Precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis

Abstract

The invention provides a precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis, and the method specifically comprises the following steps: calculating a heat load and a heat exchange area according to an actual application scene and geometric dimension constraint conditions, and determining the number of heat exchange units, the number of spiral coils of the heat exchange units, the distance between microtubes and the diameter of the microtubes; a BBD module in a response surface analysis method is adopted for conducting sensitivity analysis on geometric parameters, remarkable factors influencing flowing and heat exchange performance of the pre-cooling heat exchanger are determined, and an optimal design scheme of the pre-cooling heat exchanger is obtained; and judging whether the design scheme of the pre-cooling heat exchanger conforms to the geometric space size constraint and the technical requirement parameter of the application scene, if so, determining the geometric size of the pre-cooling heat exchanger, and if not, continuing to adjust the parameter until the constraint condition is met. According to the technical scheme, the problems that in the prior art, due to high heat exchange loads, a precooling heat exchanger is too large in overall structure size, low in heat exchange efficiency and too large in flow resistance are solved.

Description

Technical Field

[0001] The invention relates to the technical field of precooling heat exchanger design, and in particular to a precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis. Background Art

[0002] The pre-cooling heat exchanger adopts an integrated spiral thin-wall micro-tube heat exchange unit to greatly increase the heat exchange area and heat exchange rate between the hot air and the refrigerant, and effectively reduce the internal flow resistance to achieve efficient cooling of the hot air. The temperature drop is as high as 1000℃ or more, and the heat exchange rate can be flexibly adjusted according to actual needs.

[0003] The precooling heat exchanger adopts a spiral thin-walled microtube structure and an ultra-compact cross-microtube layout to achieve the dual effects of high heat exchange performance and low pressure loss. According to the actual heat exchange amount and the requirements of specific airflow conditions, thermal calculation is first used to determine the heat exchange area, overall structural parameters and corresponding heat exchange rate of the precooling heat exchanger. Then, a sensitivity analysis method based on single factors and coupling factors is used to reveal the influence weights and optimal values ​​of the main geometric factors of the precooling heat exchanger on its performance (number of microtube rows, microtube spacing, microtube diameter, etc.). Finally, the three-dimensional geometric structure of the precooling heat exchanger and the corresponding heat exchange capacity and resistance in the specific application scenario are determined. For the precooling heat exchanger, due to the high heat exchange load, its overall structural size is too large, the heat exchange efficiency is low, and the flow resistance is too large.

[0004] Therefore, there is a need for an optimization design method for a precooling heat exchanger based on geometric parameter sensitivity analysis with a small overall structural size, high heat exchange efficiency and low flow resistance. Summary of the invention

[0005] The main purpose of the present invention is to provide a precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis to solve the problems in the prior art that the high heat exchange load leads to the overall structural size of the precooling heat exchanger being too large, the heat exchange efficiency being low, and the flow resistance being too large.

[0006] To achieve the above object, the present invention provides a precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis, which specifically includes the following steps:

[0007] S1, calculate the heat load and heat exchange area according to the actual application scenario and geometric size constraints, determine the outer diameter and inner diameter of the precooling heat exchanger, and then determine the number of heat exchange units, the number of spiral coils of the heat exchange unit, the microtube spacing and the microtube diameter.

[0008] S2, the BBD module in the response surface analysis method is used to perform sensitivity analysis on the number of heat exchange units, microtube spacing and microtube diameter of geometric parameters, determine the significant factors affecting the flow and heat transfer performance of the precooling heat exchanger, and obtain the optimal design scheme of the precooling heat exchanger.

[0009] S3, judging whether the design scheme of the precooling heat exchanger obtained in step S2 meets the geometric space size constraints and technical requirement parameters of the application scenario. If so, determining the geometric size of the precooling heat exchanger; if not, continuing to execute step S1 to adjust the parameters until the geometric space size constraints and technical parameter requirements of the application scenario are met.

[0010] Furthermore, step S1 specifically includes the following steps:

[0011] S1.1, calculate the expected heat transfer Q based on the precooling heat exchanger hot air temperature, air flow, precooling heat exchanger constant pressure specific heat capacity and expected air outlet temperature air :

[0012] Q air =M air Cp air (Tt air,in -Tt air,out );

[0013] Among them, M air is the air flow rate, Cp air is the constant pressure specific heat capacity of air, Tt air,in is the hot air temperature of the precooling heat exchanger, Tt air,out is the expected air outlet temperature.

[0014] S1.2, calculating the outlet temperature of the cooling medium according to the cooling medium inlet temperature, the cooling medium pressure, the cooling medium flow rate, the specific heat capacity of the cooling medium and the expected heat exchange obtained in step S1.

[0015] S1.3, calculate the surface heat transfer coefficient h on the air side air and the surface heat transfer coefficient h on the coolant side cool ;

[0016]

[0017] Among them, Nu air is the Nusselt number of air, λ air is the thermal conductivity of air, d is the outer diameter of the microtube;

[0018]

[0019] Among them, Nu cool is the Nusselt number of the cooling medium, λ coolis the thermal conductivity of the cooling medium, d i is the inner diameter of the microtube.

[0020] Furthermore, step S1 further includes the following steps:

[0021] S1.4, determine the heat transfer coefficient and calculate the logarithmic mean temperature difference based on the precooling heat exchanger hot air temperature, the cooling medium temperature, the expected air outlet temperature and the cooling medium outlet temperature:

[0022] The heat transfer coefficient K is calculated as:

[0023]

[0024] Logarithmic mean temperature difference ΔT m The calculation formula is:

[0025]

[0026] ΔT1=Tt air,in -Tt cool,out ;

[0027] ΔT2=Tt air,out -Tt cool,in ;

[0028] Wherein, ΔT1 is the temperature difference between the air inlet and the coolant outlet, and ΔT2 is the temperature difference between the air outlet and the coolant inlet.

[0029] S1.5, calculate the heat transfer area A based on the heat transfer coefficient and logarithmic mean temperature difference:

[0030]

[0031] S1.6. Based on the heat exchange area, preliminarily determine the number of heat exchange units, microtube spacing and microtube diameter.

[0032] Furthermore, step S1.2 specifically includes the following steps:

[0033] S1.2.1, the cooling medium is liquid nitrogen or liquid helium, and the cooling medium inlet temperature is Tt cool,in The critical temperature of the cooling medium is selected, and the cooling medium flow rate is set to 5-8 m / s based on experience.

[0034] S1.2.2, determine the specific heat capacity Cp of the cooling medium according to the cooling medium inlet temperature and cooling medium flow rate cool and cooling medium flow M cool .

[0035] S1.2.3, Expected heat transfer Q air Heat exchange with the cooling medium side Q cool Equal, i.e. Qair =Q cool , Q cool =M cool Cp cool (Tt cool,in -Tt cool,out ), thereby determining the outlet temperature Tt of the cooling medium cool,out .

[0036] Furthermore, step S1.6 specifically includes the following steps:

[0037] S1.6.1, Determine the outside and inside diameters of the precooling heat exchanger based on the spatial geometry and other constraints of the precooling heat exchanger's upstream and downstream components.

[0038] S1.6.2, the microtube diameter of the precooling heat exchanger microtube is selected in the range of 0.5-2.5mm, and the wall thickness of the microtube is 1 / 20 of the microtube diameter.

