A method for calculating heat transfer through a hydraulic line of a fuel tank

Abstract

The application belongs to the technical field of electromechanical and hydraulic pressure, and particularly relates to a method for calculating heat transfer of hydraulic pipeline through a fuel tank. The method comprises the following steps: determining whether the flow state of hydraulic oil in the conduit is turbulent flow according to the Reynolds number; if so, calculating the first heat transfer coefficient in the conduit according to the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation and the relationship equation between the first Nusselt number and the heat transfer coefficient; calculating the second heat transfer coefficient outside the conduit according to the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation and the relationship equation between the second Nusselt number and the heat transfer coefficient; obtaining the total heat transfer coefficient equation of the pipeline, and calculating the total heat transfer coefficient of the pipeline according to the first heat transfer coefficient, the second heat transfer coefficient and the total heat transfer coefficient equation of the pipeline. The application can quickly obtain the heat transfer coefficient of the hydraulic pipeline, has very high calculation accuracy, has a strong guiding role for the design of the hydraulic pipeline, and has strong engineering practicability.

Description

Technical Field

[0001] This application belongs to the field of electromechanical and hydraulic technology, and specifically relates to a method for calculating heat transfer in hydraulic pipelines flowing through a fuel tank. Background Technology

[0002] The temperature type of a hydraulic system is the most important basis for the design of the hydraulic system and its components. The appropriate selection of the hydraulic system's temperature type is crucial for the system's thermal design and temperature control design. While meeting the requirements of the aircraft and the system, improving the accuracy of the system's heat dissipation capacity calculations and adopting simple and effective system heat dissipation solutions is of great significance for ensuring the hydraulic system's functionality, performance indicators, and weight control.

[0003] Previous designs for cooling hydraulic systems primarily focused on components with significant leakage, such as hydraulic pumps and steering gears, by placing heat exchangers in their return oil lines. It was rare to incorporate piping into the fuel tank to achieve heat exchange between the hydraulic fluid and fuel. Furthermore, a suitable calculation method for calculating the heat exchange between hydraulic fluid and fuel through piping has remained elusive.

[0004] Therefore, it is desirable to have a technical solution to overcome or at least mitigate one of the aforementioned defects of the prior art. Summary of the Invention

[0005] The purpose of this application is to provide a method for calculating heat transfer in hydraulic pipelines flowing through a fuel tank, in order to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A method for calculating heat transfer in hydraulic lines flowing through a fuel tank, comprising:

[0008] Step 1: Obtain the Reynolds number equation for the hydraulic oil inside the conduit, calculate the Reynolds number of the hydraulic oil inside the conduit, and determine whether the flow state of the hydraulic oil inside the conduit is turbulent based on the Reynolds number. If so,

[0009] Obtain the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient within the duct. Calculate the first heat transfer coefficient within the duct based on the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient.

[0010] Step 2: Obtain the second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient for the fuel outside the duct. Calculate the second heat transfer coefficient outside the duct based on the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient.

[0011] Step 3: Obtain the overall heat transfer coefficient equation for the pipeline, and calculate the overall heat transfer coefficient of the pipeline based on the first heat transfer coefficient, the second heat transfer coefficient, and the overall heat transfer coefficient equation for the pipeline.

[0012] In at least one embodiment of this application, in step one, the Reynolds number equation of the hydraulic oil in the conduit is obtained, the Reynolds number of the hydraulic oil in the conduit is calculated, and the flow state of the hydraulic oil in the conduit is determined based on the Reynolds number. If it is turbulent,

[0013] Obtain the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient within the duct. Based on the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient, calculate the first heat transfer coefficient within the duct, including:

[0014] The Reynolds number equation for obtaining the hydraulic oil in the conduit is as follows:

[0015]

[0016] Where Re is the Reynolds number, V is the hydraulic oil flow rate, d1 is the inner diameter of the conduit, υ1 is the kinematic viscosity of the hydraulic oil, and Q is the hydraulic oil flow rate;

[0017] Calculate the Reynolds number of the hydraulic oil in the conduit, and determine whether the flow state of the hydraulic oil in the conduit is turbulent based on the Reynolds number. If so,

[0018] The equations for the first Prandtl number, the first heat transfer criterion, and the relationship between the first Nusselt number and the heat transfer coefficient are obtained within the duct.

