CN103150439A - Plate-fin heat exchanger oriented forecasting method for flow and heat exchange performances of fin - Google Patents

Abstract

The invention relates to a plate-fin heat exchanger oriented forecasting method for flow and heat exchange performances of a fin. The method comprises the steps of selecting basic structure parameters of a sawtoothed fin, calculating corresponding dimensionless parameters alpha, beta and gamma, checking whether the dimensionless parameters are within a correlation forecasting structure range, calculating the fin section equivalent diameter Dh and the fin passage equivalent diameter De according to the structure parameters of the sawtoothed fin, querying and obtaining air density rho and air viscosity mu at qualitative temperature and qualitative pressure, calculating Re according to a determined mean flow rate u passing through a passage of the sawtoothed fin, checking whether the Re is within the correlation forecasting range, determining a compound dimensionless parameter phi f of the sawtoothed fin, and calculating factors j and f. The method has a wider forecasting range for the flow and heat exchange performances of the sawtoothed fin for the plate-fin heat exchanger, the normal-pressure sawtoothed fin and the high-pressure sawtoothed fin are included, and forecasting is relatively accurate.

Description

Fin towards the plate type finned heat exchanger design flows and the heat exchange property Forecasting Methodology

Technical field

The invention belongs to plate type finned heat exchanger design applied technical field, be specifically related to flow and the heat exchange property Forecasting Methodology towards the fin of plate type finned heat exchanger design.

Technical background

Plate type finned heat exchanger is a kind of efficient enhanced heat exchange equipment, is widely used in Aero-Space, petrochemical complex and the industries such as gas separation and liquefaction.Serrated fin is to be applied in one of high-efficiency fin in plate type finned heat exchanger, and it has higher ratio heat interchanging area, can effectively improve the heat exchange situation of weak side (as air side) in heat interchanger.

When the layout board fin heat exchanger, the performance parameter j factor and the f factor that fin is important not only can instruct the selection of plate type finned heat exchanger fin configuration used, and the structural parameters of selected fin are determined with the size design of whole heat interchanger, important impact is arranged.The j factor and the f factor generally need to obtain according to design conditions and the selected correlation parameter prediction of deviser in design process.And the prediction of the j factor and the f factor is mainly to determine by the j factor and f factor correlation.

The early stage j factor and f factor correlation mainly obtain by the match experimental data.The serrated fin experiment of the comparatively system that can find according to documents and materials is to be undertaken by the research group headed by Kays W.Y. and London A.L., the flow media take air as experimental side, and employing wind tunnel experiment platform is tested.The data of gained are quoted by numerous scholars, thereby the j factor and the f factor correlation of various serrated fins have occurred.The serrated fin j factor that domestic empty branch trade is used and the prediction of the f factor are mainly to draw from day fin performance curve of Benshen's steel " ALEX ".Fast development along with computer technology and Fluid Mechanics Computation (CFD), make and adopt method for numerical simulation to find the solution the fin channels interior flow field and the temperature field becomes possibility, by field data is carried out analyzing and processing, just can obtain the performance factor of fin, and as long as numerical model foundation is reasonable, fin performance data and the experimental data of gained have consistance preferably.Therefore, the combination of experiment and CFD method also more and more is applied in the middle of the design of plate type finned heat exchanger.

Because the serrated fin model of experiment use is less, traditional serrated fin j factor and f factor correlation are examined comprehensively not on the structural factor that affects fluid interchange performance in the serrated fin passage, effectively estimation range is less, and often there are larger error in the j that calculates and the f factor, are unfavorable for the engineering design of plate type finned heat exchanger.Thereby, propose a kind of can be in relative broad range the Accurate Prediction serrated fin flow most importantly with the Forecasting Methodology of heat exchange property, have important practical significance.

Summary of the invention

In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide towards the fin of plate type finned heat exchanger design and flow and the heat exchange property Forecasting Methodology, this Forecasting Methodology is at first to serrated fin j, the f factor is predicted more accurately, secondly effectively estimation range is larger, has contained normal pressure serrated fin (fin thickness less) and high pressure serrated fin (fin thickness is relatively large).