[0039] S1.6.3, after selecting the micro-tube diameter of the pre-cooling heat exchanger, under the size constraints of the outer diameter and inner diameter of the pre-cooling heat exchanger, select the number of heat exchange units of the pre-cooling heat exchanger, the number of spiral coils z of the heat exchange unit, and the number of micro-tube rows arranged in a radially staggered manner in each heat exchange unit; use a plane equidistant Archimedean spiral to design the spiral geometric line of the heat exchange unit inside the pre-cooling heat exchanger, and the selection range of z is between 0.2 and 1.0. The starting position of each spiral heat exchange unit inside the pre-cooling heat exchanger is located at The end position is located on the inner diameter circular contour line of the precooling heat exchanger, and the end position is located on the outer diameter circular contour line of the precooling heat exchanger. Each heat exchange unit is evenly distributed along the circumferential direction inside the precooling heat exchanger, and the arc lengths between the starting positions or the end positions of adjacent heat exchange units are equal; each heat exchange unit contains 4 to 6 rows of micro-tube structures arranged in a staggered manner along the radial direction of the precooling heat exchanger. The spacing between the micro-tubes arranged in a staggered manner in the heat exchange unit is 1 to 1.5 times the diameter of the micro-tubes, and the spacing between the micro-tubes is the straight-line distance between the centers of adjacent micro-tubes arranged in a staggered manner.

[0040] Furthermore, step S1.6 also includes the following steps:

[0041] S1.6.4, under the constraints of the outer diameter and inner diameter of the precooling heat exchanger, combined with the selected number of heat exchange units, the number of spiral coils of the heat exchange unit and the number of microtube rows arranged radially in each heat exchange unit, all heat exchange units are integrated and arranged under the overall framework structure of the precooling heat exchanger to obtain the geometric layout structure of the cross section of the precooling heat exchanger perpendicular to the axial direction, and then the microtube spacing size between adjacent microtubes of different heat exchange units on the cross section is obtained.

[0042] S1.6.5, the radius of the inner circle O1 of the precooling heat exchanger is a i, the radius of the outer circle O2 of the precooling heat exchanger is a o , the growth rate b is calculated as:

[0043]

[0044] Determine the specific Cartesian coordinates x, y of each point on the spiral according to the following formula:

[0045] x=(a i +b·θ)cosθ

[0046] y=(a i +b·θ)sinθ;

[0047] Wherein, θ is any value within the circumferential angle range of the helix [0,2πz].

[0048] S1.6.6, the recommended value of the microtube spacing between adjacent microtubes of different heat exchange units on the cross section is 4 to 8 times the microtube diameter; if the microtube spacing between adjacent microtubes of different heat exchange units exceeds the recommended value, the number of heat exchange units, the number of spiral coils of the heat exchange units, the number of microtube rows arranged in a staggered manner inside the heat exchange units, and the microtube spacing shall be readjusted until the adjacent microtube spacing between different heat exchange units meets the recommended value.

[0049] S1.6.7. Based on the number of heat exchange units that have been determined, the number of spiral coils of the heat exchange units, and the number of rows of microtubes arranged in a staggered pattern inside the heat exchange units, the total number of microtubes in the cross section of the precooling heat exchanger perpendicular to the axial direction and the corresponding surface heat exchange area are obtained. Combined with the calculated heat exchange area A of the precooling heat exchanger, the number of microtube rows arranged along the axial direction of each heat exchange unit of the precooling heat exchanger and the total number of microtubes required to be arranged inside the precooling heat exchanger are calculated, thereby obtaining the axial length of the precooling heat exchanger.

[0050] S1.6.8, reserve inlet and outlet transition areas at the outer diameter and inner diameter of the precooling heat exchanger to determine the starting position, end position and corresponding liquid collecting cavity position of different heat exchange units in the precooling heat exchanger.

[0051] Further, step S2 includes the following steps:

[0052] S2.1, select the optimal number of test levels and center points according to the number of test factors selected by the BBD module, namely the number of microtube radial tube groups, the microtube tube spacing and the microtube tube diameter.

[0053] S2.2, the number of test factor levels is 3, and the sample plan of the test factor levels is determined based on the increment of 5%-20% of the prototype value, and the number of center points is selected as 2.

[0054] S2.3, determine the number of sensitivity test schemes and the corresponding sample characteristics based on the number of experimental factor levels and the number of center points; the number of test schemes n is defined as: n = 2s(s-1) + C; where s is the number of experimental factors and C is the number of center points.

[0055] Furthermore, step S2 further includes the following steps:

[0056] S2.4, conduct variance analysis on the test results to determine whether the test results meet the fitting accuracy. For the test results that meet the fitting accuracy, analyze the influence and significance of the test factors on the flow and heat transfer characteristics of the precooling heat exchanger.

[0057] S2.5, obtain the recommended optimal parameter values ​​through sensitivity analysis method to form the optimal design scheme of precooling heat exchanger.

[0058] S2.6, use numerical simulation method to obtain the flow and heat transfer characteristics of the optimal geometric scheme of the precooling heat exchanger, and compare it with each test scheme to verify the authenticity and rationality of the optimal geometric scheme, and summarize the exhaust temperature, flow rate and corresponding total pressure loss of the hot air after cooling by the precooling heat exchanger, thereby completing the optimal design scheme of the precooling heat exchanger based on geometric parameter sensitivity analysis.

[0059] Furthermore, in step S2.4, the variance analysis is based on the multivariate correlation coefficient R 2 To judge the fitting accuracy of the obtained response surface model, R 2 The range is between [0,1], when R 2 The closer it is to 1, the more significant the response surface model is, which means that the fitting accuracy is met.

[0060] The significance of the experimental factors on the total pressure loss and heat exchange effect of the precooling heat exchanger is judged by the P value in the variance analysis table. The P value is less than 0.05, indicating that the factor is a significant item.

[0061] The influence of the test factors on the total pressure loss and heat transfer effect of the precooling heat exchanger is judged according to the F value in the variance analysis table. The larger the F value, the greater the influence, thereby determining the influence of the test factors on the flow and heat transfer performance of the precooling heat exchanger.

[0062] Furthermore, step S3 is specifically as follows:

[0063] If the calculated axial length of the precooling heat exchanger does not meet the spatial geometric dimension constraints of the overall structure of the precooling heat exchanger, it is necessary to return to steps S1.6.2 to S1.6.8 to iteratively adjust the number of heat exchange units, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, and the microtube spacing and microtube diameter between adjacent microtubes of different heat exchange units until the total axial length meets the geometric constraints, and determine the corresponding number of heat exchange units of the precooling heat exchanger, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, the microtube spacing between adjacent microtubes of different heat exchange units, the total axial length of the precooling heat exchanger, and the total number of microtubes inside the heat exchange unit.

[0064] The present invention has the following beneficial effects:

[0065] The present invention proposes a pre-cooling heat exchanger optimization design method based on geometric parameter sensitivity analysis, which can not only meet the geometric size constraints and heat exchange requirements of actual application scenarios, but also effectively take into account the optimization of heat exchange rate and flow resistance characteristics, thereby achieving relatively optimized comprehensive flow and heat exchange characteristics of the pre-cooling heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the specific implementation or the prior art description. Obviously, the drawings described below are some implementations of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0067] Figure 1 The three-dimensional geometric structure diagram of the pre-cooling heat exchanger preliminarily determined in the second embodiment of the present invention is shown.

[0068] Figure 2 Shows Figure 1 A simplified diagram of .

[0069] Figure 3 A simplified diagram of the precooling heat exchanger structure with a minimum calculation unit model is shown.

[0070] Figure 4 Shows Figure 3 Structural diagram of fan-shaped thin layer unit A.

[0071] Figure 5 Shows Figure 4 Enlarged detail of point B.

[0072] Figure 6 A diagram showing a model of a precooling heat exchanger after optimization design based on a geometric parameter sensitivity analysis method according to the method provided by the present invention is shown.

