Simulation analysis method and device for improving resistance coefficient calculation accuracy

Abstract

The invention discloses a simulation analysis method and device for improving resistance coefficient calculation accuracy, the simulation analysis method and device are applied to simulation calculation of the resistance coefficient of an air conditioner heat exchanger based on a fin model, the heat exchanger comprises a fin and a copper pipe arranged on the fin in a penetrating and sleeving mode, and the method comprises the steps that the fin slotting condition is quantitatively evaluated to calculate a slotting influence factor x; intercepting a corresponding local fin model as a calculation model according to the slotting influence factor x; filling a copper pipe area of the calculation model to obtain a copper pipe-free model; constructing an outer boundary of a calculation domain of the copper-pipe-free model, and dividing to generate a grid to obtain a grid file; simulating and calculating pressure drops at different wind speeds by using the grid file, and fitting to obtain a speed-pressure drop curve of the fin so as to obtain a speed-pressure drop formula; the speed-pressure drop formula is compared with the porous medium source item expression to obtain the resistance coefficient, and the resistance coefficient comprises a viscous resistance coefficient and an inertial resistance coefficient. The accuracy of resistance coefficient calculation can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger resistance coefficient simulation analysis technology, specifically relating to a simulation analysis method and device for improving the accuracy of calculating the resistance coefficient of air conditioning heat exchangers based on fin models. Background Technology

[0002] Accurate and efficient methods for calculating heat exchanger drag coefficients are crucial for improving the accuracy and reliability of computational fluid dynamics (CFD) simulations for air conditioning systems. Due to the extremely complex structure of finned-tube heat exchangers in air conditioning indoor units, completely reproducing all geometric details in the simulation model would result in a massive mesh size and exorbitant computational costs. Therefore, in engineering practice, heat exchangers are generally treated as porous media models, ignoring the complex microscopic geometry within the heat exchanger and characterizing the drag effect experienced by the fluid flowing through this region through macroscopic physical parameters (primarily momentum source terms). When setting up a porous media model, determining the drag coefficients (including viscous drag coefficients and inertial drag coefficients) is a core step, directly determining the strength of the momentum source term in the model.

[0003] Currently, there are three main methods for handling the drag coefficient of heat exchangers: experimental methods, trial-and-error methods, and fin-based numerical simulation methods. The fin-based numerical simulation method involves taking a representative minimum unit period and using CFD simulation to obtain the relationship between local fin pressure drop and wind speed, directly fitting the velocity-pressure drop curve of the heat exchanger, and then calculating the viscous drag coefficient and inertial drag coefficient by comparing coefficients. The fin-based numerical simulation method is essentially the same as the experimental method, except that it calculates the relationship between pressure drop and wind speed through numerical simulation, eliminating the need for experimental setups and equipment, and overcoming the limitation of the narrow applicability of the trial-and-error method's backfitting.

[0004] From the currently published literature, literature [1] establishes a three-dimensional model of the heat exchanger fins, simulates and calculates the pressure drop of gas flowing through the fins at different flow rates, obtains the relationship between pressure drop and flow rate through curve fitting, and then solves for the drag coefficient. This literature does not introduce how the fins are cut, and from the pictures provided in the literature ( Figure 1 The fins retain the copper pipe wall surface. However, in the actual two-dimensional simulation model of the air conditioner indoor unit, the copper pipe wall surface (obstructing fluid flow) has already been established, such as... Figure 2 Therefore, when calculating the drag characteristics of the fins, the copper tube wall should not be retained, that is, the method in reference [1] repeatedly considers the obstruction effect of the copper tube on the fluid twice. At the same time, since the slit conditions at different positions of the three-dimensional fins are different, the selection of which local fin position will also affect the calculation result of the drag coefficient, but the relevant research has not been conducted in the literature.

[0005] REFERENCES:

[0006] [1] Chen Xiaolin. Numerical simulation and experimental research on noise of air conditioner indoor unit[D]. Qingdao University of Technology: 2014. SUMMARY

[0007] To solve the above problems, the application provides a simulation analysis method and device for improving the accuracy of resistance coefficient calculation, which is applied to simulate and calculate the resistance coefficient of an air conditioner heat exchanger based on a fin model, and can effectively improve the accuracy of resistance coefficient calculation.

