Channel heat pipe heat transfer limit obtaining method and device considering selective laser melting manufacturing error

Abstract

The invention belongs to the related technical field of heat pipe heat transfer, and discloses a channel heat pipe heat transfer limit obtaining method and device considering selective laser melting manufacturing errors, and the method comprises the steps: (1) employing a linear least square method to carry out the fitting of the design size and the corresponding actual size of a channel type heat pipe, and obtaining a size prediction model; (2) replacing corresponding geometric dimension parameters in the classical one-dimensional heat transfer flow model with a calculation formula of geometric dimension parameters in the dimension prediction model to obtain a heat pipe heat transfer flow model; and (3) carrying out iterative solution on the heat pipe heat transfer flow model based on the design geometric dimension parameters of the channel type heat pipe to be tested until the radius of the meniscus reaches the minimum value, and stopping iteration, wherein the heating power adopted when the radius of the meniscus reaches the minimum value is the heat transfer limit. The prediction accuracy of the heat transfer limit of the channel is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to heat transfer of heat pipes, and more specifically, relates to a method and device for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing errors of selective laser melting. Background Art

[0002] Channel heat pipes have excellent heat transfer performance and working stability, and have been widely used in the thermal management of electronic devices, aerospace, and energy industries. There have been many research results on the theoretical study of the heat transfer performance of heat pipes. For example, Chinese invention patent CN201110029101.8 discloses a mathematical modeling method for studying the heat transfer performance of microchannel flat heat pipes, and compares the calculation results, simulation results, and experimental results, proving that the mathematical model is consistent with the actual situation. Many studies have shown that the shape and size of the channel wick are closely related to the heat transfer performance of the heat pipe.

[0003] The traditional manufacturing process of channel heat pipes is relatively complex. It is necessary to first machine a channel wick in the pipe by broaching, extrusion, etc., and then weld the channel wick together with the two end caps and the liquid filling pipe. With the rapid development of additive manufacturing technology, metal additive manufacturing technologies represented by selective laser melting (SLM) have been applied to the manufacturing of channel heat pipes, simplifying the manufacturing process of heat pipes and improving the manufacturing flexibility. However, the SLM process may cause phenomena such as balling and thermal deformation in parts, so there will be certain manufacturing errors in the channels inside the manufactured heat pipes. When designing heat pipes, the heat transfer limit is often used as the design goal of the heat pipe. In the existing thermal management theory models, due to the lack of consideration of the manufacturing errors of SLM, the prediction of the heat transfer limit of the heat pipe is inaccurate, which may lead to the actual heat transfer limit of the finally manufactured heat pipe not meeting the design requirements, hindering the application of SLM technology in heat pipe manufacturing. Summary of the Invention

[0004] In view of the above defects or improvement requirements of the prior art, the present invention provides a method and device for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing errors of selective laser melting, aiming to solve the problem that the prediction accuracy of the heat transfer limit of the channel is relatively low due to the lack of consideration of the manufacturing errors of SLM in the existing model.

[0005] To achieve the above object, according to one aspect of the present invention, a method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing errors of selective laser melting is provided. The method includes the following steps:

[0006] (1) Use the linear least squares method to fit the design dimensions and the corresponding actual dimensions of the channel heat pipe to obtain a dimension prediction model;

[0007] (2) Replace the calculation formula of the geometric dimension parameters in the dimension prediction model with the corresponding geometric dimension parameters in the classical one-dimensional heat transfer and flow model to obtain the heat pipe heat transfer and flow model;

[0008] (3) Based on the designed geometric dimension parameters of the to-be-tested channel heat pipe, perform iterative solution on the heat pipe heat transfer and flow model until the meniscus radius reaches the minimum value and stop the iteration. The heating power adopted when the meniscus radius reaches the minimum value is the heat transfer limit.

[0009] Further, the mathematical expression of the dimension prediction model is the mapping relationship between the designed dimension and the actual dimension obtained by fitting, which is:

[0010] w1 = -235.9333 + 1.0455w0 - 0.0155h g0 + 0.3775w t

[0011] h g = -235.0467 + 0.1228w0 + 1.0001h g0 + 0.3123w t

[0012] w2 = -21.7067 + 0.9624w0 - 0.0042h g0 + 0.6110w t

[0013] α = 45°

[0014] In the formula, w1 is the actual groove width of the channel, w2 is the groove width at the opening of the channel, α is the inclination angle at the actual channel opening; h g is the actual groove depth; w0 is the designed groove width, h g0 is the designed groove depth, w t is the designed groove tooth thickness.

