1 to obtain the outer wall temperature under various combined conditions.

[0012] S3. Obtain datasets for different combinations of pipe materials and fluid media, specifically including:

[0013] For different combinations of pipe materials and fluid media, the external wall temperature and the corresponding seven key parameters under various combined working conditions in S2 are extracted to form a dataset.

[0014] The seven key parameters include external air temperature, medium flow rate, fluid temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness.

[0015] S4. Construct fluid temperature-outer wall temperature regression models for different pipe materials and fluid medium combinations, specifically including:

[0016] Based on the datasets obtained in S3 for different combinations of pipe materials and fluid media, fluid temperature is used as the response variable, and the corresponding external air temperature, medium flow rate, external wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness and insulation layer thickness are used as prediction variables.

[0017] Multiple linear regression was used to construct regression models for different pipe materials and fluid media combinations.

[0018] S5. Construct fluid temperature correction formulas for different combinations of pipe materials and fluid media, specifically including:

[0019] Based on the regression model described in S4, obtain the regression coefficients and intercept;

[0020] Based on the regression coefficients and intercepts, a fluid temperature correction formula is constructed for different combinations of pipe materials and fluid media.

[0021] Preferably, the pipe material includes metal pipes and plastic pipes;

[0022] The insulation layer material includes rubber and plastic sponge;

[0023] The fluid medium includes water and antifreeze;

[0024] The fluid temperature is 30°C to 50°C;

[0025] The medium flow velocity is from 0.6 m / s to 1.4 m / s;

[0026] The outside air temperature is -15°C to 15°C;

[0027] The ambient wind speed is between 0 m / s and 3.0 m / s.

[0028] Preferably, the metal pipe is a galvanized steel pipe; the plastic pipe is a PPR pipe.

[0029] The different pipe materials and fluid media combinations include: galvanized steel pipe-water, galvanized steel pipe-antifreeze, PPR pipe-water, and PPR pipe-antifreeze.

[0030] Preferably, the following variable symbols are defined:

[0031] P1: External wall surface temperature;

[0032] P2: Medium flow rate;

[0033] P3: Fluid temperature;

[0034] P4: Ambient air temperature;

[0035] P5: Ambient wind speed;

[0036] P6: Pipe outer diameter;

[0037] P7: Pipe wall thickness;

[0038] P8: Insulation layer thickness;

[0039] The fluid temperature correction formulas are as follows:

[0040] Galvanized steel pipe-water combination:

[0041] P3=9.3029-0.0670×P1+0.0254×P2+0.9036×P4+1.4165×P5-0.0057×P6-0.2492×P8

[0042] Galvanized steel pipe-antifreeze combination:

[0043] P3=9.3421-0.0686×P1+0.0793×P2+0.9002×P4+1.4133×P5-0.0032×P6-0.2545×P8

[0044] PPR pipe-water combination:

[0045] P3=8.6460-0.0974×P1+0.1321×P2+0.8557×P4+2.1374×P5-0.0114×P6+0.4311×P7-0.2633×P8

[0046] PPR pipe-antifreeze combination:

[0047] P3=17.1756-0.0936×P1+0.1329×P2+0.7136×P4+1.7353×P5-0.0312×P6 +0.4352×P7-0.3380×P8

[0048] According to another aspect of the present invention, a method for correcting the temperature difference between supply and return water in heating pipes is also provided, comprising the following steps:

[0049] Obtain temperature measurements of the outer wall surfaces of water supply and return pipes;

[0050] Based on the fluid temperature correction formula obtained by any of the above-described methods for testing and correcting the fluid temperature of heating pipes, and the fluid temperature correction formula corresponding to the current pipe and medium, calculate the supply water temperature correction value and the return water temperature correction value respectively.

[0051] Calculate the supply and return water temperature difference correction value based on the supply water temperature correction value and the return water temperature correction value.

[0052] Preferably, the formula for calculating the supply and return water temperature difference correction value ΔP3 is as follows:

[0053] Under the galvanized steel pipe-water combination: ΔP3 = 0.9036 × ΔP1

[0054] Under the combination of galvanized steel pipe and antifreeze: ΔP3 = 0.9002 × ΔP1

[0055] Under the PPR pipe-water combination: ΔP3 = 0.8557 × ΔP1

[0056] Under the PPR pipe-antifreeze combination: ΔP3 = 0.7136 × ΔP1

[0057] Wherein, ΔP1 is the difference between the measured temperatures of the outer walls of the water supply pipe and the return pipe.

