阅读说明：本技术 用于旋转热交换器的传热元件 (Heat transfer element for a rotary heat exchanger ) 是由 M·里德 D·霍格 于 2018-06-18 设计创作，主要内容包括：一种用于利用废热对空气进行预热的旋转热交换器,其包括多个传热元件,所述多个传热元件可在壳体中的第一开口与第二开口之间移动,以在加热的废气与新鲜空气流之间交换热量。至少一个传热元件包括第一板,该第一板具有在其中以隔开的间隔相对于流动方向以第一角度定向的多个细长凹口。所述板还包括多个细长起伏部,所述多个细长起伏部在所述板中以隔开的间隔形成并且相对于流动方向定向成第二角度定向,其中,第一角度不同于第二角度。所述多个细长凹口中的每个的第一高度大于所述多个细长起伏部中的每个的第二高度。传热元件可以堆叠在容器中以安装在旋转热交换器中。(A rotary heat exchanger for preheating air using waste heat includes a plurality of heat transfer elements movable between first and second openings in a housing to exchange heat between heated exhaust gas and a fresh air stream. The at least one heat transfer element includes a first plate having a plurality of elongated notches therein oriented at spaced intervals at a first angle relative to the flow direction. The plate also includes a plurality of elongated undulations formed in the plate at spaced intervals and oriented at a second angle relative to the flow direction, wherein the first angle is different than the second angle. The first height of each of the plurality of elongated recesses is greater than the second height of each of the plurality of elongated undulations. The heat transfer elements may be stacked in a container for installation in a rotary heat exchanger.)

1. A heat transfer element for a rotary heat exchanger having a flow direction, the heat transfer element comprising:

a plate having a plurality of elongated notches formed therein at spaced intervals, each of the elongated notches being oriented at a first angle relative to the flow direction and having a first height relative to a surface of the plate;

the plate further having a plurality of elongated undulations formed in the plate at spaced intervals, the elongated undulations each being oriented at a second angle relative to the flow direction and having a second height relative to the surface of the plate;

wherein the first height of each of the plurality of elongated recesses is greater than the second height of each of the plurality of elongated undulations; and is

Wherein the first angle is different from the second angle.

2. The heat transfer element of claim 1, wherein the first angle is in a range of 5 ° to 45 ° relative to the flow direction.

3. The heat transfer element of claim 1, wherein the first angle is 20 ° relative to the flow direction.

4. The heat transfer element according to claim 1, wherein the second angle is in the range of 0 ° to-90 ° with respect to the flow direction.

5. The heat transfer element according to claim 1, wherein the second angle is-30 ° relative to the flow direction.

6. The heat transfer element of claim 1, wherein the second height is 20% to 70% of the first height.

7. The heat transfer element of claim 1, wherein each of the plurality of elongated notches has a first depth relative to the surface of the plate and each of the plurality of undulations has a second depth relative to the surface of the plate, and wherein the second depth is less than the first depth.

8. A heat transfer element container for a rotary heat exchanger having a housing with a first opening in fluid communication with a first air flow and a second opening in fluid communication with a second air flow, the first and second air flows having flow directions, and the heat transfer element container comprising:

a pair of support members defining a space therebetween;

a plurality of heat transfer elements stacked in the space between the pair of support members, wherein at least one of the plurality of heat transfer elements comprises:

a first plate having a plurality of elongated notches formed therein at spaced intervals, the elongated notches each oriented at a first angle relative to the flow direction and having a first height relative to a surface of the first plate;

the first plate further having a plurality of elongated undulations formed therein at spaced intervals, the elongated undulations each being oriented at a second angle relative to the flow direction and having a second height relative to the surface of the first plate;

wherein the first height of each of the plurality of elongated recesses is greater than the second height of each of the plurality of elongated undulations to define channels for the first and second air flows between adjacent heat transfer elements; and is

Wherein the first angle is different from the second angle.

9. The heat transfer element container of claim 8, wherein the first angle is in a range of 5 ° to 45 ° relative to the flow direction.

