CN-121997821-A - Flow distribution simulation method for parallel flow channel heat exchanger based on general flow resistance model

Abstract

The flow distribution simulation method of the parallel flow channel heat exchanger based on the general flow resistance model comprises the steps of firstly establishing the general flow resistance model, carrying out single-channel fine modeling and simulation, obtaining pressure drop-flow velocity data, carrying out fitting to determine flow resistance coefficients, secondly, establishing a complete machine flow distribution simulation stage, namely establishing a three-dimensional geometric model of a macroscopic flow channel system of a target heat exchanger, carrying out grid division to obtain a macroscopic flow channel CFD model, abstracting all parallel micro channels of a core heat exchange section of the target heat exchanger into a parallel flow resistance network consisting of a plurality of flow resistance elements, endowing each flow resistance element with the general flow resistance model which is determined in the stage one and has a specific flow resistance coefficient, carrying out coupling solving, establishing an iterative process, enabling the error between the driving pressure difference of each flow resistance element and the pressure drop calculated according to the general flow resistance model to be smaller than a preset threshold value, carrying out iterative convergence, and outputting flow distribution results of all the parallel flow channels of the complete machine of the target heat exchanger.

Inventors

• Fu Yanguo
• HUANG QINGPING

Assignees

• 上海积鼎信息科技有限公司

Dates

Publication Date

20260508

Application Date

20260120

Claims (5)

1. 1. The flow distribution simulation method of the parallel flow channel heat exchanger based on the universal flow resistance model is characterized by comprising the following steps of: 1. single-channel general flow resistance model construction stage S11, creating a general flow resistance model ; Where Δp is the total pressure drop across the channel, The fluid density is u is the fluid speed, and A and B are the flow resistance coefficients to be fitted; S12, single-channel fine modeling and simulation, namely selecting a geometrically representative single channel of a target heat exchanger, establishing a complete three-dimensional geometric model of the target heat exchanger, accurately restoring channel characteristics of the target heat exchanger, carrying out grid division on the three-dimensional geometric model, carrying out grid independence verification, and then carrying out high-precision CFD simulation to simulate the flowing condition of working media under different inlet flow rates u; s13, acquiring pressure drop-flow velocity data, namely extracting and recording each group of inlet flow velocity u and the total pressure drop delta p of the corresponding channels to form a data set (u, delta p); S14, fitting the universal flow resistance model by utilizing a data set to determine flow resistance coefficients A and B of a channel and working medium suitable for a target heat exchanger; 2. complete machine flow distribution simulation stage S21, building a complete machine simulation model, namely building a three-dimensional geometric model of a macroscopic flow channel system of a target heat exchanger, which comprises a header and a flow dividing cavity, performing grid division to obtain a macroscopic flow channel CFD model, abstracting all parallel micro-channels of a core heat exchange section of the target heat exchanger into a parallel flow resistance network consisting of a plurality of flow resistance elements, wherein each flow resistance element is endowed with a general flow resistance model which is determined in a stage and has specific flow resistance coefficients A and B, and each flow resistance element corresponds to one micro-channel; S22, coupling solving, namely coupling a flow resistance network with a macroscopic flow channel CFD model in a CFD solver, establishing an iteration process, enabling the error between the driving pressure difference delta P drive of each flow resistance element and the pressure drop delta P model calculated according to the general flow resistance model to be smaller than a preset threshold value, and calculating iteration convergence; s23, outputting a result, namely outputting flow distribution results of all parallel flow channels of the whole target heat exchanger.
2. 2. The flow distribution simulation method for the parallel flow channel heat exchanger based on the universal flow resistance model as recited in claim 1, wherein in S22, the iterative process: s221, a CFD solver calculates a three-dimensional flow field of the macroscopic flow channel system aiming at the macroscopic flow channel CFD model; S222, for each flow resistance element, according to the inlet and outlet positions defined in the macroscopic flow channel system, acquiring pressure values P in and P out under the current iteration step, and calculating a driving pressure difference acting on the flow resistance element, wherein the driving pressure difference is denoted as delta P drive = P in - P out ; S223, regarding DeltaP drive as the current known quantity, substituting the current known quantity into a general flow resistance model of the flow resistance element Wherein the density of the fluid Inquiring an NIST physical property library according to the working medium state to determine that the flow velocity u is the quantity to be calculated; s224, solving the equilibrium equation about u Solving to obtain the flow velocity u of the flow resistance element under the current driving pressure difference, and according to the flow cross section Acs of the flow resistance element, obtaining the flow velocity u by the formula Calculating the mass flow rate of the flow resistance element Based on which the calculated mass flow rates for all flow resistance elements are obtained; S225, feeding the mass flow calculated by all the flow resistance elements back to the macroscopic flow channel CFD model by taking the mass flow as a boundary condition or global constraint; S226, repeating the steps S221 to S225, and solving iteratively, wherein when the error between the driving pressure difference DeltaP drive of all the flow resistance elements and the pressure drop DeltaP model calculated by the general flow resistance model according to the current flow speed is smaller than a preset threshold value, the flow field and the mass flow distribution are not changed any more, the mass and momentum conservation equation of the coupling system comprising the macroscopic flow channel system and the flow resistance network is satisfied, and the calculation convergence is realized; S23, outputting accurate mass flow distribution, namely flow distribution results, of all parallel flow channels of the whole machine of the target heat exchanger, and simultaneously obtaining key performance parameters of the whole machine.
3. 3. A parallel flow channel heat exchanger flow distribution simulation system based on a common flow resistance model, comprising: a flow resistance model creation module for creating a general flow resistance model Where Δp is the total pressure drop across the channel, The fluid density is u is the fluid speed, and A and B are the flow resistance coefficients to be fitted; The channel modeling simulation module is used for selecting a geometrically representative single channel of the target heat exchanger, establishing a complete three-dimensional geometric model of the target heat exchanger, accurately restoring channel characteristics of the target heat exchanger, carrying out grid division on the three-dimensional geometric model, carrying out grid independence verification, and then carrying out high-precision CFD simulation to simulate the flow condition of working media under different inlet flow rates u; The data acquisition module is used for extracting and recording each group of inlet flow velocity u and the total pressure drop delta p of the corresponding channel to form a data set (u, delta p); The flow resistance coefficient determining module is used for fitting the universal flow resistance model by utilizing the data set to determine flow resistance coefficients A and B of a channel and working medium suitable for the target heat exchanger; The whole machine simulation model construction module is used for establishing a three-dimensional geometric model of a macroscopic flow channel system of the target heat exchanger, which comprises a header and a flow dividing cavity, and carrying out grid division to obtain a macroscopic flow channel CFD model, abstracting all parallel micro-channels of a core heat exchange section of the target heat exchanger into a parallel flow resistance network consisting of a plurality of flow resistance elements, wherein each flow resistance element is endowed with a general flow resistance model which is determined in a stage and has specific flow resistance coefficients A and B, and each flow resistance element corresponds to one micro-channel; The coupling solving module is used for coupling the flow resistance network with the macroscopic flow channel CFD model in the CFD solver, establishing an iterative process, enabling the error between the driving pressure difference delta P drive of each flow resistance element and the pressure drop delta P model calculated according to the general flow resistance model to be smaller than a preset threshold value, and calculating iteration convergence; And the output module is used for outputting flow distribution results of all parallel flow passages of the whole target heat exchanger.
4. 4. An electronic device, comprising: A processor; A memory for storing processor-executable instructions; Wherein the processor is configured to invoke the instructions stored by the memory to perform the parallel flow channel heat exchanger flow distribution simulation method of any of claims 1-2.
5. 5. A computer readable storage medium having stored thereon computer program instructions, which when executed by a processor, implements the parallel flow channel heat exchanger flow distribution simulation method of any of claims 1-2.