[0008] The technical scheme adopted by the application is as follows:

[0009] In a first aspect, the application discloses a simulation analysis method for improving the accuracy of resistance coefficient calculation, which is applied to simulate and calculate the resistance coefficient of an air conditioner heat exchanger based on a fin model, and the heat exchanger includes fins and copper pipes sleeved on the fins, and the simulation analysis method includes:

[0010] Quantitative evaluation of the fin opening condition to calculate an opening influence factor x;

[0011] According to the opening influence factor x, a corresponding local fin model is intercepted as a calculation model;

[0012] The copper pipe region of the calculation model is filled to obtain a no-copper pipe model;

[0013] The outer boundary of the calculation domain of the no-copper pipe model is constructed, and a grid is divided to obtain a grid file;

[0014] The grid file is used to simulate and calculate the pressure drop under different wind speeds, and a velocity-pressure drop curve of the fin is fitted to obtain a velocity-pressure drop formula;

[0015] The velocity-pressure drop formula is compared with a porous medium source term expression to obtain its resistance coefficient, and the resistance coefficient includes a viscous resistance coefficient and an inertial resistance coefficient.

[0016] As an optional technical scheme, the quantitative evaluation of the fin opening condition to calculate the opening influence factor x includes:

[0017] A perpendicular line is drawn from the center of the copper pipe to the edge wall surface of the fin, and each adjacent two perpendicular lines form a sub-region, and there are a total of -1 sub-regions, wherein, is the number of copper pipes, and is the number of perpendicular lines drawn;

[0018] The -1 sub-regions formed are classified and counted: the number of first-class sub-regions is denoted as N1, the number of second-class sub-regions is denoted as N2, and the number of other-class sub-regions is denoted as N3;

[0019] The opening influence factor x is calculated according to the following formula:

[0020]

[0021] Wherein, N1+N2+N3=-1, the first type of sub-region is a complete full-open slit sub-region, and the second type of sub-region is a complete half-open slit sub-region.

[0022] As an optional technical solution, the corresponding local fin model is intercepted according to the slit influence factor x as the calculation model, which includes:

[0023] If the slit influence factor x is greater than or equal to 0.7, a first type of sub-region is intercepted as the calculation model;

[0024] If the slit influence factor x is less than or equal to 0.3, a second type of sub-region is intercepted as the calculation model;

[0025] If the slit influence factor 0.3

[0026] As an optional technical solution, the outer boundary includes an inlet face, an outlet face, two periodic faces and two symmetric faces.

[0027] As an optional technical solution, the velocity-pressure drop formula includes:

[0028] Simulation settings: import the grid file into the CFD software, set the inlet as a wind speed condition, set the outlet as a pressure reference condition, set the fluid boundary on the upper and lower sides of the fin as a periodic boundary condition, and set the two side boundaries along the original longitudinal pipe spacing direction as a symmetric boundary condition. The calculation formula of the pressure drop is as follows:

[0029] Δp=p in -p out

[0030] Wherein, p in is the inlet average pressure, and p out is the outlet average pressure.

[0031] Based on the simulation settings, the wind speed is continuously changed for simulation analysis, and the pressure drop under different wind speeds is obtained, so as to fit the velocity-pressure drop curve and obtain the velocity-pressure drop formula.

[0032] As an optional technical solution, the velocity-pressure drop formula is:

[0033] Δp=Av 2 +Bv

[0034] The porous medium source term expression is:

[0035]

[0036] According to the correspondence between the linear term and the quadratic term coefficients, the following relationship is obtained:

[0037]

[0038] Further, the viscous resistance coefficient is obtained The inertial resistance coefficient C2 is respectively:

[0039]

[0040] Wherein, A is the fitted quadratic term coefficient, B is the fitted linear term coefficient; S i is a source term added to the momentum equation of the N-S equation, representing the force received by the unit volume of porous medium; v i is the velocity component of the fluid; |v| is the modulus of the velocity vector; μ is the dynamic viscosity of the fluid; ρ is the density of the fluid; α is the permeability of the medium; C2 is the inertial resistance coefficient.

[0041] In a second aspect, the application also discloses a simulation analysis device for improving the accuracy of resistance coefficient calculation, which is used to realize the simulation analysis method of the first aspect, and comprises:

[0042] A quantification module is configured to quantitatively evaluate the slotted condition of the fins to calculate a slotted influence factor x.

[0043] A calculation model generation module is configured to intercept a corresponding local fin model as a calculation model according to the slotted influence factor x.

[0044] A copper tube-free model generation module is configured to fill the copper tube region of the calculation model to obtain a copper tube-free model.

[0045] A grid division module is configured to construct an outer boundary of the calculation domain of the copper tube-free model and divide to generate a grid to obtain a grid file.