10. The heat transfer element container of claim 8, wherein the first angle is 20 ° relative to the flow direction.

11. The heat transfer element container of claim 8, wherein the second angle is in the range of 0 ° to-90 ° relative to the flow direction.

12. The heat transfer element container of claim 8, wherein said second angle is-30 ° relative to said flow direction.

13. The heat transfer element container of claim 8, wherein the second height is 20% to 70% of the first height.

14. The heat transfer element container of claim 8, wherein each of the plurality of elongated indentations has a first depth relative to the surface of the plate and each of the plurality of undulations has a second depth relative to the surface of the plate, and wherein the second depth is less than the first depth.

15. The heat transfer element container of claim 8, wherein at least a second heat transfer element of the plurality of heat transfer elements comprises:

a second plate parallel to and adjacent to the first plate and having a plurality of elongated indentations formed therein at spaced intervals and a plurality of elongated undulations formed therein between the plurality of elongated indentations;

wherein the plurality of elongated indentations in the second plate are oriented crosswise relative to the plurality of elongated indentations in the first plate, and wherein the plurality of undulations in the second plate are oriented crosswise relative to the plurality of undulations in the first plate.

16. A heat transfer element for a rotary heat exchanger having a flow direction, the heat transfer element comprising:

a plate having a plurality of elongated notches formed therein at spaced intervals, each of the elongated notches oriented at a first angle relative to the flow direction; and

a plurality of turbulators formed in spaced intervals between the plurality of elongated notches, the plurality of turbulators arranged in a two-dimensional pattern.

17. The heat transfer element of claim 16, wherein the two-dimensional pattern comprises rows and columns of turbulators.

18. The heat transfer element of claim 16, wherein the plurality of turbulators comprises a plurality of hemispherical dimples.

19. The heat transfer element of claim 16, wherein the plurality of turbulators comprises a plurality of diamond-shaped protrusions.

20. The heat transfer element of claim 16, wherein each of the plurality of elongated notches has a first height and each of the plurality of turbulators has a second height, and wherein the first height is greater than the second height.

21. The heat transfer element of claim 16, wherein the spacing between adjacent turbulators is less than the spacing between adjacent elongate notches.

22. The heat transfer element of claim 17, wherein the rows of turbulators are oriented at a second angle relative to the flow direction, and wherein the second angle is different from the first angle.

23. The heat transfer element of claim 22, wherein the second angle is 45 °.

24. A heat transfer element container for a rotary heat exchanger having a housing with a first opening in fluid communication with a first air flow and a second opening in fluid communication with a second air flow, the first and second air flows having flow directions, and the heat transfer element container comprising:

a pair of support members defining a space therebetween;

a plurality of heat transfer elements stacked in a space between the pair of support members, wherein at least one of the plurality of heat transfer elements comprises:

a first plate having a plurality of first elongated notches formed therein at spaced intervals, each of the plurality of first elongated notches oriented at a first angle relative to the flow direction; and

a plurality of first turbulators formed in the first plate at spaced intervals between the plurality of first elongated notches, the plurality of first turbulators arranged in a two-dimensional pattern.

25. The heat transfer element container of claim 24, wherein the two-dimensional pattern comprises rows and columns of turbulators.

26. The heat transfer element container of claim 24, wherein the first plurality of turbulators comprises a plurality of hemispherical dimples.

27. The heat transfer element container of claim 24, wherein the first plurality of turbulators comprises a plurality of diamond-shaped protrusions.

28. The heat transfer element container of claim 24, wherein each of the plurality of first elongated indentations has a first height, each of the plurality of first turbulators has a second height, and wherein the first height is greater than the second height.

29. The heat transfer element container of claim 24, wherein a spacing between adjacent turbulators in the first plate is less than a spacing between adjacent elongated notches in the first plate.

30. The heat transfer element container of claim 25, wherein the rows of turbulators in the first plate are oriented at a second angle relative to the flow direction, and wherein the second angle is different than the first angle.

