CN116680838B

CN116680838B - Heat transfer calculation method of plate-fin heat exchanger

Info

Publication number: CN116680838B
Application number: CN202310933467.0A
Authority: CN
Inventors: 谭军华; 林学星; 李林华; 张铭
Original assignee: Dongguan Pengjin Machinery Technology Co ltd
Current assignee: Dongguan Pengjin Machinery Technology Co ltd
Priority date: 2023-07-27
Filing date: 2023-07-27
Publication date: 2024-04-26
Anticipated expiration: 2043-07-27
Also published as: CN116680838A

Abstract

The invention belongs to the technical field of heat exchangers, and particularly relates to a heat transfer calculation method of a plate-fin heat exchanger, which comprises the following steps of: s1: acquiring fin structure parameters of different fluid working conditions or different plate-fin heat exchanger types; s2: respectively constructing calculation expressions of fin channel parameters, fluid physical property parameters and convection heat transfer parameters of the plate-fin heat exchanger; s3: based on different fluid working conditions or different plate-fin heat exchanger types, respectively establishing a corresponding parallel flow model, a corresponding countercurrent model and a corresponding cross flow model, and solving the outlet temperature of a fin channel of the fluid under different fluid working conditions or different plate-fin heat exchanger types by adopting programming software; s4: and respectively solving the heat exchange efficiency and the total heat transfer coefficient of different fluid working conditions or different plate-fin heat exchanger types of lower plate-fin heat exchangers based on the outlet temperature of the fluid in the fin channels.

Description

Heat transfer calculation method of plate-fin heat exchanger

Technical Field

The invention belongs to the technical field of heat exchangers, and particularly relates to a heat transfer calculation method of a plate-fin heat exchanger.

Background

In the prior art, the heat exchanger is a general device for chemical industry, petroleum, steel, automobile, video and many other industrial departments, plays an important role in production, and particularly in chemical industry production, and can be widely applied as a heater, a cooler, a condenser, an evaporator and the like. The heat transfer efficiency and the resistance characteristic of the heat exchanger can directly influence the investment cost, the operation cost and the occupied area of the whole system, so that the heat exchanger has great significance for researching the heat exchange performance of the heat exchanger.

At present, the plate-fin heat exchanger can form strong turbulence for fluid due to the special structure of the fins, so that the thermal resistance is effectively reduced, the heat transfer efficiency is improved, and meanwhile, the fins are thin and compact in structure and can be made of aluminum alloy, so that the plate-fin heat exchanger is small in size, light in weight and low in cost, and further, the plate-fin heat exchanger is widely applied to industries such as aerospace, chemical industry and refrigeration, and particularly in the field of waste heat recovery. However, in the research and development process of actual industrial products, the determination of sample parameters needs to be determined through continuous experimental analysis, and the process is complicated; meanwhile, as shown in fig. 1, in the existing NMP waste gas waste heat recovery device, a plate-fin heat exchanger with higher heat transfer efficiency mostly adopts a design mode of 'inlet and outlet section cross flow-middle section countercurrent' (i.e. an 'i+z' type or an 'l+l' type) so as to realize efficient heat exchange of two fluids without mixing. The simulation research of the plate-fin heat exchanger mostly adopts the more commonly used model software fluid dynamics (CFD) simulation software Ansys Fluent to perform model establishment, grid division and model solving, and the software has a certain degree of expertise and is difficult to directly operate by non-technical personnel; meanwhile, the systematic parameter optimization solution of the fluid dynamics (CFD) simulation software Ansys Fluent on the heat exchange mode of 'inlet and outlet section cross flow-middle section countercurrent' (namely 'I+Z' type or 'L+L' type) is difficult to realize, so that the design and optimization of the plate-fin heat exchanger capable of carrying out efficient heat exchange consume very much time cost and experiment cost.

Wherein, countercurrent section all sets up to the sawtooth structure in the plate-fin heat exchanger to strengthen heat transfer, triangle-shaped cross flow area is flat structure, in order to reduce windage pressure drop. As shown in fig. 2, in the "i+z" type plate-fin heat exchanger, the inlet and outlet directions of the hot fluid are "I", and the inlet and outlet directions of the cold fluid are "Z"; as shown in fig. 3, in the "l+l" type plate-fin heat exchanger, the inlet and outlet directions of the hot fluid and the cold fluid are both "L"; in addition, the inlets for the cold fluid and the hot fluid are respectively located at the opposite ends of the plate-fin heat exchanger.

Therefore, it is necessary to design a heat transfer algorithm of the plate-fin heat exchanger for the "i+z" type and the "l+l" type plate-fin heat exchangers capable of performing efficient heat exchange, so that the heat transfer algorithm can optimally solve the fin structure of the heat exchanger by adopting programming software, and further improve the heat transfer performance of the plate-fin heat exchanger.

Disclosure of Invention

The invention provides a heat transfer calculation method of a plate-fin heat exchanger, which is characterized in that corresponding models are respectively established through different fin types, fin structure parameters and fluid working conditions of the fins of the plate-fin heat exchanger, different fluid working conditions and different types of lower fin channel outlet temperatures of the plate-fin heat exchanger are solved, corresponding heat exchange efficiency and a heat transfer system are obtained, the heat exchange effect of the current plate-fin heat exchanger structure can be obtained, further, the experiment and labor cost are reduced, and further, a reference is provided for the design of a high-efficiency low-resistance heat exchanger.

The heat transfer calculation method of the plate-fin heat exchanger comprises the following steps:

S1: acquiring fin structure parameters of different fluid working conditions or different plate-fin heat exchanger types;

S2: respectively constructing calculation expressions of fin channel parameters, fluid physical property parameters and convection heat transfer parameters of the plate-fin heat exchanger;

S3: based on different fluid working conditions or different plate-fin heat exchanger types, respectively establishing a corresponding parallel flow model, a corresponding countercurrent model and a corresponding cross flow model, and solving the outlet temperature of a fin channel of the fluid under different fluid working conditions or different plate-fin heat exchanger types by adopting programming software;

S4: and respectively solving the heat exchange efficiency and the total heat transfer coefficient of different fluid working conditions or different plate-fin heat exchanger types of lower plate-fin heat exchangers based on the outlet temperature of the fluid in the fin channels.

Corresponding models are respectively established through different fin types, fin structure parameters and fluid working conditions of the plate-fin heat exchanger fins, different fluid working conditions and different plate-fin heat exchanger lower fin channel outlet temperatures are solved, corresponding heat exchange efficiency and a corresponding heat transfer system are obtained, the heat exchange effect of the current plate-fin heat exchanger structure can be obtained, further the experiment and labor cost are reduced, and further reference is provided for the design of the efficient low-resistance heat exchanger.

Further, in the step S1,

The fluid conditions include: parallel flow, counter flow and cross flow;

the plate fin heat exchanger types include: an 'I+Z' -shaped plate-fin heat exchanger and an 'L+L' -shaped plate-fin heat exchanger;

the fin types include: straight fins, corrugated fins, saw-tooth fins;

the fin structure parameters include: fin spacing, fin width, number of fin channel layers, fin core width, fin height, fin thickness, separator thickness, seal thickness.

