CN111125943A - Gridding division method for finite element model of pile foundation spiral pipe-laying heat exchanger - Google Patents
Gridding division method for finite element model of pile foundation spiral pipe-laying heat exchanger Download PDFInfo
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Abstract
The invention provides a grid division method of a finite element model of a pile foundation spiral pipe-laying heat exchanger in a fan-shaped soil area, which comprises the steps of establishing the finite element model of the pile foundation spiral pipe-laying heat exchanger in the fan-shaped soil area; dividing a finite element model of the pile foundation spiral pipe laying heat exchanger in the built fan-shaped soil area into four parts, namely lining concrete, soil, an inner cylinder of a pile foundation and an outer cylinder of the pile foundation; and respectively carrying out grid division on the divided parts. The invention has reasonable sequence of grid region division and minimum size setting of grid generation, can ensure the successful generation of the grid, effectively reduces the grid generation quantity, improves the grid generation time and lays a foundation for the subsequent numerical calculation.
Description
Technical Field
The invention belongs to the technical field of finite element modeling of ground source heat pump systems, and particularly relates to a mesh division method of a finite element model of a pile foundation spiral pipe-buried heat exchanger in a fan-shaped soil region.
Background
The ground source heat pump technology is an effective energy-saving technology which utilizes the shallow soil on the earth surface as a low-temperature heat source to transfer the heat of a building into the low-temperature soil to realize the air conditioning effect of the building. The ground source heat pump system consists of a heat pump unit, a geothermal energy exchange system and an in-building system. The buried pipe heat exchanger is a key component for forming a geothermal energy exchange system, and is characterized in that a pipeline is placed in superficial soil on the ground surface, and heat is exchanged and transferred between circulating water and the soil through water circulation. The pile foundation spiral pipe laying heat exchanger is an innovative development of the ground pipe laying heat exchanger, the spiral PE pipe is embedded into the pile foundation by utilizing the cylindrical pile foundation of a building, the heat is exchanged and transferred among circulating water, the pile foundation and surrounding soil, compared with a common pipe laying heat exchanger, the pile foundation spiral pipe laying heat exchanger saves a hole digging link, saves cost and has a great application prospect. However, due to the complex geometry of the spiral buried pipe and the fluid heat exchange mechanism, the heat exchange process of the heat exchanger is difficult to predict through a theoretical analysis method. For the complex structure of the pile foundation pipe laying heat exchanger in the actual sector area soil, the heat exchange characteristics of the complex structure are analyzed by a finite element simulation method, so that the time can be greatly saved. The two most important processes for establishing the finite element model of the pile foundation heat exchanger in the sector soil area comprise establishment of a geometric model and division of grids.
Disclosure of Invention
Technical problem to be solved
The invention provides a meshing method of a finite element model of a pile foundation spiral pipe-laying heat exchanger, which aims to solve the technical problem of ensuring the meshing quality and improving the meshing speed.
(II) technical scheme
In order to solve the technical problem, the invention provides a meshing method of a finite element model of a pile foundation spiral pipe laying heat exchanger, wherein the meshing is carried out in CFD finite element software, and the meshing method comprises the following steps:
s1, establishing a finite element model of the pile foundation spiral pipe laying heat exchanger in the sector soil area;
s2, dividing the finite element model of the pile foundation spiral pipe-laying heat exchanger in the built fan-shaped soil area into four parts, namely lining concrete, soil, an inner column of the pile foundation and an outer column of the pile foundation;
and S3, respectively carrying out grid division on the divided parts.
Further, in step S1, selecting a soil region depth of 50 m; the depth of the pile foundation is 45m, and the radius of the pile foundation is 0.5 m; the depth of the spiral pipe is 44m, the radius of the coil pipe is 0.4m, the pitch is 0.4m, the inner diameter of the spiral pipe is 26mm, the outer diameter of the spiral pipe is 32mm, the wall thickness of the spiral pipe is 6mm, the length of the straight pipe section at the inlet of the spiral pipe is 0.5m, the length of the straight pipe section at the outlet of the spiral pipe is 44.5m, and the water inlet and return pipes are arranged along the symmetrical line.