[0046] A fitting module is configured to simulate and calculate the pressure drop under different wind speeds according to the grid file, fit to obtain a velocity-pressure drop curve of the fins, and further obtain a velocity-pressure drop formula.

[0047] A solving module is configured to compare the velocity-pressure drop formula with a porous medium source term expression to obtain a resistance coefficient, wherein the resistance coefficient comprises a viscous resistance coefficient and an inertial resistance coefficient.

[0048] In a third aspect, the present application discloses an electronic device, comprising: one or more processors; one or more memories; the one or more memories store one or more computer programs, the one or more computer programs comprise instructions, when the instructions are executed by the one or more processors, make the electronic device execute the simulation analysis method of the first aspect.

[0049] In a fourth aspect, the present application discloses a computer readable medium, comprising a computer program, when the computer program runs on a computer, makes the computer execute the simulation analysis method of the first aspect.

[0050] The present application has the following beneficial effects: on the one hand, it fills the copper pipe area in the calculation model, obtains a copper pipe-free model, and avoids repeated consideration of the copper pipe wall surface; on the other hand, it uses a slitting factor to intercept a representative local fin model as a calculation model, reduces the influence of selecting local fins at different positions on the calculation result of the resistance coefficient; the combination of the two greatly improves the accuracy of the resistance coefficient calculation. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is a fin model schematic diagram in the prior art which retains the copper pipe wall surface.

[0052] Figure 2 is a two-dimensional simulation model schematic diagram of an air conditioner indoor unit in the prior art.

[0053] Figure 3 is a structure schematic diagram of a heat exchanger whole fin of a certain type of air conditioner.

[0054] Figure 4 is a flow schematic diagram of the simulation analysis method for improving the accuracy of the resistance coefficient calculation in an exemplary embodiment.

[0055] Figure 5 is Figure 3 is a sub-region schematic diagram of fin division.

[0056] Figure 6 is a schematic diagram of intercepting a complete full-slitting sub-region.

[0057] Figure 7 is a schematic diagram of filling the copper pipe area of the calculation model.

[0058] Figure 8 is a schematic diagram of the outer boundary of the constructed calculation domain.

[0059] Figure 9 is a mesh schematic diagram of the calculation model generation.

[0060] Figure 10 is a fitted velocity-pressure drop curve schematic diagram.

[0061] Figure 11 is a schematic view of an air conditioner indoor unit according to the first aspect.

[0062] Figure 12 is a schematic view of a full-slit local fin model of another heat exchanger.

[0063] Figure 13 is a schematic view of a simulation analysis device for improving the accuracy of the calculation of the resistance coefficient in an exemplary embodiment.

[0064] Figure 14 is a schematic view of four local fin models in an exemplary embodiment.

[0065] Figure 15 is a schematic view of a full-slit sub-region and a half-slit sub-region when 0.3 < x < 0.7 in an exemplary embodiment.

[0066] Figure 16 is a schematic view of the division of the heat exchanger region in the simulation of the two-dimensional flow field of the air conditioner indoor unit in an exemplary embodiment. DETAILED DESCRIPTION

[0067] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components, steps, and / or data structures of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0068] The present application will be further described below with reference to the drawings and specific embodiments.

[0069] EMBODIMENT

[0070] The present embodiment discloses a simulation analysis method for improving the accuracy of the calculation of the resistance coefficient, which is applied to the simulation calculation of the resistance coefficient of the heat exchanger of an air conditioner based on a fin model. The heat exchanger includes fins (the structure of the whole fin of the heat exchanger of a certain type of air conditioner is shown in the schematic view as Figure 3 ) and a copper pipe sleeved on the fins. As shown in Figure 4 , the simulation analysis method mainly includes steps S1-S6.

[0071] S1, quantitatively evaluate the fin slitting condition to calculate the slitting influence factor x. Specifically, it includes:

[0072] S11, the center of the copper tube is perpendicular to the edge wall of the fin, and each adjacent two perpendicular lines form a sub-region, a total of -1 sub-regions, where -1 is the number of copper tubes, and also the number of perpendicular lines, as shown in Figure 5 When = 30, that is, the number of copper tubes is 30, a total of 29 sub-regions are divided.

[0073] S12, classify and count the -1 sub-regions formed: the number of first-class sub-regions is N1, the number of second-class sub-regions is N2, and the number of other sub-regions is N3. As shown in Figure 5 , the total number of first-class sub-regions is N1=18; the total number of second-class sub-regions is N2=6; and the number of other sub-regions N3=5.