[0019] The first Prandtl number equation is:

[0020]

[0021] Where Pr is the Prandtl number, C P1 ρ is the specific heat capacity of the hydraulic oil, ρ1 is the density of the hydraulic oil, and λ1 is the thermal conductivity of the hydraulic oil.

[0022] The first heat transfer criterion equation is:

[0023] Nu = 0.023Re 0.8 Prn (3)

[0024] Where Nu is the Nusselt number and Pr is the Prandtl number;

[0025] n is 0.4 when the liquid is heated and 0.3 when the liquid is cooled;

[0026] The equation relating the first Nusselt number to the heat transfer coefficient is as follows:

[0027]

[0028] Where k1 is the first heat transfer coefficient;

[0029] The first heat transfer coefficient inside the duct is calculated based on the Reynolds number equation (1), the first Prandtl number equation (2), the first heat transfer criterion equation (3), and the first Nusselt number and heat transfer coefficient relationship equation (4).

[0030] In at least one embodiment of this application, step two, which involves obtaining the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient of the fuel outside the duct, and calculating the second heat transfer coefficient outside the duct based on the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient, includes:

[0031] The second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and equation relating the second Nusselt number to the heat transfer coefficient are obtained for the fuel oil outside the duct.

[0032] The second Prandtl number equation is:

[0033]

[0034] Where Pr is Prandtl number, υ2 is fuel kinematic viscosity, and C P2 ρ2 is the specific heat capacity of the fuel, ρ2 is the density of the fuel, and λ2 is the thermal conductivity of the fuel.

[0035] The Grashof number equation is:

[0036]

[0037] Where g is the acceleration due to gravity, β t d2 is the volume expansion coefficient, Δt is the temperature difference between the fuel and the duct wall, and d2 is the outer diameter of the duct.

[0038] The second heat transfer criterion equation is:

[0039] Nu = C(Gr·Pr) N (7)

[0040] Where Nu is the Nusselt number, C is a constant, Gr is the Grashof number, Pr is the Prandtl number, and N is 1 / 3;

[0041] The equation relating the second Nusselt number to the heat transfer coefficient is as follows:

[0042]

[0043] Where k2 is the second heat transfer coefficient;

[0044] The second heat transfer coefficient outside the duct is calculated based on the second Prandtl number equation (5), the Grashof number equation (6), the second heat transfer criterion equation (7), and the second Nusselt number and heat transfer coefficient relationship equation (8).

[0045] In at least one embodiment of this application, step three, which involves obtaining the overall heat transfer coefficient equation for the pipeline and calculating the overall heat transfer coefficient of the pipeline based on the first heat transfer coefficient, the second heat transfer coefficient, and the overall heat transfer coefficient equation, includes:

[0046] Equation for obtaining the overall heat transfer coefficient of the pipeline:

[0047]

[0048] Where K is the overall heat transfer coefficient of the pipeline, k1 is the first heat transfer coefficient, d1 is the inner diameter of the conduit, k2 is the second heat transfer coefficient, d2 is the outer diameter of the conduit, and λ is the thermal conductivity of the pipe wall.

[0049] Substitute the first heat transfer coefficient and the second heat transfer coefficient into the equation for the overall heat transfer coefficient of the pipeline to calculate the overall heat transfer coefficient of the pipeline.

[0050] In at least one embodiment of this application, step four is also included.

[0051] Obtain the heat dissipation equation for the duct flowing through the fuel tank:

[0052]

[0053] Among them, C P1 Let ρ be the specific heat capacity of the hydraulic oil, Q be the hydraulic oil flow rate, ρ1 be the density of the hydraulic oil, K be the overall heat transfer coefficient of the pipeline, A be the outer surface area of ​​the conduit flowing through the fuel tank, and T be the specific heat capacity of the hydraulic oil. 0 T represents the initial temperature of the hydraulic oil. 1 T represents the temperature of the hydraulic oil after it flows through the fuel tank. a Ambient temperature;

[0054] The hydraulic oil temperature rise caused by the motor operation is obtained, and the hydraulic oil temperature drop after flowing through the fuel tank is obtained based on the hydraulic oil temperature rise caused by the motor operation, wherein the hydraulic oil temperature drop is equal to the hydraulic oil temperature rise.

