Plate-type heat exchanger

Abstract

The present invention includes, among a plurality of heat transfer plates, a set of a first plate and a second plate that are formed to have the same shape and are overlapped in a positional relationship rotated by 180°. Each heat transfer plate has a plurality of rows of herringbone waveforms arranged in parallel to each other, each of the herringbone waveforms having a bent portion where the inclination is reversed in a plan view. Two rows adjacent to each other among the plurality of rows of herringbone waveforms are arranged at a pitch of less than or equal to 80 mm in a parallel direction. The bent portion of the first plate and the bent portion of the second plate overlap each other in a plan view direction at both of two bent portions that are adjacent to each other in the direction in which a groove extends in each heat transfer plate.

Description

Plate Heat Exchanger CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2024-120755, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a plate heat exchanger.

[0003] Among the heat transfer plates constituting a plate-type heat exchanger, there are some that have a herringbone corrugation. For example, Japanese Patent No. 3650657 describes a heat transfer plate that has a herringbone corrugation formed on the main heat transfer surface.

[0004] The invention described in the above document aims to improve heat transfer performance. However, the solution in this invention is considered to be complete for each heat transfer plate (single heat transfer plate), and does not take into consideration the pair of overlapping heat transfer plates that face each other. Therefore, there is still room for improvement in heat transfer performance. In addition, it is also important in plate heat exchangers to reduce the flow resistance of the fluid passing between the heat transfer plates.

[0005] Japanese Patent No. 3650657

[0006] Therefore, an object of the present invention is to suppress the flow resistance of fluids when heat exchange is performed in units of pairs of opposing heat transfer plates in a plate heat exchanger constructed by stacking heat transfer plates with herringbone corrugations, and to obtain high heat transfer performance.

[0007] The present invention provides a plate-type heat exchanger configured by stacking a plurality of heat transfer plates, including a set of a first plate and a second plate, which are two heat transfer plates of the same shape facing each other, the first plate and the second plate being stacked in a positional relationship rotated by 180° in a plan view of each heat transfer plate, each of the heat transfer plates having a waveform formed by a plurality of grooves formed to be recessed in the plate thickness direction, and a plurality of parallel rows of herringbone waveforms having bent portions where the slope is reversed in a plan view, each of the plurality of herringbone waveform rows being arranged at a pitch of 80 mm or less in the parallel direction, and the bent portions of the herringbone waveform belonging to the first plate and the bent portions of the herringbone waveform belonging to the second plate overlap in a plan view of each of the heat transfer plates at both of the two bent portions that are adjacent to each other in the extension direction of the grooves in each of the heat transfer plates.

[0008] Furthermore, the overlapping relationship can be such that the bent portion in the first plate and the bent portion in the second plate are misaligned by 20% or less based on the distance between the herringbone waveforms in the first plate or the second plate.

[0009] Furthermore, the overlapping relationship can be such that the bent portions of the first plate and the bent portions of the second plate are offset by 0.5 mm or more in the direction in which each row of the herringbone waveform extends.

[0010] In each of the plurality of rows of the herringbone waveform, two adjacent grooves in the extending direction of each row may be arranged at a pitch of 6 mm or more.

[0011] In addition, two adjacent rows of the herringbone waveforms may be arranged at a pitch of 40 mm or less in the parallel direction.

[0012] FIG. 1 is a perspective view showing an example of the configuration of a plate heat exchanger. FIG. 2 is an exploded perspective view showing an example of a partial configuration of a plate heat exchanger, with arrows indicating the movement of a fluid that exchanges heat. FIG. 3 is a perspective view of a heat transfer plate according to an embodiment of the present invention, showing a state in which a first plate and a second plate are combined with a partial region of the main heat transfer section cut out, as viewed from the first plate side (front side). FIG. 4 is a perspective view of a state in which a partial region of the main heat transfer section is cut out, as viewed from the second plate side (rear side), showing the state in which the first plate and the second plate are combined with a partial region of the main heat transfer section cut out. FIG. 5 is a partially cutaway enlarged perspective view illustrating the occurrence of a "transfer" of fluid between the first plate and the second plate, with the flow of the "transfer" indicated by arrows. FIG. 6 is a schematic view illustrating the sequential occurrence of a "transfer" of fluid between the first plate and the second plate. FIG. 7 is a schematic view illustrating the flow of a fluid assuming that the bent portions of the first plate and the second plate do not overlap. Fig. 8A is a schematic diagram for explaining a case where the bent portions of the first plate and the second plate overlap without being misaligned in the longitudinal direction of the heat transfer plate. Fig. 8B is a schematic diagram for explaining a case where the bent portions of the first plate and the second plate are misaligned in the width direction of the heat transfer plate from the state of Fig. 8A. Fig. 9A is a schematic diagram for explaining a case where the bent portions of the first plate and the second plate are misaligned in the longitudinal direction of the heat transfer plate. Fig. 9B is a schematic diagram for explaining a case where the bent portions of the first plate and the second plate are misaligned in the width direction of the heat transfer plate in addition to the state of Fig. 9A. Fig. 10 is a diagram showing the results of an analysis performed by the inventor on the heat transfer plate.

[0013] The present invention will be described below with reference to one embodiment and the accompanying drawings. Regarding the directional expressions in the following description, as shown in FIG. 1 , the direction in which the heat transfer plates 3 are stacked (the thickness direction of each heat transfer plate 3 macroscopically (ignoring the convex portions 3A and concave portions 3B)) is referred to as the "X-axis direction," the short side direction (width direction) of each heat transfer plate 3 is referred to as the "Y-axis direction," and the long side direction (longitudinal direction) of each heat transfer plate 3 is referred to as the "Z-axis direction" (all of these directions are directions in a Cartesian coordinate system). Furthermore, in the following description, the line of sight toward the X-axis direction is also referred to as a "planar view" since each heat transfer plate 3 is symmetrical. Furthermore, when multiple functionally identical parts are shown in the drawings, a reference symbol is generally assigned to only one representative part.