Further, in the step S2, the fin channels of the plate-fin heat exchanger are formed by continuously stamping a whole aluminum plate, and the adjacent fins have a height dislocation of the fin thickness t, and the current fin and the adjacent baffle are regarded as a whole, namely, the upper side and the lower side of each fin channel can be divided into two thicknesses of the baffle, the fin and the whole baffle; the calculation of fin channel parameters of the plate-fin heat exchanger comprises the following steps:

(1) Calculation of equivalent diameter of individual Fin channels ；

Equivalent diameter of straight finThe calculated expression of (2) is: /(I)；

Equivalent diameter of corrugated finThe calculated expression of (2) is: /(I)；

Equivalent diameter of sawtooth finThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,Is fin spacing, which includes cross-flow section hot side fin spacing/>Cross-flow section Cold side Fin spacing/>Fin pitch of counterflow section/>；/>Is the fin height, which comprises the height/>, of the hot side fin of the cross flow sectionCross-flow section Cold side Fin height/>；/>Is fin thickness; /(I)Is the ratio of the corrugated fin flow length to the radial length; /(I)Is the pitch of the sawtooth fins;

(2) Counting the number of channels of a monolayer fin ；

Number of single-layer fin channels on hot side of cross-flow sectionThe calculated expression of (2) is: /(I)；

Number of single-layer fin channels on cold side of cross-flow sectionThe calculated expression of (2) is: /(I)；

Number of single layer fin channels of the counterflow sectionThe calculated expression of (2) is: /(I)；

Wherein [ (formula) is a whole symbol; Fin width at hot side of cross flow section; /(I) Fin width is the cold side of the cross flow section; The thickness of the seal is the thickness of the seal;

(3) Calculating fin core height ；

Height of fin coreThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,The number of layers of fin channels; /(I)Is the thickness of the separator;

(4) Calculating the windward area of the fin channel ；

Hot side fin channel windward areaThe calculated expression of (2) is: /(I)；

Windward area of cold side fin channelThe calculated expression of (2) is: /(I)；

(5) Calculating the flow area of each fin channel；

Hot side fin channel flow areaThe calculated expression of (2) is: /(I)；

Flow area of cold side fin channelThe calculated expression of (2) is: /(I)；

(6) Calculating the ratio of the flow area to the windward area；

Hot side fin channel flow areaAnd frontal area/>Ratio of/>The calculated expression of (2) is:；

Flow area of cold side fin channel And frontal area/>Ratio of/>The calculated expression of (2) is:；

(7) Calculating the thickness of each fin channel separator ；

Thickness of separatorThe calculated expression of (2) is: /(I)；

The integral thickness of the fin and the baffleThe calculation expression of the relative position is: /(I)；

Wherein use is made ofRepresents the heat transfer baffle thickness in each fin channel,/>。

Further, in the step S2, the fluid is dry air, that is, the calculation of the corresponding fluid physical property parameter includes:

(1) Calculating the density of air in the fin channels ；

Density of air in hot side fin channelsThe calculated expression of (2) is: /(I)；

Density of air in cold side fin channelsThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,To thermally measure the fin channel temperature; /(I)The temperature of the fin channel is measured cold;

(2) Calculating specific heat capacity of air in fin channels ；

Specific heat capacity of air in hot side fin channelsThe calculated expression of (2) is: /(I)；

Specific heat capacity of air in cold side fin channelsThe calculated expression of (2) is: /(I)；

(3) Calculating the thermal conductivity of air in the Cold side Fin channel；

Thermal conductivity of air in hot side fin channelsThe calculated expression of (2) is:；

Thermal conductivity of air in cold side fin channels The calculated expression of (2) is:；

(4) Calculating the viscosity coefficient of air in fin channels ；

Viscosity coefficient of air in hot side fin channelThe calculated expression of (2) is:；

Viscosity coefficient of air in cold side fin channel The calculated expression of (2) is:；

(5) Calculating the inlet density of air in the fin channels ；

Air inlet density at hot side fin channelThe calculated expression of (2) is: /(I)；

Air inlet density in cold side fin channelThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,Inlet temperature for air at the hot side fin channel; /(I)Inlet temperature for air at the hot side fin channel;

(6) Calculating the inlet flow velocity of air in the fin channels ；

Air inlet flow rate at hot side fin channelThe calculated expression of (2) is: /(I)；

Air inlet flow rate at cold side fin channelThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,The inlet air quantity of the hot side fin channel; /(I)The air return ratio is the cold side air return ratio;

(7) Calculating the mass flow rate of air in fin channels ；

Air on hot side fin channel mass flow rateThe calculated expression of (2) is: /(I)；

Air on the cold side fin channel mass flow rateThe calculated expression of (2) is: /(I)；

(8) Calculating the flow velocity of air in the fin channels；

Air flow rate in hot side fin channelThe calculated expression of (2) is: /(I)；

Air flow rate in cold side fin channelThe calculated expression of (2) is: /(I)；

(9) Calculating Reynolds number of air in fin channel；

Reynolds number of air on hot side fin channelThe calculated expression of (2) is: /(I)；

Reynolds number of air on cold side fin channelThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,Equivalent diameter of fin channels for hot side fluid flow; /(I)Equivalent diameter of fin channels for cold side fluid flow;

(10) Calculating the prandtl number of air in fin channels ；

Prandtl number of air on hot side fin channelThe calculated expression of (2) is: /(I)；

Prandtl number of air on cold side fin channelThe calculated expression of (2) is: /(I)。

Further, in S2, the calculating the convective heat transfer parameter includes:

(1) Calculating the convective heat transfer coefficient of air in fin channels ；

Convection heat transfer coefficient of air in hot side fin channelThe calculated expression of (2) is: /(I)；

Convective heat transfer coefficient of air in cold side fin channelThe calculated expression of (2) is: /(I)；

Wherein,；

。

(2) Calculating wind resistance of air in fin channels；

Windage of air on hot side fin channelThe calculated expression of (2) is: /(I)；

Windage of air on cold side fin channelThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,，/>，，/>Is the coefficient of shrinkage of the hot side fin channel,/>The sudden expansion coefficient of the hot side fin channel; /(I)，/>，，/>Is the coefficient of protrusion of the cold side fin channel,/>Is the sudden expansion coefficient of the cold side fin channel;

wherein, ；

；

Further, in the step S3, the establishing of the parallel flow model and the counter flow model includes:

(1) Establishing a parallel flow model;

dividing air into infinite microelements along the flowing direction of the fin channel, and establishing a parallel flow model equation within the temperature change range of the hot fluid and the cold fluid at the corresponding temperature, namely:

；

In the method, in the process of the invention, For primary heat transfer of air in the fin channels through the baffles,/>Secondary heat transfer of air in the fin channels through the fins is performed; namely:

；

In the method, in the process of the invention, For hot side fin efficiency at the current fin infinitesimal length, its computational expression is: /(I)Wherein/>；/>For the cold side fin efficiency at the current fin infinitesimal length, the calculation expression is: /(I)Wherein/>；

Wherein, the boundary conditions are:

；

Establishing the temperature of air in the fin passages 、/>Regarding fin length/>The differential equation set of (2) is:

；

(2) Establishing a countercurrent model;

；

Wherein, the boundary conditions are:

；

。

Further, in the step S3, based on different fluid working conditions and different plate-fin heat exchanger types, the process of establishing the cross flow model specifically includes:

single layer fin channel number based on hot side and cold side of plate fin heat exchanger 、/>Dividing a single layer fin channel into/>I.e. each grid cell/>, of the heat exchange grid matrixThe hot side temperature matrix element/>, is represented in the regionCold side temperature matrix element/>And corresponding thermal resistance/>Wherein/>,/>；

In grid cellsEstablishing a heat balance equation in the region, namely:

；

In the method, in the process of the invention, For grid cell/>The heat transfer of the region is calculated as:

；

wherein, the boundary conditions of the 'I+Z' -shaped plate-fin heat exchanger are as follows:

；

Wherein, the boundary conditions of the L+L-shaped plate-fin heat exchanger are as follows:

。

further, in the step S3, the process of solving the outlet temperature of the fin channel of the fluid under different fluid working conditions by using programming software specifically includes:

S311: when the fluid working condition is parallel flow, based on a parallel flow model, adopting programming software to obtain a numerical solution, and respectively obtaining the outlet temperature of the hot side fin channel and the outlet temperature of the cold side fin channel under the parallel flow working condition;

S312: when the fluid working condition is countercurrent, based on a countercurrent model, adopting programming software to obtain a numerical solution, and respectively obtaining the outlet temperature of the hot side fin channel and the outlet temperature of the cold side fin channel under the countercurrent working condition;

S313: when the fluid working condition is cross flow, based on a cross flow model, adopting programming software to iteratively acquire the outlet temperature of the hot side fin channel and the outlet temperature of the cold side fin channel under the cross flow working condition;

s3131: divided based on construction of cross-flow models Is to/>，/>Obtaining grid cell/>Hot side temperature matrix element in region/>Cold side temperature matrix element/>And corresponding thermal resistance/>Establishing a heat balance equation to realize iteration of the whole heat exchange grid matrix;

s3132: based on the heat balance equation, solving the grid cell area Hot side temperature matrix element in (a)Grid cell area/>Cold side temperature matrix element/>；

S3133: order theIterative computation in columns until/>Stopping iteration;

S3134: order the Iterative computation is sequentially carried out according to rows until/>Stopping iteration;

S3135: acquiring a hot side temperature matrix Last row/>Obtaining the outlet temperature/>, of the hot-side fin channel under the cross flow condition；

Acquiring a cold side temperature matrix/>Obtaining the average temperature of the rows to obtain the outlet temperature/>, of the cold-side fin channels under the cross flow condition。

Further, in the step S3, the process of solving the outlet temperature of the fin channels of the fluid under different plate-fin heat exchanger types by using programming software specifically includes:

S321: obtaining inlet temperature of hot side fin channel Presetting inlet temperature/>, of cold-side fin channelsSolving and obtaining the approximate outlet temperature of the first fin channel of the cold side close to the hot side as/>, by combining a countercurrent model and a cross-flow model；

S322: inlet temperature based on hot side fin channelsAnd the approximate outlet temperature of the first fin channel on the cold side near the hot side is/>Establishing a heat exchange grid matrix and a heat balance equation, and solving the outlet temperature/>, of a first fin channel at the cold side；

S3221: based on the first fin channel with the cold side close to the hot side, gradually calculating and solving the inlet temperature of the first fin channel with the cold side close to the hot side according to the sequence of the first cross flow section, the counter flow section and the second cross flow section；

S3222: calculation ofWhen its value is less than/>When the accuracy condition is met, namely the inlet temperature/>, of the first fin channel of the current cold side close to the hot side is obtained；

S323: sequentially solving the outlet temperature of the next fin channel of the cold side close to the hot side until the outlet temperature of the nth fin channel of the cold side close to the hot side is completedIs solved;

S324: acquiring a temperature matrix of each fluid working condition stage, sequentially assigning values, and solving the outlet temperature of the hot side fin channel Outlet temperature of Cold side Fin channel/>；

S3241: inlet temperature based on acquired hot side fin channelAnd a preset inlet temperature/>, of the cold side fin channels；

S3242: solving a first cross-flow section hot side temperature matrix by combining a cross-flow modelFirst cross-flow section cold side temperature matrix/>And assigning the elements on the diagonal lines to the hot side temperature matrix/>, respectivelyCold side temperature matrix/>, of the first row and counter-current sectionRespectively serving as an inlet temperature of a hot side fin channel of the countercurrent section and an outlet temperature of a cold side fin channel of the countercurrent section;

S3243: solving the outlet temperature of the hot side fin channel of the countercurrent section and the inlet temperature of the cold side fin channel of the countercurrent section by combining the countercurrent model, and respectively assigning the outlet temperature and the inlet temperature to a hot side temperature matrix of the countercurrent section Is a second row and countercurrent section cold side temperature matrixAnd then the hot side temperature matrix/>, of the countercurrent sectionThe second row and countercurrent section cold side temperature matrix/>The elements of the second column of the first cross-flow section are assigned to the second cross-flow section hot side temperature matrix/>, respectivelySecond cross-flow section cold side temperature matrix/>Respectively serving as the inlet temperature of the hot side fin channel of the second cross-flow section and the outlet temperature of the cold side fin channel of the second cross-flow section;

s3244: solving the outlet temperature of the second cross-flow section hot side fin channel and the inlet temperature of the second cross-flow section cold side fin channel by combining the cross-flow model, and respectively assigning the outlet temperature and the inlet temperature to a second cross-flow section hot side temperature matrix The last row, second cross-flow section cold side temperature matrix/>Is the last column of (2);

S3245: solving a second cross-flow section hot side temperature matrix The row average temperature of the last row or the column average temperature of the last column of the heat exchanger to obtain the outlet temperature/>；

Solving a second cross-flow section cold side temperature matrixThe row average temperature of the first row or the column average temperature of the first column to obtain the outlet temperature/>, of the hot side fin channels of the I+Z-type or L+L-type plate-fin heat exchanger。

Further, in the step S4, the heat exchange efficiency, the hot side total heat transfer coefficient and the cold side total heat transfer coefficient are calculated based on the hot side outlet temperature and the cold side outlet temperature; namely:

Efficiency of heat exchange The calculated expression of (2) is: /(I)；

Total heat transfer coefficient of hot sideThe calculated expression of (2) is: /(I)；

Total heat transfer coefficient of cold sideThe calculated expression of (2) is: /(I)；

In the method, in the process of the invention,，/>；/>。

A computer device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory in communication over the bus when the computer device is running, the machine-readable instructions when executed by the processor performing the method of any of the above.

A computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the method of any of the preceding claims.