[0058] The aforementioned method for correcting the fluid temperature in heating pipes first utilizes CFD simulation technology. By setting different combinations of pipe materials, media, insulation, flow velocity, and environmental conditions (external air temperature, ambient wind speed), it systematically simulates the heat transfer state under various real-world scenarios, generating a high-quality dataset that covers a wide range of conditions and more comprehensively reflects the complex heat exchange processes in the real world. Then, based on this dataset, a multiple linear regression method is used to establish accurate prediction models for different pipe material-fluid medium combinations, providing a complete method for correcting the fluid temperature in heating pipes. A concise linear correction formula is generated, enabling testing personnel to quickly and accurately obtain the fluid temperature on-site by using the provided formula, after obtaining known parameters such as external air temperature, medium flow velocity, outer wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness. Furthermore, this invention provides a method for correcting the supply and return water temperature difference. Based on the correction of the heating pipe fluid temperature, it further derives the relationship between the supply and return water temperature difference and the outer wall temperature under different pipe material and fluid medium combinations. The linear correlation between surface temperature difference and other parameters is established. Compared with existing technologies, this invention, on the one hand, constructs a complete method for correcting the fluid temperature test and the supply and return water temperature difference test of heating pipes, based on a comprehensive consideration of environmental radiation and heat conduction errors. It considers other environmental parameters and the influence of pipes and related materials on fluid temperature, based on the external wall surface temperature. This allows testing personnel to correct the fluid temperature test and the supply and return water temperature difference using the correction formulas provided by this invention, thus addressing the deficiencies of current building energy conservation testing standards. It provides testing personnel in engineering practice with applicable correction formulas and improves the accuracy and precision of fluid temperature and supply and return water temperature difference measurements, providing reliable data support for building energy conservation optimization and policy implementation. On the other hand, the fluid temperature test and supply and return water temperature difference test correction methods constructed by this invention are differentiated according to pipe material and fluid medium combination, ensuring that the correction methods are optimized under their most suitable physical conditions, resulting in higher prediction accuracy and meeting the diverse application scenarios of pipe materials and fluid media in professional heating systems. Attached Figure Description

[0059] Figure 1 This is a flowchart of the method for correcting the temperature of fluid in heating pipes in this invention.

[0060] Figure 2 This is a flowchart of the method for correcting the temperature difference between supply and return water in heating pipelines in this invention.

[0061] Figure 3 This is a residual scatter plot of the fluid temperature correction formula under the galvanized steel pipe-water combination in this invention during residual distribution analysis.

[0062] Figure 4 This is a residual QQ plot of the fluid temperature correction formula under the galvanized steel pipe-water combination in this invention during residual distribution analysis.

[0063] Figure 5 This is a residual scatter plot of the fluid temperature correction formula under the galvanized steel pipe-antifreeze combination in the residual distribution analysis of the present invention.

[0064] Figure 6 This is a residual QQ plot of the fluid temperature correction formula under the galvanized steel pipe-antifreeze combination in the residual distribution analysis of the present invention.

[0065] Figure 7 This is a residual scatter plot of the fluid temperature correction formula under the PPR pipe-water combination in this invention during residual distribution analysis.

[0066] Figure 8 This is a residual QQ plot of the fluid temperature correction formula under the PPR pipe-water combination in this invention during residual distribution analysis.

[0067] Figure 9 This is a residual scatter plot of the fluid temperature correction formula under the PPR pipe-antifreeze combination in this invention during residual distribution analysis.

[0068] Figure 10 This is a residual QQ plot of the fluid temperature correction formula under the PPR pipe-antifreeze combination in this invention during residual distribution analysis. Detailed Implementation

[0069] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0070] Please refer to Figure 1 A method for correcting the temperature of fluid in heating pipes, comprising the following steps:

[0071] S0. Construct a CFD three-dimensional simulation geometric model to simulate the temperature transfer between the outer wall of the pipe and the fluid, specifically including:

[0072] A three-dimensional simulation geometric model is established based on the pipe material and specifications, the insulation layer material and thickness, and the fluid medium type.