[0055] The hydraulic oil temperature after flowing through the fuel tank is calculated based on the initial hydraulic oil temperature and the hydraulic oil temperature drop.

[0056] Substitute the temperature of the hydraulic oil flowing through the fuel tank into the heat dissipation equation of the duct flowing through the fuel tank to calculate the outer surface area of ​​the duct flowing through the fuel tank.

[0057] In at least one embodiment of this application, the method further includes step five: calculating the length of the conduit flowing through the fuel tank based on the outer surface area of ​​the conduit.

[0058] The invention has at least the following beneficial technical effects:

[0059] The heat transfer calculation method for hydraulic pipelines flowing through the fuel tank presented in this application can quickly obtain the heat transfer coefficient of the hydraulic pipeline with very high calculation accuracy. It has a strong guiding role in the design of hydraulic pipelines and has strong engineering applicability. Attached Figure Description

[0060] Figure 1 This is a flowchart of a heat transfer calculation method for a hydraulic pipeline flowing through a fuel tank, according to one embodiment of this application. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0063] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0064] This application provides a method for calculating heat transfer in hydraulic pipelines flowing through a fuel tank, including the following steps:

[0065] Step 1: Obtain the Reynolds number equation for the hydraulic oil in the conduit, calculate the Reynolds number of the hydraulic oil in the conduit, and determine whether the flow state of the hydraulic oil in the conduit is turbulent based on the Reynolds number. If so, obtain the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient in the conduit. Calculate the first heat transfer coefficient in the conduit based on the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient.

[0066] Step 2: Obtain the second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient for the fuel outside the duct. Calculate the second heat transfer coefficient outside the duct based on the second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient.

[0067] Step 3: Obtain the equation for the overall heat transfer coefficient of the pipeline, and calculate the overall heat transfer coefficient of the pipeline based on the first heat transfer coefficient, the second heat transfer coefficient, and the equation for the overall heat transfer coefficient of the pipeline.

[0068] The heat transfer calculation method for the hydraulic pipeline flowing through the fuel tank in this application includes, in step one:

[0069] The heat transfer within the duct is a forced convection heat transfer mode. The Reynolds number equation for the hydraulic oil within the duct is as follows:

[0070]

[0071] Where Re is the Reynolds number, V is the hydraulic oil flow rate, d1 is the inner diameter of the conduit, υ1 is the kinematic viscosity of the hydraulic oil, and Q is the hydraulic oil flow rate;

[0072] Calculate the Reynolds number of the hydraulic oil in the conduit, and determine whether the flow state of the hydraulic oil in the conduit is turbulent based on the Reynolds number. The hydraulic oil in the conduit is usually turbulent.

[0073] When the flow state of the hydraulic oil inside the conduit is turbulent, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient are obtained.

[0074] The equation for the first Prandtl number is:

[0075]

[0076] Where Pr is the Prandtl number, C P1 ρ is the specific heat capacity of the hydraulic oil, ρ1 is the density of the hydraulic oil, and λ1 is the thermal conductivity of the hydraulic oil.

[0077] In this embodiment, υ1 is 4.5 × 10 -6 m 2 / s, C P1 Take 2.2 KJ / (kg·K), and ρ1 take 833.3 kg / m³. 3 If λ1 is taken as 0.109 W / (m·K), then equation (2) is:

[0078]

[0079] The first heat transfer criterion equation for forced convection heat transfer turbulent flow within the duct is:

[0080] Nu = 0.023Re 0.8 Pr n (3)

[0081] Where Nu is the Nusselt number and Pr is the Prandtl number;

[0082] n is 0.4 when the liquid is heated and 0.3 when the liquid is cooled;

[0083] Substituting formulas (1) and (2) into formula (3), the Nusselt number when the hydraulic oil is heated is calculated:

[0084] Nu = 0.023 × 8462.2 0.8 ×75.7 0.4 ≈180

[0085] The equation relating the first Nusselt number to the heat transfer coefficient is:

[0086]

[0087] Where k1 is the first heat transfer coefficient;

[0088] Substitute the Nusselt number into the equation (4) relating the first Nusselt number to the heat transfer coefficient to calculate the first heat transfer coefficient k1.