The beneficial effects of the invention are as follows:

According to the invention, through different fin types, fin structural parameters and fluid working conditions of the fin of the plate-fin heat exchanger, corresponding models are respectively established, different fluid working conditions and the outlet temperatures of fin channels under different plate-fin heat exchanger types are solved, corresponding heat exchange efficiency and a corresponding heat transfer system are obtained, the heat exchange effect of the current plate-fin heat exchanger structure can be obtained, further, the experiment and labor cost are reduced, and further, reference is provided for the design of the high-efficiency low-resistance heat exchanger.

Drawings

FIG. 1 is a schematic diagram of an "I+Z" or "L+L" plate-fin heat exchanger;

FIG. 2 is a schematic diagram of an "I+Z" plate-fin heat exchanger;

FIG. 3 is a schematic diagram of an "L+L" plate-fin heat exchanger;

FIG. 4 is a flow chart of the present invention;

FIG. 5 is a schematic illustration of a heat exchange grid matrix in a cross-flow model;

FIG. 6 is a flow chart for calculating the fin channel outlet temperature of a plate-fin heat exchanger under cross-flow conditions;

FIG. 7 is a flow chart for calculating the fin channel outlet temperature of a plate fin heat exchanger for different plate fin heat exchanger types;

FIG. 8 is a flow chart of a method of inlet and outlet temperature correction for cross-flow and counter-flow sections;

FIG. 9 (a) is a schematic diagram showing the distribution of the hot side temperature field of the plate-fin heat exchanger under the cross-flow condition in example 2;

FIG. 9 (b) is a schematic diagram showing the distribution of the cold side temperature field of the plate-fin heat exchanger under the cross-flow condition in example 2;

FIG. 10 (a) is a thermal side temperature field distribution diagram of an "I+Z" plate-fin heat exchanger of example 2;

FIG. 10 (b) is a graph showing the cold side temperature field profile of the "I+Z" plate-fin heat exchanger of example 2;

FIG. 11 is a system of a heat transfer calculation method for a plate-fin heat exchanger of example 3;

Fig. 12 is a schematic structural diagram of a computer device.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.

Furthermore, in the following description, specific details are provided for the purpose of providing a thorough understanding of the examples, and it will be apparent to one skilled in the art that the specific meaning of the terms described above in the present application will be practiced with specificity.

Example 1

Fig. 4 shows a heat transfer calculation method of a plate-fin heat exchanger, wherein corresponding models are respectively built through different fin types, fin structure parameters and fluid working conditions of the plate-fin heat exchanger fins, solution of different fluid working conditions and fin channel outlet temperatures under different plate-fin heat exchanger types is carried out, corresponding heat exchange efficiency and a heat transfer system are obtained, the heat exchange effect of the current plate-fin heat exchanger structure can be obtained, further experiment and labor cost are reduced, and reference is provided for design of a high-efficiency low-resistance heat exchanger. The method specifically comprises the following steps:

Wherein, fluid operating mode includes: parallel flow, counter flow and cross flow;

Wherein the plate fin heat exchanger types include: an 'I+Z' -shaped plate-fin heat exchanger and an 'L+L' -shaped plate-fin heat exchanger;

Wherein, the fin includes: straight fins, corrugated fins, saw-tooth fins;

Wherein, fin structure parameters include: fin spacing, fin width, number of fin channel layers, fin core width, fin height, fin thickness, separator thickness, seal thickness.

The fin channels of the plate-fin heat exchanger are formed by continuously stamping a whole aluminum plate, the adjacent fins are staggered in height by the fin thickness t, and the current fins and the adjacent baffle plates are regarded as a whole, namely, the upper side and the lower side of each fin channel can be divided into two thicknesses of the baffle plates, the fins and the whole baffle plates; the calculation of fin channel parameters of the plate-fin heat exchanger comprises the following steps:

(1) Calculation of equivalent diameter of individual Fin channels ；

Equivalent diameter of straight finThe calculated expression of (2) is: /(I)；

Equivalent diameter of sawtooth finThe calculated expression of (2) is: /(I)；

the cold side fin spacing of the countercurrent section is the same as the hot side fin spacing of the countercurrent section, and is all 。

(2) Counting the number of channels of a monolayer fin；

Number of single-layer fin channels on hot side of cross-flow sectionThe calculated expression of (2) is: /(I)；/>

Wherein, [ ] is a whole symbol; Fin width at hot side of cross flow section; /(I) Fin width is the cold side of the cross flow section; /(I)The thickness of the seal is the thickness of the seal;

(3) Calculating fin core height Calculate fin core height/>；

Height of fin coreThe calculated expression of (2) is: /(I)；

(4) Calculating the windward area of the fin channel ；

Hot side fin channel windward areaThe calculated expression of (2) is: /(I)；

(5) Calculating the flow area of each fin channel；

Hot side fin channel flow areaThe calculated expression of (2) is: /(I)；

Flow area of cold side fin channelThe calculated expression of (2) is: /(I)；

(6) Calculating the ratio of the flow area to the windward area；

(7) Calculating the thickness of each fin channel separator ；

Thickness of separatorThe calculated expression of (2) is: /(I)；

The integral thickness of the fin and the baffleThe calculated expression of (2) is: /(I)；

The fluid is dry air, physical parameters with the minimum relative error are obtained by adopting least square fitting, and the calculation of the corresponding physical parameters of the fluid at the temperature of 0-120 ℃ comprises the following steps:

(1) Calculating the density of air in the fin channels ；

Density of air in cold side fin channelsThe calculated expression of (2) is: /(I)；/>

(2) Calculating specific heat capacity of air in fin channels ；

(3) Calculating the thermal conductivity of air in the Cold side Fin channel；

(4) Calculating the viscosity coefficient of air in fin channels ；

(5) Calculating the inlet density of air in the fin channels ；

(6) Calculating the inlet flow velocity of air in the fin channels ；

(7) Calculating the mass flow rate of air in fin channels ；

(8) Calculating the flow velocity of air in the fin channels；/>

(9) Calculating Reynolds number of air in fin channel；

(10) Calculating the prandtl number of air in fin channels ；

Wherein, the calculation of the convection heat transfer parameter comprises:

Wherein,；

；

(2) Calculating wind resistance of air in fin channels；

wherein, ；

。

(1) Establishing a parallel flow model;

；

Wherein, the boundary conditions are:

；

Establishing the temperature of air in the fin passages 、/>Regarding fin length/>The differential equation set of (2) is: /(I)

；

(2) Establishing a countercurrent model;

；

Wherein, the boundary conditions are:

；

。

(3) Establishing a cross-flow model;

As shown in FIG. 5, the number of single layer fin channels based on the hot side and the cold side of the plate fin heat exchanger 、/>Dividing a single layer fin channel into/>I.e. each grid cell/>, of the heat exchange grid matrixRepresenting hot side temperature matrix elements in a regionCold side temperature matrix element/>And corresponding thermal resistance/>Wherein/>,；

In grid cellsEstablishing a heat balance equation in the region, namely: /(I)