[0014] As shown in Figure 1, a plate heat exchanger (hereinafter referred to as "heat exchanger") 1 according to this embodiment includes a plate stack 2 having a plurality of heat transfer plates 3. The heat exchanger 1 also includes a pair of frames 5a, 5b whose opposing spacing is variable so as to sandwich the plate stack 2, a guide section 6 extending in the X-axis direction to guide the plate stack 2 and the pair of frames 5a, 5b to their respective positions, and a plurality of fastening members 7 that can fasten the pair of frames 5a, 5b in a direction that reduces the spacing between them. Note that the configuration for supporting the plate stack 2 is not limited to the configuration shown in Figure 1, and various configurations can be adopted.

[0015] The plate stacking unit 2 has a plurality of heat transfer plates 3 stacked opposite each other in the X-axis direction. A gasket (only the shape is shown in FIG. 2 ) is sandwiched between two adjacent heat transfer plates 3 in the X-axis direction to prevent fluid leakage between the heat transfer plates 3.

[0016] As shown in FIG. 2 , the plate stacking unit 2 includes a plurality of flow paths Ra, Rb (indicated by arrows) through which fluids A and B of different temperatures flow through separate paths, thereby allowing heat exchange between these fluids A and B, and a plurality of communication paths Rc, Rd through which the fluids A and B flow from the outside of the plate stacking unit 2 into each of the flow paths Ra, Rb, or through which the fluids A and B flow from each of the flow paths Ra, Rb to the outside of the plate stacking unit 2.

[0017] Specifically, the plate stacking unit 2 has flow paths Ra and Rb between each of the multiple overlapping heat transfer plates 3. In the plate stacking unit 2 of this embodiment, two types of rectangular heat transfer plates 3 (first plates 3X and second plates 3Y) are alternately overlapped, so that first flow paths Ra through which a first fluid A can flow and second flow paths Rb through which a second fluid B can flow are alternately formed in the X-axis direction, with each heat transfer plate 3 as a boundary. The overlapping configuration of the first plates 3X and second plates 3Y will be described in detail later. In the plate stacking unit 2, the first fluid A flowing through the first flow paths Ra and the second fluid B flowing through the second flow paths Rb exchange heat through (across) the heat transfer plates 3 that separate the first flow paths Ra and the second flow paths Rb.

[0018] The plate stacking unit 2 also has a pair of first communication passages Rc1, Rc2, each extending in the X-axis direction and communicating only with the first flow passage Ra, and a pair of second communication passages Rd1, Rd2, each extending in the X-axis direction and communicating only with the second flow passage Rb. One of the pair of first communication passages Rc1, Rc2, the first communication passage Rc1, passes through the frame 5a and allows the first fluid A to flow into each of the first flow passages Ra from the outside of the plate stacking unit 2, while the other first communication passage Rc2 passes through the frame 5a and allows the first fluid A to flow out from each of the first flow passages Ra to the outside of the plate stacking unit 2. Further, one second communication passage Rd1 of the pair of second communication passages Rd1, Rd2 allows the second fluid B to flow from the outside of the plate stacking unit 2 through the frame 5a and into each second flow path Rb, and the other second communication passage Rd2 allows the second fluid B to flow from each second flow path Rb to the outside of the plate stacking unit 2 through the frame 5a and out. Note that the fluids A and B do not reach the frame 5b, and as shown in Fig. 2, the first fluid A turns back to the front (towards the frame 5a) at the first flow path Ra that contacts the heat transfer plate 3 located furthest back in the X-axis direction (towards the frame 5b) of the plate stacking unit 2, and the second fluid B turns back to the front at the second flow path Rb that contacts the heat transfer plate 3 one step forward from the furthest back.

[0019] Macroscopically, each of the heat transfer plates 3 extends in a direction perpendicular to the X-axis direction (the Y-axis and Z-axis directions). Each of the heat transfer plates 3 has a first surface S1, which is one surface in the X-axis direction, and a second surface S2, which is the surface opposite the first surface S1 (the other surface in the X-axis direction), with a plurality of convex portions 3A and a plurality of concave portions 3B (see FIGS. 3 and 4). Note that in FIG. 2, the configurations (shape, position, number, etc.) of the convex portions 3A and the concave portions 3B are simplified. Of the convex portions 3A and the concave portions 3B, the convex portions 31A and the concave portions 31B formed in the main heat transfer section 31 will be described in detail later.

[0020] Each of the heat transfer plates 3 is formed by press-molding a metal plate (thin sheet). Due to the press-molding process, on the second surface S2, recesses 3B are located at positions corresponding to the protrusions 3A on the first surface S1 (i.e., on the rear side of the protrusions 3A), and protrusions 3A are located at positions corresponding to the recesses 3B on the first surface S1 (i.e., on the rear side of the recesses 3B). That is, on each heat transfer plate 3, the protrusions 3A on the first surface S1 and the recesses 3B on the second surface S2 corresponding to the protrusions 3A are in an inseparable relationship, and the recesses 3B on the first surface S1 and the protrusions 3A on the second surface S2 corresponding to the recesses 3B are in an inseparable relationship.