[0073] S1. Set the simulation parameters and boundary conditions for the above CFD three-dimensional simulation geometric model, specifically including:

[0074] Set simulation parameters, including pipe material and specifications, insulation layer material and thickness, and thermal properties of pipe material, insulation layer material and fluid medium;

[0075] Set boundary conditions, including fluid temperature and medium flow rate, and external air temperature and ambient wind speed;

[0076] S2. Perform numerical simulation calculations within the CFD three-dimensional simulation geometric model, specifically including:

[0077] Coupled heat transfer simulation was performed using the Standard k-epsilon turbulence model, the Standard Wall Function (SWF), and the Rosseland radiation model. Steady-state heat transfer calculations were performed under various combinations of simulation parameters and boundary conditions set in S1 to obtain the outer wall temperature under various combined conditions.

[0078] S3. Obtain datasets for different combinations of pipe materials and fluid media, specifically including:

[0079] For different combinations of pipe materials and fluid media, the external wall temperature and the corresponding seven key parameters under various combined working conditions in S2 are extracted to form a dataset.

[0080] The seven key parameters include external air temperature, medium flow rate, fluid temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness.

[0081] S4. Construct fluid temperature-outer wall temperature regression models for different pipe materials and fluid medium combinations, specifically including:

[0082] Based on the datasets obtained in S3 for different combinations of pipe materials and fluid media, fluid temperature is used as the response variable, and the corresponding external air temperature, medium flow rate, external wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness and insulation layer thickness are used as prediction variables.

[0083] Multiple linear regression was used to construct regression models for different pipe materials and fluid media combinations.

[0084] S5. Construct fluid temperature correction formulas for different combinations of pipe materials and fluid media, specifically including:

[0085] Based on the regression model described in S4, obtain the regression coefficients and intercept;

[0086] Based on the regression coefficients and intercepts, a fluid temperature correction formula is constructed for different combinations of pipe materials and fluid media.

[0087] In this embodiment, the construction of the CFD three-dimensional simulation geometric model and the numerical simulation calculation can be implemented in the simulation software ANSYS Fluent.

[0088] In step S2, the coupling mechanism of the Standard k-epsilon turbulence model, the Standard Wall Function (SWF), and the Roselland radiation model in coupling the turbulence-radiation heat transfer process is as follows: the Standard k-epsilon turbulence model influences momentum and energy transport, the Standard Wall Function (SWF) provides wall boundary closure, and the Roselland radiation model corrects the effective thermal conductivity. The Standard k-epsilon turbulence model is suitable for wall-constrained flows with high Reynolds numbers, and its robustness and computational economy for industrial flows have been extensively verified. The SWF uses the Launder-Spalding logarithmic law to handle the near-wall region, which significantly reduces the mesh requirements. The Roselland radiation model, for media with optical thickness τ≥3, couples to the energy equation through the equivalent radiation thermal conductivity, avoiding the computational cost of directly solving the angular intensity distribution.

[0089] In step S4, the least squares method is used to fit the parameters when constructing the regression model;

[0090] The aforementioned method for correcting the fluid temperature in heating pipes first utilizes CFD simulation technology. By setting different combinations of pipe materials, media, insulation, flow velocity, and environmental conditions (external air temperature, ambient wind speed), it systematically simulates the heat transfer state under various real-world scenarios, generating a high-quality dataset that covers a wide range of conditions and more comprehensively reflects the complex heat exchange processes in the real world. Then, based on this dataset, a multiple linear regression method is used to establish accurate prediction models for different pipe material-fluid medium combinations, providing a complete method for correcting the fluid temperature in heating pipes. A concise linear correction formula is generated, enabling testing personnel to quickly and accurately obtain the fluid temperature on-site by using the provided formula, after obtaining known parameters such as external air temperature, medium flow velocity, outer wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness. This method is superior to existing methods. Compared with other technologies, this invention, on the one hand, constructs a complete method for correcting the fluid temperature test of heating pipes by comprehensively considering environmental radiation and heat conduction errors. Based on the external wall temperature, it comprehensively considers other environmental parameters and the influence of pipes and related materials on fluid temperature, enabling testing personnel to correct fluid temperature tests according to the correction path provided by this invention. This addresses the deficiencies of current building energy efficiency testing standards, provides testing personnel in engineering practice with applicable correction formulas, and improves the accuracy and precision of fluid temperature measurement, providing reliable data support for building energy efficiency optimization and policy implementation. On the other hand, the fluid temperature test correction method for heating pipes constructed in this invention differentiates based on pipe material and fluid medium combination, ensuring that the correction method is optimized under its most suitable physical conditions, resulting in higher prediction accuracy and meeting the diverse application scenarios of pipe materials and fluid media in professional heating systems.