Further, in step S2, the inside of the pile foundation is divided into two parts, and a circular auxiliary line is added at the same distance from the inner edge of the spiral tube to the outer edge of the pile foundation on the basis of the distance from the outer edge of the spiral tube to the outer edge of the pile foundation, so as to divide the inside area of the pile foundation into two parts, namely an inner cylindrical part of the pile foundation and an outer cylindrical part of the pile foundation; when dividing, the length of the inlet and outlet of the spiral pipe from the pile foundation inner cylinder and the pile foundation outer cylinder is equal.
Further, in step S3, a mesh is generated in the following order:
(1) grid division of lining concrete: selecting a hexahedral Multizone, setting the minimum size of a grid to be 50mm, and sweeping the grid;
(2) grid division of the inner cylinder of the pile foundation: selecting a hexahedral Multizone, setting the minimum size of a grid to be 10mm, and sweeping the grid;
(3) gridding of fluid area and spiral pipe in pipe of outer ring of pile foundation
① fluid area in the pipe, dividing the fluid area in the pipe into water inlet and outlet straight line sections and spiral sections, dividing the spiral sections into a unit according to each section of spiral, selecting all the units, selecting hexahedral MultiZone, setting the minimum size of the grid to be 5mm, and sweeping the grid;
② spiral tube, in the same tube fluid area dividing method, dividing the spiral tube area into straight line section and spiral section, the spiral section is divided into a unit according to each section of spiral, selecting all the units, selecting hexahedral MultiZone, setting the minimum size of the mesh to be 5mm, and sweeping the mesh;
(4) grid division of soil: selecting a hexahedral Multizone, setting the minimum size of a grid to be 50mm, and sweeping the grid;
(5) and (3) grid division of a transition region of the outer circular column of the pile foundation: removing the fluid area and the spiral tube in the tube, selecting the residual area, selecting hexahedral tetrahedral DOMINAT, setting the minimum size of the grid to be 10mm, and automatically generating the grid.
Further, the final number of generated grids of the grid division method is 678 ten thousand.
(III) advantageous effects
The invention provides a grid division method of a finite element model of a pile foundation spiral pipe-laying heat exchanger in a fan-shaped soil area, which comprises the steps of establishing the finite element model of the pile foundation spiral pipe-laying heat exchanger in the fan-shaped soil area; dividing a finite element model of the pile foundation spiral pipe laying heat exchanger in the built fan-shaped soil area into four parts, namely lining concrete, soil, an inner cylinder of a pile foundation and an outer cylinder of the pile foundation; and respectively carrying out grid division on the divided parts. The invention has reasonable sequence of grid region division and minimum size setting of grid generation, can ensure the successful generation of the grid, effectively reduces the grid generation quantity, improves the grid generation time and lays a foundation for the subsequent numerical calculation.
Drawings
FIG. 1 is a schematic diagram of a finite element model of a spiral borehole heat exchanger according to the present embodiment;
FIG. 2 is a schematic diagram of a finite element model segmentation of the spiral borehole heat exchanger in accordance with the present embodiment;
fig. 3 is a schematic view of the internal cutting of the pile foundation in the embodiment;
FIG. 4 is a schematic view of the lined concrete meshing of the present embodiment (including the soil portion);
fig. 5 is a schematic diagram of meshing of the inner cylinder of the pile foundation in the embodiment: (a) integral, (b) section (including the external cylindrical column part of the pile foundation);
fig. 6 is a schematic diagram of meshing of fluid regions in a pipe in an outer ring of a pile foundation according to this embodiment: (a) bulk, (b) detail;
fig. 7 is a schematic diagram of the meshing of the spiral tube in the outer circular ring of the pile foundation in the embodiment: (a) bulk, (b) detail;
FIG. 8 is a schematic diagram illustrating soil gridding according to the present embodiment;
fig. 9 is a schematic diagram of the meshing division of the transition region of the outer circular column of the pile foundation in this embodiment: (a) overall, (b) cross-section.
Detailed Description
In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.