In order to achieve the above object, the technical scheme taked of the present invention is:

Fin towards the plate type finned heat exchanger design flows and the heat exchange property Forecasting Methodology, comprises the following steps:

Step 1, the thermal load of the plate type finned heat exchanger that will design according to the deviser and flow operating mode are selected the elementary structure parameter of serrated fin, and the elementary structure parameter of serrated fin has: fin height h _f, fin width s _f, fin thickness δ _f, the fin unit length l _f, fin height h _fRefer to the distance from the feather edge of serrated fin to high rim, fin width s _fBe the distance between adjacent two serrated fins;

Step 2, basic dimensionless group α, β corresponding according to the elementary structure parameter calculating of selected serrated fin, γ, each basic dimensionless group is calculated as follows:

$\mathrm{\α}=\frac{{\mathrm{\δ}}_f}{h_f},$ $\mathrm{\β}=\frac{{\mathrm{\δ}}_f}{s_f},$ $\mathrm{\γ}=\frac{{\mathrm{\δ}}_f}{l_f}$

And verify α, β, γ whether in scope of design, and α, β, γ scope of design are: 0＜α＜0.5,0＜β＜0.5, γ〉0.01;

Step 3 is according to the elementary structure parameter calculating fin cross section equivalent diameter D of serrated fin _hWith fin channels equivalent diameter D _e,

D _hComputing method as follows:

$D_h=\frac{2h_f{s}_f}{h_f+s_f}$

D _eObtain by dual mode, the first is that the elementary structure parameter that directly passes through serrated fin calculates:

$D_e=\frac{2l_f(h_f-{\mathrm{\δ}}_f)(s_f-{\mathrm{\δ}}_f)}{l_f(h_f+s_f-2{\mathrm{\δ}}_f)+{\mathrm{\δ}}_f(h_f-{\mathrm{\δ}}_f)+\frac{2{\mathrm{\δ}}_f(s_f-2{\mathrm{\δ}}_f)}{4}}$

The second is the basic dimensionless group that drawn by the step 1 height h in conjunction with serrated fin _fWith fin width s _fCalculate:

$D_e=\frac{2(1-\mathrm{\α})(1-\mathrm{\β})}{\frac{1}{s_f}(1-\mathrm{\α})(1+\mathrm{\β})+\frac{1}{h_f}(1+\frac{1}{2}\mathrm{\γ}-\mathrm{\β}(1+\mathrm{\γ}))}$

Step 4, inquiry air physical property table or air physical property query software obtain density p and the kinetic viscosity μ of air under qualitative temperature and qualitative pressure, and the flow velocity u designed according to the deviser calculates the Re number, $\mathrm{Re}=\frac{\mathrm{\ρu}{D}_e}{\mathrm{\μ}}$

If the deviser adopts the MAF m by the unit fin channels _fDesign, Re also can be obtained by following mode:

$\mathrm{Re}=\frac{m_f}{A_{\mathrm{front}}}\frac{D_e}{\mathrm{\μ}}$

In formula: A _Front=(h _f-δ _f) (s _f-δ _f)

Then verify the Re number whether in the scope of design of the serrated fin j factor and the f factor, Re counts scope of design and is: 200≤Re≤10000;

Step 5 is determined the compound dimensionless group Φ of serrated fin _f, formula is as follows:

${\mathrm{\Φ}}_f={(\frac{1}{\mathrm{\α}}+\frac{1}{2\mathrm{\β}}-2)}^{\mathrm{\α}(1-2\mathrm{\β})+2\mathrm{\β}(1-\mathrm{\α})}+\frac{4(1-\mathrm{\α})\mathrm{\β}+\mathrm{\α}(1-2\mathrm{\β})}{4(\mathrm{\α}+\mathrm{\β}-2\mathrm{\α\β})}$

Step 6 according to by the resulting parameter of step 1-4, is calculated the j factor and the f factor of serrated fin used, and computing formula is as follows:

$j=2.34812{\left(\frac{l_f}{D_h}\right)}^{0.19411}{{\mathrm{\Φ}}_f}^{0.00656}{\mathrm{\α}}^{-0.35987}{\mathrm{\β}}^{0.10391}{\mathrm{\γ}}^{0.45337}R{e}^{-1.01546+0.05633\ln \left(\mathrm{Re}\right)-0.00064{\left(\frac{h_f}{D_h}\right)}^{0.49317}{\mathrm{\β}}^{-0.16019}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

$f=2300.24{\left(\frac{l_f}{D_h}\right)}^{-1.42491}{{\mathrm{\Φ}}_f}^{0.26188}{\left(\frac{1}{1-2\mathrm{\α}}\right)}^{2.04570}{\left(\frac{1}{1-2\mathrm{\β}}\right)}^{2.16338}{\mathrm{\γ}}^{-0.93414}$

$\×R{e}^{-4.52412+0.49785\ln \left(\mathrm{Re}\right)-0.01580{\left(\frac{h_f}{D_h}\right)}^{0.00222}{\mathrm{\β}}^{-0.08664}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

step 7, determine the total length of serrated fin used according to the thermal load of the j factor of the serrated fin that calculates and the plate type finned heat exchanger that will design, and then satisfying total heat interchanging area and the volume of determining selected serrated fin under the condition of design heating load, the f factor by the serrated fin that calculates and the total length of serrated fin calculate pressure drop and the pump merit of selected serrated fin under the flow operating mode of the plate type finned heat exchanger that the deviser will design, then the pressure condition of importing and exporting according to the actual plate fin heat exchanger or the actual maximum pump merit that can provide for the plate type finned heat exchanger import, verify selected serrated fin and whether satisfy design flow operating mode condition, if do not satisfy the design flow condition condition of starting building, the deviser need to reselect the elementary structure parameter of serrated fin, and repeating step 2-step 7, until selected serrated fin had not only satisfied the design heating load of plate type finned heat exchanger but also had satisfied the flow operating mode of fin heat exchanger, satisfy the design heating load and flow operating mode of plate type finned heat exchanger when selected serrated fin after, then serrated fin is optimized type selecting, the heat exchange core of plate type finned heat exchanger is determined.

Advantage of the present invention mainly be can be in wider fin structure scope the j factor and the f factor of Accurate Prediction serrated fin, the architectural characteristic that can fully reflect serrated fin due to the compound dimensionless group of serrated fin that sums up according to simulated data in the j factor and the f factor, the j factor and f factor correlation all adopt the simulated performance data of index-a large amount of different model serrated fins of polynomial form match simultaneously, and the check by the related experiment data, thereby can realize Accurate Prediction to the j factor and the f factor of serrated fin.The j factor of Accurate Prediction serrated fin and the f factor, can so that the fluid interchange performance of the designed plate type finned heat exchanger that goes out in actual moving process more near design performance, thereby can reduce the material consumption that causes because of j, f factor predicated error, reduce the material cost of producing plate type finned heat exchanger; In addition, the Accurate Prediction of the serrated fin j factor and the f factor makes the fluid interchange performance of serrated fin in actual motion after optimization best, therefore can reduce the fluid interchange irreversible loss of plate type finned heat exchanger, thereby improve the heat exchange efficiency of plate type finned heat exchanger.

Description of drawings

Accompanying drawing is the serrated fin structural parameters schematic diagram that uses in the present invention.

Embodiment

Below in conjunction with accompanying drawing and example, the present invention is described in detail.

Fin towards the plate type finned heat exchanger design flows and the heat exchange property Forecasting Methodology, comprises the following steps:

Step 1, with reference to accompanying drawing, the thermal load of the plate type finned heat exchanger that will design according to the deviser and flow operating mode are selected the elementary structure parameter of serrated fin, the model of choosing serrated fin be 95JC1402 fin unit length be the serrated fin of 5mm as calculating object, model is that the elementary structure parameter of the serrated fin of 95JC1402 is: fin height h _f=9.5mm, fin width s _f=1.4mm, fin thickness δ _f=0.2mm, the fin unit length l _f=5.0mm;

Step 2, basic dimensionless group α, β corresponding according to the elementary structure parameter calculating of selected serrated fin, γ,