[0015] Further, when reaching the heat transfer limit, the meniscus radius of the liquid surface in the evaporation end groove is the smallest, and r(x) is used to represent the meniscus radius; the groove depth h g1 of the lower part of the channel is:

[0016]

[0017] The contact angle θ between the working fluid liquid and the channel is:

[0018]

[0019] The liquid area A l on the cross-section of the channel is:

[0020]

[0021] According to the definition of hydraulic diameter, the hydraulic diameter D of the liquid hl is as follows:

[0022]

[0023] Furthermore, the axial heat flux density distributions in the evaporation section, adiabatic section, and condensation section of the heat pipe are as follows:

[0024]

[0025] From mass conservation, the reflux flow rate of the liquid in the channel is equal to the evaporation rate of the liquid evaporated into steam, and the axial mass flow rates of the liquid and steam are:

[0026]

[0027] In the formula, Q in is the heating power; L e is the length of the evaporation section; L a is the length of the adiabatic section; L c is the length of the condensation section.

[0028] Furthermore, considering the shear force at the liquid-vapor interface, the liquid flow resistance coefficient f l Re l is as follows:

[0029]

[0030] In the formula, the liquid flow resistance coefficient f without liquid-vapor interaction l Re l0 The calculation formula is:

[0031]

[0032] where v l is the kinematic viscosity of the liquid; v v is the kinematic viscosity of the gas.

[0033] Furthermore, substitute the calculated geometric dimension parameters and axial mass flow rate into the calculation formula of the liquid flow pressure drop to calculate the flow pressure drops of the liquid and steam. The calculation formula of the liquid flow pressure drop is:

[0034]

[0035] In the formula, μ l is the dynamic viscosity of the liquid working medium; f l Re l is the liquid flow resistance coefficient; is the axial mass flow rate of the liquid, N is the number of channels; ρ l is the density of the liquid; A lis the liquid flow area of a single channel;

[0036] The calculation formula for the steam flow pressure drop is:

[0037]

[0038] In the formula, μ v is the dynamic viscosity of the steam; f v Re v is the liquid flow resistance coefficient; is the axial mass flow rate of the steam, N is the number of channels; ρ v is the density of the liquid; D hv is the hydraulic diameter of the gas flow; A v is the gas flow area.

[0039] Furthermore, the Laplace Young equation is used to represent the surface tension of the liquid:

[0040]

[0041] Differentiating the Laplace Young equation gives:

[0042]

[0043] In the formula, σ is the surface tension coefficient of the working fluid liquid

[0044] Converting the differential form of the Laplace Young equation to obtain the mathematical expression of the heat pipe heat transfer flow model and substituting the liquid flow pressure drop dP l / dx and the steam flow pressure drop dP v / dx into the mathematical expression of the heat pipe heat transfer flow model to form a differential equation about the meniscus radius r.

[0045] Furthermore, the mathematical expression of the heat pipe heat transfer flow model is:

[0046]

[0047] The input of the heat pipe heat transfer flow model is the geometric dimension parameters of the channel heat pipe, and the output is the meniscus radius.

[0048] The present invention also provides a system for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting. The system includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it executes the method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting as described above.

[0049] The present invention also provides a computer-readable storage medium storing machine-executable instructions, which, when called and executed by a processor, cause the processor to implement the method for obtaining the heat transfer limit of a microchannel heat pipe considering the manufacturing error of selective laser melting as described above.

[0050] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the method and device for obtaining the heat transfer limit of a microchannel heat pipe considering the manufacturing error of selective laser melting provided by the present invention mainly have the following beneficial effects:

[0051] 1. Using the calculation formula of the geometric dimension parameters in the dimension prediction model to replace the corresponding geometric dimension parameters in the classical one-dimensional heat transfer and flow model to obtain the heat pipe heat transfer and flow model. The dimension prediction model can accurately predict the shape and size of the microchannel after forming. Introducing it into the heat pipe heat transfer and flow model can consider the influence of SLM manufacturing deviation on the heat pipe performance, thereby improving the prediction accuracy of the microchannel heat transfer limit.

