JP2004198020A - Heat storage type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat storage type heat exchanger improved in handling when laminating with high accuracy by eliminating the generation of deflection of laminating members and fray of an end, reduced in price, and improved in functional performance by deciding a shape following the optimal design based on a result of numerical computing. <P>SOLUTION: A metal thin sheet 1 having a thickness of 0.1-0.2 mm is formed with multiple fine holes 2 by etching or electric casting. One surface or both surfaces of the thin sheet 1 are provided with grooves 3 for connecting the fine holes 2, and a peripheral part 9 of the thin sheet 1 is formed into a flat smooth surface without providing a fine hole to obtain high dimensional accuracy. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an engine having a heat regeneration mechanism such as a Stirling engine, a Stirling refrigerator, a Birmier cycle device, a pulse tube refrigerator, a thermoacoustic device, and a regenerative heat exchanger of a regenerative gas turbine.
[0002]
[Prior art]
9 to 11 schematically show a conventional heat storage type heat exchanger, which is a lamination type (see FIG. 10) using a wire mesh, a foamed metal, a mat-like metal fiber, a spring mesh (see FIG. 10), a thin tube, a honeycomb, and a helipack. , A twisted wire arrangement (see FIG. 11), a flocculent metal fiber, and a pebble (particle) pack (see FIG. 12). The laminated type has a large specific surface area, a high heat transfer coefficient with the working gas, and the flow loss is not so large.The array type can considerably reduce the flow loss, but has a small specific surface area and a low heat transfer coefficient. The pack type has a large specific surface area and can adjust the flow loss, but it is difficult to make the two performances compatible, and the handleability is poor. Therefore, the laminated type is excellent in performance, and the superiority of the laminated wire netting is demonstrated in the actual machine test of the Stirling engine and the Stirling refrigerator, and is used in many engines.
[0003]
[Problems to be solved by the invention]
When using such a laminated wire mesh for a regenerative heat exchanger, the strain of the wire mesh generated when forming the wire mesh, fraying of the ends, low processing accuracy, the handling at the time of lamination is very poor, It has the disadvantage of increasing the price, and reduces the engine performance due to wire mesh distortion, edge fraying, and low machining accuracy. In addition, considering the price, the wire mesh uses an off-the-shelf product, and the wire diameter, wire pitch, and wire material are determined.
[0004]
Since the wire mesh is woven with a thin metal wire, if the material is punched out from a wide sheet of a ready-made wire mesh into a small diameter (usually 5 to 9 cm) by press working or the like, the wire mesh is not flat but distorted. It takes a lot of time and effort to stack the sheets (usually about 300 to 500 sheets) so as to fit in the casing, and furthermore, a gap is formed between the wire meshes, the ineffective volume increases, the compression ratio decreases, and the engine performance decreases. Lower. In addition, the processed end is easily frayed, and the frayed metal wire not only significantly lowers the assemblability, but also creates a gap between the casing and the laminated wire mesh at the frayed part, and the gap is part of the working gas. Does not pass through the heat exchanger to reduce engine efficiency. Also, in the case of punching and molding by press working, etc., a thin metal wire is cut from various directions, processing accuracy is deteriorated, assemblability is poor, and a gap is generated between the casing and the laminated wire mesh. Thus, a part of the working gas leaks through the gap and does not pass through the laminated wire mesh, thereby lowering the engine efficiency. In addition, many wire meshes actually used are off-the-shelf products, and their wire diameters, pitches, and materials are fixed, and it is not possible to apply or adjust the optimal design values so as to obtain optimal heat transfer and friction loss characteristics for the engine.
[0005]
The present invention has been made to solve the above-mentioned conventional problems, and its object is to eliminate the distortion of the laminated member and the fray of the end, to improve the processing accuracy, to improve the handling at the time of laminating, and to reduce the cost. It is an object of the present invention to provide a regenerative heat exchanger capable of improving engine performance by determining the shape according to an optimal design based on the results of numerical calculations and the like.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method of etching a metal thin plate having a thickness of about 0.1 to 0.2 mm (a method of processing a metal by erosion by a corrosive liquid) or an electroforming method (the metal is formed on a base pattern by an electrode). A large number of pores are opened by the method of deposition), grooves are formed on one or both sides of this thin plate to connect the pores, and the outer peripheral portion of the thin plate has no pores to obtain high dimensional accuracy. I do.