[0074] S13, the slitting influence factor x is calculated according to the following formula:

[0075]

[0076] Where N1+N2+N3=-1, the first-class sub-region is a complete full-slitting sub-region, and the second-class sub-region is a complete half-slitting sub-region. According to Figure 5 , the slitting influence factor x is calculated as:

[0077]

[0078] S2, according to the slitting influence factor x, the corresponding local fin model is intercepted as the calculation model, as follows:

[0079] S21, if the slitting influence factor x≥0.7, a first-class sub-region is intercepted as the calculation model.

[0080] S22, if the slitting influence factor x≤0.3, a second-class sub-region is intercepted as the calculation model.

[0081] S23, if the slitting influence factor 0.3

[0082] As shown in Figure 6 , when x=0.75, the schematic diagram of intercepting a complete full-slitting sub-region.

[0083] S3, fill the copper tube region of the calculation model to obtain a copper tube-free model, and the filling schematic diagram is shown in Figure 7 .

[0084] S4, build the outer boundary of the copper-free tube model calculation domain, the built outer boundary is as shown in Figure 8 , the outer boundary includes an inlet face, an outlet face, two periodic faces and two symmetric faces; then divide to generate a grid to obtain a grid file, and the generated grid is as shown in Figure 9 .

[0085] S5, simulate and calculate the pressure drop under different wind speeds by using the grid file, and fit to obtain the velocity-pressure drop curve of the fin, and then obtain the velocity-pressure drop formula. Specifically, it includes:

[0086] S51, simulation setting: import the grid file into the CFD software, set the inlet as the wind speed condition, set the outlet as the pressure reference condition, set the upper and lower sides of the fin as the periodic boundary condition, and set the two side boundaries along the original longitudinal tube spacing direction as the symmetric boundary condition. The calculation formula of the pressure drop is as follows:

[0087] Δp=p in -p out

[0088] Wherein, p in is the average pressure at the inlet, and p out is the average pressure at the outlet.

[0089] S52, based on the simulation setting, constantly change the wind speed for simulation analysis to obtain the pressure drop under different wind speeds, thereby fitting the velocity-pressure drop curve and obtaining the velocity-pressure drop formula.

[0090] The calculation results of the simulation model are shown in Table 1 as shown in Figure 8 .

[0091] Table 1, velocity-pressure drop calculation results

[0092] Velocity (m / s) Pressure drop (Pa) Pressure loss per unit length (Pa / m) 1 6.5 288.63 3 30.1 1336.59 5 62.8 2788.63

[0093] The velocity-pressure drop curve shown in Figure 10 can be fitted, and the obtained velocity-pressure drop formula is as follows:

[0094] Δp=60.04v 2 +258.7v.

[0095] S6, compare the velocity-pressure drop formula with the porous medium source term expression to obtain the resistance coefficient, which includes the viscous resistance coefficient and the inertial resistance coefficient.

[0096] Further, the general form of the velocity-pressure drop formula is:

[0097] Δp=Av 2 +Bv

[0098] The porous medium source term expression is:

[0099]

[0100] According to the correspondence between the first-order term and the second-order term coefficient, the following relationship is obtained:

[0101]

[0102] Further, the viscous resistance coefficient is obtained The inertial resistance coefficient C2 is respectively:

[0103]

[0104] Wherein, A is the fitted second-order term coefficient, B is the fitted first-order term coefficient; S i is the source term added to the momentum equation of the N-S equation, which represents the force received by the unit volume of porous medium; v i is the velocity component of the fluid; |v| is the modulus of the velocity vector; μ is the dynamic viscosity of the fluid; ρ is the density of the fluid; α is the permeability of the medium; C2 is the inertial resistance coefficient.

[0105] For example, according to the velocity-pressure drop formula Δp = 60.04v 2 +258.7v in step S52, A = 60.04 and B = 258.7 are obtained, and then ρ and μ are respectively brought into formula (1) and (2) to obtain: the viscous resistance coefficient 1 / α = 1.446×10 7 m -2 , and the inertial resistance coefficient C2 = 98.02m -1 .

[0106] In order to better understand the embodiment, the simulation analysis method of the embodiment is further described below, which generally includes the following processes:

[0107] (1) Based on the whole fin model, the fin slitting condition is quantitatively evaluated.

[0108] The air conditioner indoor unit tube-fin heat exchanger is mainly composed of a dense array of continuous fins and a copper tube bundle sleeved therein. As shown in a certain heat exchanger fin, Figure 3 Due to the different slitting conditions of the three-dimensional fins at different positions, some areas are fully slitted and some areas are half slitted. The real porous medium resistance coefficient should be between "fully slitted" and "half slitted".