[0052] 2. Experimental verification shows that the average relative errors between the predicted values and the measured values of the actual microchannel width w1, the actual microchannel width w2 at the opening, and the actual microchannel depth h g are 4.90%, 0.35%, and 4.48% respectively, further verifying that the method provided by the present invention can more accurately predict the size of the microchannel of the heat pipe formed by SLM manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a flowchart of a method for obtaining the heat transfer limit of a microchannel heat pipe considering the manufacturing error of selective laser melting provided by the present invention;

[0054] Figure 2 is an aluminum alloy rectangular microchannel after SLM forming photographed by a laser confocal microscope;

[0055] Figure 3 is a comparison between the theoretical design size and the actual size after forming of the microchannel. (a) is the theoretical design size, and (b) is the prediction model of the actual size after forming of the microchannel proposed by the present invention;

[0056] Figure 4 is a schematic diagram of the geometric dimensions and liquid phase distribution of the microchannel cross-section;

[0057] Figure 5 is a flowchart of iterative solution;

[0058] FIG. 6(a) is an overall schematic diagram of a microchannel heat pipe manufactured by SLM;

[0059] FIG. 6(b) is a cross-sectional schematic diagram of a microchannel heat pipe manufactured by SLM.

[0060] In all the figures, the same reference numerals are used to denote the same elements or structures, where: 1 - heat pipe substrate, 2 - heat pipe body, 3 - heat pipe groove teeth, 4 - heat pipe rectangular groove. Detailed implementation mode

[0061] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0062] The present invention provides a method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting (SLM). The obtaining method constructs a size prediction model of the channel after SLM forming according to the forming characteristics of the rectangular channel manufactured by SLM, and introduces the size prediction model into the one-dimensional heat transfer and flow model of the heat pipe to form a heat transfer and flow model of the heat pipe considering the manufacturing deviation of SLM, and then uses the heat transfer and flow model of the heat pipe to obtain the heat transfer limit of the channel heat pipe to be measured. The present invention has certain guiding significance for the structural design and performance research of the channel heat pipe manufactured by SLM. Among them, on the basis of the one-dimensional heat transfer and flow model of the heat pipe, the manufacturing deviation of SLM is considered to correct the one-dimensional heat transfer and flow model to obtain the heat transfer and flow model of the heat pipe.

[0063] Please refer to Figure 1 , the obtaining method mainly includes the following steps:

[0064] Step 1, use the linear least squares method to fit the designed size and the corresponding actual size of the channel heat pipe to obtain a size prediction model.

[0065] Manufacture a series of channel samples with different sizes by SLM, Figure 2 is an aluminum alloy rectangular channel after SLM forming photographed by a laser confocal microscope. It can be observed that the shape of the actually formed channel shows a trend that the channel width gradually increases at the opening of the channel, and the shape is similar to the letter "T".

[0066] The comparison between the theoretical designed size and the actual size after forming of the channel is as Figure 3 shown. The theoretically designed channel shape is rectangular, and the designed sizes include the designed channel width w0, the designed channel depth h g0 and the designed channel tooth thickness w t ; extract the characteristic sizes of the formed channel, the actual channel width w1, the channel width w2 at the opening, and the actual channel depth h gThe inclination angle α at the opening of the channel is measured in terms of size by using a laser confocal microscope. According to the actual size after forming obtained by measurement, a mathematical model between the actual size corresponding to the designed size is fitted by using the linear least squares method for predicting the actual size after the channel is formed, and the size unit is μm for all.

[0067] The mathematical expression of the size prediction model is the mapping relationship between the designed size obtained by meshing and the actual size, specifically as follows:

[0068] w1 = -235.9333 + 1.0455w0 - 0.0155h g0 + 0.3775w t

[0069] h g = -235.0467 + 0.1228w0 + 1.0001h g0 + 0.3123w t

[0070] w2 = -21.7067 + 0.9624w0 - 0.0042h g0 + 0.6110w t

[0071] α = 45°

[0072] Step 2: Replace the geometric dimension parameters in the classical one-dimensional heat transfer and flow model with the calculation formulas of the geometric dimension parameters in the size prediction model to obtain the heat pipe heat transfer and flow model.