[0089] The heat transfer calculation method for the hydraulic pipeline flowing through the fuel tank in this application, step two, specifically includes:

[0090] The second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and equation relating the second Nusselt number to the heat transfer coefficient are obtained for the fuel oil outside the duct.

[0091] The equation for the second Prandtl number is:

[0092]

[0093] Where Pr is Prandtl number, υ2 is fuel kinematic viscosity, and C P2 ρ2 is the specific heat capacity of the fuel, ρ2 is the density of the fuel, and λ2 is the thermal conductivity of the fuel.

[0094] The Grashof number equation is:

[0095]

[0096] Where g is the acceleration due to gravity, β t d2 is the volume expansion coefficient, Δt is the temperature difference between the fuel and the duct wall, and d2 is the outer diameter of the duct.

[0097] The second heat transfer criterion equation is:

[0098] Nu = C(Gr·Pr) N (7)

[0099] Where Nu is the Nusselt number, C is a constant, Gr is the Grashof number, Pr is the Prandtl number, and N is 1 / 3;

[0100] In one embodiment of this application, the fuel oil has a limiting temperature of 60°C, and its thermal properties are as follows:

[0101] υ2=0.89×10 -6 m 2 / s

[0102] C P = 2.1 kJ / (kg·K)

[0103] ρ2=749.8kg / m3

[0104] λ² = 0.1105 W / (m·K)

[0105] β t =1.123×10 -3 K -1

[0106] Therefore, in this embodiment,

[0107] Gr·Pr=5.27×10 7

[0108] Substituting Prandtl number and Grashof number into the second heat transfer criterion equation (7), the Nusselt number is calculated;

[0109] Nu = 0.135 × (5.27 × 10) 7 ) 1 / 3 =50.614

[0110] The equation relating the second Nusselt number to the heat transfer coefficient is:

[0111]

[0112] Where k2 is the second heat transfer coefficient;

[0113] In this embodiment, the Nusselt number is substituted into the equation relating the second Nusselt number and the heat transfer coefficient to calculate the second heat transfer coefficient as follows:

[0114] k2 = 349.6

[0115] The heat transfer calculation method for the hydraulic pipeline flowing through the fuel tank in this application, step three specifically includes:

[0116] Equation for obtaining the overall heat transfer coefficient of the pipeline:

[0117]

[0118] Where K is the overall heat transfer coefficient of the pipeline, k1 is the first heat transfer coefficient, d1 is the inner diameter of the conduit, k2 is the second heat transfer coefficient, d2 is the outer diameter of the conduit, and λ is the thermal conductivity of the pipe wall.

[0119] Substitute the first heat transfer coefficient and the second heat transfer coefficient into the overall heat transfer coefficient equation (9) of the pipeline to calculate the overall heat transfer coefficient K of the pipeline.

[0120] In a certain model design, a hydraulic motor is added to the hydraulic system. During motor operation, leakage causes a temperature rise in the hydraulic oil at the motor's return point compared to the inlet. The design must consider how to effectively reduce the temperature rise caused by the motor's operation. Besides integrating the motor's return oil into the main system radiator, another approach is to have the motor's return oil line flow through the relatively cooler fuel tank, thus achieving heat dissipation. The design must ensure a good match between the material, diameter, and length of the motor's return oil line, so that the temperature rise of the hydraulic oil caused by the motor's operation is consistent with the temperature drop of the return oil after flowing through the fuel tank, thereby canceling each other out.

[0121] The heat transfer calculation method for hydraulic pipelines flowing through the fuel tank in this application also includes step four: obtaining the heat dissipation equation of the conduit flowing through the fuel tank.

