HEAT TRANSFER ELEMENTS FOR ROTARY HEAT EXCHANGERS

Abstract

A rotary heat exchanger for preheating air using waste heat comprises a plurality of heat transfer elements movable between a first and second opening in a housing for exchanging heat between heated exhaust gases and a fresh air stream. At least one of the heat transfer elements comprises a first plate having a plurality of elongated notches formed therein at spaced intervals and oriented at a first angle with respect to the flow direction. The plate further comprises a plurality of elongated corrugations formed therein at spaced intervals and oriented at a second angle with respect to the flow direction, wherein the first angle differs from the second angle. A first height of each of the plurality of elongated notches is greater than a second height of each of the plurality of elongated corrugations.The heat transfer elements can be stacked in a container for installation in the rotary heat exchanger.

Description

HEAT TRANSFER ELEMENTS FOR ROTARY HEAT EXCHANGERS TECHNICAL FIELD The embodiments of the present invention relate to heat transfer elements for rotary heat exchangers. BACKGROUND Conventional coal-fired power plants generate electricity using steam-driven turbines. Coal is burned to heat water in a boiler to produce steam. While the efficiency of coal-fired power plants has improved over the years, the process of burning coal results in particulate matter that can lead to fouling and corrosion of the back-end components, such as the cold-end levels of heat transfer elements in rotary air preheaters and rotary gas / gas heaters, resulting in costly maintenance.Until now, research on such heat exchangers has focused mainly on developing heat transfer element profiles compatible with coal-fired boilers and mitigating the problems associated with fouling of the cold end in particular. ο^ηζηη / ζζηζ / Β / γ Natural gas is an attractive alternative to coal in terms of thermal efficiency and reduced emissions, but until recently it was more expensive and not as readily available. Recent developments in hydraulic fracturing have increased the availability and reduced the cost of natural gas. As a result, many coal-fired boilers are now being converted to natural gas. However, components such as rotary heat exchangers originally designed for coal-fired boilers do not fully take advantage of the lower-emission, cleaner gas flow and higher thermal potential associated with natural or fracked gas. Thus, there is a need for improvements to rotary heat exchangers and the heat transfer elements used within them for clean-fuel applications. BRIEF DESCRIPTION OF THE INVENTION One aspect of the present invention comprises 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 comprises a pair of support members defining a space between them, 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 comprises a first plate having a plurality of elongated notches formed therein at spaced intervals and oriented at a first angle with respect to the flow direction.The plate further comprises a plurality of elongated wavinesses formed therein between the notches and oriented at a second angle with respect to the flow direction, wherein the first angle is different from the second angle. A first height of each of the plurality of elongated notches is greater than a second height of each of the plurality of elongated wavinesses. The embodiments of the present invention may include a plurality of substantially the same heat transfer elements as described above, stacked alternately between the support members, with adjacent heat transfer elements being oriented in opposite directions relative to each other to maintain a desired spacing between the elements and to induce turbulence in order to increase heat exchange between the gas flows and the elements. For example, the heat transfer element vessel may comprise a second heat transfer element including a second plate parallel and adjacent to the first plate and having a plurality of elongated notches formed therein at spaced intervals and a plurality of elongated wavinesses formed therein between the plurality of elongated notches.The plurality of elongated notches on the second plate can be oriented transversely with respect to the plurality of elongated notches on the first plate to define a spacing between the plates, and the plurality of undulations on the second plate can be oriented transversely with respect to the plurality of undulations on the first plate to induce turbulence in the gas flows in order to improve heat transfer. Another aspect of the present invention comprises a heat transfer element for a rotary heat exchanger having a flow direction. In one embodiment, the heat transfer element comprises a plate having a plurality of elongated notches formed therein at spaced intervals. Each elongated notch is oriented at a first angle with respect to the flow direction and has a first height relative to a surface of the plate. The plate further has a plurality of elongated wavinesses formed therein at spaced intervals. Each elongated waviness is oriented at a second angle with respect to the flow direction and has a second height relative to a surface of the plate.The first height of each of the plurality of elongated notches is greater than the second height of each of the plurality of elongated undulations, and the first angle is different from the second angle. The notch configuration helps maintain a desired spacing between the element and adjacent elements when stacked in a heat transfer element vessel, and the ripple configuration helps induce turbulence in order to increase heat exchange between the air or gas and the element. The inventive heat transfer element and vessel can significantly reduce the flue gas outlet temperatures of a rotary heat exchanger, resulting in lower heat costs. These benefits can offset any increased fan power required to compensate for the pressure drop caused by increased turbulence. When used in a power plant emitting clean flue gas, fouling should be minimal to prevent pressure drop deviation. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a power plant with a rotary heat exchanger that can utilize heat transfer element vessels according to an exemplary embodiment of the present invention. Fig. 2 is a partially cropped perspective view of a rotary heat exchanger of a type that can utilize heat transfer element vessels according to an exemplary embodiment 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 planar 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 through section 4A-4A. Fig. 5 is a perspective view of the adjacent heat transfer elements according to an exemplary embodiment of the present invention. Fig. 6 is a perspective view of the adjacent heat transfer elements according to another exemplary embodiment of the present invention. Fig. 7 is a planar view of a heat transfer element according to yet another embodiment of the present invention. Fig. 7A is a cross-sectional view of the heat transfer element of Fig. 7 taken through section 7A-7A. Fig. 8 is a planar view of a heat transfer element according to yet another embodiment of the present invention. Fig. 8A is a cross-sectional view of the heat transfer element of Fig. 8 taken through section 8A-8A. Fig. 9 is a perspective view of a heat transfer element according to a further example embodiment of the present invention. Fig. 10 is a perspective view of a heat transfer element according to a further example embodiment of the present invention. DESCRIPTION OF EXAMPLE MODALITIES The present inventive concept is best described by certain embodiments thereof, which are detailed herein with reference to the accompanying drawings, where similar reference numbers refer to similar features. It is understood that the term "invention," when used herein, is intended to denote the inventive concept implicit in the ο^ηζηη / ζζηζ / Β / γ Qfrnznn / zznz / e / Y modalities described below and not simply the modalities themselves. It is further understood that the general inventive concept is not limited to the illustrative modalities described below and the following descriptions should be read in that regard. An exemplary power plant 10 of a type that may incorporate a rotary heat exchanger 12 with heat transfer elements according to the present invention is illustrated in Fig. 1. The power plant 10 includes a generator 14 coupled with a steam turbine 16 to produce electricity. The turbine 16 is driven by steam from a boiler 18, which receives combustion air via an air intake 20 and expels combustion gases via an exhaust 22. Fans 24a and 24b may be used to supply air to the boiler intake 20 and to remove combustion gases from the exhaust 22 through a dust removal system 26 before release to the atmosphere. A rotary regenerative heat exchanger 12 may be positioned adjacent to the air intake 20 and the exhaust 22 to preheat the air entering the boiler 18 using heat from the combustion gases expelled from the boiler.Rotary regenerative heat exchangers can also be used in gas-gas heaters to control plant emissions. ο^ηζηη / ζζηζ / Β / γ With reference to Fig. 2, a partially cropped perspective view of a rotary heat exchanger 12 is shown, which uses heat transfer elements and vessels according to an exemplary embodiment of the present invention. The rotary heat exchanger 12 includes a housing 28 with a first duct or opening 30 and a second duct or opening 32. The first opening 30 communicates with the air intake of the boiler 20, and the second opening 32 communicates with the exhaust of the boiler 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 past 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. Figure 3 is a perspective view of a heat transfer element container or bundle 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 in the form of sheets or plates arranged in a stack between a pair of support members 40. In one exemplary embodiment, the support members may be end plates. In the example shown, the sheets are vertically oriented rectangular sheets between the horizontally spaced end plates. The sheets are of the same height and their width increases in the horizontal direction to provide a trapezoidal cross-section when viewed from above.The trapezoidal shape of the vessel 36 in this example allows multiple such vessels to be arranged in a circular or ring pattern within a rotor of a rotary heat exchanger. The heat transfer element vessel of example 36 may also include one or more support bars 42 extending above and below the heat transfer elements 38 between the support members 40 to help provide structural support for the assembly and / or one or more stiffening bars 44 extending transversely across the one or more support bars 42 for additional support. One or more steel bands 46 may be wrapped around the assembly to help retain the elements 38 in position during transportation. Any of the heat transfer elements described herein may be used in such a vessel. Figure 4 is a planar view of a heat transfer element 38 according to an embodiment of the present invention. The heat transfer element 38 comprises a rectangular sheet or plate formed from a thermally conductive material, such as steel, which can withstand being heated to high temperatures when exposed to exhaust gases and cooled when exposed to incoming air at ambient temperature. A plurality of ribs or notches 48 are formed in the sheet at a first angle θι with respect to the direction of the air or gas flowing through the heat transfer element vessel (e.g., by feeding the sheet material through a pair of rollers with notched profiles). The notches 48 can be parallel, as shown, with a first spacing Pi between the notches.While two notches 48 are shown as an example, it will be appreciated that the heat transfer element can be formed with more than two notches. As best seen in the cross-sectional view of the heat transfer element 38 shown in