31. The heat transfer element container of claim 30, wherein the second angle is 45 °.

32. The heat transfer element container of claim 24, wherein at least a second heat transfer element of the plurality of heat transfer elements comprises:

a second plate parallel to and adjacent to the first plate and having a plurality of second turbulators formed therein, the plurality of second turbulators arranged in a two-dimensional pattern.

33. The heat transfer element container of claim 32, wherein the two-dimensional pattern of the plurality of second turbulators in the second plate is different from the two-dimensional pattern of the plurality of first turbulators in the first plate.

34. The heat transfer element container of claim 32, wherein the two-dimensional pattern of the second plurality of turbulators comprises rows and columns of turbulators.

Technical Field

Embodiments of the present invention relate to heat transfer elements for rotary heat exchangers.

Background

Conventional coal-fired power plants use steam-driven turbines to generate electricity. Coal is burned in a boiler to heat water to produce steam. Over the years, while the efficiency of coal-fired power plants has improved, the coal-fired process has produced large quantities of particulates that can cause fouling of components and back-end corrosion, such as fouling and corrosion of cold end layers of heat transfer elements in rotary air preheaters and rotary gas/gas heaters, which can result in high maintenance costs. Research to date on such heat exchangers has focused primarily on developing heat transfer element profiles compatible with coal-fired boilers, particularly to mitigate problems associated with cold end fouling.

Natural gas is an attractive coal alternative in terms of thermal efficiency and reduced emissions, but until recently, natural gas has remained expensive and less readily available than coal. Recent developments in hydraulic fracturing have increased the utilization of natural gas and reduced the cost of natural gas. As a result, many coal fired boilers are now converted to firing natural gas. However, components such as rotary heat exchangers originally designed for coal-fired boilers do not take full advantage of the cleaner, less gas stream emissions, and higher thermal potential associated with natural gas or "frac" gas. Accordingly, there is a need for improvements in rotary heat exchangers and heat transfer elements used therewith for clean fuel applications.

Disclosure of Invention

One aspect of the invention includes a heat transfer element container for a rotary heat exchanger having a housing with a first opening in fluid communication with a first gas flow and a second opening in fluid communication with a second gas flow, the first and second gas flows having a flow direction. The heat transfer element container includes a pair of support members defining a space therebetween and a plurality of heat transfer elements stacked in the space between the pair of support members. At least one of the plurality of heat transfer elements includes a first plate having a plurality of elongated notches formed therein at spaced intervals and oriented at a first angle relative to the flow direction. The plate further includes a plurality of elongated undulations formed in the plate between the notches and oriented at a second angle relative to the flow direction, wherein the first angle is different than the second angle. The first height of each of the plurality of elongated recesses is greater than the second height of each of the plurality of elongated undulations.

Embodiments of the invention may include a plurality of heat transfer elements substantially identical to those described above and stacked in an alternating manner between the support members, wherein adjacent heat transfer elements have opposite orientations relative to one another to maintain a desired spacing between the elements and induce turbulence to increase heat exchange between the airflow and the elements. For example, the heat transfer element container may include a second heat transfer element comprising a second plate parallel to and adjacent to the first plate and having a plurality of elongated indentations formed in the second plate at spaced intervals and a plurality of elongated undulations formed in the second plate between the plurality of elongated indentations. The plurality of elongated recesses in the second plate may be oriented crosswise relative to the plurality of elongated recesses in the first plate to define a spacing between the plates, and the plurality of undulations in the second plate may be oriented crosswise relative to the plurality of undulations in the first plate to induce turbulence in the airflow to improve heat transfer.

Another aspect of the invention includes a heat transfer element for a rotary heat exchanger having a flow direction. In one embodiment, the heat transfer element includes a plate having a plurality of elongated notches formed therein at spaced intervals. The elongated recesses are each oriented at a first angle with respect to the flow direction and have a first height with respect to the surface of the plate. The plate also has a plurality of elongated undulations formed therein at spaced intervals. The elongated undulations are each oriented at a second angle relative to the flow direction and have a second height relative to the surface of the plate. The first height of each of the plurality of elongated recesses is greater than the second height of each of the plurality of elongated undulations, and the first angle is different than the second angle.