[0073] Figure 7 Shows Figure 6 A simplified diagram of .

[0074] Figure 8 A schematic diagram of the geometric structure of a single heat exchange unit is shown.

[0075] Fig. 9 The schematic diagram of the structure of the spiral heat exchange unit designed in the present invention is shown.

[0076] The reference numerals in the above drawings are:

[0077] 10. micro-tube; 20. micro-tube group; 30. heat exchange unit; 40. spiral line of heat exchange unit. DETAILED DESCRIPTION

[0078] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0079] Embodiment 1

[0080] A precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis specifically includes the following steps:

[0081] S1, calculate the heat load and heat exchange area according to the actual application scenario and geometric size constraints, determine the outer diameter and inner diameter of the precooling heat exchanger, and then determine the number of heat exchange units, the number of spiral coils of the heat exchange unit, the micro-tube spacing and the micro-tube diameter. Figure 1 As shown, the outer diameter of the precooling heat exchanger is the diameter of the outer large circle, and the inner diameter of the precooling heat exchanger is the diameter of the inner large circle.

[0082] S2, the BBD module in the response surface analysis method is used to perform sensitivity analysis on the number of heat exchange units, microtube spacing and microtube diameter of geometric parameters, determine the significant factors affecting the flow and heat transfer performance of the precooling heat exchanger, and obtain the optimal design scheme of the precooling heat exchanger.

[0083] S3, judging whether the design scheme of the precooling heat exchanger obtained in step S2 meets the geometric space size constraints and technical requirement parameters of the application scenario. If so, determining the geometric size of the precooling heat exchanger; if not, continuing to execute step S1 to adjust the parameters until the geometric space size constraints and technical parameter requirements of the application scenario are met.

[0084] Specifically, step S1 includes the following steps:

[0085] S1.1, calculate the expected heat transfer Q based on the precooling heat exchanger hot air temperature, air flow, precooling heat exchanger constant pressure specific heat capacity and expected air outlet temperature air :

[0086] Q air =M air Cp air (Tt air,in -Tt air,out );

[0087] Among them, M air is the air flow rate, Cp air is the constant pressure specific heat capacity of air, Tt air,in is the hot air temperature of the precooling heat exchanger, Tt air,out is the expected air outlet temperature.

[0088] S1.2, calculating the outlet temperature of the cooling medium according to the cooling medium inlet temperature, the cooling medium pressure, the cooling medium flow rate, the specific heat capacity of the cooling medium and the expected heat exchange obtained in step S1.

[0089] S1.3, calculate the surface heat transfer coefficient h on the air side air and the surface heat transfer coefficient h on the coolant side cool ;

[0090]

[0091] Among them, Nu air is the Nusselt number of air, λ air is the thermal conductivity of air, d is the outer diameter of the microtube;

[0092]

[0093] Among them, Nu cool is the Nusselt number of the cooling medium, λ cool is the thermal conductivity of the cooling medium, d i is the inner diameter of the microtube.

[0094]

[0095] Among them, Re air is the Reynolds number of air, Pr air is the Prandtl number of air, Re cool is the Reynolds number of the cooling medium, Pr cool is the Prandtl number of the cooling medium, μ air is the dynamic viscosity of air, μ cool is the dynamic viscosity of the cooling medium; the dynamic viscosity of air is calculated using the Sutherland formula, where μ0 = 1.7894 × 10 -5, B = 110.4K; where μ0 is the initial aerodynamic viscosity and B is an empirical constant;

[0096] The formula for calculating the Reynolds number is:

[0097]

[0098] Among them, ρ air and ρ cool are the densities of air and cooling medium, v air and v cool are the flow rates of air and cooling medium, μ air and μ cool are the viscosity coefficients of air and coolant, respectively.

[0099] Specifically, step S1 also includes the following steps:

[0100] S1.4, determine the heat transfer coefficient and calculate the logarithmic mean temperature difference based on the precooling heat exchanger hot air temperature, the cooling medium temperature, the expected air outlet temperature and the cooling medium outlet temperature:

[0101] The heat transfer coefficient K is calculated as:

[0102]

[0103] Logarithmic mean temperature difference ΔT m The calculation formula is:

[0104]

[0105] ΔT1=Tt air,in -Tt cool,out ;

[0106] ΔT2=Tt air,out -Tt cool,in ;

[0107] Wherein, ΔT1 is the temperature difference between the air inlet and the coolant outlet, and ΔT2 is the temperature difference between the air outlet and the coolant inlet.

[0108] S1.5, calculate the heat transfer area A based on the heat transfer coefficient and logarithmic mean temperature difference:

[0109]

[0110] S1.6. Based on the heat exchange area, preliminarily determine the number of heat exchange units, microtube spacing and microtube diameter.

[0111] Specifically, step S1.2 includes the following steps:

[0112] S1.2.1, the cooling medium is liquid nitrogen or liquid helium, and the cooling medium inlet temperature is Tt cool,in The critical temperature of the cooling medium is selected, and the cooling medium flow rate is set to 5-8 m / s based on experience.

[0113] S1.2.2, determine the specific heat capacity Cp of the cooling medium according to the cooling medium inlet temperature and cooling medium flow rate cool and cooling medium flow M cool .

[0114] S1.2.3, Expected heat transfer Q air Heat exchange with the cooling medium side Q cool Equal, i.e. Q air =Q cool , Q cool =M cool Cp cool (Tt cool,in -Tt cool,out ), thereby determining the outlet temperature Tt of the cooling medium cool,out .

[0115] Specifically, step S1.6 includes the following steps:

[0116] S1.6.1, determine the outer diameter and inner diameter of the precooling heat exchanger based on the spatial geometric dimension constraints and other technical requirement parameters of the upstream and downstream components of the precooling heat exchanger.

[0117] S1.6.2, the microtube diameter of the precooling heat exchanger microtube is selected in the range of 0.5-2.5mm, and the wall thickness of the microtube is 1 / 20 of the microtube diameter.

[0118] S1.6.3, after selecting the diameter of the microtubes of the precooling heat exchanger, select the number of heat exchange units of the precooling heat exchanger, the number of spiral coils of the heat exchange unit, and the number of microtube rows arranged in radial staggered rows along the precooling heat exchanger in each heat exchange unit, subject to the size constraints of the outer diameter and inner diameter of the precooling heat exchanger. The spiral geometric profile of the heat exchange unit inside the precooling heat exchanger can be designed using a planar equidistant Archimedean spiral after determining the outer diameter and inner diameter of the precooling heat exchanger and selecting the number of spiral coils z. The selection range of z is between 0.2 and 1.0. The selected value of z determines the length of the spiral microtubes in the heat exchange unit and the corresponding surface area. In order to reduce the processing difficulty and cost of the heat exchanger and microtubes, the z value should be selected as small as possible while ensuring that the heat load is met. Fig. 9As shown, the starting position of each spiral heat exchange unit inside the precooling heat exchanger is located on the inner diameter circle contour line of the precooling heat exchanger, and the ending position is located on the outer diameter circle contour line of the precooling heat exchanger. Each heat exchange unit is evenly distributed along the circumferential direction inside the precooling heat exchanger, and the arc lengths between the starting positions or ending positions of corresponding adjacent heat exchange units are equal; each heat exchange unit contains 4 to 6 rows of microtube structures arranged in a staggered manner along the radial direction of the precooling heat exchanger; the spacing between the microtubes arranged in a staggered manner in the heat exchange unit is 1 to 1.5 times the microtube diameter value, and the microtube spacing is the straight-line distance between the centers of adjacent microtubes arranged in a staggered manner. Figure 8 It is a schematic diagram of the geometric structure of a single heat exchange unit. The heat exchange unit is spiral-shaped and is composed of a plurality of micro-tubes 10.