[0073] Step 2 is specifically as follows:

[0074] (1) Simplify the one-dimensional heat transfer and flow model

[0075] When the heat pipe works, the working medium at the evaporation end absorbs heat and changes phase into steam. The steam flows to the condensation end under the pressure difference inside the heat pipe, then releases heat and condenses into liquid working medium. Subsequently, the working medium returns to the evaporation end under the capillary force of the wick and circulates continuously.

[0076] Since the channel-type heat pipe is a symmetric structure, a single channel is taken for analysis and modeling. The geometric dimensions of the channel cross-section and the liquid phase distribution are as Figure 4As shown, based on the classical one-dimensional flow and heat transfer model of the rectangular channel heat pipe, the characteristics of the SLM process are introduced to correct the classical one-dimensional flow and heat transfer model. The establishment of the heat pipe heat transfer and flow model requires the following assumptions: (1) The flows of both the gas and liquid phases are one-dimensional laminar incompressible flows; (2) The physical property parameters of the working fluid and the tube shell material remain unchanged during the operation of the heat pipe; (3) The working fluid liquid completely wets the wick; (4) The heat pipe is placed horizontally, ignoring the influence of gravity; (5) The evaporation section of the heat pipe is uniformly heated, and the condensation section is uniformly cooled.

[0077] (2) Calculation of the geometric dimension parameters of the channel cross-section

[0078] According to Figure 4 the geometric relationships in, calculate the relevant geometric dimension parameters of the channel cross-section. During the operation of the heat pipe, the meniscus radius at the evaporation end and the condensation end is constantly changing. When reaching the heat transfer limit, the meniscus radius of the liquid surface in the groove at the evaporation end is the smallest, and r(x) is used to represent the meniscus radius.

[0079] The groove depth h of the lower part of the channel g1 is:

[0080]

[0081] The contact angle θ between the working fluid liquid and the channel is:

[0082]

[0083] The liquid area A on the channel cross-section l is:

[0084]

[0085] According to the definition of the hydraulic diameter, the liquid hydraulic diameter D hl is:

[0086]

[0087] (3) Calculate the axial mass flow rate according to mass conservation

[0088] According to the actual working conditions of the heat pipe and mass conservation, calculate and obtain the axial mass flow rates of the liquid and the vapor.

[0089] Under uniform heating and cooling, when the heating power is Q in , the heat gradually increases in the evaporation section, remains unchanged in the adiabatic section, and gradually decreases in the condensation section. The axial heat flux density distributions in the evaporation section, adiabatic section, and condensation section of the heat pipe are:

[0090]

[0091] According to the law of conservation of mass, the reflux flow rate of the liquid in the channel is equal to the evaporation rate of the liquid evaporated into steam. Therefore, the axial mass flow rates of the liquid and steam are as follows:

[0092]

[0093] (4) Calculate the pressure drop of vapor-liquid flow

[0094] During the flow process, the vapor and liquid will be subject to certain resistance, and due to the opposite flow directions of the vapor and liquid, there is a shear force at the vapor-liquid interface.

[0095] For laminar incompressible steam in a circular steam cavity, the steam flow resistance coefficient f can be taken v Re v = 16.

[0096] The liquid flow resistance coefficient f considering the shear force at the vapor-liquid interface l Re l is as follows:

[0097]

[0098] In the formula, the liquid flow resistance coefficient f without vapor-liquid interaction l Re l0 The calculation formula is:

[0099]

[0100] where v l is the kinematic viscosity of the liquid; ν v is the kinematic viscosity of the gas.

[0101] Substitute the geometric dimension parameters and axial mass flow rate calculated in step (2) into the calculation formulas of the liquid flow pressure drop and the steam flow pressure drop to calculate the flow pressure drops of the liquid and steam respectively.

[0102] The calculation formula for the liquid flow pressure drop is:

[0103]

[0104] In the formula, μ l is the dynamic viscosity of the liquid working medium; f l Re l is the liquid flow resistance coefficient; is the axial mass flow rate of the liquid, N is the number of channels; ρ l is the density of the liquid; A l is the liquid flow area of a single channel.