Fig. 4A, each notch 48 has a peak with a first height Hi and a channel with a first depth Di, which are selected to establish a desired spacing between the stacked elements. The spacing between the stacked elements is chosen to define a channel through which air and / or exhaust gases can flow. A plurality of ripples 50 are also formed in the sheet between the notches 48 (for example, when feeding the sheet material through a pair of rollers with corrugated profiles before or simultaneously as the notches are formed). The ripples 50 are configured to induce turbulence in the air and / or gas flowing through the channel defined between the adjacent heat transfer elements 38. The ripples 50 are oriented at a second angle Θ2 with respect to the direction of the air or gas flowing through the heat transfer element vessel. In the example heat transfer element shown in Fig. 4, the second angle Θ2 is selected to be in a direction opposite to the first angle θι with respect to the flow direction (e.g., clockwise versus counterclockwise) so that the ripples 50 cross the notches 48.For example, if the first angle is measured counterclockwise from the direction of air / gas flow, the second angle can be measured clockwise from the direction of air / gas flow. The ripples 50 can be parallel to each other as shown, with a second spacing P2 that is smaller than the first spacing Pi. As best seen in the cross-sectional view of the heat transfer element 38 shown in Fig. 4A, the ripples 50 can each have a second height H2 that is smaller than the first height Hi and a second depth D2 that is smaller than the first depth Di. In one example, the first angle θι can be in the range of 5° to 45°, and the second angle θ2 can be in the range of 0° to -90°. In another example, the first angle θι can be 20° and the second angle θ2 can be -30°. In one example, the first height Hi and depth Di can each be 5-9 mm, the second height and depth H2 and D2 can each be 3 mm, the first space Pi can be 35 mm, and the second space P2 can be 15 mm. Figure 5 is a perspective view of a pair of heat transfer elements 38 and 38' stacked according to an exemplary embodiment of the present invention. The first heat transfer element 38 is shown in partial cutout so that details of the second heat transfer element 38' can be observed. Both heat transfer elements 38 and 38' have a configuration as shown in Figure 4. However, their respective orientations with respect to the airflow direction are reversed relative to each other.That is, the first heat transfer element 38 has a first orientation and the second heat transfer element 38' in a second orientation that is rotated 180° with respect to the first orientation so that the diagonally spaced notches in one heat transfer element cross the diagonally spaced notches in the adjacent heat transfer elements and so on through the stack. The diagonally spaced cross notches 48 and 48' maintain the desired spacing between adjacent heat transfer elements. The number of notches, their angle, and their spacing contribute to providing sufficient contact points for a rigid, airtight pack when compressed. The diagonal crossing of notches 48 and 48' also helps prevent skewed flow, maintaining uniform flow across the entire cross-sectional flow area of ​​the element pack. The angled undulations 50 and 50' between the notches in the respective heat transfer elements 38 and 38' act as turbulent elements to induce turbulence. These turbulence-inducing angled undulations 50 and 50' are incorporated to enhance heat transfer, particularly at lower gas velocities and Reynolds numbers. High-efficiency heat transfer elements of the type described herein are thus suitable for heating gas obtained by fracking, where flue gas outlet temperatures can be significantly reduced compared to conventional coal-fired boilers. The increased pressure drop resulting from the higher turbulence is minimal, and the heat gain benefits outweigh any additional fan power that may be required.Clean flue gas will also not cause fouling, so there is no tendency for pressure drop deviation. While two heat transfer elements are shown for illustrative purposes, it should be noted that a stack may comprise more than two heat transfer elements in alternating orientations as shown. The heat transfer elements shown in Fig. 5 may be stacked in an alternating manner with each other or with any of the heat transfer elements described herein. Figure 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 configured the same but are reversed in orientation. 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 or holes 54 or 54', respectively. The angled notches 48 and 48' are the same as described above. However, dimples 54 and 54' are formed between notches 48 and 48' (for example, by feeding sheet material through a pair of dimpled rollers before or simultaneously as the notches are formed), rather than ripples. In one example embodiment, dimples 54 and 54' can be hemispherical, either concave or convex.In one example embodiment, two or three rows of dimples are formed between each pair of angled notches. The rows may be parallel to the notches, as shown, or oriented at an angle to the notches. The dimples in adjacent rows may be aligned with each other or staggered. In one example embodiment, the depth of the dimples is less than the height / depth of the notches, and the spacing between adjacent dimples is smaller than the spacing between the notches. Similar to ripples, the dimples between the notches act as turbulent agents to induce turbulence. The turbulence-inducing dimples enhance heat transfer, facilitating their use in fracking and other gas heating applications.Again, while two heat transfer elements are shown for illustrative purposes, it will be appreciated that a stack may comprise more than two heat transfer elements in alternating orientations as shown. The heat transfer elements in Fig. 6 may be stacked in an alternating manner with any of the other