[0091] Furthermore, in order to ensure that the simulation parameters and boundary conditions are more in line with the actual application scenario and to improve the reliability of the dataset, the pipe material includes metal pipes and plastic pipes;

[0092] The insulation layer material includes rubber and plastic sponge;

[0093] The fluid medium includes water and antifreeze;

[0094] The fluid temperature is 30°C to 50°C;

[0095] The medium flow velocity is from 0.6 m / s to 1.4 m / s;

[0096] The outside air temperature is -15°C to 15°C;

[0097] The ambient wind speed is between 0 m / s and 3.0 m / s.

[0098] In this embodiment, specifically...

[0099] The fluid temperature includes 30°C, 40°C, and 50°C;

[0100] The medium flow velocity includes 0.6 m / s, 1.0 m / s, and 1.4 m / s;

[0101] The external air temperature includes -15°C, 0°C, and 15°C;

[0102] The ambient wind speeds include 0 m / s, 1.5 m / s, and 3.0 m / s;

[0103] The metal pipe is a galvanized steel pipe; the plastic pipe is a PPR pipe.

[0104] The specifications of the galvanized steel pipes include an outer diameter of 76.1 mm / wall thickness of 4.0 mm, an outer diameter of 88.9 mm / wall thickness of 4.0 mm, and an outer diameter of 114.3 mm / wall thickness of 4.0 mm.

[0105] The PPR pipe specifications include outer diameter 32mm / wall thickness 4.4mm, outer diameter 32mm / wall thickness 5.4mm, outer diameter 50mm / wall thickness 6.9mm, and outer diameter 50mm / wall thickness 8.3mm.

[0106] The thickness of the insulation layer includes 0mm, 20mm and 30mm;

[0107] The thermal properties of the pipe material, fluid medium, air, and insulation layer are shown in Table 1.

[0108] Table 1

[0109] parameter galvanized steel pipe PPR pipe water antifreeze Air Rubber and plastic sponge <![CDATA[Density (kg / m 3 )]]> 8030 900 998.2 1080 1.225 40 Thermal conductivity (W / mK) 16.27 0.25 0.6 0.45 0.0242 0.03

[0110] Furthermore, in order to ensure that the correction method provided by the present invention is optimized under its most suitable physical conditions, has higher prediction accuracy, and meets the diverse application scenarios of pipe materials and fluid media in professional heating systems, the different combinations of pipe materials and fluid media include: galvanized steel pipe-water, galvanized steel pipe-antifreeze, PPR pipe-water, and PPR pipe-antifreeze.

[0111] Furthermore, to ensure that the correction method provided by this invention is optimized under its most suitable physical conditions, has higher prediction accuracy, and meets the diverse pipe materials and fluid media application scenarios in professional heating systems, the following variable symbols are defined:

[0112] P1: External wall surface temperature;

[0113] P2: Medium flow rate;

[0114] P3: Fluid temperature;

[0115] P4: Ambient air temperature;

[0116] P5: Ambient wind speed;

[0117] P6: Pipe outer diameter;

[0118] P7: Pipe wall thickness;

[0119] P8: Insulation layer thickness;

[0120] The fluid temperature correction formulas are as follows:

[0121] Galvanized steel pipe-water combination:

[0122] P3=9.3029-0.0670×P1+0.0254×P2+0.9036×P4+1.4165×P5-0.0057×P6-0.2492×P8

[0123] Galvanized steel pipe-antifreeze combination:

[0124] P3=9.3421-0.0686×P1+0.0793×P2+0.9002×P4+1.4133×P5-0.0032×P6-0.2545×P8

[0125] PPR pipe-water combination:

[0126] P3=8.6460-0.0974×P1+0.1321×P2+0.8557×P4+2.1374×P5-0.0114×P6+0.4311×P7-0.2633×P8

[0127] PPR pipe-antifreeze combination:

[0128] P3=17.1756-0.0936×P1+0.1329×P2+0.7136×P4+1.7353×P5-0.0312×P6 +0.4352×P7-0.3380×P8

[0129] Reliability analysis:

[0130] In this embodiment, the reliability of the fluid temperature correction formulas under different pipe material-fluid medium combinations is analyzed by goodness-of-fit test, statistical significance test (F-test), and residual distribution analysis. The specific results are as follows:

[0131] (1) The reliability analysis of the fluid temperature correction formula under the galvanized steel pipe-water combination is as follows:

[0132] Goodness of fit: The R² value is 0.8291, indicating that the model can explain about 82.91% of the variation of the response variable "fluid temperature P3 (°C)", which has a strong explanatory power; the adjusted R² value is 0.8274, which remains high after considering the number of independent variables, indicating that the regression model on which the modified formula is based does not show obvious overfitting and has good generalization performance.

[0133] The statistical significance test, namely the F-test, shows that the F-statistic is 505.86, and the corresponding p-value is 1.1102e-16, which is much smaller than the significance level of 0.05. This indicates that the regression model on which the modified formula is based has high statistical significance as a whole, and the combined effect of the predictor variables on the response variable is extremely significant.

[0134] Residual distribution analysis: Please refer to Figure 3 The residual scatter plot shows that the residuals are basically randomly distributed around the zero line within the predicted value range, without showing obvious trends, bending patterns, or funnel-shaped diffusion. This indicates that the regression model on which the modified formula is based has good linearity assumptions and homoscedasticity, i.e., the error variance is constant. Although there are a few relatively large residuals in the higher predicted value region, with a maximum of 12.21, the overall distribution is concentrated and symmetrical, meeting the basic requirements of random error. At the same time, there are no significant clustering or systematic deviations, indicating that the regression model on which the modified formula is based has not omitted key explanatory variables or has serious misspecifications in its functional form.

[0135] Please refer to Figure 4 The Quantile-Quantile plot of the residuals shows that the residual points roughly fall on the standard normal reference line with small deviations, suggesting that the residuals follow the normality assumption. At the same time, no significant heteroscedasticity or systematic bias was found, satisfying the basic preconditions of the linear regression model.

[0136] (2) The reliability analysis of the fluid temperature correction formula under the galvanized steel pipe-antifreeze combination is as follows:

[0137] The goodness-of-fit R² is 0.8227, indicating that the regression model on which the modified formula is based can explain about 82.27% of the variation in the dependent variable; the adjusted R² is 0.8210, which remains at a high level after considering the number of variables, indicating that the regression model on which the modified formula is based does not show obvious overfitting.

[0138] The F-test statistic is 484.0511, which is much higher than the critical value, proving that the regression model is significantly effective overall.

[0139] Please refer to Figure 5 Residual scatter plot, and Figure 6The residual QQ plot shows that the residuals are basically randomly distributed around zero and approximately follow a normal distribution, satisfying the basic assumptions of linear regression, further verifying the stability and rationality of the regression model on which the modified formula is based.

[0140] (3) The reliability analysis of the fluid temperature correction formula under PPR pipe-water combination is as follows:

[0141] Goodness-of-fit analysis: The R² value is 0.7511, and the adjusted R² value is 0.7494, indicating that the regression model on which the modified formula is based can explain about 75% of the variation and has a good fit effect.

[0142] The significance test, namely the F-test, shows that the F-statistic is 420.8327, and the corresponding p-value is 0.0000, which is much smaller than the significance level of 0.05. This indicates that the regression model on which the modified formula is based has high statistical significance as a whole, and at least one predictor variable has a significant impact on the response variable.

[0143] Residual analysis: Please refer to Figure 7 The residual scatter plot shows that the residual distribution basically fluctuates randomly around the zero line, with no obvious trend or heteroscedasticity, satisfying the homoscedasticity and independence assumptions of linear regression. Please refer to... Figure 8 The residual QQ plot shows that the residual points roughly fall on the theoretical normal distribution line, indicating that the residuals are close to a normal distribution and satisfy the normality assumption of the regression model.