[0021] In this embodiment, the multiple heat transfer plates 3 include two types of heat transfer plates 3 (first plate 3X and second plate 3Y) that are arranged differently in the plate stacking section 2. Of these two types of heat transfer plates 3X and 3Y, one heat transfer plate (first plate) 3X has the same configuration as the other heat transfer plate (second plate) 3Y when inverted (upside down) in the Z-axis direction. Specifically, the arrangement pattern (shape as viewed in the X-axis direction, cross-sectional shape, concave / convex direction, etc.) of the convex portions 3A and concave portions 3B of the first plate 3X is as shown in FIG. 3 for a partial region of the main heat transfer section 31, and the arrangement pattern of the convex portions 3A and concave portions 3B of the second plate 3Y is as shown in FIG. 4 for a partial region of the main heat transfer section 31, and is the same as the convex portions 3A and concave portions 3B of the first plate 3X when inverted. Therefore, the individual shapes of the two types of heat transfer plates 3X and 3Y are exactly the same. In other words, in this embodiment, the first plate 3X and the second plate 3Y do not exist as physically separate plates, but rather the names of these plates are convenient names for distinguishing one from the other, which are placed opposite each other in the X-axis direction by overlapping to form the plate stack section 2.

[0022] Specifically, each heat transfer plate 3 has a main heat transfer section 31 disposed in the center in the Z-axis direction (the center in the vertical direction in the figure), communicating sections 32 disposed at both ends in the Z-axis direction, and weir sections 33 disposed between the main heat transfer section 31 and the communicating sections 32. Each heat transfer plate 3 of this embodiment has the communicating sections 32 at both ends in the Z-axis direction, and has weir sections 33 between the main heat transfer section 31 and one of the communicating sections 32, and between the main heat transfer section 31 and the other communicating section 32. That is, each heat transfer plate 3 has a pair of communicating sections 32 and a pair of weir sections 33. Each heat transfer plate 3 also has a gasket arrangement section 34 in which a gasket is arranged.

[0023] The main heat transfer section 31 is a portion of the heat transfer plate 3 where most of the heat exchange occurs between the fluids (between the first fluid A and the second fluid B) flowing through the first flow path Ra and the second flow path Rb formed on both sides of the heat transfer plate 3. The main heat transfer section 31 in this embodiment is a quadrangular (more specifically, rectangular) portion when viewed from the X-axis direction.

[0024] The main heat transfer section 31 has a plurality of convex portions 31A and a plurality of concave portions 31B on both sides (see FIGS. 3 and 4). The arrangement and shape of the plurality of convex portions 31A and the plurality of concave portions 31B are determined depending on the heat transfer efficiency and the type of fluid (first fluid A and second fluid B) to be heat exchanged. In this embodiment, the plurality of convex portions 31A and the plurality of concave portions 31B arranged on each side of the main heat transfer section 31 are wavy, specifically, herringbone-shaped (a waveform that forms a "V" shape in a plan view). Details of the shapes of the convex portions 31A and the concave portions 31B and the positional relationship between the convex portions 31A and the concave portions 31B when the first plate 3X and the second plate 3Y are overlapped will be described later. Note that the shape of the main heat transfer section 31 shown in FIG. 2 is merely a rough representation to indicate that a herringbone waveform is formed, and the illustrated content is not precise. Furthermore, the plurality of protrusions 31A are included in the plurality of protrusions 3A of the heat transfer plate 3, and the plurality of recesses 31B are included in the plurality of recesses 3B of the heat transfer plate 3.

[0025] Each of the pair of communication portions 32 has a plurality of through holes 321 penetrating in the X-axis direction. The through hole 321 is composed of two through holes 321a, 321b. Fluid A passes through the through hole 321a, and fluid B passes through the through hole 321b. Although specific shapes are not shown, each of the pair of communication portions 32 also has a plurality of protrusions 3A and a plurality of recesses 3B on both sides. The arrangement and shape of the plurality of protrusions 3A and the plurality of recesses 3B are determined depending on the desired strength of the heat transfer plate 3, the desired size of the flow space for fluids A and B, the types of fluids A and B to be heat exchanged, etc.

[0026] Specifically, in each communication portion 32, the two through holes 321a, 321b are arranged at an interval in the Y-axis direction. As a result, the through holes 321 are arranged at the four corners of each heat transfer plate 3.

[0027] These through holes 321 are connected in the X-axis direction when the heat transfer plates 3 are stacked (i.e., in the plate stacking section 2), thereby forming communication passages Rc, Rd. In each heat transfer plate 3 of this embodiment, these four through holes 321 are circular holes, and the size (diameter) of each through hole 321 is the same.

[0028] The configuration of the communicating portion 32u on one side (upper side in FIG. 2 ) of the pair of communicating portions 32 and the configuration of the communicating portion 32d on the other side (lower side in FIG. 2 ) of the pair of communicating portions 32 are line-symmetrical (vertically symmetrical in the arrangement of FIG. 2 ) with respect to a horizontal center line, which is an imaginary line extending in the Y-axis direction through the center of the heat transfer plate 3 in the Z-axis direction, as the axis of symmetry. Furthermore, the configurations of the communicating portions 32u, 32d are line-symmetrical (left-right symmetrical in the arrangement of FIG. 2 ) with respect to a vertical center line, which is an imaginary line extending in the Z-axis direction through the center of the heat transfer plate 3 in the Y-axis direction, as the axis of symmetry.

[0029] Each of the pair of weir sections 33 is a section that diffuses the flow of fluids A and B from the through hole 321 toward the main heat transfer section 31 along the first surface S1 or the second surface S2 in the Y-axis direction, or concentrates the flow of fluids A and B from the main heat transfer section 31 toward the through hole 321 along the first surface S1 or the second surface S2 in the Y-axis direction.