heat transfer elements described herein. ο^ηζηη / ζζηζ / Β / γ Fig. 7 is a planar view of the 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 through section 7I-7A. The heat transfer element 56 includes a pair of notches 48 oriented parallel to the direction of airflow and a plurality of dimples 54 formed between the notches. The dimples 54 are arranged in two columns of angled rows, each row comprising three dimples oriented at an angle to the direction of airflow and / or gas flow. In one exemplary embodiment, the rows of dimples 54 are each arranged at an angle of approximately 45° to the direction of airflow and / or gas flow. Similar to the heat transfer element of Fig. 6, the dimples in the heat transfer element of Fig.The dimples in Fig. 7 can be hemispherical in shape and can have a depth less than the height / depth of the notches, and a spacing between adjacent dimples that is smaller than the spacing between the notches. The dimples between the notches act as turbulent elements to induce turbulence. The turbulence-inducing dimples improve heat transfer to facilitate use in fracking gas heating and other applications. The heat transfer element of Fig. 7 can be stacked in an alternating manner with the heat transfer element of Fig. 6 or with any of the other heat transfer elements described herein. Figure 8 is a planar view of a heat transfer element 58 according to yet another exemplary embodiment of the present invention. Figure 8A is a cross-sectional view of the heat transfer element 58 of Figure 8 taken through section 8A-8A. In this embodiment, a plurality of dimples 54 are formed in the heat transfer element 58 in a plurality of columns and rows. In one exemplary embodiment, at least three row columns comprising three dimples each are shown. However, the rows may contain fewer or more dimples than shown. The rows of dimples are oriented at an angle with respect to the direction of airflow. In one exemplary embodiment, the rows of dimples are arranged at an angle of approximately 45° with respect to the direction of airflow. The dimples act as turbulent elements to induce turbulence.The dimples that induce turbulence improve heat transfer to facilitate use in fracking gas heating and other applications. The heat transfer element of Fig. 8 is stacked in an alternating manner with the heat transfer element of Fig. 7 or with any of the other heat transfer elements described herein. Figure 9 is a perspective view of a heat transfer element 60 according to a further embodiment of the present invention. The heat transfer element 60 of Figure 9 includes a repeating pattern of rhomboid-shaped protrusions or ridges 62 that serve as turbulent elements to induce turbulence. The turbulence-inducing rhomboid pattern 62 increases the number of contact points and improves heat transfer to facilitate use in heating with qas obtained by fracturing in other applications. The rhomboid-shaped protrusions or ridges 62 can be formed by double rolling a sheet with the angle of the corrugations on the first roll opposite to the angle of the corrugations on the second roll.For example, the first roller can be configured to produce ripples oriented at an angle of +30° relative to the air / gas flow direction, and the second roller can be configured to produce ripples oriented at an angle of -30° relative to the air / gas flow direction. This process results in a rhombus-shaped profile, and the ripple angles can be varied to alter the shape of the rhombus. The heat transfer element of Fig. 9 can be stacked alternately with the heat transfer element of Fig. 7, with a heat transfer element having a ripple or corrugated profile parallel to the air / gas flow direction, or with any of the other heat transfer elements described herein. Figure 10 is a perspective view of a heat transfer element 64 according to a further embodiment of the present invention. The heat transfer element 64 in Figure 10 includes a complex pattern of ridges or flanges 66 that serve as turbulent elements to induce turbulence. The turbulence-inducing pattern in Figure 10 increases the number of contact points and improves heat transfer to facilitate use in heating with fracking gas and other applications. The pattern shown in Figure 10 can be formed by passing a sheet through a corrugated roller to produce undulations oriented at an angle to the direction of the air / gas flow, followed by a corrugated roller that produces corrugations oriented parallel to the air / gas flow direction. This process creates protrusions 66 on the sides of the corrugations to induce turbulence and improve heat transfer.The heat transfer element of Fig. 10 can be stacked in an alternating manner with a heat transfer element having angled ripples (e.g., oriented at an angle opposite to the ripples on the heat transfer element of Fig. 10), with the heat transfer element of Fig. 9, or with any of the other heat transfer elements described herein. It will be appreciated that the embodiments described above and illustrated in the drawings represent only a few of the many ways to implement embodiments of the present invention. For example, in the embodiment shown in Fig. 4, the angle of the corrugations relative to the notch angles and the height of the corrugations relative to the notch height can be varied to optimize heat transfer / pressure drop performance depending on the particular application or customer specification. Also, while the dimples have been described as being hemispherical, it will be appreciated that they can comprise a smaller spherical segment (e.g., the height or depth of the dimples can be less than the radius) or have other configurations such as a pyramid shape.Furthermore, while a heat transfer element vessel having a trapezoidal cross-section has been shown, it will be appreciated that the vessel can be configured to have a rectangular cross-section, a curved cross-section, or any other shape suitable for installation in a rotary heat exchanger.