[0144] (4) The reliability analysis of the fluid temperature correction formula under PPR pipe-water combination is as follows:

[0145] Goodness-of-fit analysis: The R² value is 0.6049, indicating that the regression model on which the modified formula is based can explain approximately 60.49% of the variation in the response variable, demonstrating a moderately high goodness of fit. The adjusted R² value is 0.6021, which is relatively close to the R² value, indicating that the regression model on which the modified formula is based performs well in controlling the number of predictor variables, without excessively including redundant variables, and the predictor variables contribute effectively to the regression model on which the modified formula is based.

[0146] The significance test, namely the F-test, has an F-statistic of 213.4658, which is much larger than the critical value. This indicates that at a significance level of 0.05, the significance test, namely the F-test, is highly statistically significant, meaning that the combined effect of the selected predictor variables on fluid temperature is significant.

[0147] Please refer to Figure 9 and Figure 10 The residual analysis showed that the residuals basically exhibited a random uniform distribution with no obvious regularity or systematic bias, which satisfied the basic assumption of the linear regression model that the error term is independent and random, further supporting the reliability and applicability of the model.

[0148] Please refer to Figure 2 A method for correcting the temperature difference between supply and return water in heating pipes, comprising the following steps:

[0149] Obtain temperature measurements of the outer wall surfaces of water supply and return pipes;

[0150] Based on the fluid temperature correction formula obtained by any of the above-described methods for testing and correcting the fluid temperature of heating pipes, and the fluid temperature correction formula corresponding to the current pipe and medium, calculate the supply water temperature correction value and the return water temperature correction value respectively.

[0151] Calculate the supply and return water temperature difference correction value based on the supply water temperature correction value and the return water temperature correction value.

[0152] In this embodiment, based on the current combination of pipeline and fluid medium, the measured values ​​of the outer wall temperature of the water supply pipeline and the return water pipeline are respectively substituted into the corresponding fluid temperature correction formula to obtain the water supply temperature correction value, i.e., the water supply pipeline fluid temperature correction value, and the return water temperature correction value, i.e., the return water pipeline fluid temperature correction value; the difference between the water supply temperature correction value and the return water temperature correction value is the water supply and return temperature difference correction value.

[0153] This embodiment, based on the correction of the fluid temperature in heating pipes, further derives the linear correlation between the supply and return water temperature difference and the external wall temperature difference under different pipe materials and fluid medium combinations. Compared with the prior art, on the one hand, this invention constructs a complete method for correcting the supply and return water temperature difference in heating pipes by comprehensively considering environmental radiation and heat conduction errors. Based on the external wall temperature, it comprehensively considers other environmental parameters and the influence of pipes and related materials on fluid temperature, enabling testing personnel to correct the supply and return water temperature difference according to the correction formula provided by this invention. This addresses the deficiencies of current building energy conservation testing standards, provides testing personnel in engineering practice with an applicable correction formula, and improves the accuracy and precision of supply and return water temperature difference measurement, providing reliable data support for building energy conservation optimization and policy implementation. On the other hand, the heating pipe supply and return water temperature difference testing correction method constructed by this invention differentiates based on pipe material and fluid medium combination, ensuring that the correction method is optimized under its most suitable physical conditions, resulting in higher prediction accuracy and meeting the diverse application scenarios of pipe materials and fluid media in professional heating systems.

[0154] Furthermore, the formula for calculating the supply and return water temperature difference correction value ΔP3 is as follows:

[0155] Under the galvanized steel pipe-water combination: ΔP3 = 0.9036 × ΔP1

[0156] Under the combination of galvanized steel pipe and antifreeze: ΔP3 = 0.9002 × ΔP1

[0157] Under the PPR pipe-water combination: ΔP3 = 0.8557 × ΔP1

[0158] Under the PPR pipe-antifreeze combination: ΔP3 = 0.7136 × ΔP1

[0159] Wherein, ΔP1 is the difference between the measured temperatures of the outer walls of the water supply pipe and the return pipe.

