DIMPLE CHILLER WITH SECONDARY DIMPLES

Abstract

A heat exchanger with at least one plate includes main dimples between which secondary dimples are formed which are flatter and/or smaller with respect to their dimensions as seen in a plan view. A depth of the secondary dimples may be at most 0.5 times a channel height and/or at most 0.5 times the depth of the main dimples.

Description

TECHNICAL FIELD

Dimple plates in heat exchanger (HEX) applications often suffer from low specific heat exchange rates due to low velocities of the heat-exchanging fluids.

PRIOR ART

One known solution is the increase of dimple size to increase local velocities and change the flow directions in the fluid.

However, an increase of dimple size directly leads to a reduced surface for the heat exchange and to an increase of pressure drop in the channel. Therefore, a solution must be found to increase heat exchange rates with a minimal increase in pressure drop in the fluid at an accelerated rate and taking away from the surface of heat exchange.

DESCRIPTION OF THE INVENTION

The above problem is solved by the subject matter as shown and described herein.

The invention can be regarded as being a plate of a heat exchanger or a heat exchanger having at least one plate which is preferably rectangular and comprises main dimples, between which secondary dimples are formed that are flatter and/or smaller with respect to their dimensions as seen in a plan view.

The plate thus has main dimples, depressions, bumps and/or protrusions or bulges which are preferably arranged in rows preferably extending obliquely to the edges of the preferably rectangular plate. According to the invention, secondary dimples are formed between the main dimples, which can alternatively be designated as the main dimples as above. The rows are thereby seen in those directions in which the dimples are lined up one behind the other with minimal spacing. These rows can extend at any angle to the edges, as well as perpendicular to the one edges and therefore parallel to the other edges.

As a result of the secondary dimples, the present invention leads to increased heat exchange rates in a dimple heat exchanger, in particular a cooler plate, while the active surface for heat exchange is not reduced. In fact, the surface of heat exchange is increased without changing the use of material. In addition, the velocities of the fluids around the secondary dimples are increased, which results in an increased heat exchange. The invention further leads to a change in flow directions not only in the horizontal plane, but also perpendicular thereto, thus leading to a mixing of temperature layers in the channels between the dimple heat exchanger plates.

Preferred further developments are described herein.

The depth of the secondary dimples is set to a maximum of 0.5 times the channel height and/or 0.5 times the depth of the main dimples. The depth of the main dimples can be set to a maximum corresponding to the channel height.

The distance between the main and secondary dimples in an x direction (a first diagonal direction) can be varied between 1.9 and 2.5 mm and in they direction (a second diagonal direction) between 1.9 and 2.5 mm.

In each case one secondary dimple can be formed between two main dimples. Preferably at least one, preferably precisely one, secondary dimple is formed in each case on the entire plate between two main dimples, or several, preferably four, and preferably spaced apart by 90 degrees, secondary dimples are formed in the vicinity of each main dimple.

At least some, preferably all, of the secondary dimples can be arranged on the lines or rows that are described by the main dimples.

The main dimples are preferably arranged in rows which preferably extend obliquely to the edges of the preferably rectangular plate. The rows are designated above as diagonals; however, they do not have to correspond to the diagonals of the rectangular plate, but can extend at an angle thereto. The rows can be formed in two directions extending at an angle to each other, wherein the angle can be equal or not equal to 90 degrees. For all of the above-mentioned embodiments, favorable properties could be determined in initial tests and simulations.

The sheet thickness of the plate can thereby be less in the area of the main and/or secondary dimples than between the dimples.

The main and/or secondary dimples can be circular, elliptical, or oval in plan view. The main axes of elliptical or oval main dimples can extend parallel to a plate edge, in particular parallel to the longer edge of a rectangular plate. The main axes of elliptical or oval secondary dimples can extend at an angle to the plate edges of a rectangular plate. The main axes of several elliptical or oval secondary dimples can extend parallel to each other and at an angle to the main axes of several other secondary dimples.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention can be seen from the drawings.

FIG. 1 shows a plan view of a plate of a conventional heat exchanger with dimples.

FIG. 2 shows a plate similar to that of FIG. 1, which additionally comprises the secondary dimples according to the invention.

FIG. 3 is a graph showing the increase in performance of a heat exchanger with the plates of FIG. 2 compared to the heat exchanger with the plates of FIG. 1.

FIGS. 4 and 5 show plates similar to those of FIGS. 1, 2, 4 and 5 including their dimensions.

FIG. 6 shows the plate of FIG. 8 including one detail and preferred sizes of the dimples.