[0109] The slitting condition is quantitatively evaluated by the sub-region division method: a vertical line is drawn from the center of the copper tube to the edge wall surface of the fin, Figure 5As shown, a total of 30 copper tubes are thus 30 vertical lines; between each two vertical lines, a sub-region is formed, a total of 29 sub-regions, and the sub-regions are sequentially labeled; the complete full-slit and half-slit sub-regions are counted respectively, such as Figure 5 , sub-regions 2-8, 12, 13, 20-28 are all complete full-slit sub-regions, the total number is 18; sub-regions 14-19 are all complete half-slit sub-regions, the total number is 6. The remaining 1, 9, 10, 29 sub-regions are incomplete sub-regions, and the 11th sub-region is a special slit, the number is 1 and can be ignored.

[0110] The calculation formula of the slitting influence factor x is as follows:

[0111]

[0112] If x≥0.7, the fin is approximated as a full-slit; if x≤0.3, the fin is approximated as a half-slit; if 0.3

[0113] (2) On the whole fin model, a local fin model is cut off.

[0114] If the slitting influence factor x≥0.7, only one complete full-slit sub-region needs to be cut off as a calculation model, Figure 5 The slitting influence factor x calculated by the model shown in Figure 6 Any one of the sub-regions 2-8, 12, 13, 20-28 in Figure 5 If the slitting influence factor x≤0.3, only one complete half-slit sub-region needs to be cut off as a calculation model. If the slitting influence factor 0.3

[0115] (3) Based on the local fin model, the copper tube region is filled.

[0116] In order to consider the copper tube flow effect, in the actual two-dimensional simulation model of the air conditioner indoor unit, the copper tube wall has been established, which plays a role in hindering the fluid from passing through, so when calculating the fin resistance characteristics, the model should ignore the copper tube, so as to avoid repeated consideration of the role of the copper tube.

[0117] The copper tube region on the local fin cut off in step (2) is filled, as shown in Figure 7 After filling, the original copper tube region is no longer retained.

[0118] (4) Construct the outer boundary of the local fin model calculation domain, and divide the grid to obtain the grid file.

[0119] The established outer boundary is composed of an inlet face, an outlet face, two periodic faces and two symmetric faces, as shown in Figure 8 . In order to fully ensure that there is no backflow at the inlet and outlet, the inlet is extended by 2 times the fin length, and the outlet is extended by 5 times the fin length in the direction of air flow, and the fin length is L. The distance from the periodic face to the fin is 1 / 2 of the fin pitch. After the outer boundary of the calculation domain is created, the grid is generated in the grid division software, and the effect is shown in Figure 9 .

[0120] (5) Simulate the pressure drop under a batch of different wind speeds, and fit the fin velocity-pressure drop curve. According to the corresponding relationship between the first-order and second-order coefficients, the drag coefficient is solved.

[0121] First, perform simulation settings, import the grid file in step (4) into the CFD software for calculation, set the inlet as the wind speed condition, and the wind speed is uniform; the outlet is set as the pressure reference condition; the upper and lower sides of the fin are set as the periodic boundary condition; the two side boundaries along the original longitudinal pipe pitch direction are set as the symmetric boundary condition.

[0122] The formula for calculating the pressure drop is as follows:

[0123] Δp=p in -p out ………………(3)

[0124] Where p in is the average pressure at the inlet, and p out is the average pressure at the outlet. After the calculation is completed in the CFD software, the average pressures at the inlet and outlet are counted respectively, and the pressure drop under the corresponding wind speed can be calculated according to formula (3).

[0125] Based on the above setting method, the wind speed is changed continuously, and the simulation analysis can obtain the pressure drop under a batch of different wind speeds, so as to obtain the fin velocity-pressure drop curve (resistance characteristic curve). For example Figure 8 The simulation model calculation results are shown in Table 1 above, and the velocity-pressure drop curve shown in Figure 10 can be fitted based on the table.

[0126] Compare the fitted velocity-pressure drop formula (4) with the porous medium source term expression (5):

[0127] Δp=60.04v 2 +258.7v………………(4)

[0128]

[0129] Based on the correspondence between the coefficients of the linear and quadratic terms, the following relationship is obtained:

[0130]

[0131] Substituting the fluid density ρ and dynamic viscosity μ, the viscous drag coefficient is calculated. The inertial drag coefficient C2 = 98.02m -1 .

[0132] (6) Verification of the accuracy of damping coefficient calculation.