[0105] The calculation formula for the steam flow pressure drop is:

[0106]

[0107] In the formula, μ v is the dynamic viscosity of the steam; f v Re v is the liquid flow resistance coefficient; is the axial mass flow rate of the steam, N is the number of channels; ρ v is the density of the liquid; D hv is the hydraulic diameter of the gas flow; A v is the gas flow area.

[0108] (5) Obtain the mathematical expression of the heat pipe heat transfer flow model

[0109] Use the Laplace Young equation to represent the surface tension of the liquid:

[0110]

[0111] For the grooved wick, the meniscus of the liquid inside it can be approximately regarded as cylindrical, and the axial meniscus radius r ca is much larger than the radial meniscus radius r cr , that is, r ca →∞, and r cr ≈r.

[0112] Differentiate the Laplace Young equation to obtain the following formula:

[0113]

[0114] In the formula, σ is the surface tension coefficient of the working fluid liquid.

[0115] Convert the differential form of the Laplace Young equation to obtain the mathematical expression of the heat pipe heat transfer flow model, and substitute the aforementioned liquid flow pressure drop dP l / dx and the steam flow pressure drop dP v / dx into the mathematical expression of the heat pipe heat transfer flow model to form a differential equation about the meniscus radius r. When the geometric parameters of the channel, the working fluid material parameters, and the heating power are determined, this equation can be solved to obtain the axial distribution of r, and then other parameters can be calculated.

[0116] The mathematical expression of the heat pipe heat transfer flow model is:

[0117]

[0118] The input of the heat pipe heat transfer flow model is the geometric dimension parameters of the grooved heat pipe, and the output is the meniscus radius.

[0119] Step 3: Based on the designed geometric dimension parameters of the heat pipe to be measured, the heat transfer and flow model of the heat pipe is iteratively solved until the radius of the meniscus reaches the minimum value and the iteration stops. The heating power adopted when the radius of the meniscus reaches the minimum value is the heat transfer limit.

[0120] During the operation of the heat pipe, the liquid accumulates in the grooves of the condensation section, and the radius of the meniscus reaches the maximum value r at the end of the condensation section max , which is the radius of the vapor chamber and is used as the boundary condition for calculation. As the heating power increases, the evaporation rate in the evaporation section increases, and the radius of the meniscus gradually decreases. When the heat transfer limit is reached, the radius of the meniscus reaches the minimum value r min . Among them,

[0121]

[0122] The heat transfer and flow model of the heat pipe is iteratively solved. As shown in Figure 5 , the solution process is as follows:

[0123] (1) Assume a relatively small heating power Q in = 0.2 W as the initial value for calculation.

[0124] (2) Take the radius of the meniscus r(L) = r at the end of the condensation section max as the initial condition, solve the heat transfer and flow model of the heat pipe to obtain the flow and heat transfer parameters of the heat pipe under this power. The heat transfer and flow model of the heat pipe can be solved by numerical methods, and the iteration step size is taken as dx = L e / 1000.

[0125] (3) Compare the obtained r(0) with r min . If r(0) > r min , it means that the heat transfer limit has not been reached, increase Q in and solve again, increasing by 0.2 W each time; if r(0) ≤ r min (the judgment condition is that the difference between the two is less than 10 -5 ) means that the heat transfer limit has been reached, and output the Q in at this time, which is the calculation result of the heat transfer limit.

[0126] The physical meanings represented by the symbols involved in this embodiment are:

[0127] w1: The actual groove width of the groove

[0128] w2: The groove width at the opening of the groove

[0129] h g : The actual groove depth of the groove

[0130] w0 - : The theoretical designed groove width of the groove

[0131] hg0 : The theoretically designed channel depth

[0132] w t / 2: The theoretically designed channel tooth thickness

[0133] Δp cap : The capillary pressure of the wick

[0134] Δp v : The pressure drop of the vapor flowing from the evaporation end to the condensation end

[0135] Δp l ; The pressure drop of the liquid working medium flowing back from the condensation end to the evaporation end

[0136] σ: The surface tension of the liquid working medium

[0137] μ l : The dynamic viscosity of the liquid, μ v : The dynamic viscosity of the vapor

[0138] v l : The kinematic viscosity of the liquid, v v : The kinematic viscosity of the vapor

[0139] f l Re l : The liquid flow resistance coefficient, f v Re v : The vapor flow resistance coefficient

[0140] The liquid mass flow rate, The vapor mass flow rate

[0141] D hl : The hydraulic diameter of the liquid flow, D hv : The hydraulic diameter of the vapor flow

[0142] N: The number of channels

[0143] A l : The liquid flow area of a single channel, A v : The vapor flow area

[0144] ρ l : The liquid density, ρ v : The vapor density

[0145] θ: The contact angle between the liquid and the channel

[0146] Q(x): The heating power

[0147] r: The radius of the meniscus

[0148] L e : The length of the evaporation section, L a : The length of the adiabatic section, Lc : Condensing section length.