[0030] Specifically, each weir portion 33 is a triangular portion with its base at the boundary with the main heat transfer portion 31 and its apex at the midpoint between the two through holes 321a and 321b of the communication portion 32. Each weir portion 33 has multiple projections and recesses on both sides (these are indicated by hatching in FIG. 2 , and the specific shapes of the projections and recesses are not shown). The arrangement and shape of these multiple projections and recesses are determined depending on the dimension of the main heat transfer portion 31 in the Y-axis direction, the distance from the through holes 321 to the main heat transfer portion 31, the types of fluids A and B to be heat exchanged, and other factors; however, the shape and arrangement are not particularly limited. Note that each weir portion 33 also performs heat exchange between the fluids (between the first fluid A and the second fluid B) flowing through the first flow path Ra and the second flow path Rb formed by the heat transfer plate 3 as a boundary. These multiple projections and recesses are included in the multiple projections 3A and recesses 3B of the heat transfer plate 3.

[0031] In the heat exchanger 1 of this embodiment configured as described above, the following description will focus on a set 3G (see FIGS. 3 and 4) of two identically shaped heat transfer plates 3, a first plate 3X and a second plate 3Y, which are included in the plurality of heat transfer plates 3 that make up the plate stacking section 2 and face each other in the X-axis direction. Note that FIG. 3 is a view seen from one side (front side) in the X-axis direction, and FIG. 4 is a view seen from the other side (rear side) in the X-axis direction.

[0032] Typically, a single heat exchanger 1 includes multiple sets 3G of first plates 3X and second plates 3Y in a number that corresponds to the required heat exchange performance. Each heat transfer plate 3 other than those located at both ends in the X-axis direction (the overlapping direction) forms a set 3G with another heat transfer plate 3 that faces it on its front surface (one side in the X-axis direction), and also forms a set 3G with another heat transfer plate 3 that faces it on its back surface (the other side in the X-axis direction). In other words, each heat transfer plate 3 has flow paths (first flow paths Ra or second flow paths Rb that are alternately formed in the X-axis direction) formed on both the front and back surfaces.

[0033] As described above, the first plate 3X and the second plate 3Y have the same shape. Therefore, during the manufacture of the heat exchanger 1, they are indistinguishable from each other and can be treated as the same heat transfer plate 3 until they are stacked to form the plate stack section 2. The first plate 3X and the second plate 3Y are stacked in a positional relationship rotated 180° in a plan view of each heat transfer plate 3 (upside-down positional relationship in the state shown in Figures 2 and 3). For example, if the herringbone corrugations of the first plate 3X are arranged downward in each row L (V-shaped in plan view) as shown in Figure 3, the herringbone corrugations of the second plate 3Y are arranged in the opposite direction, facing upward in each row L (inverted V-shaped in plan view) as shown in Figure 4. The combined state of the first plate 3X and the second plate 3Y that constitute the plate stack section 2 is shown in Figure 2.

[0034] As shown in Figures 3 and 4, the main heat transfer portion 31 of each heat transfer plate 3 of this embodiment has multiple grooves (recesses) formed in the plate thickness direction, i.e., the X-axis direction. These grooves are composed of recesses 31B and protrusions 31A adjacent to the recesses 31B in the Z-axis direction. As described above, since the main heat transfer portion 31 is formed by press-molding a metal plate, when the recesses 31B, which are recesses in the X-axis direction, are formed on the first surface S1 of one heat transfer plate 3, the shape formed directly behind them on the second surface S2 is the protrusions 31A, which are protrusions. These grooves form a waveform, forming a herringbone waveform with bends 31C, where the slope is reversed in a plan view. The shape of one unit of the herringbone waveform is a "V" (or inverted "V") waveform in a plan view, and is composed of grooves that extend linearly in diagonal directions in the Y-axis direction and Z-axis direction so as to be symmetrical with respect to a virtual line that passes through the center in the Y-axis direction (the width direction of each heat transfer plate 3) and extends in the Z-axis direction. The inclination angle of the grooves can be set to various angles depending on the required performance of the heat exchanger 1. In one unit of the herringbone waveform, a bend 31C is located in the center in the Y-axis direction. For each groove that constitutes one unit of the herringbone waveform, the inclination angle on one side of the bend 31C in the Y-axis direction is the same as the inclination angle on the other side.

[0035] A virtual line CL is set connecting the position of the "bottom" of the recessed portion 31B, which is the deepest in the X-axis direction, and the position of the "peak" of the protruding portion 31A, which is the deepest in the X-axis direction, in the extension direction of each groove. That is, the virtual line CL coincides with the bottom line of the recessed portion 31B and the peak line of the protruding portion 31A. The position of the bent portion 31C corresponds to the position of an inflection portion (more specifically, an inflection point) on the virtual line CL (see FIG. 6 ) where the extension direction changes (e.g., from upward to downward). The bent solid and dashed lines shown in FIGS. 9A and 9B (as well as FIGS. 8A and 8B for comparative examples) are lines drawn at the position of the virtual line. When the line is "V" shaped, the sharp central portion corresponds to the inflection portion. In design, this inflection portion is an angle (either acute, right, or obtuse) where two straight lines meet. However, in the actual heat transfer plate 3, the recessed portion 31B and the protruding portion 31A are formed by press molding, resulting in an inflection portion with a radius rather than a geometrically pure (sharp) corner. The dimension of the radius is not particularly limited, but considering the manufacturing process by press molding, the radius of curvature in a plan view is preferably 5 mm or less, and more preferably 2 mm or less. The lower limit of the radius dimension corresponds to a value at which the metal plate (thin sheet) from which the heat transfer plate 3 is made does not crack during press molding. The specific numerical value varies depending on the material of the metal plate and the press speed and pressure of the press molding. On the other hand, although there is no particular upper limit to the radius dimension, if the radius dimension (radius of curvature) is too large, it is likely that misalignment will occur in the contact between the bent portions 31C at the convex portions 31A of the first plate 3X and the second plate 3Y, and the radius will affect the flow of fluid, which may impair the "flow transfer" described below. Therefore, it is preferable to set the radius dimension as small as possible within a range that does not cause difficulties in manufacturing.

