JP2006153290A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger free of the degradation of heat exchanging efficiency while improving the rigidity of a fin. <P>SOLUTION: On the fin 6, a rib 15 is formed extending approximately parallel to an outer edge 25 of the fin 6 and insertion holes 22 are arranged in zigzag for heat transfer tubes to be inserted therethrough. The insertion hole 22 and the rib 15 are formed to satisfy 0.4<La<(L-D/2-0.5), 0.15<LL1<0.5, 0.05<t<0.15, 0.5t<h1<2.5t, D<7.5, 15<P, and D/P<0.5, where D (mm) is the inner diameter of the insertion hole 22, L (mm) is a distance between the center of the insertion hole 22 and the outer edge 25, La (mm) is a distance between the center of the rib 15 and the outer edge 25, LL1 (mm) is the width of the rib 15, t (mm) is the plate thickness of the fin 6, h1 (mm) is the height of the rib 15, and P (mm) is the minimum value for a distance between the insertion holes 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat exchanger, and more particularly to a heat exchanger suitable for use in an air conditioner.

  Conventional heat exchangers include those described in JP-A-2-309195 (Patent Document 1).

  This heat exchanger includes fins and pipes. The fin is made of a rectangular flat plate. A plurality of the fins are arranged at intervals. The fin is formed with a plurality of insertion holes for inserting pipes. The plurality of insertion holes are staggered on the fins. Further, a plurality of substantially linear protrusions are formed between the insertion holes in the fins arranged in a staggered manner. The plurality of protrusions are substantially parallel to each other. The said protrusion is extended in the direction different from the longitudinal direction of a fin.

  The pipe is arranged to be orthogonal to each fin. Specifically, the pipe is inserted into the insertion hole of the fin and extends in the normal direction of the surface of the fin.

  The conventional heat exchanger is formed in the vicinity of the fin insertion hole when a pipe is inserted into the insertion hole by increasing the rigidity of the fin by forming a protrusion between the insertion holes in the fin. Etc. are prevented from being deformed.

  However, in the conventional heat exchanger, since the protrusions extend in a direction different from the longitudinal direction of the fins, longitudinal reinforcement that has the greatest influence on the strength of the fins cannot be sufficiently performed, There is a problem that fins cannot be reinforced efficiently.

  In addition, in the above conventional heat exchanger, even if the protrusion is formed when the diameter of the insertion hole is large, the minimum value between adjacent insertion holes is small, or the width of the fin is narrow, There is a problem that the rigidity cannot be increased.

Further, in the conventional heat exchanger, when the height of the protrusion provided on the fin is high, the flow of the wind flowing outside the pipe is hindered, and the heat exchange efficiency of the heat exchanger is reduced. is there.
JP-A-2-309195

  Then, the subject of this invention is providing the heat exchanger which can enlarge the rigidity of a fin and does not reduce the heat exchange efficiency of a heat exchanger.

In order to solve the above problems, the heat exchanger of the present invention is
A plurality of heat transfer tubes;
A plate-like fin having a first rib substantially parallel to the outer edge and having an insertion hole for inserting the plurality of heat transfer tubes,
The first rib is disposed on the outer edge side from all the insertion holes,
The insertion holes are arranged in a row or staggered in the fins,
The inner diameter of the insertion hole is D [mm], the distance between the center of the insertion hole closest to the first rib and the outer edge is L [mm], and the center of the first rib and the outer edge The distance is La [mm], the width of the first rib is LL1 [mm], the plate thickness of the fin is t [mm], and the height of the first rib is h1 [mm], which are adjacent to each other. When the minimum value of the distance between the insertion holes is P [mm],
0.4 <La <(LD / 2-0.5),
0.15 <LL1 <0.5,
0.05 <t <0.15,
0.5t <h1 <2.5t,
D <7.5,
15 <P,
And D / P <0.5.

  The center of the rib is the center in the width direction of the rib.

  According to the present invention, since the first rib is formed so as to extend substantially parallel to the outer edge of the fin, the strength of the fin can be effectively increased.

  Further, according to the present invention, the insertion holes for inserting the heat transfer tubes are arranged in a row or staggered in the fins, so that more heat transfer tubes are arranged without reducing the strength of the fins. it can.