The configuration of the notches helps to maintain a desired spacing between the element and an adjacent element when the elements are stacked in the heat transfer element container, and the configuration of the undulations helps to induce turbulence, thereby increasing heat exchange between the air or gas and the elements.

The heat transfer element and vessel of the present invention may enable a significant reduction in the flue gas outlet temperature of the rotary heat exchanger and may result in a reduced heat rate, the benefit of which may offset any slight increase in fan power required to cause a pressure drop due to increased turbulence. When used in a power plant that emits clean flue gas, fouling should be minimal and therefore should not have a tendency to drift in pressure drop.

Drawings

FIG. 1 is a schematic illustration of a power plant having a rotary heat exchanger that may utilize a heat transfer element container according to an exemplary embodiment of the present invention;

FIG. 2 is a perspective view, partially in section, of a rotary heat exchanger that may be used with heat transfer elements according to exemplary embodiments of the present invention;

FIG. 3 is a perspective view of a heat transfer element container for a rotary heat exchanger according to an exemplary embodiment of the present invention;

FIG. 4 is a plan view of a heat transfer element according to an exemplary embodiment of the present invention;

fig. 4A is a cross-sectional view of the heat transfer element of fig. 4 taken along section 4A-4A;

FIG. 5 is a perspective view of adjacent heat transfer elements according to an exemplary embodiment of the present invention;

FIG. 6 is a perspective view of adjacent heat transfer elements according to another exemplary embodiment of the present invention;

FIG. 7 is a plan view of a heat transfer element according to yet another exemplary embodiment of the present invention;

fig. 7A is a cross-sectional view of the heat transfer element of fig. 7, taken along section 7A-7A;

FIG. 8 is a plan view of a heat transfer element according to yet another exemplary embodiment of the present invention;

fig. 8A is a cross-sectional view of the heat transfer element of fig. 8 taken along section 8A-8A;

FIG. 9 is a perspective view of a heat transfer element according to another exemplary embodiment of the present invention;

FIG. 10 is a perspective view of a heat transfer element according to another exemplary embodiment of the present invention.

Detailed Description

The concepts of the present invention may be best described with reference to certain embodiments thereof, which are described in detail herein with reference to the accompanying drawings, wherein like reference numerals refer to like features throughout. It should be understood that the term "invention" as used herein is intended to refer to the inventive concept based on the embodiments described below, rather than to the embodiments themselves. It is further to be understood that the general inventive concept is not limited to the illustrative embodiments described below and that the following description is read in light thereof.

An exemplary power plant 10 of the type shown in FIG. 1, the power plant 10 may include a rotary heat exchanger 12 having heat transfer elements in accordance with the present invention. The power plant 10 includes a generator 14, the generator 14 coupled with a steam turbine 16 to generate electricity. The turbine 16 is driven by steam from a boiler 18, which boiler 18 receives air for combustion through an intake 20 and discharges combustion gases through an exhaust 22. Fans 24a and 24b may be used to supply air to the boiler air intake 20 and to extract combustion gases from the exhaust gas through a dust extraction system 26 before the combustion gases are released into the atmosphere. The rotary regenerative heat exchanger 12 may be positioned adjacent the air inlet 20 and the air outlet 22 to preheat air entering the boiler 18 with heat from the combustion gases exiting the boiler. Rotary regenerative heat exchangers can also be used in flue gas heaters to control emissions from power plants.

Referring now to FIG. 2, a partial cut-away perspective view of a rotary heat exchanger 12 utilizing heat transfer elements and vessels is shown in accordance with an exemplary embodiment of the present invention. The rotary heat exchanger 12 includes a housing 28 having a first conduit or opening 30 and a second conduit or opening 32. The first opening 30 communicates with the boiler inlet port 20 and the second opening 32 communicates with the boiler exhaust port 22. A rotor 34 containing a plurality of heat transfer element receptacles 36 is mounted for rotation in the housing 28 such that the heat transfer element receptacles 36 in the rotor circulate through the openings 30 and 32, thereby causing the heat transfer elements in the receptacles to be heated by the exhaust gases when aligned with the second opening and to preheat the incoming air when aligned with the first opening.