；

In the method, in the process of the invention,For grid cell/>The heat transfer of the region is calculated as:

；

Wherein the grid cells Zone thermal resistance/>The calculated expression of (2) is:

；

。

The process of iteratively solving the outlet temperature of the fin channel of the fluid under different fluid working conditions by adopting programming software specifically comprises the following steps:

S3132: based on heat balance equation, solve Hot side temperature matrix element in (a)Grid cell area/>Cold side temperature matrix element/>；

S3133: order theIterative computation in columns until/>Stopping iteration; /(I)

S3134: order theIterative computation is sequentially carried out according to rows until/>Stopping iteration;

S3135: acquiring a hot side temperature matrix Last row/>Obtaining the row average temperature to obtain the outlet temperature/>, of the hot side fin channel under the cross flow condition；

Acquiring a cold side temperature matrixLast column/>Obtaining the average temperature of the rows to obtain the outlet temperature/>, of the cold-side fin channels under the cross flow condition。

FIG. 6 is a flow chart for calculating the outlet temperature of fin channels of the plate-fin heat exchanger under the cross-flow working condition.

The process of iteratively solving the outlet temperature of the fin channels of the fluid under different plate-fin heat exchanger types by adopting programming software specifically comprises the following steps:

It should be noted that the "I+Z" type plate-fin heat exchanger can fix the inlet temperature of the hot-side fin channels onlyPresetting inlet temperature/>, of cold-side fin channels; The L+L-shaped fin heat exchanger can fix the inlet temperature/>, of the hot side fin channelPresetting inlet temperature/>, of cold-side fin channelsThe inlet temperature/>, of the cold-side fin channels can also be fixedPresetting inlet temperature/>, of hot-side fin channels。

Wherein after the first iterationWhen you first pair/>Gradually reducing 1 ℃ untilFurther to the last step/>Gradually increasing the temperature by 0.1 ℃ until/>Further to the last step/>Gradually reducing the temperature by 0.01 ℃ until/>Sequentially until the precision/>Until that, the accuracy condition is satisfied.

S324: acquiring a temperature matrix of each fluid working condition stage, sequentially assigning values, and solving the outlet temperature of the hot side fin channel Outlet temperature of Cold side Fin channel/>；/>

FIG. 7 is a flow chart for calculating the fin channel outlet temperature of a plate-fin heat exchanger for different plate-fin types; wherein,For iteration number,/>The value is 0.01 as the precision condition.

In this embodiment, when the fluid flows between the fin channels with different fin pitches in the same plate-fin heat exchanger, the process of solving the temperature assignment of the fin channels between the first cross-flow section and the counter-flow section and between the counter-flow section and the second cross-flow section is further deepened, which is: as the fin spacing between the cross-flow and counter-flow sections is different, and the fin spacing between the hot and cold sides of the cross-flow sections may also be different, this results in a different number of their fin channels. To facilitate calculation of temperature change of fluid flowing through different numbers of fin channels to cross-flow hot sideThe fin channels are taken as a reference, and/>, the cold side of the cross flow section is taken as the referenceThe individual fin channels are subdivided according to flow area/>Equal parts, but equivalent diameter is considered constant, whereby/>And (5) a cross-flow model of the heat exchange grid matrix. After all fin channel temperatures are solved, the obtained/>, of the cold side of the cross flow section is further solvedActual/>, individual fin channel temperature versus cross-flow section cold sideCorrecting the inlet and outlet temperatures of each fin channel, and obtaining the/>, of the hot side and the cold side of the countercurrent sectionActual/>, individual fin channel temperature versus hot side and cold side of the counterflow sectionThe inlet and outlet temperatures of the individual fin passages are temperature corrected. The specific process comprises the following steps:

T1: assume that the hot side fin spacing of the cross-flow section is The cold side fin spacing of the cross flow section is/>The fin spacing of the countercurrent section isCross-flow section hot side to cold side core width ratio/>; Solving a temperature matrix of the hot side fin channels and the cold side fin channels;

T2: the first to cold side of cross flow section, hot side and cold side of countercurrent section Correcting the temperature of each fin channel to obtain corrected/>Individual fin channel temperature/>。

Assuming temperatures of nth fin channels of the cold side of the cross-flow section, the hot side of the counter-flow section, and the cold sideBy corresponding/>, before correctionTemperature/>To/>Temperature/>The heat exchanger is obtained by numerical average mixing according to the proportion of fin spacing, namely:

Temperature of nth fin channel on cold side of cross flow section The calculated expression of (2) is:

When (when) Time,/>；

Otherwise, and whenTime,/>；

In the formula, [ ] is a rounding symbol,；/>For/>Temperature of individual Fin channels,/>The value range is/>To/>。

Temperature of nth fin channel on hot side and cold side of counterflow sectionThe calculated expression of (2) is:

When (when) Time,/>；

Otherwise, and whenTime,/>；

FIG. 8 is a flow chart of a method for correcting inlet and outlet temperatures of a cross flow section and a counter flow section; wherein,The iteration times; /(I)For/>At/>，/>) Within/>Is calculated.

S4: and respectively solving the heat exchange efficiency and the total heat transfer coefficient of different fluid working conditions or different plate-fin heat exchanger types of lower plate-fin heat exchangers based on the outlet temperature of the fluid in the fin channels. Namely:

Efficiency of heat exchange The calculated expression of (2) is: /(I)；/>

In the method, in the process of the invention,，/>；/>。

In this embodiment, MATLAB software is used as the programming software.

Example 2

In this embodiment, the difference from embodiment 1 is that: the fluid is two drying air streams, and the mass flow rate of the air entering the hot side fin channelsInlet temperature of air at hot side fin channel/>Inlet temperature of air at hot side fin channel/>Cold side Return air ratio/>。

In this embodiment, under different fluid working conditions, the fin structure parameters adopted are:

；

In this embodiment, the "i+z" type plate-fin heat exchanger, or the "l+l" type plate-fin heat exchanger, adopts the fin structure parameters:

；

After being calculated by MATLAB programming software, the obtained different fluid working conditions, the outlet temperatures of fin channels of different types of plate-fin heat exchangers, the heat exchange efficiency of the plate-fin heat exchangers, the total heat transfer coefficient and the wind resistance are specifically as follows:

；

in this embodiment, based on the above results, the OriginPro software is used to map the temperature field profiles for different fluid conditions, or different plate-fin heat exchangers.

The distribution shown in fig. 9 (a) and 9 (b) is a hot side and cold side temperature field distribution diagram of the plate-fin heat exchanger under the cross-flow working condition; FIGS. 10 (a) and 10 (b) are graphs showing hot side and cold side temperature field profiles of an "I+Z" type plate-fin heat exchanger, respectively, wherein each 25 scale on the abscissa represents a length of 1.25 m.