The embodiment provides a meshing method of a finite element model of a pile foundation spiral pipe-laying heat exchanger in a sector soil area, which specifically comprises the following steps:
s1, establishing a finite element model of the pile foundation spiral pipe laying heat exchanger in the sector soil area
And (3) carrying out three-dimensional modeling on a finite element model of the pile foundation pipe-laying heat exchanger in the sector soil region by using design N model software of ANSYS. Wherein, the depth of the soil area is selected to be 50 m; the depth of the pile foundation is 45m, and the radius of the pile foundation is 0.5 m; the depth of the spiral pipe is 44m, the radius of the coil pipe is 0.4m, the pitch is 0.4m, the inner diameter of the spiral pipe is 26mm, the outer diameter of the spiral pipe is 32mm, the wall thickness of the spiral pipe is 6mm, the length of the straight pipe section at the inlet of the spiral pipe is 0.5m, the length of the straight pipe section at the outlet of the spiral pipe is 44.5m, and the water inlet and return pipes are arranged along the symmetrical line. The finite element model is shown in fig. 1.
S2, dividing the finite element model of the pile foundation spiral pipe-laying heat exchanger in the built fan-shaped soil area into four parts of lining concrete, soil, inner column of pile foundation and outer column of pile foundation
And dividing the finite element model of the pile foundation spiral pipe laying heat exchanger in the built fan-shaped soil area into four parts of lining concrete 1, soil 2, an inner pile foundation cylinder 3 and an outer pile foundation ring cylinder 4. The cut finite element model is shown in fig. 2. Wherein, the inside two parts of cutting apart into of pile foundation to 5 outer edges of spiral pipe are along the distance to the pile foundation outward as the benchmark, and in the same distance department of edge in 5 interior edges of spiral pipe apart from, add circular auxiliary line, divide into pile foundation inner cylinder 3 and pile foundation outer cylinder 4 two parts with the pile foundation inner zone. When dividing, it is noted that the length of the inlet and outlet of the spiral pipe 5 from the pile inner cylinder 3 and the pile outer cylinder 4 is equal, as shown in fig. 3.
S3, respectively carrying out grid division on the divided parts
Because the spiral pipe wall thickness is 3mm, on XY plane dimension, and whole pile foundation diameter is 1000mm, and the spiral pipe wall is outer along being 50mm apart from the pile foundation, therefore the pile foundation leans on interior cylinder diameter of inside to be 900mm, and the pile foundation is outer along being about 1000mm apart from the regional side shortest distance in soil. From the wall of the spiral pipe to the outer circular column of the pile foundation and then to the inner circular column of the pile foundation and the soil area, the size increase of 2 orders of magnitude is experienced. Therefore, when selecting the minimum size of mesh division and the generation sequence of the area meshes, optimization consideration is needed, which specifically includes:
1. grid division of lining concrete: a hexahedral MultiZone is selected, the minimum size of the mesh is set to 50mm, the mesh is swept, and the mesh division result is shown in fig. 4.
2. Grid division of the inner cylinder of the pile foundation: a hexahedral MultiZone is selected, the minimum size of the mesh is set to 10mm, the mesh is swept, and the mesh division result is shown in fig. 5.
3. Gridding of fluid area and spiral pipe in pipe of outer ring of pile foundation
(1) In-tube fluid region: dividing the fluid area in the pipe into a water inlet and outlet straight line section and a spiral section, dividing the spiral section into a unit according to each section of spiral, selecting all the units, selecting hexahedral MultiZones, setting the minimum size of the mesh to be 5mm, sweeping the mesh, and the mesh division result is shown in FIG. 6.
(2) A spiral tube: the method for dividing the fluid area in the same pipe divides the spiral pipe area into a straight line section and a spiral section, the spiral section is divided into a unit according to each section of spiral, all the units are selected, a hexahedral MultiZone is selected, the minimum size of a grid is set to be 5mm, the grid is swept, and the grid division result is shown in FIG. 7.
4. Grid division of soil: a hexahedral MultiZone is selected, the minimum size of the mesh is set to 50mm, the mesh is swept, and the mesh division result is shown in fig. 8.
5. And (3) grid division of a transition region of the outer circular column of the pile foundation: removing the fluid area and the spiral tube in the tube, selecting the residual area, selecting hexahedral tetrahedral DOMINANT, setting the minimum size of the mesh to be 10mm, automatically generating the mesh, and the mesh division result is shown in fig. 9.