Description

Flow distribution simulation method for parallel flow channel heat exchanger based on general flow resistance model Technical Field The invention relates to the technical field of heat exchanger simulation, in particular to a flow distribution simulation method of a parallel flow channel heat exchanger based on a general flow resistance model. Background The heat exchanger is a core component of the energy conversion and transmission system. The compact heat exchanger with parallel flow channel structure, such as a printed circuit board heat exchanger (PCHE), a plate-fin heat exchanger (PFHE) and a micro-channel heat exchanger (MCHE), has become key equipment in the front fields of supercritical CO 2 Brayton cycle power generation, advanced nuclear energy, aerospace and the like by virtue of the advantages of high heat exchange efficiency per unit volume, high temperature and high pressure resistance and the like. The performance of the heat exchanger can be fully exerted, and the fluid can be uniformly distributed to thousands of parallel flow channels in the heat exchanger after passing through a flow channel system such as a header pipe, a flow distribution cavity and the like. However, because the flow channel system has a complex structure and a plurality of parallel flow channels, and the physical properties of the working medium (such as supercritical CO 2) are often changed with working conditions, uneven flow distribution becomes a common and serious technical problem. The flow distribution can directly cause a series of serious consequences such as the reduction of the heat exchange efficiency of the whole machine, local overheating, thermal stress failure and the like. Therefore, accurate prediction of the flow distribution of the whole machine in the design stage is a key for ensuring the performance and safety of equipment. At present, simulation methods for the problem in engineering practice mainly comprise the following three types, and all the three types have obvious defects: 1. The full-size complete machine fine computational fluid dynamics simulation is that a complete three-dimensional geometric model comprising all parallel flow channels, headers and flow distribution cavities is constructed based on a complete machine drawing of the heat exchanger, and a Computational Fluid Dynamics (CFD) method is adopted for direct solving. Although the method can reflect the real physical process of the flow field, as the whole machine contains thousands of parallel micro-channels, the number of grids often reaches tens of millions or even hundreds of millions, the consumption of calculation resources is huge, the simulation period is as long as days, and the requirements of multi-working condition optimization and parameter rapid iteration in engineering design are difficult to adapt, so that the engineering practicability is poor. 2. The local unit idealized modeling method is used for extracting a local core unit of the heat exchanger to construct a fine model, simulating based on the idealized assumption of uniform inlet flow, and attempting to predict the whole machine performance through equivalent amplification of a local result. Although the calculation efficiency is improved, the method has the fundamental defect that the depended 'uniform inlet' assumption is seriously different from the physical facts of the runner system, the decisive influence of the macrostructures such as a header, a flow distribution cavity and the like on the fluid distribution is completely ignored, the true flow distribution of the whole machine layer cannot be revealed, and the simulation result and the engineering actual deviation are obvious. 3. The system level estimation method based on the empirical formula is used for estimating the overall pressure drop of the heat exchanger based on the empirical formula of the pipeline resistance. The method has the core limitation that the method can not reveal and quantify the uneven distribution of the actual flow on the premise of 'uniform flow' in principle, and meanwhile, the experience coefficient of the method is seriously dependent on a specific structure and working medium, so that the universality is not enough. In summary, the existing method has difficulty in combining the three types of accuracy, efficiency and universality. Therefore, a heat exchanger flow distribution simulation method capable of achieving the three functions has been proposed, and has become an urgent need in the art. Namely, the existing flow distribution simulation method of the parallel flow passage heat exchanger mainly has the following three technical defects: 1. The calculation efficiency is low, the engineering practicability is limited, although the full-size fine modeling method can keep physical reality, the full-size fine modeling method is limited by huge quantity (thousands) of parallel flow channels, tens of millions to hundreds of millions of meshes are needed to be gen