[0036] The macroscopic flow direction of the fluid along the flow paths Ra and Rb in each heat transfer plate 3 is the longitudinal direction (up-down direction) of each heat transfer plate 3. For the "V" or inverted "V" shape of the herringbone waveform, it is the direction from the tip to the wide side, or from the wide side to the tip. In each heat transfer plate 3 of this embodiment, the shapes of the multiple herringbone waveforms are the same. The depth (X-axis direction) of the herringbone-shaped recesses 31B is set to a range of 1.4 mm to 5 mm, preferably 2 mm to 4 mm. Note that a depth of less than 1.4 mm results in high pressure loss and a high risk of clogging the flow paths Ra and Rb. Furthermore, a depth of more than 5 mm reduces the likelihood of turbulence in the fluid flowing through the flow paths Ra and Rb, and increases the proportion of fluid that flows without touching the surface of the heat transfer plate 3, resulting in reduced heat transfer performance.

[0037] In the main heat transfer section 31, multiple rows L, each consisting of a plurality of herringbone wave units lined up in the Z-axis direction, are formed in parallel in the Y-axis direction. The multiple herringbone wave units are arranged in parallel at regular intervals (equal pitch) in the Z-axis direction. The number of rows L formed in the main heat transfer section 31 is not particularly limited, but in this embodiment, four or more rows are used ( FIG. 2 shows a schematic configuration of four rows, and FIGS. 3 and 4 show a cut-out portion of the main heat transfer section 31).

[0038] The bends 31C are located at the center of one unit of the herringbone waveform in the Y-axis direction and at both ends in the Y-axis direction. Therefore, at the boundary between two adjacent rows L, the bends 31C are formed by both ends of the two herringbone waveforms.

[0039] In the multiple rows L of herringbone waveforms, two adjacent rows L in the Y-axis direction are arranged at a row pitch PL of 80 mm or less, preferably 40 mm or less, in the parallel direction. The "row pitch" refers to the distance between each of the multiple rows L composed of multiple herringbone waveforms. This row pitch PL (separation distance) can be evaluated, for example, by focusing on the position of the bend 31C of each row L in two adjacent rows in the width direction (short direction) of each heat transfer plate 3 (more specifically, the bend 31C at the center of one unit of herringbone waveform in the Y-axis direction). Note that the row pitch PL may be any value greater than 0 mm. However, from the perspective of practical manufacturing feasibility of each heat transfer plate 3, 3.0 mm is the lower limit.

[0040] In this embodiment, the bend 31C in the herringbone waveform belonging to the first plate 3X and the bend 31C in the herringbone waveform belonging to the second plate 3Y are adjacent to each other in the direction in which the grooves extend in each heat transfer plate 3 (diagonal directions in the Y-axis direction and the Z-axis direction), and overlap each other in a planar view of each heat transfer plate 3. As shown schematically in Figure 6, when two plates 3X and 3Y are stacked on top of each other, the recess 31B of the second plate 3Y (first surface S1 side) at the back in the X-axis direction is shown by a solid line, and the recess 31B of the first plate 3X (second surface S2 side) at the front in the X-axis direction is shown by a dashed line, the center lines CL (dash-dotted lines) of each plate 3Y and 3X overlap in the Z-axis direction (the up-down direction in the figure) as indicated by circles (note that the diagram in Figure 6 is exaggerated for the purpose of explanation, and adjacent recesses 31B in the Z-axis direction are shown separated from each other).

[0041] Meanwhile, a protrusion 31A is located on the thickness-wise opposite side of the recess 31B in each plate 3X, 3Y. Here, we will change the perspective of the "overlapping" portion from the above and explain the relationship between the protrusions 31A of each plate 3X, 3Y. As shown in FIG. 5 , the protrusion 31A of the first plate 3X and the protrusion 31A of the second plate 3Y are in point contact (strictly speaking, a very short line contact) at contact point 3C. This contact relationship ensures the abutment between the first plate 3X and the second plate 3Y (contact at contact point 3C), which is important for the structure of the plate stacking unit 2. This abutment positioning of the opposing plates 3X, 3Y ensures stable determination of the distance in the X-axis direction between the multiple heat transfer plates 3. Accordingly, the distance between the recess 31B of the first plate 3X and the recess 31B of the second plate 3Y is also stable. The positional relationship between the recess 31B of the first plate 3X and the recess 31B of the second plate 3Y at the bent portion 31C is important for generating a "flow transfer" which will be described later.