Example 3

As shown in fig. 11, the embodiment provides a system of a heat transfer calculation method of a plate-fin heat exchanger, which comprises a data acquisition module, a data calculation module, a model building module and a data solving module, wherein the data acquisition module is used for acquiring fin structure data of the plate-fin heat exchanger, and performing related parameter calculation to build models under different fluid working conditions so as to solve heat exchange efficiency and total heat transfer coefficient of the plate-fin heat exchanger under different fluid working conditions or different plate-fin heat exchanger types, and further acquire heat exchange conditions of the plate-fin heat exchanger, so that in practical operation, time cost and sample own cost are saved, and optimization of a fin structure is facilitated.

Specifically, the data acquisition module is used for acquiring fin structure parameters of different fluid working conditions or different plate-fin heat exchanger types;

Specifically, the data calculation module is used for calculating fin channel parameters, fluid physical property parameters and convection heat transfer parameters of the plate-fin heat exchanger;

specifically, the model building module is used for respectively building a corresponding parallel flow model, a corresponding countercurrent model and a corresponding cross flow model based on different fluid working conditions or different plate-fin heat exchanger types;

Specifically, the data solving module is used for solving the outlet temperature of the fin channels of the fluid under different fluid working conditions or different plate-fin heat exchanger types, and the heat exchange efficiency and the total heat transfer coefficient of the plate-fin heat exchanger under different fluid working conditions or different plate-fin heat exchanger types.

Example 4

Based on the same technical concept, as shown in fig. 12, the present embodiment further provides a computer device corresponding to the method provided in the foregoing embodiment, including a processor 2, a memory 1, and a bus, where the memory stores machine-readable instructions executable by the processor, and when the computer device is running, the processor and the memory communicate through the bus, and the machine-readable instructions are executed by the processor to perform any one of the methods described in the foregoing.

The memory 1 includes at least one type of readable storage medium including flash memory, a hard disk, a multimedia card, a card type memory (e.g., SD or DX memory, etc.), a magnetic memory, a magnetic disk, an optical disk, etc.

The memory 1 may in some embodiments be an internal storage unit of a heat transfer computing system of a plate-fin heat exchanger, such as a hard disk. The memory 1 may in other embodiments also be an external storage device of a heat transfer computing system of a plate-fin heat exchanger, such as a plug-in hard disk, a smart memory card (SMART MEDIA CARD, SMC), a Secure Digital (SD) card, a flash memory card (FLASH CARD), etc. Further, the memory 1 may also include both internal and external storage devices of the heat transfer computing system of the substrate fin heat exchanger. The memory 1 may be used not only for storing application software of a heat transfer computing system installed in a plate-fin heat exchanger and various types of data, such as codes of a heat transfer computing system program of a plate-fin heat exchanger, etc., but also for temporarily storing data that has been output or is to be output.

The processor 2 may in some embodiments be a central processing unit (Central Processing Unit, CPU), controller, microcontroller, microprocessor or other data processing chip for running program code or processing data stored in the memory 1, for example a heat transfer calculation program for a plate-fin heat exchanger or the like.

The disclosed embodiments also provide a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the method described in the method embodiments above. Wherein the storage medium may be a volatile or nonvolatile computer readable storage medium.

The computer program product for applying the page content refreshing method provided by the embodiment of the present invention includes a computer readable storage medium storing program codes, and the instructions included in the program codes may be used to execute the steps of the method described in the method embodiment, specifically, refer to the method embodiment and are not repeated herein.

The disclosed embodiments also provide a computer program which, when executed by a processor, implements any of the methods of the previous embodiments. The computer program product may be realized in particular by means of hardware, software or a combination thereof. In an alternative embodiment, the computer program product is embodied as a computer storage medium, and in another alternative embodiment, the computer program product is embodied as a software product, such as a software development kit (Software Development Kit, SDK), or the like.

It is to be understood that the same or similar parts in the above embodiments may be referred to each other, and that in some embodiments, the same or similar parts in other embodiments may be referred to.

It should be noted that in the description of the present invention, the terms first, second, and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present invention, unless otherwise indicated, a plurality of meanings means at least two.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and further implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.

It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.

Those of ordinary skill in the art will appreciate that all or a portion of the steps carried out in the method of the above-described embodiments may be implemented by a program to instruct related hardware, where the program may be stored in a computer readable storage medium, and where the program, when executed, includes one or a combination of the steps of the method embodiments.

In addition, each functional unit in the embodiments of the present invention may be integrated in one processing module, or each unit may exist alone physically, or two or more units may be integrated in one module. The integrated modules may be implemented in hardware or in software functional modules. The integrated modules may also be stored in a computer readable storage medium if implemented in the form of software functional modules and sold or used as a stand-alone product.

The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, or the like.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims

1. The heat transfer calculation method of the plate-fin heat exchanger is characterized by comprising the following steps of:

S4: based on the outlet temperature of the fluid in the fin channels, respectively solving the heat exchange efficiency and the total heat transfer coefficient of different fluid working conditions or different plate-fin heat exchanger types of lower plate-fin heat exchangers;

in the step S1, a step of, in the above-mentioned step,

The fluid conditions include: parallel flow, counter flow and cross flow;

the fin types include: straight fins, corrugated fins, saw-tooth fins;

The fin structure parameters include: fin spacing, fin width, number of fin channel layers, fin core width, fin height, fin thickness, separator thickness, seal thickness;

In the step S2, the fin channels of the plate-fin heat exchanger are formed by continuously stamping a whole aluminum plate, the adjacent fins are staggered in height by the fin thickness t, and the current fins and the adjacent baffle plates are regarded as a whole, namely, the upper side and the lower side of each fin channel are divided into two thicknesses of the baffle plates, the fins and the whole baffle plates; the calculation of fin channel parameters of the plate-fin heat exchanger comprises the following steps:

(1) Calculation of equivalent diameter d of individual Fin channels _eq

The equivalent diameter d _{eq_pz} of the straight fin is calculated as:

the equivalent diameter d _{eq_bw} of the corrugated fin is calculated as:

the equivalent diameter d _{eq_jc} of the saw-tooth fin is calculated as:

Wherein s is fin spacing, which comprises cross-flow section hot side fin spacing s _h, cross-flow section cold side fin spacing s _c and counter-flow section fin spacing s _hc; h is fin height, which includes cross-flow section hot side fin height h _h, cross-flow section cold side fin height h _c; t is the thickness of the fin; delta is the ratio of the corrugated fin flow length to the radial length; l is the pitch of the sawtooth fins;

(2) Counting the number n of single-layer fin channels

The calculation expression of the number n ₁ of single-layer fin channels at the hot side of the cross-flow section is as follows:

The calculation expression of the number n ₂ of single-layer fin channels on the cold side of the cross-flow section is as follows:

the calculated expression of the number n ₃ of single-layer fin channels of the countercurrent section is:

Wherein [ (formula) is a whole symbol; w _h is the fin width on the hot side of the cross-flow section; w _c is the fin width of the cold side of the cross-flow section; t _f is the seal thickness;

(3) Calculating the height H of the fin core

The calculated expression of the fin core height H is: h= (H _h+h_c) m+ (2m+1) b;

wherein M is the number of fin channel layers; b is the thickness of the separator;