[0133] To verify the beneficial effects of the method in this embodiment, the following research work was carried out: Figure 3 The heat exchanger fins were processed to obtain the following results: Figure 14 The “fully open-slit - with copper tubing” shown Figure 14 -a) "Fully open seam - no copper pipe" Figure 14 -b), "Semi-open slit - with copper pipe" ( Figure 14 -c), "Semi-open seam - no copper pipe" Figure 14 Four local fin models, including -d), were used, and the drag coefficient was calculated in accordance with steps (4) and (5). The results are shown in Table 2 below.

[0134] Table 2. Comparison of Calculation Results of Fin Drag Coefficient

[0135] Treatment Viscous drag coefficient Inertial drag coefficient Full open slot - with copper tube 2.627 x 10 7 ]]> 240.6 Full open slot - without copper tube 1.446 x 10 7 ]]> 98.02 Half open slot - with copper tube 2.005 x 10 7 ]] 165.5 Half open slot - without copper tube 1.146 x 10 7 ]]> 64.85

[0136] It can be seen that both the slit configuration and the copper pipe affect the calculated resistance coefficient. When keeping the copper pipe factor constant, considering only the slit configuration, the resistance coefficient of a fully slit unit is greater than that of a partially slit unit. Similarly, when keeping the slit factor constant, considering only the copper pipe, the resistance coefficient with copper pipe is greater than that without. Therefore, when calculating the fin resistance coefficient, the copper pipe and slit configuration should be reasonably considered according to the method in this embodiment to avoid calculating the resistance coefficient too high or too low, which would affect the accuracy of the two-dimensional simulation airflow calculation for the indoor unit of the air conditioner.

[0137] The following is a brief introduction to the calculation of the air volume of the indoor unit of an air conditioner using the gap influence factor and the corresponding resistance coefficient calculated by the method of this embodiment.

[0138] If x≥0.7, first calculate the resistance characteristics of the fully slotted local fins according to the above steps (2)-(5), and then directly set the corresponding set of viscous resistance coefficients and inertial resistance coefficients as the viscous resistance coefficients and inertial resistance coefficients of the indoor unit tube-fin heat exchanger.

[0139] If x≤0.3, first calculate the resistance characteristics of the semi-opened local fin according to the above steps (2)-(5), and then set the obtained set of viscous resistance coefficients and inertial resistance coefficients as the viscous resistance coefficients and inertial resistance coefficients of the indoor unit tube-fin heat exchanger.

[0140] If 0.3

[0141] For example, the indoor unit of the air conditioner of Clause A shown in Figure 11 uses the heat exchanger fin shown in Figure 3 , and the slit influence factor x is 0.75. Therefore, when simulating the two-dimensional flow field of the air conditioner indoor unit (the two-dimensional simulation model can refer to Figure 2 , which is prior art and will not be described here), the viscous resistance coefficients and inertial resistance coefficients of the tube-fin heat exchanger are directly set to 1 / a = 1.446 x 10 7 m -2 and C2 = 98.02 m -1 , respectively. The simulation result shows that the simulated air volume is 704 m 3 / h at a speed of 1250 rpm, the actual measured air volume is 745 m 3 / h, and the calculation error is -5.5%.

[0142] For example, if 0.3 Figure 15 , that is, as described in step (2): a complete full-opened slit sub-region and a complete semi-opened slit sub-region are intercepted as the calculation model, as shown in Figure 16 , where the region 151 is a complete full-opened slit sub-region, and the region 152 is a complete semi-opened slit sub-region; then steps (3)-(5) are performed to calculate the resistance coefficients of the full-opened slit region (including the first viscous resistance coefficient 1 / α1 and the first inertial resistance coefficient C 21 ) and the resistance coefficients of the semi-opened slit region (including the second viscous resistance coefficient 1 / α2 and the second inertial resistance coefficient C 22 ) respectively. When simulating the two-dimensional flow field of the air conditioner indoor unit, the heat exchanger region is divided according to the actual slit condition of the fin, as shown in Figure 16 , where the regions 161, 163, and 165 are full-opened slit regions, and the regions 162 and 164 are semi-opened slit regions. The viscous resistance coefficients of the full-opened slit regions are set to 1 / α1, and the inertial resistance coefficients of the full-opened slit regions are set to C 21The viscous resistance coefficients of the semi-open slit regions are set as 1 / a2, and the inertial resistance coefficients of the semi-open slit regions are set as C 22 .

