Abstract
A multilayer heat exchanger device comprising: a stack of plates arranged to provide multiple fluid flow paths separated by the plates; wherein at least some of the plates are pin fin plates that each have an array of pins extending outwards from the pin fin plate into the fluid flow paths; and wherein each pin comprises an inner end integrally formed with the pin fin plate, a mid-point along a longitudinal axis of the pin, and an outer end to be bonded to an adjacent plate; wherein the cross sectional area of the pin at the outer end is larger than the cross sectional area at the mid-point.
Claims
1. A multilayer heat exchanger device comprising: a stack of plates arranged to provide multiple fluid flow paths separated by the plates; wherein at least some of the plates are pin fin plates that each have an array of pins extending outwards from the pin fin plate into the fluid flow paths; and wherein each pin comprises an inner end integrally formed with the pin fin plate, a mid-point along a longitudinal axis of the pin, an outer end to be bonded to an adjacent plate; wherein the cross sectional area of the pin at the outer end is larger than the cross sectional area at the mid-point; and wherein the cross sectional area of the outer end is equal to the cross sectional area of the inner end.
2. The multilayer heat exchanger device as claimed in claim 1, wherein the array of pins is distributed across the body of the plate in a grid pattern.
3. The multilayer heat exchanger device as claimed in claim 2, wherein the array of pins have the same distribution across the body of each plate within the stack of plates.
4. The multilayer heat exchanger device as claimed in claim 1, wherein the pins have a circular cross section.
5. The multilayer heat exchanger device as claimed in claim 1, wherein the cross sectional area of the outer end is larger than the cross sectional area of the inner end.
6. The multilayer heat exchanger device as claimed in claim 1, wherein any change in cross sectional area is linear along the longitudinal axis of the pin.
7. The multilayer heat exchanger device as claimed in claim 1, wherein any change in cross sectional area is exponential along the longitudinal axis of the pin.
8. The multilayer heat exchanger device as claimed in claim 1, wherein the outer ends of the pins are bonded to the adjacent plate by brazing.
9. The multilayer heat exchanger device as claimed in claim 1, wherein the pins have a width in the range 0.5 to 5 mm.
10. The multilayer heat exchanger device as claimed in claim 1, wherein a spacing between the pins is similar to the width of the pins.
11. The multilayer heat exchanger device as claimed in claim 1, wherein a spacing between the pins is between 1 and 2 times a width of the pins.
12. The multilayer heat exchanger device as claimed in claim 1, wherein a spacing between the pins is up to 5 times a width of the pins.
13. The multilayer heat exchanger device as claimed in claim 1, wherein the increase in cross sectional area from the minimum point to the outer end is between 5% and 50%.
14. The multilayer heat exchanger device as claimed in claim 13, wherein the increase in cross sectional area from the minimum point to the outer end is between 20% and 30%.
15. The multilayer heat exchanger device as claimed in claim 1, wherein the pin geometry varies across each plate within the stack of plates.
16. The multilayer heat exchanger device as claimed in claim 1, wherein the pin geometry is the same across each plate within the stack of plates.
17. The multilayer heat exchanger as claimed in claim 16, wherein the pin geometry varies between each plate within the stack of plates.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Preferred embodiments of the invention are described below by way of example only and with reference to the accompanying drawings.
[0037] FIG. 1 is a cross section view showing a first pin geometry;
[0038] FIG. 2 is a cross section view showing another pin geometry;
[0039] FIG. 3 is a cross section view showing another pin geometry;
[0040] FIG. 4 is a cross section view showing another pin geometry;
[0041] FIG. 5 is a cross section view showing another pin geometry;
[0042] FIG. 6 is a cross section view showing another pin geometry;
[0043] FIG. 7 is a cross section view showing another pin geometry;
[0044] FIGS. 8a and 8b show examples of a typical stack of heat exchange plates separated by pin fins, for example using pin fin plates with pins according to any FIGS. 1 to 7; and
[0045] FIG. 9 shows a typical pin fin being manufactured using machining techniques.
DETAILED DESCRIPTION
[0046] The proposed heat exchanger device can be considered an improvement over known pin fin designed due to the geometry of the pins that are used with pin fin plates. FIG. 1 illustrates one proposed geometry for the pins to be formed integrally with the pin fin plates. These pin fin plates (and likewise pin fin plates with pins as shown in any of FIGS. 2 to 7) could be used in a heat exchanger with a stack of heat exchange plates as described below with reference to FIG. 8. In FIG. 1 the pin fin plate 1 is one of a plurality of plate surfaces within a stack of plates forming the heat exchanger. The pin 6 is integrally mounted to the plate 1 at the inner end of the pin fin. The pin 6 extends from the plate along a longitudinal axis 7. The pin 6 comprises two main sections, a first section 3 extends from the plate with a constant cross section. A second section 4, positioned further from the pin fin plate 1 than the first section 3 along the longitudinal axis 7, extends from the pin fin plate 1 with a linearly increasing cross section, such that the side walls of the pin are diverging, until an outer end 5 is reached, such that the cross section of the outer end 5 is larger than the inner end 2. The cross section of the pin 6 in FIG. 1 is typically circular, therefore the first section 3 is cylindrical and the second section 4 is conical in shape.