[0149] To verify the accuracy of the method proposed in the present invention, three heat pipes with different-sized channels were designed and manufactured. The heat transfer limits of the heat pipes were measured through experiments, and the measured heat transfer limits were compared with the theoretically calculated values.

[0150] The structural schematic diagram and cross-sectional view of the heat pipe are shown in Figures 6(a) and 6(b), including a heat pipe substrate 1, a heat pipe body 2, heat pipe groove teeth 3, and a heat pipe rectangular groove 4. The heat pipe shell material is AlSi10Mg, manufactured using the SLM process, with a laser power of 500 W, a scanning speed of 2 m / s, and a powder layer thickness of 0.1 mm. The heat pipe is printed along the direction perpendicular to the cross-section of the channel to avoid collapse and deformation of the channel during printing. The working fluid of the heat pipe is anhydrous ethanol, and the filling ratio is 100%.

[0151] The shell sizes of the three heat pipes are the same, as shown in Table 1.

[0152] Table 1 Structural parameters of the heat pipe shell

[0153]

[0154]

[0155] The channel sizes of the three heat pipes are different. The channel widths of the three heat pipes are 0.4 mm, 0.5 mm, and 0.6 mm respectively. The width-to-height ratio of the channels is 2, and the thickness of the groove teeth is 0.4 mm. According to the channel width, spacing, and pipe diameter dimensions, the number of channels is determined to be 25, 22, and 19 respectively. The theoretically designed dimensions of the channel width and depth, the formed dimensions predicted using the dimension prediction model proposed in the present invention, and the measured actual dimensions are shown in Table 2. It can be seen that there are certain differences between the actual dimensions of the channels and the theoretically designed dimensions. The average relative errors between the predicted values and the measured values of the actual channel width w1, the actual channel width w2 at the opening, and the actual channel depth h g are 4.90%, 0.35%, and 4.48% respectively; the method proposed in the present invention can more accurately predict the dimensions of the heat pipe channels formed by SLM manufacturing.

[0156] Table 2 Designed dimensions, predicted dimensions, and actual dimensions of the heat pipe channel structure parameters

[0157]

[0158]

[0159] The heat transfer limits of the three heat pipes were calculated respectively using the original calculation model without considering the SLM manufacturing deviation and the SLM-oriented model proposed in the present invention, and compared with the experimental measurement values. The results are shown in Table 3.

[0160] After forming by SLM, the channel size will be smaller than the original design value, resulting in an increase in the liquid flow resistance coefficient, and the channel width at the opening is larger than the design value, reducing the capillary pressure. Therefore, the calculated heat transfer limit without process correction is much larger than the measured value. The model proposed in the present invention tends to be the same as the measured value after correction and is closer to the measured value than before correction. Compared with the original model, the error between the predicted heat transfer limit value obtained by using the model proposed in the present invention and the measured value is significantly reduced, and the absolute error is stable at about 5W, which can prove the effectiveness of the model of the present invention and solve the problem of inaccurate performance prediction of heat pipes caused by manufacturing deviations of SLM.

[0161] Table 3 Comparison between the calculated value and the experimental value of the heat transfer limit

[0162]

[0163] The present invention also provides a system for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting as described above.

[0164] The present invention also provides a computer-readable storage medium. The computer-readable storage medium stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions cause the processor to implement the method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of selective laser melting as described above.

[0165] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting, characterized in that: The method comprises the following steps: (1) The linear least squares method is used to fit the design size of the channel heat pipe with the corresponding actual size to obtain a size prediction model; (2) The calculation formula of the geometric size parameters in the size prediction model is used to replace the corresponding geometric size parameters in the classical one-dimensional heat transfer flow model to obtain the heat pipe heat transfer flow model; (3) Based on the design geometric dimension parameters of the channel-type heat pipe to be tested, the heat transfer flow model of the heat pipe is iteratively solved until the radius of the meniscus reaches a minimum value and the iteration is stopped. The heating power used when the radius of the meniscus reaches the minimum value is the heat transfer limit.

2. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 1, characterized in that: The mathematical expression of the size prediction model is the mapping relationship between the designed size obtained by fitting and the actual size, which is: w1=-235.9333+1.0455w0-0.0155h g0 +0.3775w t h g =-235.0467+0.1228w0+1.0001h g0 +0.3123w t w2=-21.7067+0.9624w0-0.0042h g0 +0.6110w t α＝45° Where w1 is the actual width of the slot, w2 is the width of the slot at the opening, α is the inclination angle at the actual slot opening; h g is the actual groove depth; w0 is the designed groove width, h g0 is the designed groove depth, w t is the designed tooth thickness.

3. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 2, characterized in that: When the heat transfer limit is reached, the radius of the meniscus of the liquid surface in the evaporation end groove is the smallest, and r(x) is used to represent the radius of the meniscus; the groove depth h in the lower half of the groove g1 for: The contact angle θ between the working fluid and the channel is: Liquid area A on the channel cross section l for: According to the definition of hydraulic diameter, the liquid hydraulic diameter D hl for:

4. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 3, characterized in that: The axial heat flux density distribution of the heat pipe evaporation section, adiabatic section and condensation section is: According to the law of conservation of mass, the amount of liquid reflux in the channel is equal to the amount of evaporation into steam. The axial mass flow rates of liquid and steam are: In the formula, Q in is the heating power; L e is the length of the evaporation section; L a is the length of the insulation section; L c is the length of the condensation section.

5. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 4, characterized in that: Liquid flow resistance coefficient f considering the shear force at the vapor-liquid interface l Re l for: Where, the liquid flow resistance coefficient f when there is no vapor-liquid interaction is l Re l0 The calculation formula is: where ν l is the kinematic viscosity of the liquid; ν v is the kinematic viscosity of the gas.

6. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 5, characterized in that: The calculated geometric dimension parameters and axial mass flow rate are brought into the calculation formula of liquid flow pressure drop to calculate the flow pressure drop of liquid and steam. The calculation formula of liquid flow pressure drop is: In the formula, μ l is the dynamic viscosity of the liquid working medium; f l Re l is the liquid flow resistance coefficient; is the axial mass flow rate of the liquid, N is the number of channels; ρ l is the density of the liquid; A l is the liquid flow area of ​​a single channel; The calculation formula for steam flow pressure drop is: In the formula, μ v is the dynamic viscosity of steam; f v Re v is the liquid flow resistance coefficient; is the axial mass flow rate of steam, N is the number of channels; ρ v is the density of the liquid; D hv A is the hydraulic diameter of gas flow; v is the gas flow area.

7. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 1, characterized in that: The Laplace Young equation is used to express the surface tension of the liquid: Differentiating the Laplace Young equation, we obtain: Where σ is the surface tension coefficient of the working fluid The differential form of the Laplace Young equation is transformed to obtain the mathematical expression of the heat pipe heat transfer flow model and the liquid flow pressure drop dP l / dx and steam flow pressure drop dP v / dx is brought into the mathematical expression of the heat pipe heat transfer flow model to form a differential equation about the meniscus radius r.

8. The method for obtaining the heat transfer limit of a channel heat pipe considering the manufacturing error of laser selective melting according to claim 7, characterized in that: The mathematical expression of the heat transfer flow model of the heat pipe is: The input of the heat transfer flow model of the heat pipe is the geometric dimension parameters of the channel heat pipe, and the output is the radius of the meniscus.

9. A heat transfer limit acquisition system for a channel heat pipe taking into account manufacturing errors of laser selective melting, characterized in that: The system includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for obtaining the heat transfer limit of a channel heat pipe taking into account the manufacturing error of laser selective melting as described in any one of claims 1 to 8 is executed.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores machine executable instructions. When the machine executable instructions are called and executed by the processor, the machine executable instructions prompt the processor to implement the method for obtaining the heat transfer limit of a channel heat pipe taking into account the manufacturing error of laser selective melting as described in any one of claims 1-8.

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