Fig. 3 is a perspective view of a heat transfer element container or pack 36 for a rotary heat exchanger according to an exemplary embodiment of the present invention. The heat transfer element container 36 includes a plurality of heat transfer elements 38 arranged in a stack in sheet or plate form between a pair of support members 40. In an exemplary embodiment, the support member may be an end plate. In the example shown, the sheets are rectangular sheets oriented vertically between horizontally spaced end plates. The sheets have the same height and a width gradually increasing in the horizontal direction to have a trapezoidal cross section when viewed from above. In this example, the trapezoidal shape of the container 36 allows a plurality of containers of this type to be arranged in a circular or annular pattern within the rotor of the rotary heat exchanger. The exemplary heat transfer element container 36 may also include: one or more support rods 42 extending above and below the heat transfer element 38 between the support members 40 to help provide structural support to the assembly; and/or one or more reinforcing bars 44 extending laterally across the one or more support bars 42 to provide additional support. One or more steel straps 46 may be wrapped around the assembly to help hold the elements 38 in place during transport. Any of the heat transfer elements described herein may be used in such a container.

Fig. 4 is a plan view of a heat transfer element 38 according to an exemplary embodiment of the present invention. The heat transfer element 38 comprises a rectangular sheet or plate formed of a thermally conductive material such as steel that is capable of withstanding repeated heating to high temperatures (when exposed to exhaust gas) and cooling (when exposed to ambient temperature intake air). At a first angle theta with respect to the direction of air or gas flowing through the heat transfer element container₁A plurality of ribs or notches 48 are formed in the sheet material (e.g., sheet material is fed through a pair of rollers having a notched profile). The notches 48 may be parallel as shown with a first pitch P between the notches₁. Although two notches 48 are shown by way of example, it should be understood that the heat transfer element may be formed with more than two notches. As best seen in the cross-sectional view of the heat transfer member 38 shown in FIG. 4A, each notch 48 has a recess with a first height H₁And has a first depth D₁The peaks and valleys being selected to establish a desired spacing between the stacked elements. The spacing between the stacked elements is selected to define channels through which air and/or exhaust gas may flow.

A plurality of undulations 50 are also formed in the sheet between the notches 48 (e.g., by feeding the sheet stock through a pair of rollers having an undulating profile prior to or simultaneously with forming the notches). The undulations 50 are configured to induce turbulence in air and/or gas flowing through the channels defined between adjacent heat transfer elements 38. The undulations 50 are at a second angle θ relative to the direction of air or gas flow through the heat transfer element container₂And (4) orientation. In the exemplary heat transfer element shown in FIG. 4, the second angle θ₂Is selected at a first angle theta with respect to the flow direction₁Oriented in the opposite direction (e.g., clockwise versus counterclockwise) such that the undulations 50 pass through the notches 48. For example, if the first angle is measured counterclockwise from the direction of air/gas flow, the second angle may be measured clockwise from the direction of air/gas flow. As shown, the undulations 50 can be parallel to one another with a second pitch P₂Less than the first pitch P₁. A cross-sectional view of the heat transfer member 38 as shown in FIG. 4AAs best seen therein, the undulations 50 may each have a height that is less than the first height H₁Second height H of₂And less than the first depth D₁Second depth D of₂。

In an exemplary embodiment, the first angle θ₁May be in the range of 5 ° to 45 °, and the second angle θ₂May range from 0 ° to-90 °. In another example, the first angle θ₁May be 20 deg., and the second angle theta₂May be-30 deg.. In an exemplary embodiment, the first height H₁And a first depth D₁Can be 5 mm-9 mm, and the second height H₂And a second depth D₂May all be 3mm, the first pitch P₁May be 35mm, the second pitch P₂May be 15 mm.