  Further, according to the present invention, since 0.4 <La, the center of the rib does not come too close to the outer edge of the fin, and the edge of the fin and the rib do not deform. Further, since La <(LD−2-0.5), the center of the rib does not come too close to the insertion hole, and the rib does not deform.

  Further, according to the present invention, 0.15 <LL1, 0.05 <t, 0.5t <h1, D <7.5, 15 <P, and D / P <0.5, which is equal to or greater than a predetermined value. Since the rib having a predetermined size or more is formed on the fin having the above strength, the fin having the predetermined strength or more can be reliably reinforced with the rib having a high reinforcing effect. Therefore, the strength of the fin can be made without any problem, and the bending of the fin during the stacking of the fin and the collapse of the fin can be surely prevented.

  Further, according to the present invention, since LL1 <0.5 and h1 <2.5t, the rib does not become excessively large, and the rib does not become the resistance of the heat transfer medium. No turbulence or the like occurs in the flow of the heat transfer medium. Therefore, the flow of the heat transfer medium can be made smooth, and a decrease in heat exchange efficiency with respect to a change in the flow of the heat transfer medium due to the formation of the rib can be reliably prevented.

  Further, according to the present invention, since t <0.15, the fin thickness does not become excessively large. Therefore, the integration property of the fin arrangement direction can be increased, the heat exchange efficiency can be improved, and the manufacturing cost of the fin can be reduced.

  Further, in the heat exchanger according to an embodiment, the insertion holes are staggered in the fins, and one of the arrangement directions of the insertion holes is substantially parallel to the outer edge, and the outer edge in the fin A second rib extending substantially parallel to the outer edge is formed between the insertion holes adjacent to each other in a direction substantially perpendicular to the direction in which the second rib extends, and the width of the second rib is LL2 [mm. When the height of the second rib is h2 [mm], 0.15 <LL2 <0.5 and 0.5t <h2 <2.5t.

  According to the embodiment, since the second rib is formed between the insertion holes adjacent to each other in the substantially vertical direction in the fin, the strength near the center of the fin can be increased. The strength of can be further increased.

  Further, according to the above embodiment, since 0.15 <LL2 <0.5 and 0.5t <h2 <2.5t, the fins can be reliably reinforced and the flow of the heat transfer medium can be reduced. It can be smooth.

  According to the heat exchanger of the present invention, since the first rib is formed so as to extend along the outer edge of the fin, the strength of the fin can be effectively increased.

  Further, according to the heat exchanger of the present invention, a plurality of heat transfer tubes are arranged in a row or staggered on the fins, so that more heat transfer tubes can be arranged without reducing the strength of the fins. .

  Further, according to the heat exchanger of the present invention, 0.4 <La <(LD−2-0.5), 0.15 <LL1, 0.05 <t, 0.5t <h1, D < Since 7.5, 15 <P, and D / P <0.5, the fin having a predetermined strength or more can be reliably reinforced with a rib having a high reinforcing effect. Therefore, the strength of the fins can be made without any problem, and the bending of the fins in the middle of stacking the fins and the collapse of the fins can be surely prevented.

  Further, according to the heat exchanger of the present invention, since LL1 <0.5 and h1 <2.5t, the rib does not become the resistance of the heat transfer medium, and the flow of the heat transfer medium is smooth. Can be. Therefore, it is possible to reliably prevent a decrease in heat exchange efficiency due to a change in the flow of the heat transfer medium.

  Further, according to the heat exchanger of the present invention, since t <0.15, the integration property of the fin arrangement direction can be increased, and the heat exchange efficiency can be improved.

  Moreover, according to the heat exchanger of one embodiment, since the second rib is formed between the rows of adjacent insertion holes in the fin, the strength near the center of the fin can be increased, The strength of the fin can be further increased.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of an air conditioner using a heat exchanger according to a first embodiment of the present invention. In FIG. 1, 1 is a ventilation fan and 2 is a heat exchanger. Moreover, in FIG. 1, the arrow a shows the vertical direction upper direction in the state arrange | positioned in the air conditioner of a use state, and the arrow b shows the direction of the flow of the wind as a heat transfer medium. Yes. In FIG. 1, the case etc. which accommodate the ventilation fan 1 and the heat exchanger 2 are abbreviate | omitted for simplicity.