[0160] In this embodiment, since the external wall temperature measurements of the water supply pipe and the return pipe are performed simultaneously during actual on-site measurements, other key parameters, namely medium flow velocity P2, external air temperature P4, ambient wind speed P5, pipe outer diameter P6, pipe wall thickness P7, and insulation layer thickness P8, are the same when obtaining the supply water temperature correction value and the return water temperature correction value. The supply and return water temperature difference correction value ΔP3 is only caused by the difference ΔP1 between the measured external wall temperature values ​​of the water supply pipe and the return water pipe. Therefore, the calculation formula for the supply and return water temperature difference correction value ΔP3 in this embodiment can be derived.

[0161] In this embodiment, by constructing a correction formula for the supply and return water temperature difference under different pipe material-fluid medium combinations, technicians can directly obtain the supply and return water temperature difference correction value based on the difference between the measured outer wall temperatures of the supply and return water pipes, according to the actual pipe material-fluid medium combination and the correction formula provided in this embodiment. Compared with the prior art, this can directly correct the systematic errors caused by environmental radiation and heat conduction errors, thus improving the accuracy and precision of the supply and return water temperature difference measurement.

[0162] The aforementioned method for correcting the fluid temperature in heating pipes first utilizes CFD simulation technology. By setting different combinations of pipe materials, media, insulation, flow velocity, and environmental conditions (external air temperature, ambient wind speed), it systematically simulates the heat transfer state under various real-world scenarios, generating a high-quality dataset that covers a wide range of conditions and more comprehensively reflects the complex heat exchange processes in the real world. Then, based on this dataset, a multiple linear regression method is used to establish accurate prediction models for different pipe material-fluid medium combinations, providing a complete method for correcting the fluid temperature in heating pipes. A concise linear correction formula is generated, enabling testing personnel to quickly and accurately obtain the fluid temperature on-site by using the provided formula, after obtaining known parameters such as external air temperature, medium flow velocity, outer wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness. Furthermore, this invention provides a method for correcting the supply and return water temperature difference. Based on the correction of the heating pipe fluid temperature, it further derives the relationship between the supply and return water temperature difference and the outer wall temperature under different pipe material and fluid medium combinations. The linear correlation between surface temperature difference and other parameters is established. Compared with existing technologies, this invention, on the one hand, constructs a complete method for correcting the fluid temperature test and the supply and return water temperature difference test of heating pipes, based on a comprehensive consideration of environmental radiation and heat conduction errors. It considers other environmental parameters and the influence of pipes and related materials on fluid temperature, based on the external wall surface temperature. This allows testing personnel to correct the fluid temperature test and the supply and return water temperature difference using the correction formulas provided by this invention, thus addressing the deficiencies of current building energy conservation testing standards. It provides testing personnel in engineering practice with applicable correction formulas and improves the accuracy and precision of fluid temperature and supply and return water temperature difference measurements, providing reliable data support for building energy conservation optimization and policy implementation. On the other hand, the fluid temperature test and supply and return water temperature difference test correction methods constructed by this invention are differentiated according to pipe material and fluid medium combination, ensuring that the correction methods are optimized under their most suitable physical conditions, resulting in higher prediction accuracy and meeting the diverse application scenarios of pipe materials and fluid media in professional heating systems.

[0163] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for correcting the temperature of fluid in heating pipes, characterized in that, Includes the following steps: S0. Construct a CFD three-dimensional simulation geometric model to simulate the temperature transfer between the outer wall of the pipe and the fluid, specifically including: A three-dimensional simulation geometric model is established based on the pipe material and specifications, the insulation layer material and thickness, and the fluid medium type. S1. Set the simulation parameters and boundary conditions for the above CFD three-dimensional simulation geometric model, specifically including: Set simulation parameters, including pipe material and specifications, insulation layer material and thickness, and thermal properties of pipe material, insulation layer material and fluid medium; Set boundary conditions, including fluid temperature and medium flow rate, and external air temperature and ambient wind speed; S2. Perform numerical simulation calculations within the CFD three-dimensional simulation geometric model, specifically including: Coupled heat transfer simulation was performed using the Standard k-epsilon turbulence model, the Standard Wall Function (SWF), and the Rosseland radiation model. Steady-state heat transfer calculations were performed under various combinations of simulation parameters and boundary conditions set in S1 to obtain the outer wall temperature under various combined conditions. S3. Obtain datasets for different combinations of pipe materials and fluid media, specifically including: For different combinations of pipe materials and fluid media, the external wall temperature and the corresponding seven key parameters under various combined working conditions in S2 are extracted to form a dataset. The seven key parameters include external air temperature, medium flow rate, fluid temperature, ambient wind speed, pipe outer diameter, pipe wall thickness, and insulation layer thickness. S4. Construct fluid temperature-outer wall temperature regression models for different pipe materials and fluid medium combinations, specifically including: Based on the datasets obtained in S3 for different combinations of pipe materials and fluid media, fluid temperature is used as the response variable, and the corresponding external air temperature, medium flow rate, external wall temperature, ambient wind speed, pipe outer diameter, pipe wall thickness and insulation layer thickness are used as prediction variables. Multiple linear regression was used to construct regression models for different pipe materials and fluid media combinations. S5. Construct fluid temperature correction formulas for different combinations of pipe materials and fluid media, specifically including: Based on the regression model described in S4, obtain the regression coefficients and intercept; Based on the regression coefficients and intercepts, a fluid temperature correction formula is constructed for different combinations of pipe materials and fluid media.