[0042] Due to this relationship, the recess 31B of the first plate 3X and the recess 31B of the second plate 3Y are connected linearly in a plan view at the bent portion 31C, and the flow path formed by both the recesses 31B communicates linearly. As shown by the relationship between the solid line and the dashed line in Figure 6, although they appear linear in a plan view, the recess 31B of the first plate 3X and the recess 31B of the second plate 3Y are positioned alternately (i.e., on the front side and the back side) in terms of their positional relationship in the X-axis direction. Therefore, in the overlapping portion of the set 3G of the first plate 3X and the second plate 3Y, as shown by the arrows in Fig. 5, a fluid (flow F1) that has traveled along the herringbone waveform of the first plate 3X through the recess 31B of the first plate 3X (behind the protrusion 31A in the figure) moves straight at the bent portion 31C in a plan view (flow F shown in Fig. 6), moves toward the second plate 3Y in the X-axis direction (flow F2), and then flows through the recess 31B of the second plate 3Y along the herringbone waveform of the second plate 3Y (flow F3). Although the fluid flow is said to move straight at the bent portion 31C in a plan view, in three dimensions, as shown in Fig. 5, an alternating flow is formed, in which the fluid flows from the front side to the back side in the X-axis direction (flow F2 shown) and then repeatedly moves from the back side to the front side. As the flows alternate in this way, a spiral flow is generated in the fluid, in which a flow in a rotational direction is added to the flow direction (simply shown by a spiral line in FIG. 6 ). The spiral flow is generated by the relationship between the fluid flow direction and the positional relationship between the recessed portion 31B of the first plate 3X and the recessed portion 31B of the second plate 3Y at the bent portion 31C. Because this spiral flow is a vortex-like flow, it is a flow accompanied by turbulence. However, compared to a regular flow, this spiral flow promotes fluid movement in response to turbulence, thereby improving the heat transfer performance (heat transfer efficiency) between the first fluid A and the second fluid B via the main heat transfer portion 31.

[0043] Note that not all of the fluid flows straight at the bent portion 31C in a plan view; a certain percentage of the fluid becomes a reflected flow Fr, which is redirected into a "V" shape at the bent portion 31C in a plan view, as indicated by the dashed arrow in Figure 6. This reflected flow Fr is also shown by streamlines in Figure 10, which shows the analysis results. Even in the reflected flow Fr, the fluid flow is transferred to another recess, as shown in Figure 6. Although it is expected that the pressure loss will be relatively large compared to a flow that flows straight in a plan view because the flow angle is changed, this reflected flow Fr also contributes to improving heat transfer performance (heat transfer efficiency) compared to the configuration of Figure 7, which will be described later.

[0044] As described above, in this embodiment, the bent portion 31C of the first plate 3X and the bent portion 31C of the second plate 3Y are in an overlapping relationship, which allows smooth flow transfer between the recess 31B on the first plate 3X side and the recess 31B on the second plate 3Y side, thereby suppressing flow resistance, but also causing turbulence in the flow (flow F2 shown in Figure 5) during the transfer, and this turbulence spreads to the entire flow F, thereby increasing the proportion of turbulent fluid that comes into contact with the main heat transfer section 31 and achieving high heat transfer performance.

[0045] On the other hand, assuming a configuration as shown in Figure 7 where the bent portions 31C do not overlap, a fluid (flow F11) that has traveled through the recessed portion 31B of the first plate 3X along the herringbone waveform of the first plate 3X attempts to flow through the recessed portion 31B of the second plate 3Y along the herringbone waveform of the second plate 3Y. However, because the recessed portions 31B of the second plate 3Y are not continuous in a straight line at the bent portion 31C, the fluid cannot travel in a straight line in a planar view, resulting in a bent flow (flows F12 and F13). Moreover, the bent portion of the flow has a narrowed cross section in a three-dimensional view due to the overlapping relationship between the recessed and protruding portions of the first plate 3X and the second plate 3Y. Therefore, there is a disadvantage in that the flow resistance of the fluid increases due to the influence of the bent portion of the flow.

[0046] In contrast, in this embodiment, the bent portions 31C allow the fluid to travel straight in a plan view, which allows for smoother fluid flow transfer between the heat transfer plates 3 compared to the hypothetical configuration shown in Figure 7, thereby reducing fluid flow resistance. As mentioned above, turbulence occurs in the fluid when the flow transfers (the spiral lines shown in Figure 6), and this turbulence improves heat transfer performance. When the row pitch PL is set to the preferred value of 40 mm or less, the balance between heat transfer and pressure loss is even better.

[0047] One of the results of an analysis performed by the inventors is shown in Figure 10. Note that no reference numerals are attached in Figure 10, which is an output diagram from the analysis software. The arrows in Figure 10 indicate the macroscopic flow direction of the fluid. The analysis shown here was performed with the following settings: the inclination of the "V" shape of the herringbone waveform (based on the Y-axis direction) was 60 degrees; the row pitch PL (the parallel distance of the herringbone waveforms) was 11.32 mm; the pitch of the herringbone waveforms in the Z-axis direction within each row L was 19.6 mm; the pitch in the orthogonal direction between adjacent herringbone waveforms in the Z-axis direction within each row L was 19.6 mm; and the dimension of the herringbone waveform in the X-axis direction (groove depth) was 3.0 mm. The software used for the analysis was "scFLOW," the fluid was water, and the flow velocity at the inlet was 1.0 m / s. The material of each plate 3X and 3Y was stainless steel, with a thickness of 0.6 mm. The positions indicated by solid lines in Figure 10 are the positions of the herringbone waveform of the first plate 3X, which is positioned on the front side of the second plate 3Y in the figure, and the lines are drawn so that the convex portions 31A and concave portions 31B have the same shape. The curved flow lines in Figure 10 correspond to the flow of fluid passing through the side of the second plate 3Y facing the first plate 3X. The flow lines in the portion surrounded by solid lines flow along the concave portions 31B of the first plate 3X, and the flow lines outside of this portion flow along the concave portions 31B of the second plate 3Y. As can be clearly seen from Figure 10, the fluid flow can be transferred along the slope of the "V" shape of the herringbone waveform, and it was confirmed that the flow is linear in plan view.