[0119] Specifically, step S1.6 also includes the following steps:

[0120] S1.6.4, under the constraints of the outer diameter and inner diameter of the precooling heat exchanger, combined with the selected number of heat exchange units, the number of spiral coils of the heat exchange unit and the number of micro-tube rows arranged radially in each heat exchange unit, all heat exchange units are integrated and arranged under the overall framework structure of the precooling heat exchanger to obtain the geometric layout structure of the cross-section of the precooling heat exchanger perpendicular to the axial direction, and then the tube spacing between adjacent micro-tubes of different heat exchange units on the cross-section is obtained.

[0121] S1.6.5, the distribution characteristics of the spiral geometric lines of the heat exchange unit on the cross section are obtained by designing the plane equidistant Archimedean spiral line. The value range of the spiral coil number z is between 0.2 and 1.0. The selected value of z directly determines the length and corresponding surface area of ​​the spiral microtube in the heat exchange unit. In order to ensure that the processing difficulty and cost of the heat exchanger and microtube are reduced, the z value should be selected as small as possible while ensuring that the heat load is met. The starting position of the spiral line of the heat exchange unit is located on the inner diameter circle contour line of the precooling heat exchanger, such as Fig. 9 As shown, the distance from the inner diameter to the central axis (i.e. the radius of the inner circle O1 of the precooling heat exchanger) is a i The end point is located on the outer diameter circle contour line of the precooling heat exchanger, and the distance from the outer diameter to the central axis (that is, the radius of the outer circle O2 of the precooling heat exchanger) is a o The growth rate b of the spiral can be calculated from the inner circle radius and the outer circle radius. The corresponding calculation formula is:

[0122]

[0123] like Fig. 9 As shown, after determining the inner radius a of the spiral line of the heat exchange unit i, the number of spiral coils z and the growth rate b of the spiral line, the specific Cartesian coordinates x, y of each point on the spiral line can be determined according to the following formula, that is, the spiral line distribution characteristics of the heat exchange unit are determined, and θ is any value within the circumferential angle range of the spiral line [0,2πz].

[0124]

[0125] Fig. 9 The midpoint S represents the starting position of the spiral line, and E represents the ending position of the spiral line. The spiral line between point S and point E is the heat exchange unit spiral line 40.

[0126] S1.6.6, the recommended value of the tube spacing between adjacent microtubes of different heat exchange units on the cross section is 4 to 8 times the microtube diameter; if the microtube spacing between adjacent microtubes of different heat exchange units exceeds the recommended value, the number of heat exchange units, the number of spiral coils of the heat exchange units, the number of microtube rows arranged in a staggered manner inside the heat exchange units, and the tube spacing are readjusted until the tube spacing between adjacent microtubes of different heat exchange units meets the recommended value.

[0127] S1.6.7. Based on the number of heat exchange units that have been determined, the number of spiral coils of the heat exchange units, and the number of rows of microtubes arranged in a staggered pattern inside the heat exchange units, the total number of microtubes in the cross section perpendicular to the axial direction and the corresponding surface heat exchange area of ​​the precooling heat exchanger are obtained; combined with the calculated heat exchange area A of the precooling heat exchanger, the number of microtube rows arranged along the axial direction of each heat exchange unit of the precooling heat exchanger and the total number of microtubes required to be arranged inside the precooling heat exchanger are calculated, and the axial length of the precooling heat exchanger is obtained; the microtubes inside each heat exchange unit are also arranged in a staggered pattern along the axial direction, and the microtube spacing between the microtubes in the axial staggered pattern is equal to the microtube spacing between the microtubes in the radial staggered pattern.

[0128] S1.6.8, reserve the inlet and outlet transition areas (the distance from the hot air inlet and outlet to the nearest micro-tube) at the outer diameter and inner diameter of the precooling heat exchanger, and then determine the starting position, end position and corresponding liquid collecting cavity position of different heat exchange units in the precooling heat exchanger.

[0129] High temperature hot air flows through Figure 1 After the lightweight, efficient and compact precooling heat exchanger is used, it is cooled to the expected outlet temperature. When using numerical methods to evaluate the flow and heat transfer characteristics of the precooling heat exchanger, since the entire precooling heat exchanger has a relatively large geometric size, contains a large number of microtubes, and its overall structure has symmetrical structural characteristics in both the circumferential and axial directions, in order to reduce the resource consumption of the simulation calculation, the calculation domain of the precooling heat exchanger involved in the performance simulation can be simplified. Figure 1 , Figure 4 and Figure 6 I1 represents the air inlet, I2 represents the coolant inlet, O1 represents the air outlet, and O2 represents the coolant outlet.

[0130] The specific simplification process is as follows:

[0131] Take a thin layer unit of the entire precooling heat exchanger structure along the axial direction, and the thin layer unit contains only two rows of micro-tube structures along the axial direction. Further, divide the thin layer unit of the precooling heat exchanger into a number of parts equal to the total number of heat exchange units along the circumferential direction, such as Figure 3 As shown in Figure 1, only one of the fan-shaped thin-layer units is taken as the calculation domain for the precooling heat exchanger performance simulation, as shown in Figure 1 Figure 4 When the number of spiral coils z of the heat exchange unit is fixed (that is, the length of the corresponding spiral microtube remains unchanged), the number of radial rows of microtubes in the fan-shaped domain calculation unit corresponds to the number of heat exchange units in the precooling heat exchanger, as shown in Figure 4 As shown, there are n groups of micro-tube groups 20, and the number of micro-tube groups corresponds to the number of heat exchange units.

[0132] After the minimum calculation unit model of the precooling heat exchanger is modeled, a numerical simulation method is usually used to perform numerical calculations on the minimum calculation unit model of the precooling heat exchanger to obtain information such as the total pressure loss and heat transfer rate of the precooling heat exchanger.

[0133] In actual application scenarios, the hot air inlet parameters have been given: air inlet temperature Tt air,in , inlet pressure Pt air,in 、Flow rate M air Under the premise of , three geometric parameters, namely the number of microtube radial tube groups (that is, the number of heat exchange units in the precooling heat exchanger), the microtube spacing and the microtube diameter in the fan-shaped calculation domain of the precooling heat exchanger, are selected as the geometric objects of sensitivity analysis. The heat transfer rate of the precooling heat exchanger (that is, the outlet temperature of the air after being cooled in the precooling heat exchanger) and the total pressure loss coefficient are selected as the objective functions. The response surface analysis method is used to perform sensitivity analysis on the above three geometric parameters. The geometric factors that have a more significant impact on the flow and heat transfer characteristics of the precooling heat exchanger and the corresponding optimal geometric scheme of the precooling heat exchanger are given by the variance analysis results, that is, the optimal number of radial microtube radial tube groups (that is, the number of heat exchange units), microtube spacing and microtube diameter under the constraints of heat load and spatial geometric dimensions in this application scenario.

[0134] The optimization process of the precooling heat exchanger based on the sensitivity analysis method is as follows: the BBD (Box-Behnken Design) module in the response surface analysis method is used to perform sensitivity analysis on the key geometric parameters of the precooling heat exchanger to be optimized. The sensitivity analysis includes the significance and influence of each geometric factor on the total pressure loss and heat transfer rate of the precooling heat exchanger, as well as the optimal geometric solution of the precooling heat exchanger with the maximum heat transfer rate and the minimum total pressure loss that meets the flow and heat transfer requirements of the application scenario.