(4) Calculating the windward area Y of the fin channel

The calculation expression of the windward area Y _h of the hot-side fin channel is as follows: y _h＝(w_h-2t_f)h_h;

the calculated expression of the windward area Y _c of the cold-side fin channel is: y _c＝(w_c-2t_f)h_c;

(5) Calculating the flow area S of each fin channel

The calculated expression for the hot side fin channel flow area S _h is: s _h＝(s_h-t)(h_h -t);

the calculated expression for the cold side fin channel flow area S _c is: s _c＝(s_c-t)(h_c -t);

(6) Calculating the ratio e of the flow area to the windward area

The calculated expression of the ratio e _h of hot side fin channel flow area S _h to frontal area Y _h is:

The calculated expression for the ratio e _c of cold side fin channel flow area S _c to frontal area Y _c is:

(7) Calculating the thickness B of each fin channel separator

The calculated expression of the separator thickness B ₁ is: b ₁ = B;

The calculation expression of the integral thickness B ₂ of the fin and the baffle is as follows: b ₂ = b+t;

Wherein, the thickness of the heat transfer partition plate in each fin channel is denoted by B _m, m=1, 2;

in the step S2, the fluid is dry air, that is, the calculation of the corresponding fluid physical property parameter includes:

(1) Calculating the density ρ of air in the fin channels

The calculated expression of the density ρ _h of air in the hot-side fin channel is:

The calculated expression of the density ρ _c of air in the cold-side fin channel is:

Wherein T _h is the heat-measured fin channel temperature; t _c is the cold-measured fin channel temperature;

(2) Calculating specific heat capacity c of air in fin channels

The calculated expression of the specific heat capacity c _h of air in the hot-side fin channel is: c _h = 1.009;

the calculated expression of the specific heat capacity c _c of air in the cold side fin channel is: c _c = 1.005;

(3) Calculating the thermal conductivity lambda of air in the cold side fin channel

The thermal conductivity of air at the hot side fin channel λ _h is calculated as: lambda _h＝(0.0075484T_h+2.4443)×10^-2;

the thermal conductivity of air at the cold side fin channel lambda _c is calculated as: lambda _c＝(0.0075484T_c+2.4443)×10^-2;

(4) Calculating the viscosity coefficient mu of air in fin channels

The calculated expression of the viscosity coefficient mu _h of air in the hot-side fin passage is: mu _h＝(0.0047725T_h+1.7202)×10^-5;

The calculated expression of the viscosity coefficient mu _c of air in the cold-side fin passage is: mu _c＝(0.0047725T_c+1.7202)×10^-5;

(5) Calculating the inlet density ρ of air in the fin channels ₀

The calculated expression of the air inlet density ρ _h0 at the hot side fin channel is:

The calculated expression of the air inlet density ρ _c0 at the cold side fin channel is:

Wherein T _h0 is the inlet temperature of air at the hot side fin channel; t _c0 is the inlet temperature of air at the hot side fin channel;

(6) Calculating the inlet flow velocity u of air in the fin channel ₀

The calculated expression of the air inlet flow velocity u _h0 at the hot side fin channel is:

The calculated expression of the air inlet flow velocity u _c0 at the cold side fin channel is:

Wherein F is the inlet air quantity of the hot side fin channel; a is the cold side return air ratio;

(7) Calculating the mass flow rate G of air in the fin channel ₀

The calculated expression of the air on the hot side fin channel mass flow rate G _h0 is: g _h0＝u_h0ρ_h0;

the calculated expression of the air on the cold side fin channel mass flow rate G _c0 is: g _c0＝u_c0ρ_c0;

(8) Calculating the flow velocity u of air in the fin channel

The calculated expression of the air flow velocity u _h at the hot side fin channel is:

the calculated expression of the air flow velocity u _c at the cold side fin channel is:

(9) Calculating Reynolds number Re of air in fin channel

The calculated expression of the Reynolds number Re _h of the air on the hot side fin channel is as follows:

The calculated expression of the air on the cold side fin channel reynolds number Re _c is:

Where d _heq is the equivalent diameter of the fin channel for the hot side fluid flow; d _ceq is the equivalent diameter of the fin channel for cold side fluid flow;

(10) Calculating the Plandter number Pr of air in fin channels

The calculated expression of the prandtl number Pr _h of the air in the hot side fin channel is:

The calculated expression of the prandtl number Pr _c of the air in the cold side fin channel is:

in S2, the calculating the convective heat transfer parameter includes:

(1) Calculating the convective heat transfer coefficient alpha of air in fin channels

The air in the hot side fin channel has a calculated expression of the convective heat transfer coefficient alpha _h:

the air in the cold side fin channel has a calculated expression of the convective heat transfer coefficient alpha _c:

wherein,

Wherein s ₁ is fin pitch, which includes cross-flow section hot side fin pitch s _h and counter-flow section hot side fin pitch s _hc;s₂ is fin pitch, which includes cross-flow section cold side fin pitch s _c and counter-flow section cold side fin pitch s _hc;

(2) Calculating wind resistance delta P of air in fin channels

The wind resistance Δp _h of air in the hot side fin channel is calculated as: Δp _h＝ΔP_h1+ΔP_h2+ΔP_h3;

The wind resistance Δp _c of air in the cold side fin channel is calculated as: Δp _c＝ΔP_c1+ΔP_c2+ΔP_c3;

In the method, in the process of the invention, Ζ _h is the coefficient of sudden contraction of the hot side fin channel, and ζ _ho is the coefficient of sudden expansion of the hot side fin channel; ζ _c is the coefficient of sudden contraction of the cold side fin channel, and ζ _co is the coefficient of sudden expansion of the cold side fin channel; l is the fin length;

wherein,

In the step S3, the establishing of the parallel flow model and the counter flow model includes:

(1) Establishing parallel flow model

3600c_hG_h0S_h(-dT_h)＝3600c_cG_c0S_c(dT_c)＝dQ₁+dQ₂

Wherein Q ₁ is the primary heat transfer of air in the fin channels through the partition plate, and Q ₂ is the secondary heat transfer of air in the fin channels through the fins; namely:

where η _h is the hot side fin efficiency at the current fin micro-element length, its computational expression is: wherein, Η _c is the cold side fin efficiency at the current fin infinitesimal length, which is calculated as: wherein/>

Wherein, the boundary conditions are:

T_h(0)＝T_h0,T_c(0)＝T_c0

establishing a differential equation set of the temperature T _h、T_c of air in the fin channel with respect to the fin length l, namely:

(2) Establishing a countercurrent model

3600c_hG_h0S_h(-dT_h)＝3600c_cG_c0S_c(-dT_c)＝dQ₁+dQ₂

Wherein, the boundary conditions are:

T_h(0)＝T_h0,T_c(0)＝T_c0

In the step S3, based on different fluid working conditions and different plate-fin heat exchanger types, the process of establishing the cross flow model specifically includes:

Dividing the single-layer fin channels into a heat exchange grid matrix of n ₁×n₂ based on the number n ₁、n₂ of single-layer fin channels on the hot side and the cold side of the plate-fin heat exchanger, i.e., representing a hot side temperature matrix element TH (i, j), a cold side temperature matrix element TC (i, j), and a corresponding thermal resistance R (i, j) in each grid cell (i, j) region, wherein i=1, 2, n ₁,j＝1,2,...,n₂;

establishing a heat balance equation in the grid cell (i, j) region, namely:

3600c_hG_h0S_h(TH(i,j)-TH(i+1,j))＝3600c_cG_c0S_c(TC(i,j+1)-TC(i,j))＝Q(i,j)

where Q (i, j) is the heat transfer of the grid cell (i, j) region, the calculation expression is:

T_h(1,：)＝T_h0,T_c(：,1)＝T_c0

T_h(1,：)＝T_h0,T_c(1,：)＝T_c0；

In the step S3, the process of solving the outlet temperature of the fin channel of the fluid under different fluid working conditions by adopting programming software specifically includes:

S3131: based on a heat exchange grid matrix of n1 multiplied by n2 divided by a cross flow model, letting i=1, j=1, acquiring a hot side temperature matrix element TH (i, j), a cold side temperature matrix element TC (i, j) and a corresponding thermal resistance R (i, j) in a grid unit (i, j) area, and establishing a heat balance equation to realize iteration of the whole heat exchange grid matrix;

S3132: solving a hot side temperature matrix element TH (i+1, j) in the grid cell region (i+1, j) and a cold side temperature matrix element TC (i, j+1) in the grid cell region (i, j+1) based on the heat balance equation;

s3133: let j=j+1, iterate the calculation according to the column in turn until j > n ₂, stop iterating;

S3134: let i=i+1, iterate the calculation sequentially according to the row until i > n ₁, stop iterating;

S3135: acquiring the last row TH (n ₁,:1) of a hot side temperature matrix T _h, and obtaining the row average temperature to obtain the outlet temperature T _h1 of the hot side fin channel under the cross flow condition;

Obtaining the last column TC of the cold side temperature matrix T _c (n ₂), and obtaining the average temperature of the columns to obtain the outlet temperature T _c1 of the cold side fin channel under the cross flow condition;

In the step S3, the process of solving the outlet temperature of the fin channels of the fluid under different plate-fin heat exchanger types by adopting programming software specifically includes:

S321: obtaining an inlet temperature T _h0 of a hot side fin channel, presetting an inlet temperature T _c0 of a cold side fin channel, and solving an approximate outlet temperature T _c00 of a first fin channel of the cold side, which is close to the hot side, by combining a countercurrent model and a cross-flow model;

S322: based on the inlet temperature T _h0 of the hot side fin channel and the outlet temperature T _c00 of the first fin channel of the cold side close to the hot side, establishing a heat exchange grid matrix and a heat balance equation, and solving the outlet temperature T _c01 of the first fin channel of the cold side;

S3221: based on the first fin channel of which the cold side is close to the hot side, gradually calculating and solving the inlet temperature T _c01 of the first fin channel of which the cold side is close to the hot side according to the sequence of the first cross flow section, the counter flow section and the second cross flow section;

S3222: calculating |T _c01-T_c0 |, and when the value of the absolute value is smaller than 0.01, meeting the accuracy condition, namely acquiring the inlet temperature T _c01 of the first fin channel of the current cold side close to the hot side;

S323: sequentially solving the outlet temperature of the next fin channel of the cold side close to the hot side until the solution of the outlet temperature T _c0n of the nth fin channel of the cold side close to the hot side is completed;

S324: acquiring a temperature matrix of each fluid working condition stage, sequentially assigning values, and solving the outlet temperature T _h1 of the hot side fin channel and the outlet temperature T _c1 of the cold side fin channel;

S3241: based on the obtained inlet temperature T _h0 of the hot side fin channel and a preset inlet temperature T _c0 of the cold side fin channel;

S3242: solving a first cross-flow section hot side temperature matrix TH ₁ and a first cross-flow section cold side temperature matrix TC ₁ by combining a cross-flow model, and respectively assigning elements on diagonal lines of the first cross-flow section hot side temperature matrix TH ₂ and a first column of a counter-flow section cold side temperature matrix TC ₂ to serve as inlet temperatures of a counter-flow section hot side fin channel and outlet temperatures of a counter-flow section cold side fin channel respectively;

S3243: solving the outlet temperature of the hot side fin channel of the countercurrent section and the inlet temperature of the cold side fin channel of the countercurrent section by combining the countercurrent model, respectively assigning the outlet temperature of the hot side fin channel of the countercurrent section and the inlet temperature of the cold side fin channel of the countercurrent section to the second row of the hot side temperature matrix TH ₂ of the countercurrent section and the second column of the cold side temperature matrix TC ₂ of the countercurrent section, and further respectively assigning the elements of the second row of the hot side temperature matrix TH ₂ of the countercurrent section and the second column of the cold side temperature matrix TC ₂ of the countercurrent section to the diagonals of the hot side temperature matrix TH ₃ of the second cross-flow section and the cold side temperature matrix TC ₃ of the second cross-flow section to serve as the inlet temperature of the hot side fin channel of the second cross-flow section and the outlet temperature of the cold side fin channel of the second cross-flow section;

S3244: solving the outlet temperature of the second cross-flow section hot side fin channel and the inlet temperature of the second cross-flow section cold side fin channel by combining the cross-flow model, and respectively assigning the outlet temperature and the inlet temperature to the last row of the second cross-flow section hot side temperature matrix TH ₃ and the last column of the second cross-flow section cold side temperature matrix TC ₃;

S3245: obtaining the row average temperature of the last row or the column average temperature of the last column of the second cross-flow section hot side temperature matrix TH ₃ to obtain the outlet temperature T _h1 of the hot side fin channel of the 'I+Z' or 'L+L' type plate-fin heat exchanger;

and (3) obtaining the row average temperature of the first row or the column average temperature of the first column of the second cross-flow section cold side temperature matrix TC ₃ to obtain the outlet temperature T _c1 of the hot side fin channel of the I+Z-type or L+L-type plate-fin heat exchanger.

2. The method according to claim 1, wherein in S4, the heat exchange efficiency, the hot side total heat transfer coefficient, and the cold side total heat transfer coefficient are calculated based on the outlet temperature T _h1 of the fluid in the hot side fin channel and the outlet temperature T _c1 of the cold side fin channel; namely:

the calculation expression of the heat exchange efficiency epsilon is as follows:

the calculation expression of the hot side total heat transfer coefficient K _h is:

The calculated expression of the cold side total heat transfer coefficient K _c is:

In the middle of ,R_h＝2n₁(h_h+s_h-2t)l,R_c＝2n₂(h_c+s_c-2t)l;

3. A computer device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, the processor and the memory in communication via the bus when the computer device is running, the machine-readable instructions when executed by the processor performing the method of any one of claims 1 to 2.

4. A computer-readable storage medium, characterized in that it has stored thereon a computer program which, when executed by a processor, performs the method according to any of claims 1 to 2.