Claims

1. A heat transfer element for a rotary heat exchanger having a flow direction, the heat transfer element characterized in that it comprises: a plate having a plurality of elongated notches formed therein at spaced intervals, each of the elongated notches being oriented at a first angle with respect to the flow direction, wherein the first angle is a non-zero angle in the range of 5° to 45° relative to the flow direction; and a plurality of turbulent elements formed in the spaced intervals between the plurality of elongated notches, the plurality of turbulent elements being arranged in a two-dimensional pattern; and wherein each of the plurality of elongated notches has a first height and each of the plurality of turbulent elements has a second height less than the first height;wherein the two-dimensional pattern of the plurality of turbulent elements includes rows and columns of turbulent elements, the rows of turbulent elements being oriented at a second angle of -45° with respect to the flow direction; and wherein the turbulent elements in adjacent rows are staggered such that the spaces between turbulent elements in one row are laterally displaced from the spaces between turbulent elements in an adjacent row.

2. A heat transfer element as set forth in claim 1, characterized in that the plurality of turbulent elements includes a plurality of hemispherical dimples.

3. A heat transfer element as set forth in claim 1, characterized in that the plurality of turbulent elements includes a plurality of diamond-shaped protrusions.

4. A heat transfer element as set forth in claim 1, characterized in that a space between adjacent turbulent elements is smaller than a space between adjacent elongated notches.

5. A heat transfer element vessel 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, and the heat transfer element vessel characterized in that it comprises: a pair of support members defining a space between them; and a plurality of heat transfer elements stacked in the space between the pair of support members, the plurality of heat transfer elements comprising: a first plate having: a first plurality of elongated notches formed therein at spaced intervals, the first plurality of elongated notches each being oriented at a first angle with respect to the flow direction, wherein the first angle is a non-zero angle;and a first plurality of turbulent elements formed on the first plate in the intervals spaced between the first plurality of elongated notches, the first plurality of turbulent elements being arranged in a two-dimensional pattern, wherein each of the notches of the first plurality of elongated notches has a first height and each of the turbulent elements of the first plurality of turbulent elements has a second height less than the first height, wherein the two-dimensional pattern of the first plurality of turbulent elements includes rows and columns of turbulent elements, and wherein the turbulent elements in adjacent rows are staggered so that the spaces between turbulent elements in one row are laterally displaced from the spaces between turbulent elements in an adjacent row;and a second plate that is parallel and adjacent to the first plate, the second plate having a second plurality of turbulent elements formed on the second plate, the second plurality of turbulent elements being arranged in a two-dimensional pattern that is different from the two-dimensional pattern of the first plurality of turbulent elements formed on the first plate.