  In this air conditioner, the blower fan 1 is rotated so that the air sucked through the heat exchanger 2 is blown out from a blowout port (not shown).

  The heat exchanger 2 includes fins 6 and heat transfer tubes (not shown). A plurality of the fins 6 are arranged at predetermined intervals in a direction perpendicular to the paper surface in FIG. The fin 6 has a flat plate shape. The fin 6 has a cross-sectional shape that is bent in a dogleg shape so that the upper part in the vertical direction indicated by the arrow a in FIG.

  The fin 6 has an outer edge that is inclined with respect to the vertical direction, and a first portion 8 and a second portion 9 that form the bent portion, and a second portion 9 that is continuous below the second portion 9 in the vertical direction. 3 parts 10. As shown in FIG. 1, the first portion 8 is located downstream of the second portion 9 in the wind flow. The third portion 10 extends in a substantially vertical direction. The first portion 8, the second portion 9, and the third portion 10 have a substantially elongated rectangular cross-sectional shape.

  A first rib 15 extending substantially parallel to the longitudinal direction of the second portion 9 is formed at the edge of the second portion 9 on the leeward side in the longitudinal direction. Thus, in 1st Embodiment, the fin 6 has a rectangular part, and the 1st rib 15 is extended substantially parallel to the outer edge of the longitudinal direction of this rectangular part.

  A plurality of the heat transfer tubes are arranged. Each heat transfer tube extends in the direction in which the fins 6 are arranged, that is, in a substantially normal direction of the surface of the plate-like fins 5 (direction perpendicular to the paper surface of FIG. 1). The heat transfer tube is inserted through a plurality of fins 6 arranged at predetermined intervals. As shown in FIG. 1, the heat transfer tubes are staggered in two rows in each of the first portion 8, the second portion 9, and the third portion 10.

  Specifically, in the first portion 8, the insertion holes are arranged in two rows in the width direction and 16 rows in the longitudinal direction, and in the second portion 9, two rows in the width direction and 12 rows in the longitudinal direction. Has been placed. The insertion holes are arranged in the third portion 10 in two rows in the width direction and eight rows in the longitudinal direction.

  Each row in the row of the insertion holes arranged in two rows in the width direction of the first portion 8 is substantially parallel to the outer edge in the longitudinal direction of the first portion 8, and in the width direction of the second portion 9. Each row in the row of insertion holes arranged in two rows is substantially parallel to the outer edge in the longitudinal direction of the second portion 9. In addition, each row in the row of insertion holes arranged in two rows in the width direction of the third portion 10 is substantially parallel to the outer edge in the longitudinal direction of the third portion 10.

  A fluid is circulated inside the heat transfer tube. This heat exchanger performs heat exchange between a fluid that is allowed to flow through the heat transfer tube and a wind that is allowed to flow outside the heat transfer tube.

  FIG. 2 shows the second portion 9 of the fin 6 in detail. Specifically, FIG. 2A is a partial enlarged view of the second portion 9 of the fin 6. FIG. 2B is a part of the αα line cross-sectional view of FIG.

  2A and 2B, reference numeral 15 denotes a first rib, and reference numeral 22 denotes an insertion hole for insertion of a heat transfer tube formed in the fin 6. In FIG. 2A, an arrow b indicates the wind flow. In FIG. 2A, for the sake of simplicity, only the inner diameter of the insertion hole 22 is shown, and the detailed opening shape of the insertion hole is omitted.

  The rib 15 extends substantially parallel to the outer edge 25 of the plate-like fin 6. Moreover, the said plate-shaped fin 6 has the penetration hole 22 which penetrates a some heat exchanger tube. The ribs 15 are arranged on the outer edge 25 side with respect to all the insertion holes 22.