2. The method for correcting the temperature of fluid in heating pipelines as described in claim 1, characterized in that: The pipe materials include metal pipes and plastic pipes; The insulation layer material includes rubber and plastic sponge; The fluid medium includes water and antifreeze; The fluid temperature is 30°C to 50°C; The medium flow velocity is from 0.6 m / s to 1.4 m / s; The outside air temperature is -15°C to 15°C; The ambient wind speed is between 0 m / s and 3.0 m / s.

3. The method for correcting the temperature of fluid in heating pipes as described in claim 2, characterized in that: The metal pipe is a galvanized steel pipe; the plastic pipe is a PPR pipe. The different pipe materials and fluid media combinations include: galvanized steel pipe-water, galvanized steel pipe-antifreeze, PPR pipe-water, and PPR pipe-antifreeze.

4. The method for correcting the temperature of fluid in heating pipes as described in claim 3, characterized in that: Define the following variable symbols: P1: External wall surface temperature; P2: Medium flow rate; P3: Fluid temperature; P4: Ambient air temperature; P5: Ambient wind speed; P6: Pipe outer diameter; P7: Pipe wall thickness; P8: Insulation layer thickness; The fluid temperature correction formulas are as follows: Galvanized steel pipe-water combination: P3=9.3029-0.0670×P1+0.0254×P2+0.9036×P4+1.4165×P5-0.0057×P6-0.2492×P8 Galvanized steel pipe-antifreeze combination: P3=9.3421-0.0686×P1+0.0793×P2+0.9002×P4+1.4133×P5-0.0032×P6-0.2545×P8 PPR pipe-water combination: P3=8.6460-0.0974×P1+0.1321×P2+0.8557×P4+2.1374×P5-0.0114×P6+0.4311×P7-0.2633×P8 PPR pipe-antifreeze combination: P3=17.1756-0.0936×P1+0.1329×P2+0.7136×P4+1.7353×P5-0.0312×P6 +0.4352×P7-0.3380×P8.

5. A method for correcting the temperature difference between supply and return water in heating pipes, characterized in that, Includes the following steps: Obtain temperature measurements of the outer wall surfaces of water supply and return pipes; Based on the fluid temperature correction formula corresponding to the current pipeline and medium obtained by the fluid temperature test correction method for heating pipelines as described in any one of claims 1-4, the correction values ​​for supply water temperature and return water temperature are calculated respectively. Calculate the supply and return water temperature difference correction value based on the supply water temperature correction value and the return water temperature correction value.

6. The method for correcting the temperature difference between supply and return water in heating pipelines as described in claim 5, characterized in that: The formula for calculating the supply and return water temperature difference correction value ΔP3 is as follows: Under the galvanized steel pipe-water combination: ΔP3 = 0.9036 × ΔP1 Under the combination of galvanized steel pipe and antifreeze: ΔP3 = 0.9002 × ΔP1 Under the PPR pipe-water combination: ΔP3 = 0.8557 × ΔP1 Under the PPR pipe-antifreeze combination: ΔP3 = 0.7136 × ΔP1 Wherein, ΔP1 is the difference between the measured temperatures of the outer walls of the water supply pipe and the return pipe.

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