[0122]

[0123] Among them, C P1 Let ρ be the specific heat capacity of the hydraulic oil, Q be the hydraulic oil flow rate, ρ1 be the density of the hydraulic oil, K be the overall heat transfer coefficient of the pipeline, A be the outer surface area of ​​the conduit flowing through the fuel tank, and T be the specific heat capacity of the hydraulic oil. 0 T represents the initial temperature of the hydraulic oil. 1 T represents the temperature of the hydraulic oil after it flows through the fuel tank. a Ambient temperature;

[0124] The hydraulic oil temperature rise caused by the motor operation is obtained, and the hydraulic oil temperature drop after flowing through the fuel tank is obtained based on the hydraulic oil temperature rise caused by the motor operation. The hydraulic oil temperature drop is equal to the hydraulic oil temperature rise.

[0125] The hydraulic oil temperature after flowing through the fuel tank is calculated based on the initial hydraulic oil temperature and the hydraulic oil temperature drop.

[0126] Substitute the temperature of the hydraulic oil flowing through the fuel tank into the heat dissipation equation (10) for the duct flowing through the fuel tank to calculate the outer surface area of ​​the duct flowing through the fuel tank.

[0127] It also includes step five, calculating the length of the conduit flowing through the fuel tank based on the outer surface area of ​​the conduit.

[0128] In one embodiment of this application, based on the working efficiency and flow rate of a certain model of motor, the calculated temperature rise of the hydraulic oil after passing through the motor is 3°C. If the temperature drop of the hydraulic oil returning from the motor after flowing through the fuel tank needs to reach 3°C, when the material selected for the motor return oil is 1Cr18Ni10Ti, and the inner and outer diameters of the conduit are d1 = 0.014m and d2 = 0.016m, the required conduit length inside the fuel tank is 5mm. After implementing design measures based on the calculation results, laboratory and on-board temperature tests were conducted. The test results show that the temperature drop of the hydraulic oil returning from the motor after flowing through the fuel tank reaches 3.2°C, which is very close to the calculated result of 3°C, proving that the design of the motor return oil pipeline material, diameter, and length based on the calculation results is very reasonable.

[0129] The heat transfer calculation method for hydraulic pipelines flowing through fuel tanks presented in this application can perform heat transfer calculations for hydraulic pipelines of all specifications, materials, and wall thicknesses flowing through fuel tanks and other compartments where the working medium is air. It is also applicable to conduits in fluid systems other than hydraulic systems. Furthermore, actual temperature testing has demonstrated very high calculation accuracy, providing strong guidance for design and exhibiting significant engineering practicality.

[0130] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for calculating heat transfer in a hydraulic pipeline flowing through a fuel tank, characterized in that, include: Step 1: Obtain the Reynolds number equation for the hydraulic oil inside the conduit, calculate the Reynolds number of the hydraulic oil inside the conduit, and determine whether the flow state of the hydraulic oil inside the conduit is turbulent based on the Reynolds number. If so, Obtain the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient within the duct. Calculate the first heat transfer coefficient within the duct based on the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient. Step 2: Obtain the second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient for the fuel outside the duct. Calculate the second heat transfer coefficient outside the duct based on the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient. Step 3: Obtain the overall heat transfer coefficient equation for the pipeline, and calculate the overall heat transfer coefficient of the pipeline based on the first heat transfer coefficient, the second heat transfer coefficient, and the overall heat transfer coefficient equation for the pipeline, including: Equation for obtaining the overall heat transfer coefficient of the pipeline: ； Where K is the overall heat transfer coefficient of the pipeline. The first heat transfer coefficient, The inner diameter of the catheter. The second heat transfer coefficient, The outer diameter of the catheter. The thermal conductivity of the pipe wall; Substitute the first heat transfer coefficient and the second heat transfer coefficient into the equation for the total heat transfer coefficient of the pipeline to calculate the total heat transfer coefficient of the pipeline. Step Four Obtain the heat dissipation equation for the duct flowing through the fuel tank: （10）； in, The specific heat capacity of hydraulic oil. Hydraulic oil flow rate Let K be the density of the hydraulic oil, K be the overall heat transfer coefficient of the pipeline, and A be the outer surface area of ​​the conduit flowing through the fuel tank. The initial temperature of the hydraulic oil. The temperature of the hydraulic oil after it flows through the fuel tank. The ambient temperature; The hydraulic oil temperature rise caused by the motor operation is obtained, and the hydraulic oil temperature drop after flowing through the fuel tank is obtained based on the hydraulic oil temperature rise caused by the motor operation, wherein the hydraulic oil temperature drop is equal to the hydraulic oil temperature rise. The hydraulic oil temperature after flowing through the fuel tank is calculated based on the initial hydraulic oil temperature and the hydraulic oil temperature drop. Substitute the temperature of the hydraulic oil flowing through the fuel tank into the heat dissipation equation of the duct flowing through the fuel tank to calculate the outer surface area of ​​the duct flowing through the fuel tank.