In the first embodiment, as shown in FIGS. 2A and 2B, the inner diameter of the insertion hole 22 is D [mm], and the distance between the center of the insertion hole 22 closest to the rib 15 and the outer edge 25. Is L [mm], and the distance between the center of the rib 15 and the outer edge 25 is La [mm], La is designed to satisfy the following expression (1).
0.4 <La <(LD / 2-0.5) (1)

As shown in FIG. 2A, when the minimum value of the distance between the adjacent insertion holes 22 is P [mm], the insertion hole 22 has the following expressions (2) to (4). It is formed to satisfy.
D <7.5 (2)
15 <P (3)
D / P <0.5 (4)

2B, the width of the first rib 15 is LL1 [mm], the plate thickness of the fin 6 is t [mm], and the height of the first rib 15 is h1 [mm]. , The fin 6 and the first rib 15 are set so as to satisfy the following expressions (5) to (7).
0.15 <LL1 <0.5 (5)
0.05 <t <0.15 (6)
0.5t <h1 <2.5t (7)

  According to the heat exchanger of the first embodiment, the first rib 15 is formed so as to extend along the outer edge 25 of the fin 6 (substantially parallel to the outer edge 25 of the fin 6). Can be effectively increased.

  Moreover, according to the heat exchanger of the said 1st Embodiment, since the several heat exchanger tube is arrange | positioned in the fin 6 at zigzag, more heat exchanger tubes can be arrange | positioned, without reducing the intensity | strength of the fin 6. FIG.

  Further, according to the heat exchanger of the first embodiment, since 0.4 <La, the center of the first rib 15 does not come too close to the outer edge of the fin 6, and the edge of the fin 6 or The first rib 15 is not deformed. Further, since La <(LD / 2−0.5), the center of the first rib 2 does not come too close to the insertion hole 22 and the first rib 15 is not deformed.

  Further, according to the heat exchanger of the first embodiment, 0.15 <LL1, 0.05 <t, 0.5t <h1, D <7.5, 15 <P, and D / P <0. Since the first rib 15 having a size greater than or equal to the predetermined size is formed on the fin 6 having a strength greater than or equal to a predetermined value, the first rib having a higher reinforcing effect is provided on the fin 6 having the strength greater than or equal to the predetermined value. 15 can be reinforced reliably. Therefore, the strength of the fins 6 can be made without any problem, and fin bending or fin collapse during the stacking of the fins 6 can be reliably prevented.

  Further, according to the heat exchanger of the first embodiment, since LL1 <0.5 and h1 <2.5t, the first rib 15 is not excessively large, and the first rib 15 is There is no wind resistance, and no turbulence occurs in the wind flow. Therefore, the flow of wind can be made smooth, and a decrease in heat exchange efficiency with respect to changes in the flow of wind due to the formation of the first ribs 15 can be reliably prevented.

  Further, according to the heat exchanger of the first embodiment, since t <0.15, the thickness of the fin 6 is not excessively large, and the integration property in the arrangement direction of the fin 6 can be increased. The heat exchange efficiency can be made excellent.

  In the heat exchanger of the first embodiment, as shown in FIG. 2 (B), one of the plate-like fins 6 is formed so that the first rib 15 satisfies the expressions (1) to (7). In the present invention, a plurality of first ribs satisfying the above expressions (1) to (7) are formed so as to protrude from one surface of the plate-like fin. Also good. Further, the plurality of first ribs satisfying the above expressions (1) to (7) are projected from both surfaces of the plate-like fins (for example, the surface 27 and the surface 28 in FIG. 2B). It may be formed.

  Moreover, in the heat exchanger of the said 1st Embodiment, the one 1st rib 15 substantially parallel to the outer edge 25 was formed only in the leeward side of the width direction of the 2nd part 9. FIG. However, in the present invention, a plurality of ribs may be formed so as to satisfy the expressions (1) to (7). For example, not only one or a plurality of first ribs substantially parallel to the outer edge are provided on the leeward side in the width direction of the second part, but also substantially parallel to the outer edge of the first part on the windward side in the width direction of the first part. One or more first ribs are provided, and one or more first ribs substantially parallel to the outer edge of the first portion are provided on the leeward side in the width direction of the first portion, and the leeward side in the width direction of the third portion. In addition, one or more first ribs substantially parallel to the outer edge of the third portion may be provided.

  Further, in the heat exchanger of the first embodiment, the heat transfer tubes are staggered in two rows in the width direction of the second portion 9, and one first rib is formed on the leeward side of the second portion 9. However, in the heat exchanger according to the present invention, the heat transfer tubes are arranged in one row in the width direction on at least a part of the fin, or in a plurality of rows of three or more rows in the width direction, and in the longitudinal direction in at least a part of the fin. One or more first ribs that satisfy the above expressions (1) to (7) may be formed on the edge.