Fig. 5 is a perspective view of a pair of heat transfer elements 38 and 38' stacked in accordance with an exemplary embodiment of the present invention. The first heat transfer element 38 is shown in a partial cutaway view so that details of the second heat transfer element 38' can be seen. Both heat transfer members 38 and 38' have the configuration shown in fig. 4. However, their respective orientations with respect to the direction of airflow are opposite with respect to each other. That is, the first heat transfer element 38 has a first orientation and the second heat transfer element 38' has a second orientation that is rotated 180 ° relative to the first orientation such that the diagonally spaced notches on one heat transfer element intersect the diagonally spaced notches on an adjacent heat transfer element or the like through the stack.

The diagonally spaced cross notches 48 and 48' function to maintain a desired gap or spacing between adjacent heat transfer elements. The number of notches, notch angles and spacing help to obtain sufficient contact points to achieve a tight and stiff set when compressed. The diagonal intersection of the notches 48 and 48' also helps to avoid skewed flow, thereby maintaining uniform flow across the cross-sectional flow area of the element sets.

The angled undulations 50 and 50 'between the notches in each heat transfer element 38 and 38' act as turbulators that cause turbulence. The turbulence inducing angled undulations 50 and 50' are combined to improve heat transfer, particularly at lower gas velocities and reynolds numbers. Thus, high efficiency heat transfer elements of the type described herein are suitable for use in frac gas combustion, where flue gas exit temperatures can be significantly reduced compared to conventional coal fired boilers. The increased pressure drop caused by the higher turbulence is minimized and the benefit of thermal efficiency far outweighs any slight increase in fan power that may be required. Clean flue gas also does not cause fouling and therefore does not have a tendency to drift in pressure drop. Although two heat transfer elements are shown for illustrative purposes, it should be understood that the stack may include more than two heat transfer elements in alternating orientations as shown. The heat transfer elements shown in fig. 5 may be stacked alternately with each other or with any other heat transfer element described herein.

Fig. 6 is a perspective view of a pair of stacked heat transfer elements 52 and 52' according to another exemplary embodiment of the present invention. The heat transfer elements 52 and 52' are identically constructed, but are oppositely oriented. Each of the heat transfer elements 52 and 52' includes a plurality of angled notches 48 or 48', respectively, separated by a plurality of dimples 54 or 54', respectively. The angled recesses 48 and 48' are the same as described above. However, rather than undulations, pockets 54 and 54 'are formed between notches 48 and 48' (e.g., by feeding sheet stock material through a pair of pocket-pair rollers prior to or at the same time as forming the notches). In an exemplary embodiment, the dimples 54 and 54' may be hemispherical, and may be concave or convex. In an exemplary embodiment, two or three rows of dimples are formed between each pair of inclined recesses. The rows may be parallel to the notches shown or oriented at an angle relative to the notches. The dimples in adjacent rows may be aligned or staggered with respect to each other. In an exemplary embodiment, the depth of the dimples is less than the height/depth of the recesses, and the spacing between adjacent dimples is less than the spacing between recesses. Like the undulations, the dimples between the notches act as turbulators that cause turbulence. The turbulence inducing dimples improve heat transfer and thereby facilitate use in fracturing gas combustion and other applications. Again, although two heat transfer elements are shown for illustrative purposes, it will be understood that the stack may include more than two heat transfer elements in alternating orientations as shown. The heat transfer element of fig. 6 may be stacked in an alternating manner with any other heat transfer element described herein.

Fig. 7 is a plan view of a heat transfer element 56 according to yet another exemplary embodiment of the present invention. Fig. 7A is a cross-sectional view of the heat transfer element 56 of fig. 7, taken along section 7A-7A. The heat transfer member 56 includes a pair of notches 48 oriented parallel to the direction of airflow and a plurality of pockets 54 formed between the notches. The pockets 54 are arranged in two oblique rows, each row comprising three pockets and oriented at an angle relative to the direction of the air and/or airflow. In the exemplary embodiment, the rows of dimples 54 are each arranged at an angle of approximately 45 ° with respect to the direction of the air and/or airflow. Similar to the heat transfer element of fig. 6, the dimples in the heat transfer element of fig. 7 may be hemispherical and may have a depth less than the height/depth of the dimples, and the spacing between adjacent dimples is less than the spacing between dimples. The dimples between the notches act as turbulators that cause turbulence. The turbulence inducing dimples improve heat transfer and thereby facilitate use in fracturing gas combustion and other applications. The heat transfer elements of fig. 7 may be stacked alternately with the heat transfer elements of fig. 6 or any other heat transfer element described herein.