Basic dimensionless group result of calculation is:

$\mathrm{\α}=\frac{{\mathrm{\δ}}_f}{h_f}=\frac{0.2\mathrm{mm}}{9.5\mathrm{mm}}=0.0211$

$\mathrm{\β}=\frac{{\mathrm{\δ}}_f}{s_f}=\frac{0.2\mathrm{mm}}{1.4\mathrm{mm}}=0.1429$

$\mathrm{\γ}=\frac{{\mathrm{\δ}}_f}{l_f}=\frac{0.2\mathrm{mm}}{5.0\mathrm{mm}}=0.0400$

And verify α, β, γ whether in scope of design, and α, β, γ scope of design are: 0＜α＜0.5,0＜β＜0.5, γ〉0.01, through comparison, α, β, γ value are all in given structural design scope;

Step 3 is according to the elementary structure parameter calculating fin cross section equivalent diameter D of serrated fin _hWith fin channels equivalent diameter D _e,

$D_h=\frac{2h_f{s}_f}{h_f+s_f}=\frac{2\×9.5\mathrm{mm}\×1.4\mathrm{mm}}{9.5\mathrm{mm}+1.4\mathrm{mm}}=2.4404\mathrm{mm}$

$D_e=\frac{2l_f(h_f-{\mathrm{\δ}}_f)(s_f-{\mathrm{\δ}}_f)}{l_f(h_f+s_f-2{\mathrm{\δ}}_f)+{\mathrm{\δ}}_f(h_f-{\mathrm{\δ}}_f)+\frac{2{\mathrm{\δ}}_f(s_f-2{\mathrm{\δ}}_f)}{4}}$

$=\frac{2\×5.0\mathrm{mm}\×(9.5\mathrm{mm}-0.2\mathrm{mm})\×(1.4\mathrm{mm}-0.2\mathrm{mm})}{5.0\mathrm{mm}\×(9.5\mathrm{mm}+1.4\mathrm{mm}-2\×0.2\mathrm{mm})+0.2\mathrm{mm}\×(9.5\mathrm{mm}-0.2\mathrm{mm})+\frac{2\×0.2\mathrm{mm}\×(1.4\mathrm{mm}-2\×0.2\mathrm{mm})}{4}}$

$=2.0492\mathrm{mm}$

D _eAlso can calculate by following:

$D_e=\frac{2(1-\mathrm{\α})(1-\mathrm{\β})}{\frac{1}{s_f}(1-\mathrm{\α})(1+\mathrm{\β})+\frac{1}{h_f}(1+\frac{1}{2}\mathrm{\γ}-\mathrm{\β}(1+\mathrm{\γ}))}$

$=\frac{2\×(1-0.0211)\×(1-0.1429)}{\frac{1}{1.4\mathrm{mm}}(1-0.0211)\×(1+0.1429)+\frac{1}{9.5\mathrm{mm}}(1+\frac{0.0400}{2}-0.1429\×(1+0.0400))}$

$=2.0492\mathrm{mm}$

Step 4, inquiry air physical property table or air physical property query software obtain density p and the kinetic viscosity μ of air under qualitative temperature and qualitative pressure, calculate the Re number according to the deviser mean flow rate u by the serrated fin passage determined according to flow operating mode,

For example adopting NIST-REFPROP inquiry qualitative temperature is 334K, and qualitative pressure is the physical property of air under 100000Pa:

Density p=the 1.0428kg/m of air ³, the kinetic viscosity μ of air=20.189 * 10 ^-6Pa/s,

Suppose that the flow velocity by the serrated fin passage is u=18m/s:

$\mathrm{Re}=\frac{\mathrm{\ρu}{D}_e}{\mathrm{\μ}}=\frac{1.0428\mathrm{kg}/m^3\×18m/s\×2.0492\×{10}^{-3}m}{20.189\×{10}^{-6}\mathrm{Pa}/s}=1905.2$

Then verify the Re number whether in the scope of design of the serrated fin j factor and the f factor, Re counts scope of design and is: 200≤Re≤10000; Through comparison, the Re number that calculates is in scope of design;