[0048] Regarding the "overlapping relationship," in this embodiment, the bent portions 31C of the first plate 3X and the bent portions 31C of the second plate 3Y are offset by 20% (1 / 5) or less, preferably 10% (1 / 10) or less, based on the distance between the herringbone corrugations of the first plate 3X or the second plate 3Y. Within this offset range, the decrease in efficiency of fluid flow transfer between the heat transfer plates 3 is within an acceptable range compared to when there is no offset, thereby maintaining a good balance between heat transfer and pressure loss. Note that this relationship between the offset of 20% or less (preferably 10% or less) and the function holds in the planar direction of the heat transfer plate 3 viewed macroscopically, and therefore holds for the distance between the herringbone corrugations in any direction, including the Y-axis direction, the Z-axis direction, and a composite direction of these directions.

[0049] Furthermore, with regard to the "overlapping relationship," in this embodiment, under the condition that the misalignment is 20% or less (preferably 10% or less), the bent portions 31C of the first plate 3X and the bent portions 31C of the second plate 3Y are misaligned by 0.5 mm or more in the Z-axis direction, which is the direction in which each row L of the herringbone waveform extends. Within this set range of misalignment, even if an error occurs in the overlapping of the first plate 3X and the second plate 3Y in the Y-axis direction, which is the direction perpendicular to the direction in which each row L of the herringbone waveform extends, the bent portions 31C of each heat transfer plate 3 can maintain an overlapping relationship in a plan view.

[0050] The reason for this will be explained. In Figures 8A, 9A, and 9B, the overlapping state of the bent portions 31C is shown by lines, and the intersections of the center lines of the convex portions 31A (i.e., the abutting portions of the convex portions 31A, corresponding to the contact points 3C shown in Figure 5) are shown by circles. When the misalignment is set to zero as shown in Figure 8A, even slight misalignment of the bent portions 31C in the width direction (Y-axis direction) of each heat transfer plate 3 for manufacturing reasons may result in the absence of abutting portions of the convex portions 31A between the first plate 3X and the second plate 3Y, as shown in Figure 8B. In this case, the portions that should abut between the first plate 3X and the second plate 3Y do not abut, creating gaps (raising), which reduces the strength of the plate stacking unit 2.

[0051] In contrast, when the misalignment is 0.5 mm or more (FIG. 9A), the groove of the first plate 3X (focusing on the abutment, the convex portion 31A on the back side of the groove) and the groove of the second plate 3Y (convex portion 31A) can be made to partially overlap in the direction in which the groove extends (FIG. 9B). This makes it less likely that misalignment will occur in the direction intersecting the flow direction, as described above. This is because it is expected that the reduction in strength of the plate stack portion 2 caused by the absence of abutment portions between the heat transfer plates 3 can be suppressed.

[0052] Furthermore, in each of the multiple rows L of the herringbone waveform, it is preferable that the center lines of two adjacent grooves (recesses 31B) in the direction in which each row L extends (the Z-axis direction, the vertical direction in the figure) be arranged at a groove pitch of 6 mm or more in the Z-axis direction. Setting the groove pitch in this manner can prevent increased pressure loss due to excessively narrow plate spacing and clogging due to substances contained in the fluid or precipitates from the fluid. There is no particular upper limit to the groove pitch from the perspective of solving the problem of the invention. However, a realistic upper limit of 20 mm is a value that is practical from the perspective of the strength and heat transfer performance of each heat transfer plate 3 and the plate stack 2 in which multiple heat transfer plates 3 are stacked.

[0053] In the plate-type heat exchanger 1 of this embodiment configured as described above, in the set 3G of the first plate 3X and the second plate 3Y, where the heat transfer plates 3X, 3Y overlap in a plan view, the fluid that has been flowing along the herringbone waveform of the first plate 3X flows along the herringbone waveform of the second plate 3Y at the bend 31C (flows F1 to F3 in FIG. 5 ). This allows for smooth fluid flow transfer between the heat transfer plates 3X, 3Y, reducing fluid flow resistance. Furthermore, turbulence occurs in the fluid during the flow transfer, improving heat transfer performance. Therefore, the plate-type heat exchanger 1 of this embodiment takes into consideration the set 3G of the heat transfer plates 3X, 3Y that are overlapping and facing each other. As a result, it is possible to achieve the remarkable effects of reducing fluid flow resistance during heat exchange and achieving high heat transfer performance.

[0054] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0055] For example, the individual shapes of the herringbone waveforms, and the number and spacing of the herringbone waveforms formed in the main heat transfer section 31 can be variously changed. As an example, in the above embodiment, the shape of one unit of the herringbone waveform is a shape formed by grooves extending linearly, but it may also be a shape formed by grooves extending curvedly.

[0056] Furthermore, the type (form) of the plate heat exchanger 1 to which the present invention is applied is not particularly limited. For example, with regard to the plate stacking portion 2, the plate stacking portion 2 in the above embodiment is configured by sandwiching a gasket between two adjacent heat transfer plates 3 in the multiple heat transfer plates 3 stacked opposite each other in the X-axis direction. However, the configuration of the plate stacking portion 2 is not limited to this, and the abutting portions of two adjacent heat transfer plates 3 may be joined together, for example, by brazing, without using a gasket.