Fig. 8 is a plan view of a heat transfer element 58 according to yet another exemplary embodiment of the present invention. Fig. 8A is a cross-sectional view of the heat transfer element 58 of fig. 8 taken through section 8A-8A. In this embodiment, a plurality of dimples 54 are formed in multiple columns and rows in the heat transfer element 58. In an exemplary embodiment, at least three columns of rows are shown, each row including three pits. However, the rows may contain fewer or more pits than shown. The rows of dimples are at an angle relative to the direction of airflow. In an exemplary embodiment, the rows of dimples are arranged at an angle of approximately 45 ° with respect to the air flow direction. The dimples act as turbulators that cause turbulence. The turbulence inducing dimples improve heat transfer and thereby facilitate use in fracturing gas combustion and other applications. The heat transfer elements of fig. 8 may be stacked alternately with the heat transfer elements of fig. 7 or any other heat transfer element described herein.

Fig. 9 is a perspective view of a heat transfer element 60 according to another exemplary embodiment of the present invention. The heat transfer element 60 of fig. 9 includes a repeating pattern of diamond-shaped ridges or ridges 62 that act as turbulators that cause turbulence. The diamond pattern 62 that causes turbulence increases the number of contact points and improves heat transfer to facilitate use in frac gas combustion and other applications. The diamond shaped ridges or ridges 62 may be formed by double rolling the sheet with the angle of the undulations on the first roll being opposite the angle of the undulations on the second roll. For example, the first roller may be configured to generate undulations at an angle of +30 ° relative to the air/gas flow direction, and the second roller may be configured to generate undulations at an angle of-30 ° relative to the air/gas flow direction. This process forms a diamond-shaped profile and the angles of the undulations can be varied to change the diamond shape. The heat transfer elements of fig. 9 may be stacked in an alternating fashion with the heat transfer elements of fig. 7, with heat transfer elements having an undulating or corrugated profile parallel to the direction of air/gas flow, or with other heat transfer elements described herein.

Fig. 10 is a perspective view of a heat transfer element 64 according to another exemplary embodiment of the present invention. The heat transfer element 64 of fig. 10 includes a complex pattern of ridges or ridges 66 that act as turbulators to cause turbulence. The turbulence inducing pattern of fig. 10 increases the number of contact points and improves heat transfer to facilitate use in frac gas combustion and other applications. The pattern shown in fig. 10 may be formed by: the sheet is passed through a couch roll to create undulations oriented at an angle relative to the air/gas flow direction, and then through a corrugation roll that creates corrugations oriented parallel to the air/gas flow direction. This process forms ridges 66 on the sides of the corrugations to induce turbulence and improve heat transfer. The heat transfer element of fig. 10 may be stacked in an alternating manner with heat transfer elements having angled undulations (e.g., oriented at an opposite angle to the undulations in the heat transfer element of fig. 10), the heat transfer element of fig. 9, or any of the other heat transfer elements described herein.

It should be understood that the above-described embodiments of the invention, illustrated in the accompanying drawings, represent only a few of the many ways in which embodiments of the invention may be implemented. For example, in the embodiment shown in FIG. 4, the angle of the undulations relative to the notch angle and the height of the undulations relative to the notch height can be varied to optimize heat transfer/pressure drop performance depending on the particular application or customer specifications. Also, while the dimples have been described as semi-spherical, it should be understood that they may include a smaller spherical portion (e.g., the height or depth of the dimples may be less than the radius) or have other configurations, such as a pyramidal shape. Further, while a heat transfer element container having a trapezoidal cross-section has been shown, it should be understood that the container may be configured to have a rectangular cross-section, a curved cross-section, or any other shape suitable for installation in a rotary heat exchanger.