In addition, the diameter of the pores is varied depending on the location and the position and shape of the groove are changed so that the flow of the working gas and the heat exchange amount in the radial direction or the longitudinal direction can be adjusted according to the equipment.
Further, the material of the surface of the thin plate has a low thermal conductivity to reduce the loss due to heat conduction from the high-temperature side to the low-temperature side of the regenerator.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be specifically described with reference to FIGS.
As shown in FIG. 1, one metal thin plate constituting the heat storage type heat exchanger has a structure in which a large number of fine holes 2 are provided in a thin plate 1. Although the pores 2 shown in FIG. 2 have a square or staggered arrangement (60 degrees), other pore shapes such as a circle and other pore arrangements (cross-cut arrangement) are also possible.
The optimum values for the diameter and pitch of the pores 2 are determined by the equipment to which the regenerative heat exchanger is applied. In the case of a 3 kW class Stirling engine, the size of the holes is from 0.24 x 0.24 mm to 0.30 x 0.30 mm. Approximately 500 layers with a pitch of about 0.44 mm and a thickness of 0.1 mm are used, and the shaft output is about 7 to 15% and the thermal efficiency is about 10 to 20 compared to the conventional structure using mesh sheets. % (See FIG. 9).
[0008]
Further, in order to reduce the flow loss when the working gas flows, as shown in FIG. The grooves 3 can be provided on both sides of the thin plate 1. The arrangement, number, and dimensions of the grooves 3 have specific optimum values depending on the equipment to which the heat regeneration type heat exchanger is applied. However, in the case of the above-mentioned 3 kW class Stirling engine, the groove width is determined as shown in the figure. The thickness was about 0.12 mm and the depth was about 0.06 mm.
[0009]
As shown in FIG. 4, when the flow in the regenerative heat exchanger 4 (reciprocating flow in the case of a Stirling device, unidirectional flow or counterflow in the case of a gas turbine) is not uniform due to its structure, In order to make the flow uniform, the size and arrangement of the pores in the thin plates 5 and 6 can be freely designed and installed depending on the location on the thin plates. Further, it is possible to laminate thin plates having different pore sizes and arrangements.
[0010]
As shown in FIG. 5, when the flow in the regenerative heat exchanger 4 is uneven due to its structure, in order to make the flow uniform, the size of the groove connecting the pores in the thin plates 7 and 8 is reduced. The arrangement can be changed depending on the location on the sheet. Further, it is possible to laminate thin plates having different dimensions and arrangements of the grooves.
[0011]
Further, as shown in FIG. 6, a smooth surface area having no pores is continuously provided in the outer peripheral portion 9 of the thin plate 1 in the outer peripheral direction, thereby improving the processing accuracy of the thin plate, and reducing the leakage loss of the working gas. Is reduced. Generally, in the case of a wire mesh, a dimensional tolerance of +0.1 mm is given for an outer diameter of 7 cm. However, with the method of the present invention, the accuracy can be further improved. can do. In addition, as shown in the cross-sectional view of FIG. 7, the thickness of the outer peripheral portion 9 is reduced one step continuously in the outer peripheral edge direction, so that heat conduction loss in the laminating direction due to contact in the case of lamination is reduced. Further, by providing the recess 10 at the edge of the outer peripheral portion 9, the direction of rotation of the thin plates when they are stacked can be easily determined visually from the external appearance, and positioning can be performed.
[0012]
As shown in FIG. 8, the surface of the thin plate is formed of a metal having different properties, thereby making it possible to reduce heat conduction loss and prevent corrosion. For example, it is possible to combine a surface material 13 made of a material such as stainless steel with poor heat conductivity and high corrosion resistance on the surface of a base material 12 such as copper or nickel having a good heat conductivity and a large heat capacity. In addition, the surface of the thin plate is roughened from several microns to several hundred microns, and a scratch (parallel groove) processing and a hairline (narrow groove) processing with a depth of several microns to several hundred microns are provided on the surface without grooves. Thus, the thermal contact resistance between the thin plates can be increased, and the heat conduction loss can be reduced. The plating method in FIG. 8 is a plating method on a thin plate made only of the base material.
[0013]
The hole 11 in the center of the thin plate 1 shown in FIG. 6 is a hole through which a through rod is passed when laminating, and is designed for ease of assembly. Without making a hole in this part, it can be used as a margin for crimping or joining. Also, by providing a pore in this portion, the outer peripheral portion can be used as a margin for crimping or joining.