[0047] The increase in cross section of the pin starts from the mid-point of the pin 6 along the longitudinal axis 7. The skilled person would appreciate that this increase can start from any point along the longitudinal axis.
[0048] The cross section of the outer end 5 is between 5% and 50% larger than the cross section of the inner end of the pin 6. The angle of the linear increase from the cylindrical section to the outer surface is between 5° and 45°. This angle depends on the required cross section of the outer end 2 compared to the inner end 5 and the starting point along the longitudinal axis 7 of the linear increase.
[0049] FIG. 1 shows one of the possible pin geometries. Different pin geometries can be used for other plates or for different parts of the same plate. FIG. 2 shows another possible pin geometry that can be used within the heat exchange device. As with the pin 6 of FIG. 2, the inner end 12 of pin 16, shown by FIG. 2, is integrally formed with the plate 1. In the pin of FIG. 2, the cross sectional area of the inner 12 and outer end 15 are equal. The pin comprises three distinct sections, as opposed to the two in FIG. 1. A first section 11 extends away from the plate 1, along the longitudinal axis 17, with a linearly decreasing cross section, such that the side walls are converging. A second section 13 is positioned further from the plate 1 along the longitudinal axis 17, and extends from the end of the first section 11. Second section 13 extends from the end of first section 11 with a constant cross sectional area. A third section 14 extends away from the plate 1 from the end of the second section 13. The cross sectional area of the third section is linearly increasing along the longitudinal axis, such that the side walls are diverging, so that the outer end 15 of the third section 14 has the same cross sectional area of the inner end 12 of the first section 11.
[0050] The cross section of the pin 16 is circular, therefore the first and third sections are conical, and the middle, second, section is cylindrical.
[0051] As with the pin 6 shown in FIG. 1, the maximum cross sectional area of the pin 16 may be between 5% and 50% larger than the minimum cross sectional area. The angle of converging/diverging of the outer/inner ends can be between 5° and 45°, depending on the minimum and maximum cross sectional areas required. Typically the angles of convergence and divergence off the first and third sections are equal, however, depending on the geometry required these angles can be different. Similar ranges of dimensions as the pin of FIG. 1 are applicable.
[0052] FIGS. 3 and 4 show other possible pin geometries 26, 36. As with the pin geometry of FIG. 2, the inner end 22, 32 and outer end 25, 35 have equal cross sectional areas. The pins 26, 36 comprise four distinct sections. A first section 21, 31, extends from the plate 1 along the longitudinal axis 27, 37, with a linearly decreasing cross sectional area, such that the side walls of the first section 21 are converging. The second section 28, 38 extends from the end of the first section 21, 31, away from the plate 1. The cross sectional area of the second section 28, 38 is exponentially decreasing along the longitudinal axis 27, 37 in a direction away from the plate 1. The angle of the side walls of section 28, 38 to the longitudinal axis is decreasing such that the angle gradually changes from the angle of the linear decrease of the first section 21, 31, until the side wall 28, 38 is almost parallel to the longitudinal axis 27, 37. The third section 23, 33 extends from the end of the second section 28, 38, with a constant cross sectional area, such as the side walls of the third section 23 are parallel to the longitudinal axis 27, 37. The fourth section 29, 39 extends from the end of the third section 23, 33, away from the plate 1. The cross sectional area of the fourth section 29, 39 is exponentially increasing along the longitudinal axis in a direction away from the plate 1. A fifth section 24, 34, extends from the end of the fourth section 29, 39 in a direction away from the plate 1. The cross sectional area of the fifth section is linearly increasing along the longitudinal axis in a direction away from the plate 1, such that the fifth section 24, 34 is diverging. The divergence continues to the outer end 25, 35 of the pin 26, 36, such that the cross sectional area of the outer end 25, 35 is approximately equal to the cross sectional area of the inner end 22, 32. The angle of the side walls of section 29, 39 to the longitudinal axis changes from approximately parallel to the longitudinal axis to the angle of the divergence of the fifth section 24, 34.
[0053] The relative proportions of the first to fifth sections for the pins shown in FIGS. 3 and 4 can vary. For example in FIG. 3, the length of first and fifth sections along the longitudinal axis 27, 37 are each approximately 30% of the distance between the inner and outer end, while in FIG. 4 they are each approximately 15% of the distance between the inner and outer end. The second and fourth sections in FIG. 3 are each approximately 10% of the distance between the inner and outer ends. In FIG. 4, the second and fourth sections are each approximately 30% of the distance between the inner and outer ends. The third section in the pin geometry 26 shown in FIG. 3 is 30% of the distance between the inner and outer end of the pin, whereas in FIG. 4 the third section is 10% of the distance between the inner and outer end. It will appreciate that the proportions of each of the five sections can vary, as demonstrated by the pins shown in FIGS. 3 and 4. Typically the proportions of the first and fifth sections will be equal, and so will the proportions of the second and third sections. However, depending on the structural or flow requirements they can differ. In some cases the proportion of the third section can be zero, so that the side wall of the pin forms complete parabolic curve between the inner and outer end of the pins with no distinct section where the side wall is parallel to the longitudinal axis.