[0135] Specifically, step S2 includes the following steps:

[0136] S2.1, select the optimal number of test levels and center points according to the number of test factors selected by the BBD module, namely the number of microtube radial tube groups, the microtube tube spacing and the microtube tube diameter.

[0137] S2.2, the number of test factor levels is 3, and the sample plan of the test factor levels is determined based on the increment of 5%-20% of the prototype value, and the number of center points is selected as 2.

[0138] S2.3, determine the number of sensitivity test schemes and the corresponding sample characteristics based on the number of experimental factor levels and the number of center points; the number of test schemes n is defined as: n = 2s(s-1) + C; where s is the number of experimental factors and C is the number of center points.

[0139] Specifically, step S2 also includes the following steps:

[0140] S2.4, conduct variance analysis on the test results to determine whether the test results meet the fitting accuracy. For the test results that meet the fitting accuracy, analyze the influence and significance of the test factors on the flow and heat transfer characteristics of the precooling heat exchanger.

[0141] S2.5, obtain the recommended optimal parameter values ​​through sensitivity analysis method to form the optimal design scheme of precooling heat exchanger.

[0142] S2.6, use numerical simulation method to obtain the flow and heat transfer characteristics of the optimal geometric scheme of the precooling heat exchanger, and compare it with each test scheme to verify the authenticity and rationality of the optimal geometric scheme, and summarize the exhaust temperature, flow rate and corresponding total pressure loss of the hot air after cooling by the precooling heat exchanger, thereby completing the optimal design scheme of the precooling heat exchanger based on geometric parameter sensitivity analysis.

[0143] Specifically, in step S2.4, the variance analysis is based on the multivariate correlation coefficient R 2 To judge the fitting accuracy of the obtained response surface model, R 2 The range is between [0,1], when R 2 The closer it is to 1, the more significant the response surface model is, that is, it meets the fitting accuracy. Among them, the response surface model is a model formed by the sensitivity analysis method, which is used to determine whether the sensitivity analysis is feasible. If the model is significant, the next step is to determine the significance of the experimental factors.

[0144] The significance of the experimental factors on the total pressure loss and heat exchange effect of the precooling heat exchanger is judged by the P value in the variance analysis table. The P value is less than 0.05, indicating that the factor is a significant item.

[0145] The influence of the test factors on the total pressure loss and heat transfer effect of the precooling heat exchanger is judged according to the F value in the variance analysis table. The larger the F value, the greater the influence, thereby determining the influence of the test factors on the flow and heat transfer performance of the precooling heat exchanger.

[0146] Specifically, step S3 is as follows:

[0147] If the calculated axial length of the precooling heat exchanger does not meet the spatial geometric dimension constraints of the overall structure of the precooling heat exchanger, it is necessary to return to steps S1.6.2 to S1.6.8 to iteratively adjust the number of heat exchange units, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, and the microtube spacing and microtube diameter between adjacent microtubes of different heat exchange units until the total axial length meets the geometric constraints, and determine the corresponding number of heat exchange units of the precooling heat exchanger, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, the microtube spacing between adjacent microtubes of different heat exchange units, the total axial length of the precooling heat exchanger, and the total number of microtubes inside the heat exchange unit.

[0148] Embodiment 2

[0149] Step 1: Calculate the heat load and heat exchange area according to the actual application scenario and geometric size constraints, determine the outer diameter and inner diameter of the precooling heat exchanger, and then determine the number of heat exchange units, the number of spiral coils of the heat exchange unit, the microtube spacing and the microtube diameter:

[0150] The application environment and technical requirements of the precooling heat exchanger to be designed are as follows:

[0151] Application environment air intake conditions: pre-cooling heat exchanger hot air temperature Tt air,in =1181.72K, precooling heat exchanger hot air pressure Pt air,in =39993.64Pa, air flow rate M air =15kg / s.

[0152] Technical requirements: Expected air outlet temperature Tt after cooling to be achieved air,out Not exceeding 500K, and as compact as possible with minimal flow resistance.

[0153] The preliminary geometric design process of the precooling heat exchanger is as follows:

[0154] (1) In this embodiment, Tt air,out Select 500K and determine the expected heat transfer Q air =M air Cp air (Tt air,in -Tt air,out ). Cp air is the constant pressure specific heat capacity of air, and Cp is determined according to the air temperature parameterair =1006.43J / (kg·K). Q is calculated air =10287.43kW.

[0155] (2) The cooling medium in this embodiment is liquid nitrogen (liquid helium can also be selected as the cooling medium according to actual conditions), and the cooling medium inlet temperature Tt cool,in Select the critical temperature as 77K, the cooling medium flow rate as 6m / s, and determine the specific heat capacity Cp of the cooling medium according to the cooling medium inlet temperature and flow rate. cool =806.08J / (kg·K), cooling medium flow rate M cool =85.68kg / s. Expected heat transfer Q air Heat exchange with the cooling medium side Q cool Equal, i.e. Q air =Q cool .Q cool =M cool Cp cool (Tt cool,in -Tt cool,out ). The outlet temperature Tt of the cooling medium is determined accordingly cool,out =135.8K.

[0156] (3) Determine the air side surface heat transfer coefficient h air and the surface heat transfer coefficient h on the coolant side cool , that is Where d is the outer diameter of the microtube, which is 1.05 mm. i The inner diameter of the microtube is 1 mm; the thermal conductivity of air is λ air and the thermal conductivity λ of the cooling medium cool It can be determined according to the physical parameters of air and coolant, air =0.0242W / (m·K),λ cool =0.149 W / (m·K); the Nusselt number Nu is calculated by the Dittus-Boelter formula (as follows).

[0157]

[0158] The dynamic viscosity μ is calculated using the Sutherland formula (as follows), where μ0 = 1.7894 × 10 -5 , B=110.4K.

[0159]

[0160] By using the above formula, we can calculate μ air =4.58×10 -5 kg / (m·s), μ cool=1.63×10 -4 kg / (m·s); Pr air =0.744,Pr cool =2.277; Re air =447.34,Re cool =32894.84; Nu air =12.25,Nu cool =131.34;h air =296.53W / (m 2 k), h cool =18238.73W / (m 2 ·k).

[0161]

[0162] (5) Use the following formula to calculate the logarithmic mean temperature difference ΔT m =688.09K.

[0163]

[0164] ΔT1=Tt air,in -Tt cool,out ;

[0165] ΔT2=Tt air,out -Tt cool,in ;

[0166] (6) Using the following formula, calculate the heat exchange area A = 50.34m 2 .

[0167]

[0168] (7) According to the geometric space constraint requirements of the precooling heat exchanger, the outer diameter of the precooling heat exchanger is determined to be 900 mm and the inner diameter is 430 mm. According to the heat exchange area A, after iterative adjustment, it is preliminarily determined that the number of heat exchange units of the precooling heat exchanger is 20, the number of spiral coils of the heat exchange unit is 0.36, and the circumferential angle range corresponding to the starting position and the end position of each heat exchange unit is 129.6°, as shown in Figure 2As shown. Each heat exchange unit contains 4 micro-tube group structures arranged in a staggered pattern along the radial direction. The spacing between the staggered micro-tubes arranged radially and axially inside the heat exchange unit is 2mm. The micro-tube diameter is 1mm and the wall thickness of the micro-tube is 0.05mm. According to the geometric constraints of the spatial structure of the pre-cooling heat exchanger on the axial length, the total axial length of the pre-cooling heat exchanger after iteration is 662.76mm, the micro-tube spacing between adjacent micro-tubes of different heat exchange units is 16.8mm, and the entire pre-cooling heat exchanger contains a total of 30612 micro-tube structures arranged in a staggered pattern. Therefore, a preliminary three-dimensional geometric entity structure of the pre-cooling heat exchanger is formed according to the above parameters, as shown in Figure 1 shown.