[0143] Finally, the application also verifies the accuracy of the two-dimensional flow field simulation analysis of the indoor unit based on the damping coefficient calculated by the method of the embodiment.

[0144] First, the damping coefficients of another type of heat exchanger are calculated according to the above steps (1)-(5), and the obtained damping coefficients are applied to the simulation calculation of the indoor unit air duct. The slit influence factor x of the other type of heat exchanger calculated according to step (1) is 0.8, the full-open slit local fin model intercepted according to step (2) is as shown in Figure 12 , the viscous resistance coefficient 1 / a calculated according to steps (3)-(5) is 1.339x10 7 m -2 , and the inertial resistance coefficient C2 is 74.71m -1 . The B and C air conditioners use the heat exchanger of this type, so the set of resistance coefficients is used for two-dimensional flow field simulation calculation of the B and C air conditioners. The calculation results are shown in Table 3 below, and it can be seen that the absolute error of air volume is within 3.5%.

[0145] Table 3: Comparison of simulation air volume and experimental air volume of three types of air conditioner indoor units

[0146]

[0147] The error is calculated as follows:

[0148]

[0149] As shown in Figure 13 , the embodiment also discloses a simulation analysis device for improving the accuracy of resistance coefficient calculation, which is used to realize the simulation analysis method as described in the above embodiment. The simulation analysis device comprises:

[0150] The quantification module is used to quantitatively evaluate the fin slit condition to calculate the slit influence factor x.

[0151] The calculation model generation module is used to intercept a corresponding local fin model as a calculation model according to the slit influence factor x.

[0152] The copper tube-free model generation module is used to fill the copper tube region of the calculation model to obtain a copper tube-free model.

[0153] The grid division module is used to construct the outer boundary of the calculation domain of the copper tube-free model and divide the generated grid to obtain a grid file.

[0154] The fitting module is configured to simulate and calculate pressure drops under different wind speeds according to the grid file, fit a velocity-pressure drop curve of the fin, and further obtain a velocity-pressure drop formula.

[0155] The solving module is configured to compare the velocity-pressure drop formula with a porous medium source term expression to obtain a resistance coefficient, the resistance coefficient including a viscous resistance coefficient and an inertial resistance coefficient.

[0156] The embodiment further discloses an electronic device, including one or more processors, one or more memories, and one or more computer programs stored in the one or more memories, the one or more computer programs including instructions that, when executed by the one or more processors, cause the electronic device to perform the simulation analysis method.

[0157] The embodiment further discloses a computer readable medium, including a computer program, when the computer program is executed on a computer, the computer program causes the computer to perform the simulation analysis method.

[0158] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described device, electronic device and computer readable medium can refer to the corresponding processes in the foregoing method embodiments, and will not be described here.

[0159] Those skilled in the art can understand that the above-described modules can be distributed in the device according to the description of the embodiments, and can also be changed in one or more devices different from the embodiment. The modules of the above-described embodiments can be combined into one module, or can be further split into multiple units.

[0160] Through the foregoing description of the embodiments, those skilled in the art can easily understand that the example embodiments described herein can be implemented by software, or by software combined with necessary hardware. Therefore, the technical solutions according to the embodiments of the present application can be embodied in the form of a software product, which can be stored in a readable medium or on a network, including a plurality of instructions to make an electronic device (which can be a personal computer, a server, a mobile terminal, or a network device, etc.) execute the method according to the embodiments of the present application.

[0161] The above readable medium can be a readable signal medium or a readable storage medium. The readable storage medium may, for example, be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus, or any suitable combination of the above. More specific examples (a non-exhaustive list) of the readable storage medium include a portable disc, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0162] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Any technical solution falling within the scope defined by the claims of the present application falls within the protection scope of the present application.

Claims

1. A simulation analysis method to improve the accuracy of drag coefficient calculation, applied to the simulation calculation of the drag coefficient of an air conditioning heat exchanger based on a finned model, wherein the heat exchanger includes fins and copper tubes sleeved on the fins, characterized in that, The simulation analysis method includes: Quantitatively assess the fin slotting situation to calculate the slotting influence factor x; Based on the slotting influence factor x, the corresponding local fin model is selected as the calculation model; Fill the copper pipe region of the computational model to obtain a copper pipe-free model; Construct the outer boundary of the computational domain of the copper-pipe-free model, and generate a mesh to obtain the mesh file; The pressure drop under different wind speeds is calculated by simulating using a mesh file, and the velocity-pressure drop curve of the fin is obtained by fitting, thus obtaining the velocity-pressure drop formula; The velocity-pressure drop formula is compared with the source term expression for porous media to obtain its drag coefficient, which includes the viscous drag coefficient and the inertial drag coefficient.