  For example, as shown in FIG. 3A, the holes for inserting heat transfer tubes are arranged in a row in the fin 30 in the width direction, and the longitudinal edge of the fin 30 on the downstream side of the wind flow indicated by the arrow c In addition, one first rib 32 substantially parallel to the outer edge of the edge may be formed. Further, as shown in FIG. 3B, the holes for inserting heat transfer tubes are arranged in a row in the width direction in the fin 40, and the longitudinal edge of the fin 40 on the upstream side of the wind flow indicated by the arrow d In addition, one first rib 42 substantially parallel to the outer edge of the edge may be formed. In addition, as shown in FIG. 3C, the holes for inserting heat transfer tubes are arranged in a row in the fin 50 in the width direction, and the longitudinal direction of the fin 50 on the upstream side and the downstream side of the wind flow indicated by the arrow e Each of the first ribs 52, 53 may be formed on the edge of each of the first ribs 52, 53 substantially parallel to the outer edges of these edges. As shown in FIG. 3 (D), the holes for inserting heat transfer tubes are staggered in two rows in the width direction in the fin 60, and the upstream and downstream sides of the wind flow indicated by the arrow f in the fin 60 Each of the first ribs 62, 63 may be formed on the edge in the longitudinal direction of the first rib 62, 63 substantially parallel to the outer edge of the edge.

  Moreover, in the heat exchanger of the said embodiment, although the 1st rib 15 was formed in the substantially whole edge of the leeward side of the 2nd part 9, in this invention, only a part of edge part of the leeward side of a 2nd part is used. In addition, a first rib substantially parallel to a part of the outer edge of the fin may be provided only on a part of the outer edge of the fin, such as providing a first rib substantially parallel to the outer edge of the part.

  Moreover, in the heat exchanger of the said 1st Embodiment, although the fin 6 consisted of the 1st part 8 and the 2nd part 9 which form a bending part, and the 3rd part 10, in this invention, 1st The fin in which the rib is formed is not limited to the shape of this embodiment, and may be any shape such as a single plate having a flat or arcuate cross-sectional shape.

  Further, in the heat exchanger of the first embodiment, as shown in FIG. 2B, a groove 29 on the trapezoidal cross section is formed on the back side of the portion where the first rib 15 is formed. In this invention, you may form grooves other than the groove | channel on a cross-sectional trapezoid, such as a groove | channel of V-shaped cross section or a U-shaped cross section, in the back side of the part in which the 1st rib is formed. Moreover, it is not necessary to form a groove on the back side of the portion where the first rib is formed.

  Moreover, in the heat exchanger of this invention, you may form a 1st rib in all the some fins. Further, the first rib may be formed on only a part of the plurality of fins, and there may be a fin on which the first rib is not formed.

(Second Embodiment)
FIG. 4 is a partially enlarged view of the second portion 79 of the fin 73 included in the heat exchanger according to the second embodiment. The heat exchanger of the second embodiment is substantially parallel to the first rib 75 between the rows in the width direction of the insertion holes 72 for inserting the heat transfer tubes arranged in a staggered manner in the second portion 79, and The only difference from the heat exchanger of the first embodiment is that a second rib 76 having substantially the same shape as the first rib 75 is formed.

  In the heat exchanger of the second embodiment, the description of the same components as those of the heat exchanger of the first embodiment will be omitted. Moreover, in the heat exchanger of 2nd Embodiment, description is abbreviate | omitted about the effect and modification which are common in the heat exchanger of 1st Embodiment, The structure and effect | action different from the heat exchanger of 1st Embodiment are omitted. Only the effects and modifications will be described.

  As shown in FIG. 4, the insertion holes 72 for inserting the heat transfer tubes are staggered in the second portion 79 of the fins 73 in two rows in the width direction. Each row in the width direction of the insertion holes 72 arranged in a staggered manner is substantially parallel to the outer edge 77 and the first rib 75 in the longitudinal direction of the second portion 79. The second rib 76 is formed between the rows in the width direction of the insertion holes 72 in the second portion 79 in a state substantially parallel to the outer edge 77 and the first rib 75.