[0054] FIGS. 5 and 6 show other alternative pin geometries. In the figures the inner end 42, 52 has a smaller cross sectional area than the outer end 45, 55 and the pins are made of three distinct sections. A first section 41, 51 extends from the inner end 42, 52 of the pin 46, 56 along the longitudinal axis 47, 57 in a direction away from plate 1. The cross sectional area of the first section 41, 51 decreases exponentially, such that the side wall of the first section is converging. A second section 53, 43 extends from the end of the first section 42, 52 along the longitudinal axis 47, 57 in the direction away from the plate 1. The second section 43, 53 extends in the direction of the longitudinal axis with a constant cross sectional area. A third section 44, 54 extends from the end of the second section along the longitudinal axis 47, 57 in a direction away from the plate 1. The third section 44, 54 extends from the end of the second section to outer end 45, 55 of the pin 46, 56. The cross sectional area of the third section 44, 54 increases exponentially, such that the side wall of the third section 44, 54 is diverging. The divergence of the third section 44, 54 is greater in magnitude than the convergence of the first section 41, 51 such that the cross sectional area of the outer end 45, 55 is larger than the inner end 42, 52.
[0055] As with the pins shown in FIGS. 3 and 4, the size of the three sections as a proportion of the total height of the pin can vary. As an example the first section in FIGS. 5 and 6 are approximately 15% of the distance between the inner and outer end of the pin. In FIG. 5, the second section is approximately 45% of the total distance between the inner and outer end of the pin, while in FIG. 6, the second section is approximately 5% of the total distance between the inner and outer end of the pin. In FIG. 5, the third section is approximately 40% of the total distance between the inner and outer end of the pin, while in FIG. 6, the third section is approximately 80% of the total distance between the inner and outer end of the pin. In some cases the proportion of the third section can be zero, so that the side wall of the pin forms complete parabolic curve between the inner and outer end of the pins with no distinct section where the side wall is parallel to the longitudinal axis.
[0056] Another possible geometry is shown in FIG. 7. The pin 66 comprises two distinct sections. As in the pins shown by FIGS. 5 and 6, the first section extends from the inner end 62 of the pin along the longitudinal axis 67, in the direction away from the plate 1. The cross sectional area of the first section is exponentially decreasing similar to the first section of the pins shown in FIGS. 5 and 6. The side wall of the first section 61 converges until it is approximately parallel to the longitudinal axis 67. The second section 64 extends from the end of the first section 61 to out end 65 of the pin. The cross sectional area of the second section 64 linearly increases, such that the side walls are diverging and such that the cross sectional area of the outer end 65 is greater than the inner end 62. As is the case with the other possible pin geometries the relative proportions of each section may differ. As an example, in FIG. 7, the first section is 20% the total distance between the inner and outer end, and the second section is approximately 80% of the total distance between the inner and outer ends of the pin 66. The area of the outer end may be between 5% and 50% larger than the minimum cross sectional area of the pin 66. The angle of the linear increase of the cross sectional area of the second section 64 may be between 5° and 45° depending on the required area of the outer end 65 and the minimum cross sectional area of the pin 66.
[0057] FIGS. 8A and 8B show a stack of heat exchange plates 100. Each plate 102 is separated by an array of pins 104. The geometry of the pin can be according to any of the possibilities shown in FIGS. 2 to 7, or variations thereof depending on the requirement of the fluid used in each flow paths, or the structural requirements. As will be appreciated from FIG. 8A, the spacing between each plate is determined by the height of the pins. In most cases the each pin attached to one plate will have same plate, however to accommodate for the possibility of curved plates the pins within a certain plate may differ in height.
[0058] FIGS. 8A and 8B also show an even spacing of pins throughout the heat exchange device. It is possible to use different types of fluid in each layer of the heat exchanger, which may have different fluid characteristics and will therefore require different flow paths. Therefore, it may be necessary for the spacing between pins to be different for each plate depending on the fluid used.
[0059] FIG. 8B shows the pins arranged in a diamond pattern, however they can also be arranged in a square pattern or alternatively the pins can be arranged in an irregular pattern. It is also possible for the pin on each plate within a stack of plates to be arranged with a different pattern as each fluid type will be better suited to a particular arrangement of pins.
[0060] In the stack of plates the inner end of each pin 104 is integrally formed as part of the plate and the outer end of each pin is free. When assembled as a stack the outer end is joined to the bottom surface of the adjacent plate by brazing. The larger area of the free end provides a stronger braze joint.
[0061] FIG. 9 shows a typical tool used for manufacturing the pin fin plate for use in a heat exchanger by subtractive manufacturing. The tool is required to match with the outer surface of the pin, and therefore to manufacture the different pin geometries shown in FIGS. 1 to 7, then a different tool is required in each case.
[0062] As an alternative the pin fin plate can be produced using additive manufacturing. This method allows for different pin geometries to be manufactured without the need for redesigning the tools. In additional additive manufacturing may be capable more rapidly producing the pin fin plates, especially where there are complex geometries or if there is a requirement for varying geometry, size or spacing for different plates.