2. The simulation analysis method for improving the accuracy of drag coefficient calculation according to claim 1, characterized in that, The quantitative evaluation of fin slotting conditions, to calculate the slotting influence factor x, includes: Draw a perpendicular line from the center of the copper tube to the edge wall of the fin. Each pair of adjacent perpendicular lines forms a sub-region, for a total of -1 sub-regions, where is the number of copper tubes and also the number of perpendicular lines drawn. The -1 sub-regions formed are classified and counted: the number of sub-regions of the first category is recorded as N1, the number of sub-regions of the second category is recorded as N2, and the number of other sub-regions is recorded as N3; The opening influence factor x is calculated according to the following formula: Where N1+N2+N3=-1, the first type of sub-region is a complete fully open-slit sub-region, and the second type of sub-region is a complete half-open-slit sub-region.

3. The simulation analysis method for improving the accuracy of drag coefficient calculation according to claim 2, characterized in that, The step of extracting the corresponding local fin model as the calculation model based on the slot influence factor x includes: If the gap opening influence factor x ≥ 0.7, then a sub-region of the first type is selected as the calculation model; If the gap opening influence factor x ≤ 0.3, then a sub-region of the second type is selected as the calculation model; If the slotting influence factor is 0.3 < x < 0.7, then the drag coefficient of the local fin models with the two slotting forms needs to be calculated separately, that is, a first type of sub-region and a second type of sub-region are selected as the calculation models respectively.

4. The simulation analysis method for improving the accuracy of drag coefficient calculation according to claim 1, characterized in that, The outer boundary includes an inlet surface, an outlet surface, two periodic surfaces, and two symmetric surfaces.

5. The simulation analysis method for improving the accuracy of drag coefficient calculation according to claim 1, characterized in that, The velocity-pressure drop formula is obtained by: Simulation settings: Import the mesh file into the CFD software. Set the inlet to wind speed conditions and the outlet to pressure reference conditions. Set the fluid boundaries on the upper and lower sides of the fins to periodic boundary conditions, and the two side boundaries along the original longitudinal pipe spacing direction to symmetrical boundary conditions. The pressure drop calculation formula is as follows: Δp=p in -p out Where, p in p is the average inlet pressure. out Average export pressure; Based on the simulation settings, the wind speed is continuously changed to perform simulation analysis, obtain the pressure drop under different wind speeds, and then fit the velocity-pressure drop curve to obtain the velocity-pressure drop formula.

6. The simulation analysis method for improving the accuracy of drag coefficient calculation according to any one of claims 1-5, characterized in that, The velocity-pressure drop formula is: Δp=Off 2 +Bv The expression for the porous medium source term is: Based on the correspondence between the coefficients of the linear and quadratic terms, the following relationship is obtained: Then the viscous drag coefficient can be obtained. The inertial drag coefficients C2 are as follows: Where A is the coefficient of the quadratic term in the fitting, B is the coefficient of the linear term in the fitting; ρ is the density of the fluid, and μ is the dynamic viscosity.

7. A simulation analysis device for improving the accuracy of drag coefficient calculation, used to implement the simulation analysis method as described in any one of claims 1-6, characterized in that, The simulation analysis device includes: The quantization module is used to quantitatively evaluate the fin slotting situation in order to calculate the slotting influence factor x. The calculation model generation module is used to extract the corresponding local fin model as the calculation model based on the slot influence factor x. A copper pipe-free model generation module is used to fill the copper pipe area of ​​the calculation model to obtain a copper pipe-free model; The mesh generation module is used to construct the outer boundary of the computational domain of the copper pipe-free model, generate a mesh, and obtain a mesh file; The fitting module is used to simulate and calculate the pressure drop under different wind speeds based on the mesh file, fit the velocity-pressure drop curve of the fin, and then obtain the velocity-pressure drop formula. The solution module is used to compare the velocity-pressure drop formula with the porous medium source term expression to obtain the drag coefficient, which includes the viscous drag coefficient and the inertial drag coefficient.

8. An electronic device, characterized in that, include: One or more processors; One or more memories; the one or more memories storing one or more computer programs, the one or more computer programs including instructions that, when executed by the one or more processors, cause the electronic device to perform the calculation method as described in any one of claims 1-6.

9. A computer-readable medium, characterized in that, Includes a computer program that, when run on a computer, causes the computer to perform the calculation method as described in any one of claims 1-6.

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