6. A heat transfer element vessel as set forth in claim 5, characterized in that the first plurality of turbulent elements includes a plurality of hemispherical dimples.

7. A heat transfer element vessel as set forth in claim 5, characterized in that the first plurality of turbulent elements includes a plurality of diamond-shaped protrusions.

8. A heat transfer element vessel as set forth in claim 5, characterized in that the spacing between adjacent turbulent elements on the first plate is less than the spacing between adjacent elongated notches on the first plate.

9. A heat transfer element vessel as set forth in claim 5, characterized in that the first angle is in a range of 5° to 45° with respect to the flow direction and wherein the rows of turbulent elements in the first plate are oriented at a second angle with respect to the flow direction, and wherein the second angle is different from the first angle.

10. A heat transfer element container as set forth in claim 9, characterized in that the second angle is -45°.

11. A heat transfer element vessel as set forth in claim 5, characterized in that the two-dimensional pattern of the second plurality of turbulent elements includes rows and columns of turbulent elements.

12. A heat transfer element vessel as set forth in claim 11, characterized in that the second plurality of turbulent elements are arranged in a plurality of rows and wherein the turbulent elements in adjacent rows are staggered such that the spaces between turbulent elements in one row are laterally displaced from the spaces between turbulent elements in an adjacent row.

13. A heat transfer element vessel as set forth in claim 5, characterized in that the second plate is a notched plate containing only turbulent elements.

14. A heat transfer element vessel 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 flow having a flow direction, and the heat transfer element vessel characterized in that it comprises: a pair of support members defining a space between them;and a plurality of heat transfer elements stacked in the space between the pair of support members, the plurality of heat transfer elements comprising: a first plate having: a first plurality of elongated notches formed therein at spaced intervals, the first plurality of elongated notches each being oriented at a first angle with respect to the flow direction, wherein the first angle is a non-zero angle;and a first plurality of turbulent elements formed on the first plate in the intervals spaced between the first plurality of elongated notches, the first plurality of turbulent elements being arranged in a two-dimensional pattern of rows and columns, wherein each of the notches of the first plurality of elongated notches has a first height and each of the turbulent elements of the first plurality of turbulent elements has a second height less than the first height, and wherein the turbulent elements in adjacent rows are staggered so that the spaces between turbulent elements in one row are laterally displaced from the spaces between turbulent elements in an adjacent row;and a second plate that is parallel and adjacent to the first plate, the second plate being an unnotched plate having only a second plurality of turbulent elements formed thereon, the second plurality of turbulent elements being arranged in a two-dimensional pattern.

15. A heat transfer element vessel as set forth in claim 14, characterized in that the first plurality of turbulent elements includes a plurality of hemispherical dimples.

16. A heat transfer element vessel as set forth in claim 14, characterized in that the first plurality of turbulent elements includes a plurality of diamond-shaped protrusions.

17. A heat transfer element vessel as set forth in claim 14, characterized in that a spacing between adjacent turbulent elements in the first plate is less than a spacing between adjacent elongated notches in the first plate.

18. A heat transfer element vessel as set forth in claim 14, characterized in that the first angle is in a range of 5° to 45° with respect to the flow direction and wherein the rows of turbulent Qfrnznn / zznz / e / Y elements in the first plate are oriented at a second angle with respect to the flow direction, and wherein the second angle is different from the first angle.

19. A heat transfer element container 5 as set forth in claim 18, characterized in that the second angle is -45°.

20. A heat transfer element vessel as set forth in claim 14, characterized in that the two-dimensional pattern of the second plurality of turbulent elements 10 includes rows and columns of turbulent elements and the turbulent elements in adjacent rows are staggered such that the spaces between turbulent elements in one row are laterally offset from the spaces between turbulent elements in an adjacent row.

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