By adopting the grid division method of the embodiment, the number of the finally generated grids is 678 ten thousand. In the actual operation process, compared with other grid generation methods, if the sequence of grid region division and the minimum grid generation size are not reasonably set, grid generation failure or huge grid quantity can be caused. The grid generation method of the embodiment can ensure the grid to be successfully generated, can effectively reduce the grid generation quantity, improves the grid generation time, and lays a foundation for the subsequent numerical calculation.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A meshing method for a finite element model of a pile foundation spiral pipe-laying heat exchanger is characterized in that meshing is carried out in CFD finite element software, and comprises the following steps:
s1, establishing a finite element model of the pile foundation spiral pipe laying heat exchanger in the sector soil area;
s2, dividing the finite element model of the pile foundation spiral pipe-laying heat exchanger in the built fan-shaped soil area into four parts, namely lining concrete, soil, an inner column of the pile foundation and an outer column of the pile foundation;
and S3, respectively carrying out grid division on the divided parts.
2. The mesh segmentation method as claimed in claim 1, wherein in step S1, a soil region depth of 50m is selected; the depth of the pile foundation is 45m, and the radius of the pile foundation is 0.5 m; the depth of the spiral pipe is 44m, the radius of the coil pipe is 0.4m, the pitch is 0.4m, the inner diameter of the spiral pipe is 26mm, the outer diameter of the spiral pipe is 32mm, the wall thickness of the spiral pipe is 6mm, the length of the straight pipe section at the inlet of the spiral pipe is 0.5m, the length of the straight pipe section at the outlet of the spiral pipe is 44.5m, and the water inlet and return pipes are arranged along the symmetrical line.
3. The mesh division method of claim 1, wherein in said step S2, the inside of the pile foundation is divided into two parts, and a circular auxiliary line is added at the same distance from the inner edge of the spiral pipe with reference to the distance from the outer edge of the spiral pipe to the outer edge of the pile foundation to divide the inner area of the pile foundation into two parts, i.e., an inner cylinder of the pile foundation and an outer cylinder of the pile foundation; when dividing, the length of the inlet and outlet of the spiral pipe from the pile foundation inner cylinder and the pile foundation outer cylinder is equal.
4. The mesh division method as claimed in claim 1, wherein in said step S3, the mesh is generated in the following order:
(1) grid division of lining concrete: selecting a hexahedral Multizone, setting the minimum size of a grid to be 50mm, and sweeping the grid;
(2) grid division of the inner cylinder of the pile foundation: selecting a hexahedral Multizone, setting the minimum size of a grid to be 10mm, and sweeping the grid;
(3) gridding of fluid area and spiral pipe in pipe of outer ring of pile foundation
① fluid area in the pipe, dividing the fluid area in the pipe into water inlet and outlet straight line sections and spiral sections, dividing the spiral sections into a unit according to each section of spiral, selecting all the units, selecting hexahedral MultiZone, setting the minimum size of the grid to be 5mm, and sweeping the grid;
② spiral tube, in the same tube fluid area dividing method, dividing the spiral tube area into straight line section and spiral section, the spiral section is divided into a unit according to each section of spiral, selecting all the units, selecting hexahedral MultiZone, setting the minimum size of the mesh to be 5mm, and sweeping the mesh;
(4) grid division of soil: selecting a hexahedral Multizone, setting the minimum size of a grid to be 50mm, and sweeping the grid;
(5) and (3) grid division of a transition region of the outer circular column of the pile foundation: removing the fluid area and the spiral tube in the tube, selecting the residual area, selecting hexahedral tetrahedral DOMINAT, setting the minimum size of the grid to be 10mm, and automatically generating the grid.
5. The meshing method of claim 1, wherein the number of final generated meshes of the meshing method is 678 ten thousand.
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| US20050128198A1 (en) * | 2003-11-17 | 2005-06-16 | Samsung Electronics Co., Ltd. | Method and apparatus for generating three-dimensional finite element mesh |
| CN107423459A (en) * | 2017-03-21 | 2017-12-01 | 哈尔滨工程大学 | A kind of heat exchanger porous media model porosity and Permeability Parameters processing method based on CAD software |
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