[0014]
When a groove connecting the pores is provided only on one side of the thin plate, the surface with the groove is oriented in the direction in which the low-temperature working gas flows (or in the case where the working gas flows in only one direction, the direction). In addition, it is possible to reduce friction generated when the working gas flows. By stacking the 3kW class Stirling engine with the grooved surface facing the low temperature side, the loss due to friction generated when the working gas flows through this heat exchanger could be reduced by 50W. Also, for the purpose of reducing the heat conduction loss that occurs at the time of lamination, it is possible to alternately combine the surfaces with grooves (front and back).
[0015]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the regenerative heat exchanger of the present invention, it is possible to eliminate the distortion of the laminated member and the fraying of the end portion, to achieve high processing accuracy, to improve the handling at the time of laminating, to reduce the price, and to perform numerical calculation. The engine performance can be improved by determining the shapes and dimensions of the pores and grooves according to the optimum design values obtained from the results of the above.
It was confirmed that the prototype heat storage heat exchanger of the present invention had about twice the Nusselt number representing the heat transfer characteristics as compared with the conventional laminated wire mesh, and improved the heat transfer characteristics. By using the regenerative heat exchanger of the present invention, it was confirmed that the shaft output of the 3 kW class Stirling engine was improved by about 7 to 15% and the thermal efficiency was improved by 10 to 20% (see FIG. 9). are doing.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a thin metal plate of a regenerative heat exchanger according to one embodiment of the present invention.
FIG. 2 is a schematic enlarged view showing pores of the metal thin plate.
FIG. 3 is a schematic enlarged view showing pores of the thin metal plate and grooves connecting the pores.
FIG. 4 is a schematic diagram of a regenerative heat exchanger showing a thin metal plate having pores partially different in size and shape.
FIG. 5 is a schematic view of a heat storage type heat exchanger showing a thin plate in which grooves connecting pores of the thin metal plate have partially different sizes and shapes.
FIG. 6 is a schematic plan view showing a thin metal plate of a regenerative heat exchanger according to another embodiment of the present invention.
FIG. 7 is an enlarged sectional view of the same part.
FIG. 8 is a cross-sectional view showing a thin metal plate of a regenerative heat exchanger according to still another embodiment of the present invention.
FIG. 9 is a graph showing data of a performance test of the regenerative heat exchanger according to one embodiment of the present invention.
FIG. 10 is an enlarged view of a main part showing constituent materials of a conventional regenerative heat exchanger.
FIG. 11 is an enlarged view of a main part showing another constituent material of the conventional regenerative heat exchanger.
FIG. 12 is an enlarged view of a main part showing another constituent material of a conventional regenerative heat exchanger.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... thin plate, 2 ... pore, 3 ... groove on thin plate, 4 ... regenerative heat exchanger (case), 5 ... thin plate with partially changed pore size and arrangement, 6 ... whole pore A thin plate with the same dimensions and arrangement, 7 ... a thin plate with a partially changed pore size and arrangement, a thin plate with a different arrangement, 8 ... a thin plate with a uniform pore size and arrangement with the pores, 9 ... an outer peripheral portion, 10: depression at outer periphery, 11: hole, 12: base material, 13: surface material

Claims (8)

A regenerative heat exchanger characterized by forming a large number of pores in a metal sheet and stacking the metal sheets. The heat storage type heat exchanger according to claim 1, wherein a groove is provided on one or both surfaces of the thin metal plate so as to connect the pores. The regenerative heat exchanger according to claim 1 or 2, wherein the shape and size of the pores formed in the metal sheet are different depending on the location on the metal sheet. The regenerative heat exchanger according to claim 2 or 3, wherein the shape and size of the groove provided in the metal sheet are different depending on a location on the metal sheet. The regenerative heat exchanger according to any one of claims 1 to 4, wherein a smooth surface having no pores and grooves is continuously provided in an outer circumferential direction on an outer circumferential portion of the thin metal plate. The regenerative heat exchanger according to any one of claims 1 to 5, wherein an outer peripheral portion of the thin metal plate is formed continuously thinner in an outer peripheral direction than an inner side thereof. The regenerative heat exchanger according to any one of claims 1 to 6, wherein a recess is provided in a part of an outer peripheral edge of the thin metal plate. The regenerative heat exchanger according to any one of claims 1 to 7, wherein a surface of the metal sheet is covered with a different material.

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