2. The heat transfer calculation method for hydraulic pipelines flowing through the fuel tank according to claim 1, characterized in that, In step one, the Reynolds number equation for the hydraulic oil inside the conduit is obtained, the Reynolds number of the hydraulic oil inside the conduit is calculated, and the flow state of the hydraulic oil inside the conduit is determined based on the Reynolds number. If it is turbulent, Obtain the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient within the duct. Based on the Reynolds number equation, the first Prandtl number equation, the first heat transfer criterion equation, and the equation relating the first Nusselt number to the heat transfer coefficient, calculate the first heat transfer coefficient within the duct, including: The Reynolds number equation for obtaining the hydraulic oil in the conduit is as follows: （1）； in, The Reynolds number is... Hydraulic oil flow rate The inner diameter of the catheter. The kinematic viscosity of hydraulic oil. Hydraulic oil flow rate; Calculate the Reynolds number of the hydraulic oil in the conduit, and determine whether the flow state of the hydraulic oil in the conduit is turbulent based on the Reynolds number. If so, The equations for the first Prandtl number, the first heat transfer criterion, and the relationship between the first Nusselt number and the heat transfer coefficient are obtained within the duct. The first Prandtl number equation is: （2）； Where Pr is the Prandtl number, The specific heat capacity of hydraulic oil. The density of the hydraulic oil, The thermal conductivity of the hydraulic oil; The first heat transfer criterion equation is: （3）； in, Let Pr be a Nusselt number and Pr be a Prandtl number. n is 0.4 when the liquid is heated and 0.3 when the liquid is cooled; The equation relating the first Nusselt number to the heat transfer coefficient is as follows: （4）； in, The first heat transfer coefficient; The first heat transfer coefficient inside the duct is calculated based on the Reynolds number equation (1), the first Prandtl number equation (2), the first heat transfer criterion equation (3), and the first Nusselt number and heat transfer coefficient relationship equation (4).

3. The heat transfer calculation method for hydraulic pipelines flowing through the fuel tank according to claim 2, characterized in that, In step two, obtaining the second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient for the fuel outside the duct, and calculating the second heat transfer coefficient outside the duct based on the second Prandtl number equation, the Grashof number equation, the second heat transfer criterion equation, and the equation relating the second Nusselt number to the heat transfer coefficient, includes: The second Prandtl number equation, Grashof number equation, second heat transfer criterion equation, and equation relating the second Nusselt number to the heat transfer coefficient are obtained for the fuel oil outside the duct. The second Prandtl number equation is: （5）； Where Pr is the Prandtl number, For fuel kinematic viscosity, For the specific heat capacity of fuel oil, The density of fuel, The thermal conductivity of fuel oil; The Grashof number equation is: （6）； Where g is the acceleration due to gravity. The coefficient of volume expansion is 1. The temperature difference between the fuel and the duct wall. The outer diameter of the catheter; The second heat transfer criterion equation is: （7）； in, For Nusselt numbers, It is a constant. Let Pr be a Grashof number and Pr be a Prandtl number. It is 1 / 3; The equation relating the second Nusselt number to the heat transfer coefficient is as follows: （8）； in, The second heat transfer coefficient; The second heat transfer coefficient outside the duct is calculated based on the second Prandtl number equation (5), the Grashof number equation (6), the second heat transfer criterion equation (7), and the second Nusselt number and heat transfer coefficient relationship equation (8).

4. The heat transfer calculation method for hydraulic pipelines flowing through the fuel tank according to claim 3, characterized in that, It also includes step five, calculating the length of the conduit flowing through the fuel tank based on the outer surface area of ​​the conduit.

Images