Step 5 is determined the compound dimensionless group Φ of serrated fin _f,

According to the basic dimensionless group that step 1 provides, can get compound dimensionless group Φ _f:

${\mathrm{\Φ}}_f={(\frac{1}{\mathrm{\α}}+\frac{1}{2\mathrm{\β}}-2)}^{\mathrm{\α}(1-2\mathrm{\β})+2\mathrm{\β}(1-\mathrm{\α})}+\frac{4(1-\mathrm{\α})\mathrm{\β}+\mathrm{\α}(1-2\mathrm{\β})}{4(\mathrm{\α}+\mathrm{\β}-2\mathrm{\α\β})}$

$={(\frac{1}{0.0211}+\frac{1}{2\×0.1429}-2)}^{0.0211\×(1-2\×0.1429)+2\×0.1429\×(1-0.0211)}$

$+\frac{4\×(1-0.0211)\×0.1429+0.0211\×(1-2\×0.1429)}{4(0.0211+0.1429-2\×0.0211\×0.1429)}$

$=4.05845$

Step 6, according to by the resulting calculation of parameter j factor of step 1-4 and the f factor,

Step 1-4 gained correlation parameter is brought in the correlation that provides, and calculating can obtain the j factor and the f factor is respectively:

$j=2.34812{\left(\frac{l_f}{D_h}\right)}^{0.19411}{{\mathrm{\Φ}}_f}^{0.00656}{\mathrm{\α}}^{-0.35987}{\mathrm{\β}}^{0.10391}{\mathrm{\γ}}^{0.45337}R{e}^{-1.01546+0.05633\ln \left(\mathrm{Re}\right)-0.00064{\left(\frac{h_f}{D_h}\right)}^{0.49317}{\mathrm{\β}}^{-0.16019}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

$=2.34812\×{\left(\frac{5\mathrm{mm}}{2.4404\mathrm{mm}}\right)}^{0.19411}\×{4.05845}^{0.00656}\×{0.0211}^{-0.35987}\×{0.1429}^{0.10391}\×{0.0400}^{0.45337}$

$\×{1905.2}^{-1.01546+0.05633\×\ln \left(1905.2\right)-0.00064\×{\left(\frac{9.5\mathrm{mm}}{2.4404\mathrm{mm}}\right)}^{0.49317}\×{0.1429}^{-0.16019}\×{\left(\ln \left(1905.2\right)\right)}^2}$

$=0.01012$

$f=2300.24{\left(\frac{l_f}{D_h}\right)}^{-1.42491}{{\mathrm{\Φ}}_f}^{0.26188}{\left(\frac{1}{1-2\mathrm{\α}}\right)}^{2.04570}{\left(\frac{1}{1-2\mathrm{\β}}\right)}^{2.16338}{\mathrm{\γ}}^{-0.93414}$

$\×R{e}^{-4.52412+0.49785\ln \left(\mathrm{Re}\right)-0.01580{\left(\frac{h_f}{D_h}\right)}^{0.00222}{\mathrm{\β}}^{-0.08664}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

$=2300.24\×{\left(\frac{5\mathrm{mm}}{2.4404\mathrm{mm}}\right)}^{-1.42491}\×{4.05845}^{0.26188}\×{\left(\frac{1}{1-2\×0.0211}\right)}^{2.04570}\×{\left(\frac{1}{1-2\×0.1429}\right)}^{2.16338}$

$\×{0.0400}^{-0.93414}\×{1095.2}^{-4.52412+0.49785\×\ln \left(1905.2\right)-0.01580\×{\left(\frac{9.5\mathrm{mm}}{2.4404\mathrm{mm}}\right)}^{0.00222}\×{0.1429}^{-0.08664}\×{\left(\ln \left(1905.2\right)\right)}^2}$