  According to the heat exchanger of the second embodiment, since the second ribs 76 are formed between the rows in the width direction of the insertion holes 72 in the second portions 79 of the fins 73, the second portions 79 of the fins 73. The strength near the center of the fin 73 can be increased, and the strength of the fin 73 can be further increased.

  In the heat exchanger of the second embodiment, the insertion holes 72 are staggered in two rows in the width direction of the second portion 79, and one second rib is formed between the rows in the width direction. In the invention, two or more rows of insertion holes for inserting heat transfer tubes are arranged in the width direction of at least a portion of the fin, and two or more second ribs are formed between a row in the width direction and a row adjacent to the row. You may do it. Further, three or more rows of insertion holes for inserting heat transfer tubes may be arranged in the width direction of at least a part of the fin, and one or more second ribs may be arranged between two or more different rows.

  In the heat exchanger of the second embodiment, the second ribs 76 that are substantially parallel to the first ribs 75 and substantially the same shape as the first ribs 75 are formed between the rows of the insertion holes 72. In the invention, between the rows of the insertion holes for inserting the heat transfer tubes, the equations are substantially parallel to the first rib and the above equations (5) and (7) are rewritten (here, the equations (5) and ( 7) is a formula obtained by rewriting the width LL1 [mm] of the first rib 15 to the width LL2 [mm] of the second rib 76 in the above formulas (5) and (7). The second rib may be formed so as to satisfy a formula in which the height h1 [mm] of 15 is rewritten to the height h2 [mm] of the second rib 76).

  In addition, in the said 1st and 2nd embodiment, although the heat exchanger of this invention was applied to the air conditioner, you may apply the heat exchanger of this invention to apparatuses other than an air conditioner, such as a refrigerator. Of course.

It is a schematic sectional drawing of the air conditioner using the heat exchanger of 1st Embodiment of this invention. It is a figure which shows a part of fin which the heat exchanger of 1st Embodiment has in detail. It is a figure which shows the example of the 1st rib formed in the fin. It is the elements on larger scale of the fin of the heat exchanger of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blower 2 Heat exchanger 6,30,40,50,60,73 Fin 15,32,42,52,53,62,63,75 First rib 22,72 Insertion hole 25,77 Outer edge 76 Second rib D The inner diameter of the insertion hole L The distance between the center of the insertion hole closest to the first rib and the outer edge La The distance between the center of the first rib and the outer edge LL1 The width of the first rib LL2 The width of the second rib P The adjacent insertion holes H1 height of the first rib h2 height of the second rib t thickness of the fin

Claims (2)

A plurality of heat transfer tubes;
Plate-like fins (6, 73) having first ribs (15, 75) substantially parallel to the outer edges (25, 77) and having insertion holes (22, 72) for inserting the plurality of heat transfer tubes. Prepared,
The first ribs (15, 75) are arranged closer to the outer edge (25, 77) than all the insertion holes (22, 72),
The insertion holes (22, 72) are arranged in a row or staggered in the fins (6, 73),
The inner diameter of the insertion hole (22, 72) is D [mm], and the center of the insertion hole (22, 72) closest to the first rib (15, 75) and the outer edge (25, 77) The distance is L [mm], the distance between the center of the first rib (15,75) and the outer edge (25,77) is La [mm], and the width of the first rib (15,75) is LL1 [mm], the thickness of the fin (6, 73) is t [mm], the height of the first rib (15, 75) is h1 [mm], and the insertion holes (22 , 72) is the minimum value of P [mm],
0.4 <La <(LD / 2-0.5),
0.15 <LL1 <0.5,
0.05 <t <0.15,
0.5t <h1 <2.5t,
D <7.5,
P> 15,
And D / P <0.5. The heat exchanger according to claim 1,
The insertion hole (72) is staggered in the fin (73),
One of the arrangement directions of the insertion hole (72) is substantially parallel to the outer edge (77),
Between the insertion holes (72) adjacent to each other in a direction substantially perpendicular to the extending direction of the outer edge (77) of the fin (73), a second extending substantially parallel to the outer edge (77). Ribs (76) are formed,
When the width of the second rib (76) is LL2 [mm] and the height of the second rib (76) is h2 [mm],
0.15 <LL2 <0.5,
And a heat exchanger characterized by satisfying 0.5t <h2 <2.5t.

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