[0169] Step 2: Use the BBD module in the response surface analysis method to perform a sensitivity analysis of the geometric parameters of the number of heat exchange units, microtube spacing, and microtube diameter, determine the significant factors affecting the flow and heat transfer performance of the precooling heat exchanger, and obtain the optimal design scheme of the precooling heat exchanger.

[0170] In the actual application scenario, the hot air inlet parameters have been given: pre-cooling heat exchanger hot air temperature Tt air,in , Precooling heat exchanger hot air pressure Pt air,in 、Air flow rate M air Under the premise of , the three geometric parameters of the spiral heat exchange unit number, microtube spacing and microtube diameter of the precooling heat exchanger are selected as the geometric objects of sensitivity analysis, and the heat exchange rate of the precooling heat exchanger (that is, the outlet temperature of the air after being cooled in the precooling heat exchanger) and the total pressure loss coefficient are selected as the objective function, where R1 is the total pressure loss coefficient and R2 is the heat exchange rate:

[0171]

[0172] R2=Cp air M air (Tt air,in -Tt air,out );

[0173] It should be noted that when using numerical methods to evaluate the flow and heat transfer characteristics of precooling heat exchangers with different geometric structures, since the geometric size of the entire precooling heat exchanger is relatively large, it contains a large number of microtubes, and its overall structure has symmetrical structural characteristics in both the circumferential and axial directions, in order to reduce the resource consumption of simulation calculations, the calculation domain of the precooling heat exchanger involved in the performance simulation can be simplified. The specific simplification process is as follows: Take a thin layer unit of the entire precooling heat exchanger structure along the axial direction, and the thin layer unit only contains 2 rows of microtube structures along the axial direction. Further, the thin layer unit of the precooling heat exchanger is evenly divided into 20 parts equal to the number of heat exchange units along the circumferential direction, and only one of the fan-shaped thin layer units is taken as the calculation domain for the performance simulation of the precooling heat exchanger, such as Figure 3 and Figure 4As shown in the figure. When the number of spiral coils z of the spiral heat exchange unit of the precooling heat exchanger is fixed, the number of radial tube groups of microtubes in the fan-shaped domain calculation unit corresponds to the number of heat exchange units in the precooling heat exchanger. Therefore, when performing sensitivity analysis of key geometric parameters on the fan-shaped calculation domain of the precooling heat exchanger, the number of radial tube groups of microtubes in the calculation domain can be used to replace the number of heat exchange units in the precooling heat exchanger.

[0174] The response surface analysis method is used to perform sensitivity analysis on the above three geometric parameters, and the variance analysis results give the geometric factors that have a significant impact on the flow and heat transfer characteristics of the precooling heat exchanger and the corresponding optimal geometric scheme of the precooling heat exchanger, that is, the optimal number of micro-tube radial tube groups (that is, the number of heat exchange units in the precooling heat exchanger), micro-tube spacing and micro-tube diameter under the constraints of heat load and spatial geometric dimensions in this application scenario. The optimization process of the precooling heat exchanger based on the sensitivity analysis method is as follows:

[0175] The BBD (Box-Behnken Design) module in the response surface analysis method is used to conduct a sensitivity analysis on the key geometric parameters of the precooling heat exchanger to be optimized. The sensitivity analysis includes the significance and influence of each geometric factor on the total pressure loss and heat transfer rate of the precooling heat exchanger, as well as the optimal geometric solution of the precooling heat exchanger with the maximum heat transfer rate and the minimum total pressure loss that meets the flow and heat transfer requirements of the application scenario.

[0176] According to the experimental factors selected by the BBD module (i.e. Figure 5 The number of microtube radial tube groups, microtube tube spacing S and microtube tube diameter d in the experiment, the number of experimental factor levels is 3, based on the 20% change of the prototype value. The number of center points is selected as 2, and the experimental factor level table is shown in Table 1.

[0177] Table 1 Experimental factor level table

[0178]

[0179] The number of sample plans and corresponding sample characteristics of the sensitivity test are determined according to the number of experimental factor levels and the number of center points; the number of experimental plans (n) is defined as: n = 2s (s-1) + C. Among them, s is the number of experimental factors, and C is the number of center points. 14 groups of experimental plans are formed. In addition, 6 groups of single-factor sample plans are set up, forming a total of 20 groups of experimental plans.

[0180] According to the hot air temperature Tt air,in =1181.72K, pressure Pt air,in =39993.64Pa, flow rate M dir=15kg / s (based on the total hot air flow of 15kg / s, the air flow in the simplified pre-cooling heat exchanger fan calculation domain is 0.0014kg / s), determine the boundary conditions of the air: the air inlet is the pressure inlet, with a given total pressure and total temperature, and the air outlet is the mass flow outlet, with a given mass flow. According to the liquid nitrogen inlet temperature Tt coo1,in =77K, mass flow rate M cool =85.68kg / s (based on the total liquid nitrogen flow rate of 85.68kg / s, the specific liquid nitrogen flow rate in the thin layer sector domain of the pre-cooling heat exchanger is 0.008kg / s), and the boundary conditions of liquid nitrogen are determined: the liquid nitrogen inlet is the mass flow inlet, with given mass flow rate and total temperature, and the liquid nitrogen outlet is the pressure outlet, with given static pressure. The turbulence model is selected as SST k-ω. Numerical simulations were performed on 20 groups of test schemes respectively, and 20 groups of test scheme results were obtained. The flow performance evaluation is performed on each sample scheme (usually using numerical methods) to obtain the flow and heat transfer characteristics of the pre-cooling heat exchanger corresponding to each scheme. The test scheme and results are shown in Table 2.

[0181] Table 2 Test factor sample scheme and performance evaluation results

[0182]

[0183]

[0184] The variance analysis was performed on the test results to obtain the influence degree and significance of each factor on the flow and heat transfer characteristics of the precooling heat exchanger. Variance analysis can be based on the multivariate correlation coefficient R 2 To determine the significance of the response surface model. 2 It is an evaluation index that reflects the degree of fit of the regression equation to the data. 2 The range is between [0,1], R 2 The closer it is to 1, the more significant the response surface model is. The P value in the variance analysis table is used to determine the significance of each factor on the total pressure loss and heat transfer effect of the precooling heat exchanger. If the P value is less than 0.05, it means that the factor is a significant item. Based on the significant items determined by the P value, the F value is combined to further determine the degree of influence of the significant items. Among the significant items, the F value is used to determine the degree of influence of each factor on the total pressure loss and heat transfer effect of the precooling heat exchanger. The larger the F value, the greater the degree of influence. In this way, the degree of influence of key geometric factors on the flow and heat transfer performance of the precooling heat exchanger can be determined.

[0185] Table 3 is the variance analysis table of the total pressure loss coefficient of the precooling heat exchanger. As can be seen from Table 3, the P value of the fitting model is <0.0001, indicating that the fitting model is highly significant. The R 2=0.9926, indicating that the predicted value and the measured value fit well within the test range. The P values ​​of the number of microtube radial tube groups, microtube spacing, and microtube diameter are all <0.05, which are significant influencing factors. According to the F value, the microtube spacing has the most significant effect on the total pressure loss in the precooler, followed by the microtube diameter, and the number of tube rows has the least effect. The P value of AC is greater than 0.05, which is an insignificant item. The P values ​​of AB and BC are <0.05, which are significant items, but their F values ​​are much smaller than the F values ​​under a single factor, indicating that the coupling of the two factors reduces the influence of the total pressure loss coefficient of the precooling heat exchanger.