FIG. 7 shows further experimental results indicating an increase in performance of the new type of plate by between 6.2 and 10.2%, without changing neither the size of the plate nor the amount of material used, although the secondary dimples are formed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

As can be seen in FIG. 1, a plate 100 of a heat exchanger comprises numerous dimples which in this case, in plan view, are oval dimples 102 that are arranged on lines extending obliquely to the plate edges, which do not quite correspond to the diagonals of the rectangle forming the plate shape. In particular, two groups of rows can be seen, one extending from bottom left to top right and the other from bottom right to top left, and which in the case shown intersect at an angle smaller than 90 degrees.

In the plate 10 of a heat exchanger according to the invention according to FIG. 2, the arrangement of the main dimples 12 substantially corresponds to that of the (only present) dimples 102 as shown in FIG. 1.

According to the invention, one secondary dimple 14 is formed in each case between every two main dimples 12, which in this case in plan view is both smaller and, not visible in plan view, flatter. In particular, precisely one secondary dimple 14 is formed in each case between two main dimples 12, and therefore four secondary dimples are formed in the vicinity of every main dimple. As is also preferred, the secondary dimples are located on those lines or rows that are described by the main dimples. In the case shown, the main dimples 12 are oval when viewed from the top, with their longer axis extending parallel to the longer edge of the rectangular plate 10, and the secondary dimples are circular when viewed from the top.

As is revealed in FIG. 3, which shows a performance comparison of the plates from FIGS. 1 and 2 in a two-sided heated wall, there appears an increase in performance from 2.0 to nearly 5% depending on the coolant flow.

FIG. 4 shows a further plate 100 comprising only a single type of dimple 102.

In contrast, a plate 10 according to the invention according to FIG. 5 is provided with both main dimples 12 and secondary dimples 14. Unlike the plates of FIGS. 1, 2, and 4, the main dimples 12 and the secondary dimples 14 are also arranged in intersecting rows in this embodiment, which also in this case do not correspond to the diagonals of the rectangular plate. However, they are arranged at an angle of 90 degrees to each other in this embodiment. Moreover, in this case, both the main dimples 12 and the secondary dimples 14 are circular in plan view. The plates of FIGS. 4 and 5 can typically be between 60 mm and 100 mm wide and between 80 mm and 140 mm long. According to an exemplary embodiment, they are each 64 mm wide and 102 mm long.

The shape and alignment of the main dimples 12 and the secondary dimples 14 can be seen more clearly in the detailed view of FIG. 6. In particular, four secondary dimples 14 are arranged here around one main dimple 12 at a constant spacing of 90 degrees. The main dimples of the plate of FIG. 6 can have a diameter of 4.1 mm and a depth of 1.2 mm. 67 dimples of this type can be present on the plate shown in FIG. 6. The secondary dimples can have a diameter of 1.9 mm and a depth of 0.6 mm, and 140 dimples of this type can be formed on the plate shown in FIG. 9.

As is apparent from FIG. 7, there is an increase in performance, depending on the coolant flow, between 6.2 and 10.2%.

Claims

1.-10. (canceled)

11. A heat exchanger with at least one plate having main dimples, between which secondary dimples are formed which are flatter and/or smaller with respect to their dimensions as seen in a plan view.

12. The heat exchanger according to claim 11, wherein a depth of the secondary dimples is at most 0.5 times a channel height and/or at most 0.5 times a depth of the main dimples.

13. The heat exchanger according to claim 11, wherein a distance between the main dimples and the secondary dimples in at least one direction is 1.9 to 2.5 mm.

14. The heat exchanger according to claim 11, wherein one of the secondary dimples is formed in each case between two of the main dimples.

15. The heat exchanger according to claim 11, wherein the main dimples are arranged in rows, and the secondary dimples are arranged on the rows of main dimples.

16. The heat exchanger according to claim 15, wherein the rows of the main dimples are formed obliquely to at least one edge of the at least one plate.

17. The heat exchanger according to claim 11, wherein a sheet thickness of the at least one plate in an area of the main dimples and/or the secondary dimples is less than between the dimples.

18. The heat exchanger according to claim 11, wherein the main dimples and/or the secondary dimples have a circular, an elliptical, or an oval shape in plan view.

19. The heat exchanger according to claim 18, wherein a main axis of the main dimples having the elliptical or the oval shape are parallel to an edge of the at least one plate, in particular a longer edge of a rectangular plate.

20. The heat exchanger according to claim 18, wherein a main axis of the secondary dimples having the elliptical or the oval shape extend at an angle with respect to edges of a rectangular plate.