[0057] The configurations and functions of the above-described embodiments are summarized below. In embodiment (1), a plurality of heat transfer plates 3 are stacked one on top of the other, and the plurality of heat transfer plates 3 include a set 3G of a first plate 3X and a second plate 3Y, which are two heat transfer plates 3 of the same shape facing each other, and the first plate 3X and the second plate 3Y are stacked in a positional relationship rotated by 180° in a plan view of each of the heat transfer plates 3X and 3Y. Each of the heat transfer plates 3X and 3Y has a corrugation formed by a plurality of grooves formed to be recessed in the plate thickness direction, and a herringbone corrugation row L having a bent portion 31C where the inclination is reversed in a plan view. are formed in parallel in a plurality of rows L of the herringbone corrugations, and two adjacent rows L of the herringbone corrugations are arranged at a pitch PL of 80 mm or less in the parallel direction, and the bent portions 31C in the herringbone corrugations belonging to the first plate 3X and the bent portions 31C in the herringbone corrugations belonging to the second plate 3Y are overlapped in a plan view of each of the heat transfer plates 3X and 3Y at both of the two bent portions 31C that are adjacent to each other in the direction in which the grooves extend in each of the heat transfer plates 3X and 3Y.

[0058] With this configuration, in the overlapping portions of the first plate 3X and the second plate 3Y, the fluid that has been flowing along the herringbone waveform of the first plate 3X flows at the bent portion 31C along the herringbone waveform of the second plate 3Y. This allows for smooth fluid flow transfer between the heat transfer plates 3X and 3Y, reducing fluid flow resistance. Furthermore, turbulence occurs in the fluid during the flow transfer, improving heat transfer performance.

[0059] In addition, in embodiment (2), in the embodiment (1), the overlapping relationship can be such that the bent portion 31C in the first plate 3X and the bent portion 31C in the second plate 3Y are misaligned by 20% or less based on the distance between the herringbone waveforms in the first plate 3X or the second plate 3Y.

[0060] According to this configuration, within the range of the deviation, a good balance between heat transfer and pressure loss can be maintained.

[0061] In addition, in embodiment (3), in the embodiment (2), the overlapping relationship can be such that the bent portion 31C of the first plate 3X and the bent portion 31C of the second plate 3Y are misaligned by 0.5 mm or more in the direction in which each row L of the herringbone waveform extends.

[0062] With this configuration, even if an error occurs in the overlapping of the first plate 3X and the second plate 3Y in a direction perpendicular to the direction in which each row L of the herringbone waveform extends, the bent portions 31C of each heat transfer plate 3X, 3Y can maintain an overlapping relationship in a planar view direction.

[0063] In addition, embodiment (4) is any of embodiments (1) to (3), and in each of the multiple rows of the herringbone waveform, two adjacent grooves in the direction in which each row L extends can be arranged at a pitch of 6 mm or more.

[0064] This configuration can prevent an increase in pressure loss and clogging caused by the gap between the heat transfer plates 3X and 3Y becoming too narrow.

[0065] In addition, in embodiment (5), in any of embodiments (1) to (4), two adjacent rows L of the multiple rows of the herringbone waveform can be arranged at a pitch of 40 mm or less in the parallel direction.

[0066] This configuration provides a good balance between heat transfer and pressure loss.

[0067] As described above, the embodiment can suppress the flow resistance of the fluid when heat exchange is performed, and can obtain high heat transfer performance.

[0068] REFERENCE SIGNS LIST 1...heat exchanger, 2...plate stacking portion, 3...heat transfer plate, 3A...convex portion, 3B...concave portion, 3C...contact point, 3G...set of heat transfer plates, 3X...heat transfer plate (first plate), 3Y...heat transfer plate (second plate), 5a, 5b...frame, 6...guide portion, 7...fastening member, 31...main heat transfer portion, 31A...convex portion, 31B...concave portion, 31C...bent portion, 32...communicating portion, 32d...communicating portion , 32u...communicating portion, 33...dam portion, 34...gasket arrangement portion, 321...through hole, 321a, 321b...through holes, A, B...fluid, CL...center line, F, F1 to F3, F11 to F13...flow, Fr...reflected flow, L...herringbone waveform row, PL...pitch (row pitch), Ra, Rb...flow path, Rc, Rd, Rc1, Rc2, Rd1, Rd2...communicating path, S1...first surface, S2...second surface

Claims

1. A plate type heat exchanger configured by stacking a plurality of heat transfer plates, including a set of a first plate and a second plate, which are two heat transfer plates of the same shape facing each other, and the first plate and the second plate are stacked in a positional relationship rotated 180 degrees in a plan view of each heat transfer plate, each of the heat transfer plates has a waveform formed from a plurality of grooves formed to be recessed in the plate thickness direction, and each of the heat transfer plates has a plurality of parallel rows of herringbone waveforms having bent portions where the slope is reversed in a plan view, and adjacent two of the multiple rows of herringbone waveforms are arranged at a pitch of 80 mm or less in the parallel direction, and the bent portions of the herringbone waveform belonging to the first plate and the bent portions of the herringbone waveform belonging to the second plate overlap in a plan view of each of the heat transfer plates at both of the two bent portions that are adjacent in a reference direction of extension of the grooves in each of the heat transfer plates.

2. The plate heat exchanger according to claim 1, wherein the overlapping relationship is such that the bent portion of the first plate and the bent portion of the second plate are misaligned by 20% or less based on the distance between the herringbone corrugations of the first plate or the second plate.

3. The plate heat exchanger according to claim 2, wherein the overlapping relationship is such that the bent portions of the first plate and the bent portions of the second plate are misaligned by 0.5 mm or more in the direction in which each row of the herringbone corrugations extends.

4. A plate heat exchanger as set forth in any one of claims 1 to 3, wherein in each of the multiple rows of the herringbone corrugation, two adjacent grooves in the direction in which each row extends are arranged at a pitch of 6 mm or more.

5. A plate heat exchanger according to any one of claims 1 to 3, wherein two adjacent rows of the herringbone corrugations are arranged at a pitch of 40 mm or less in the parallel direction.

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