$=0.05268$

step 7, determine the total length of serrated fin used according to the thermal load of the j factor of the serrated fin that calculates and the plate type finned heat exchanger that will design, and then satisfy again total heat interchanging area and the volume of determining selected serrated fin under the condition of design heating load, the f factor by the serrated fin that calculates and the total length of serrated fin calculate pressure drop and the pump merit of selected serrated fin under the flow operating mode of the plate type finned heat exchanger that the deviser will design, then the pressure condition of importing and exporting according to the actual plate fin heat exchanger or the actual maximum pump merit that can provide for the plate type finned heat exchanger import, check selected serrated fin whether to satisfy design flow operating mode condition, if do not satisfy the design flow condition condition of starting building, the deviser need to reselect the elementary structure parameter of serrated fin, and repeating step 2-step 7, until selected serrated fin had not only satisfied the design heating load of plate type finned heat exchanger but also had satisfied the flow operating mode of fin heat exchanger, satisfy the design heating load and flow operating mode of plate type finned heat exchanger when selected serrated fin after, then serrated fin is optimized type selecting, the concrete structure of plate type finned heat exchanger heat exchange core is determined.

Advantage of the present invention mainly be can the Accurate Prediction serrated fin the j factor and the f factor, following table has provided the some experimental data based on Kays and London, and the some experimental data of domestic Nanjing University of Technology, the root-mean-square error (RMS) that adopts the fin performance entirely to test design load under flow operating mode and experiment value at this fin contrasts the accuracy of method for designing of the present invention and traditional Manglik method for designing.

As can be seen from the table, compare with experimental data, the root-mean-square error of the method for designing gained j factor of the present invention is generally little than traditional Manlik method for designing, for the f factor, root-mean-square error is all less than 10%, obviously be better than the Manglik method for designing, illustrate that Forecasting Methodology of the present invention can predict the fluid interchange performance of serrated fin more accurately in plate type finned heat exchanger design; In addition, effective estimation range of Forecasting Methodology of the present invention is larger, from dimensionless group, 0＜α＜0.5,0＜β＜0.5, γ〉0.01, almost contain the possible structure of institute of serrated fin, can make corresponding prediction to the high pressure serrated fin with larger fin thickness.

Claims (1)

1. the fin towards the plate type finned heat exchanger design flows and the heat exchange property Forecasting Methodology, it is characterized in that, comprises the following steps:

Step 1, the thermal load of the plate type finned heat exchanger that will design according to the deviser and flow operating mode are selected the elementary structure parameter of serrated fin, and the elementary structure parameter of serrated fin has: fin height h _f, fin width s _f, fin thickness δ _f, the fin unit length l _f, fin height h _fRefer to the distance from the feather edge of serrated fin to high rim, fin width s _fBe the distance between adjacent two serrated fins;

Step 2, basic dimensionless group α, β corresponding according to the elementary structure parameter calculating of selected serrated fin, γ, each basic dimensionless group is calculated as follows:

$\mathrm{\α}=\frac{{\mathrm{\δ}}_f}{h_f},$ $\mathrm{\β}=\frac{{\mathrm{\δ}}_f}{s_f},$ $\mathrm{\γ}=\frac{{\mathrm{\δ}}_f}{l_f}$

And verify α, β, γ whether in scope of design, and α, β, γ scope of design are: 0＜α＜0.5,0＜β＜0.5, γ〉0.01;

Step 3 is according to the elementary structure parameter calculating fin cross section equivalent diameter D of serrated fin _hWith fin channels equivalent diameter D _e,

D _hComputing method as follows:

$D_h=\frac{2h_f{s}_f}{h_f+s_f}$

D _eObtain by dual mode, the first is that the elementary structure parameter that directly passes through serrated fin calculates:

$D_e=\frac{2l_f(h_f-{\mathrm{\δ}}_f)(s_f-{\mathrm{\δ}}_f)}{l_f(h_f+s_f-2{\mathrm{\δ}}_f)+{\mathrm{\δ}}_f(h_f-{\mathrm{\δ}}_f)+\frac{2{\mathrm{\δ}}_f(s_f-2{\mathrm{\δ}}_f)}{4}}$

The second is the basic dimensionless group that drawn by the step 1 height h in conjunction with serrated fin _fWith fin width s _fCalculate:

$D_e=\frac{2(1-\mathrm{\α})(1-\mathrm{\β})}{\frac{1}{s_f}(1-\mathrm{\α})(1+\mathrm{\β})+\frac{1}{h_f}(1+\frac{1}{2}\mathrm{\γ}-\mathrm{\β}(1+\mathrm{\γ}))}$

Step 4, inquiry air physical property table or air physical property query software obtain density p and the kinetic viscosity μ of air under qualitative temperature and qualitative pressure, and the flow velocity u designed according to the deviser calculates the Re number, $\mathrm{Re}=\frac{\mathrm{\ρu}{D}_e}{\mathrm{\μ}}$

If the deviser adopts the MAF m by the unit fin channels _fDesign, Re also can be obtained by following mode:

$\mathrm{Re}=\frac{m_f}{A_{\mathrm{front}}}\frac{D_e}{\mathrm{\μ}}$

In formula: A _Front=(h _f-δ _f) (s _f-δ _f)

Then verify the Re number whether in the scope of design of the serrated fin j factor and the f factor, Re counts scope of design and is: 200≤Re≤10000;

Step 5 is determined the compound dimensionless group Φ of serrated fin _f, formula is as follows:

${\mathrm{\Φ}}_f={(\frac{1}{\mathrm{\α}}+\frac{1}{2\mathrm{\β}}-2)}^{\mathrm{\α}(1-2\mathrm{\β})+2\mathrm{\β}(1-\mathrm{\α})}+\frac{4(1-\mathrm{\α})\mathrm{\β}+\mathrm{\α}(1-2\mathrm{\β})}{4(\mathrm{\α}+\mathrm{\β}-2\mathrm{\α\β})}$

Step 6 according to by the resulting parameter of step 1-4, is calculated the j factor and the f factor of serrated fin used, and computing formula is as follows:

$j=2.34812{\left(\frac{l_f}{D_h}\right)}^{0.19411}{{\mathrm{\Φ}}_f}^{0.00656}{\mathrm{\α}}^{-0.35987}{\mathrm{\β}}^{0.10391}{\mathrm{\γ}}^{0.45337}R{e}^{-1.01546+0.05633\ln \left(\mathrm{Re}\right)-0.00064{\left(\frac{h_f}{D_h}\right)}^{0.49317}{\mathrm{\β}}^{-0.16019}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

$f=2300.24{\left(\frac{l_f}{D_h}\right)}^{-1.42491}{{\mathrm{\Φ}}_f}^{0.26188}{\left(\frac{1}{1-2\mathrm{\α}}\right)}^{2.04570}{\left(\frac{1}{1-2\mathrm{\β}}\right)}^{2.16338}{\mathrm{\γ}}^{-0.93414}$

$\×R{e}^{-4.52412+0.49785\ln \left(\mathrm{Re}\right)-0.01580{\left(\frac{h_f}{D_h}\right)}^{0.00222}{\mathrm{\β}}^{-0.08664}{\left(\ln \left(\mathrm{Re}\right)\right)}^2}$

step 7, determine the total length of serrated fin used according to the thermal load of the j factor of the serrated fin that calculates and the plate type finned heat exchanger that will design, and then satisfying total heat interchanging area and the volume of determining selected serrated fin under the condition of design heating load, the f factor by the serrated fin that calculates and the total length of serrated fin calculate pressure drop and the pump merit of selected serrated fin under the flow operating mode of the plate type finned heat exchanger that the deviser will design, then the pressure condition of importing and exporting according to the actual plate fin heat exchanger or the actual maximum pump merit that can provide for the plate type finned heat exchanger import, verify selected serrated fin and whether satisfy design flow operating mode condition, if do not satisfy the design flow condition condition of starting building, the deviser need to reselect the elementary structure parameter of serrated fin, and repeating step 2-step 7, until selected serrated fin had not only satisfied the design heating load of plate type finned heat exchanger but also had satisfied the flow operating mode of fin heat exchanger, satisfy the design heating load and flow operating mode of plate type finned heat exchanger when selected serrated fin after, then serrated fin is optimized type selecting, the heat exchange core of plate type finned heat exchanger is determined.

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