[0186] Table 3 Variance analysis of the influence of geometric factors of precooling heat exchanger on the total pressure loss coefficient

[0187]

[0188]

[0189] Table 4 is a variance analysis table of the heat transfer rate of the precooling heat exchanger. It can be seen from Table 4 that the P value of the fitting model is <0.0001, indicating that the fitting model is highly significant. The R 2 =0.9984, indicating that the predicted value and the measured value fit well within the test range. The P values ​​of the number of microtube radial tube groups, microtube spacing, and microtube diameter are all <0.05, which are significant influencing factors. According to the F value, the number of microtube radial tube groups has the most significant effect on the heat transfer rate in the precooler, followed by the microtube diameter, and the microtube spacing has the least effect. The P values ​​of AB, AC, and BC are all >0.05, which are insignificant items, indicating that the degree of influence of the heat transfer rate of the precooling heat exchanger is greatly reduced after the two factors are coupled.

[0190] Table 4 Variance analysis of the influence of geometric factors of precooling heat exchanger on heat transfer rate

[0191]

[0192] Therefore, the specific sensitivity of each geometric factor in the test scheme to the flow and heat transfer characteristics of the precooling heat exchanger can be obtained, and the recommended optimal parameter values ​​can be obtained by the sensitivity analysis method. According to the sensitivity of each factor, the key geometric parameters of the precooling heat exchanger are structurally optimized to form the optimal design scheme of the precooling heat exchanger. On this basis, the numerical simulation method is used to obtain the flow and heat transfer characteristics of the optimal geometric scheme of the precooling heat exchanger, and compared with each sample scheme to verify the authenticity and rationality of the scheme, and summarize the exhaust temperature, flow rate and corresponding total pressure loss of the hot air after cooling by the precooling heat exchanger. In this way, the optimal scheme design of the precooling heat exchanger based on the sensitivity analysis of geometric parameters is completed.

[0193] The optimal design scheme of the precooling heat exchanger recommended by the sensitivity analysis method in this embodiment is: the number of micro-tube radial tube groups is 12, the micro-tube spacing is 2.4mm, and the micro-tube diameter is 1.2mm. The geometric parameters correspond to a total pressure loss coefficient of 0.0173 and a heat transfer rate of 1285.159kW (corresponding to an outlet temperature of 273.84K) for the precooling heat exchanger, and are verified by numerical calculation methods. The comparison results are shown in Table 5, and the errors are all within 5%.

[0194] Table 5 Comparison of predicted performance and numerical simulation evaluation performance of optimized precooling heat exchanger

[0195]

[0196] Optimize the design of precooling heat exchanger based on geometric parameter sensitivity analysis:

[0197] Application environment air intake conditions: pre-cooling heat exchanger hot air temperature Tt air,in =1181.72K, precooling heat exchanger hot air pressure Pt air,in =39993.64Pa, air flow rate M air =15kg / s.

[0198] The overall structure of the optimized precooling heat exchanger has an outer diameter of 900 mm, an inner diameter of 430 mm, an axial length of 795.15 mm, and contains a total of 36,734 spiral microtubes. The entire precooling heat exchanger contains 24 heat exchange units (the number of radial tube groups of microtubes corresponding to the fan-shaped calculation domain is 12), the number of spiral coils of the spiral heat exchange unit is 0.36, and 4 microtubes are arranged in a radial staggered row inside the radial tube group of each heat exchange unit. The circumferential angle range corresponding to the starting position and the ending position of each spiral heat exchange unit 30 is 129.6°, as shown in Figure 2. Figure 7 As shown in the figure, the micro-tube spacing between adjacent micro-tubes in different heat exchange units is 13.4 mm. The micro-tube spacing along the radial and axial directions of the micro-tubes arranged in a staggered pattern in each heat exchange unit is 2.4 mm, the micro-tube diameter is 1.2 mm, and the micro-tube wall thickness is 0.05 mm. The optimized three-dimensional geometric structure of the pre-cooling heat exchanger is shown in the figure. Figure 6 The outlet temperature of the hot air after cooling through the precooling heat exchanger is 273.84K, and the corresponding total pressure loss coefficient is 0.0173, that is, the precooling heat exchanger achieves a lower expected air outlet temperature with the minimum relative total pressure loss.

[0199] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis, characterized in that: The specific steps include: S1, calculate the heat load and heat exchange area according to the actual application scenario and geometric size constraints, determine the outer diameter and inner diameter of the precooling heat exchanger, and then determine the number of heat exchange units, the number of spiral coils of the heat exchange unit, the micro-tube spacing and the micro-tube diameter; S2, using the BBD module in the response surface analysis method to perform sensitivity analysis on the number of heat exchange units, micro-tube spacing and micro-tube diameter, to determine the significant factors affecting the flow and heat transfer performance of the pre-cooling heat exchanger, and to obtain the optimal design scheme of the pre-cooling heat exchanger; S3, judging whether the design scheme of the precooling heat exchanger obtained in step S2 meets the geometric space size constraints and technical requirement parameters of the application scenario. If so, determining the geometric size of the precooling heat exchanger; if not, continuing to execute step S1 to adjust the parameters until the geometric space size constraints and technical parameter requirements of the application scenario are met.

2. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 1 is characterized in that: Step S1 specifically includes the following steps: S1.1, calculate the expected heat transfer Q based on the precooling heat exchanger hot air temperature, air flow, precooling heat exchanger constant pressure specific heat capacity and expected air outlet temperature air : Q air =M air Cp air (Tt air,in -Tt air,out ); Among them, M air is the air flow rate, Cp air is the constant pressure specific heat capacity of air, Tt air,in is the hot air temperature of the precooling heat exchanger, Tt air,out is the expected air outlet temperature; S1.2, calculating the outlet temperature of the cooling medium according to the cooling medium inlet temperature, the cooling medium pressure, the cooling medium flow rate, the specific heat capacity of the cooling medium and the expected heat exchange obtained in step S1; S1.3, calculate the surface heat transfer coefficient h on the air side air and the surface heat transfer coefficient h on the coolant side cool ; Among them, Nu air is the Nusselt number of air, λ air is the thermal conductivity of air, d is the outer diameter of the microtube; Among them, Nu cool is the Nusselt number of the cooling medium, λ cool is the thermal conductivity of the cooling medium, d i is the inner diameter of the microtube.

3. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 2 is characterized in that: Step S1 also includes the following steps: S1.4, determine the heat transfer coefficient and calculate the logarithmic mean temperature difference based on the precooling heat exchanger hot air temperature, the cooling medium temperature, the expected air outlet temperature and the cooling medium outlet temperature: The heat transfer coefficient K is calculated as: Logarithmic mean temperature difference ΔT m The calculation formula is: ΔT1=Tt air,in -Tt cool,out ; ΔT2=Tt air,out -Tt cool,in ; Wherein, ΔT1 is the temperature difference between the air inlet and the coolant outlet, and ΔT2 is the temperature difference between the air outlet and the coolant inlet; S1.5, calculate the heat transfer area A based on the heat transfer coefficient and logarithmic mean temperature difference: S1.

6. Based on the heat exchange area, preliminarily determine the number of heat exchange units, microtube spacing and microtube diameter.

4. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 3 is characterized in that: Step S1.2 specifically includes the following steps: S1.2.1, the cooling medium is liquid nitrogen or liquid helium, and the cooling medium inlet temperature is Tt cool,in Select the critical temperature of the cooling medium, and set the cooling medium flow rate to 5-8 m / s based on experience; S1.2.2, determine the specific heat capacity Cp of the cooling medium according to the cooling medium inlet temperature and cooling medium flow rate cool and cooling medium flow M cool ; S1.2.3, Expected heat transfer Q air Heat exchange with the cooling medium side Q cool Equal, i.e. Q air =Q cool , Q cool =M cool Cp cool (Tt cool,in -Tt cool,out ), thereby determining the outlet temperature Tt of the cooling medium cool,out .

5. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 4 is characterized in that: Step S1.6 specifically includes the following steps: S1.6.1, determine the outer diameter and inner diameter of the precooling heat exchanger based on the spatial geometric size constraints and other technical requirement parameters of the upstream and downstream components of the precooling heat exchanger; S1.6.2, the diameter of the microtubes of the precooling heat exchanger is selected in the range of 0.5-2.5 mm, and the wall thickness of the microtube is 1 / 20 of the diameter of the microtube; S1.6.3, after selecting the micro-tube diameter of the pre-cooling heat exchanger, under the size constraints of the outer diameter and inner diameter of the pre-cooling heat exchanger, select the number of heat exchange units of the pre-cooling heat exchanger, the number of spiral coils z of the heat exchange unit, and the number of micro-tube rows arranged in a radially staggered manner in each heat exchange unit; use a plane equidistant Archimedean spiral to design the spiral geometric line of the heat exchange unit inside the pre-cooling heat exchanger, and the selection range of z is between 0.2 and 1.

0. The starting position of each spiral heat exchange unit inside the pre-cooling heat exchanger is located at The end position is located on the inner diameter circular contour line of the precooling heat exchanger, and the end position is located on the outer diameter circular contour line of the precooling heat exchanger. Each heat exchange unit is evenly distributed along the circumferential direction inside the precooling heat exchanger, and the arc lengths between the starting positions or the end positions of adjacent heat exchange units are equal; each heat exchange unit contains 4 to 6 rows of micro-tube structures arranged in a staggered manner along the radial direction of the precooling heat exchanger. The spacing between the micro-tubes arranged in a staggered manner in the heat exchange unit is 1 to 1.5 times the diameter of the micro-tubes, and the spacing between the micro-tubes is the straight-line distance between the centers of adjacent micro-tubes arranged in a staggered manner.

6. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 5 is characterized in that: Step S1.6 also includes the following steps: S1.6.4, under the constraints of the outer diameter and inner diameter of the precooling heat exchanger, combined with the number of selected heat exchange units, the number of spiral coils of the heat exchange unit and the number of micro-tube rows arranged in a radially staggered row inside each heat exchange unit, all heat exchange units are integrated and arranged under the overall framework structure of the precooling heat exchanger to obtain the geometric layout structure of the cross section of the precooling heat exchanger perpendicular to the axial direction, and then the micro-tube spacing size between adjacent micro-tubes of different heat exchange units on the cross section is obtained; S1.6.5, the radius of the inner circle O1 of the precooling heat exchanger is a i , the radius of the outer circle O2 of the precooling heat exchanger is a o , the growth rate b is calculated as: Determine the specific Cartesian coordinates x, y of each point on the spiral according to the following formula: Wherein, θ is any value within the circumferential angle range of the helix [0,2πz]; S1.6.6, the recommended value of the microtube spacing between adjacent microtubes of different heat exchange units on the cross section is 4 to 8 times the microtube diameter; if the microtube spacing between adjacent microtubes of different heat exchange units exceeds the recommended value, the number of heat exchange units, the number of spiral coils of the heat exchange units, the number of microtube rows arranged in a staggered pattern inside the heat exchange units, and the microtube spacing are readjusted until the adjacent microtube spacing between different heat exchange units meets the recommended value; S1.6.7, based on the number of heat exchange units that have been determined, the number of spiral coils of the heat exchange units, and the number of rows of microtubes arranged in a staggered pattern inside the heat exchange units, the total number of microtubes in the cross section of the precooling heat exchanger perpendicular to the axial direction and the corresponding surface heat exchange area are obtained; combined with the heat exchange area A of the precooling heat exchanger that has been calculated, the number of microtube rows arranged along the axial direction of each heat exchange unit of the precooling heat exchanger and the total number of microtubes that need to be arranged inside the precooling heat exchanger are calculated, and the axial length of the precooling heat exchanger is obtained; S1.6.8, reserve inlet and outlet transition areas at the outer diameter and inner diameter of the precooling heat exchanger to determine the starting position, end position and corresponding liquid collecting cavity position of different heat exchange units in the precooling heat exchanger.

7. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 6 is characterized in that: Step S2 includes the following steps: S2.1, according to the number of experimental factors selected by the BBD module, namely, the number of radial tube groups of microtubes, the distance between microtubes and the diameter of microtubes, the optimal number of experimental levels and center points are selected; S2.2, the number of test factor levels is 3, and the sample plan of the test factor level is determined based on the increment of 5%-20% of the prototype value, and the number of center points is selected as 2; S2.3, determine the number of sensitivity test schemes and the corresponding sample characteristics based on the number of experimental factor levels and the number of center points; the number of test schemes n is defined as: n = 2s(s-1) + C; where s is the number of experimental factors and C is the number of center points.

8. The method for optimizing the design of a precooling heat exchanger based on geometric parameter sensitivity analysis according to claim 7, characterized in that: Step S2 also includes the following steps: S2.4, perform variance analysis on the test results to determine whether the test results meet the fitting accuracy. For the test results that meet the fitting accuracy, analyze the influence and significance of the test factors on the flow and heat transfer characteristics of the precooling heat exchanger; S2.5, obtain the recommended optimal parameter values ​​through sensitivity analysis method to form the optimal design scheme of precooling heat exchanger; S2.6, use numerical simulation method to obtain the flow and heat transfer characteristics of the optimal geometric scheme of the precooling heat exchanger, and compare it with each test scheme to verify the authenticity and rationality of the optimal geometric scheme, and summarize the exhaust temperature, flow rate and corresponding total pressure loss of the hot air after cooling by the precooling heat exchanger, thereby completing the optimal design scheme of the precooling heat exchanger based on geometric parameter sensitivity analysis.

9. The method for optimizing the design of a precooling heat exchanger based on geometric parameter sensitivity analysis according to claim 8, characterized in that: The variance analysis described in step S2.4 was based on the multivariate correlation coefficient R 2 To judge the fitting accuracy of the obtained response surface model, R 2 The range is between [0,1], when R 2 The closer it is to 1, the more significant the response surface model is, that is, the fitting accuracy is met; The significance of the experimental factors on the total pressure loss and heat exchange effect of the precooling heat exchanger is judged by the P value in the variance analysis table. The P value is less than 0.05, indicating that the factor is a significant item. The influence of the test factors on the total pressure loss and heat transfer effect of the precooling heat exchanger is judged according to the F value in the variance analysis table. The larger the F value, the greater the influence, thereby determining the influence of the test factors on the flow and heat transfer performance of the precooling heat exchanger.

10. The precooling heat exchanger optimization design method based on geometric parameter sensitivity analysis according to claim 9, characterized in that: Step S3 is specifically as follows: If the calculated axial length of the precooling heat exchanger does not meet the spatial geometric dimension constraints of the overall structure of the precooling heat exchanger, it is necessary to return to steps S1.6.2 to S1.6.8 to iteratively adjust the number of heat exchange units, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, and the microtube spacing and microtube diameter between adjacent microtubes of different heat exchange units until the total axial length meets the geometric constraints, and determine the corresponding number of heat exchange units of the precooling heat exchanger, the number of spiral coils of the heat exchange unit, the microtube diameter, the microtube spacing within the heat exchange unit, the microtube spacing between adjacent microtubes of different heat exchange units, the total axial length of the precooling heat exchanger, and the total number of microtubes inside the heat exchange unit.

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