Patent Publication Number: US-11642647-B2

Title: Fill sheets and related fill pack assemblies

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 17/082,589, filed Oct. 28, 2020, now U.S. Pat. No. 11,433,370 and titled, “Fill Sheets and Related Fill Pack Assemblies,” and claims the benefit of U.S. Provisional Patent Application No. 62/951,365, filed on Dec. 20, 2019 and titled “Fill Sheets and Related Fill Pack Assemblies,” the entire contents of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     A variety of film fills and fill sheets are available for cross-flow cooling towers that may be assembled together into fill packs. In order to distinguish and create advantages in the marketplace, it is important for a fill manufacturer to offer a product with improvements over competing fill options. Some examples of these advantages include improved tower performance through a higher efficiency fill, ease of installation, product longevity, product cost, and reduction of drift exiting the fill. 
     The performance of a cooling tower can be characterized by the quantity of water or other cooling fluid that can be cooled to a specified operating temperature for a certain set of ambient conditions. In order to achieve this cooling, water is sprayed onto the cooling tower fill and is exposed to an air flow, thereby causing evaporation of a small portion of water into the air, which cools the remaining water. By increasing the amount of evaporation occurring within the cooling tower, the overall performance of the tower may also be increased or improved. Since most of this evaporation occurs within the fill, changes to the fill design can significantly impact the amount of cooling a tower can achieve during operation. Specifically, changes to a cooling tower fill that reduce the pressure drop across a fill for a given air flow or otherwise improve the thermal performance of the fill, will result in a better performing cooling tower. By reducing the pressure drop across a fill, the resistance to airflow through the tower is decreased, allowing more air to pass over the water film for the same fan power, thereby causing the amount of evaporation to increase. To improve the thermal performance of a fill, increased mixing of the air and water can increase the amount of evaporation of water into the air by improving the conditions at the air-water interface. Generating mixing of the air, however, typically requires changes to the fill which also increases the pressure drop across the fill, indicating the need for fill designs which can either reduce pressure drop over existing designs with minimal impact to mixing or improved strategies for mixing which require equal or less pressure drop. 
     For cross-flow cooling towers, film fills are installed in the tower as a hanging fill, or as a bottom supported fill. For hanging fills, holes are punched near the top of the fill sheets to accept rails or for mounting on rails where the fill sheets are spaced along the length of the rails. This causes the individual fill sheets to be under tensile loading under the holes, but under compressive loading at the rail-sheet interface. For bottom supported fills, sheets are secured together into rigid blocks of fill, then placed on top of a support structure in the tower. Typically, bottom supported fills are easier to install into towers than hanging fills but the bottom supported fill sheets require additional structural features to resist the compressive loading seen during use, particularly during operation under loading from the water or other cooling fluid utilized in the tower or from the accumulation of external deposits, such as ice, biological foulants, scale or related other accumulated deposits that all apply additional weight and forces onto the fill. These structural features of the fill sheets, such as structural ribs or glue boss features, usually provide little to no thermal benefit for the fill and increase the pressure drop, thereby resulting in reduced tower performance. Alternative to the structural ribs and glue bosses, thicker gauge sheets may be used for the fill construction, however the increase in gauge thickness increases the total cost of the fill by adding more material to each fill sheet. 
     For film fills used in cross-flow towers, all fills contain a dedicated heat transfer area, while some also contain an integral drift eliminator near the air outlet of the fill and/or a louver section near the air inlet of the fill. The heat transfer area of the fill is responsible for the thermal performance of the fill by providing a large surface area for water to spread out on the surfaces of the fill to increase contact with the air, mixing the air as it flows through the fill and mixing the water film as it flows over the sheets, while maintaining a low pressure drop across the fill. Typically, the heat transfer surface for cross-flow fills consists of fluted fill sheets with small surface features (microstructure) patterned across the surface or fill sheets with more aggressive patterned features and less pronounced flute features. For fills with flutes, the flutes are usually continuous across the heat transfer area or have a generally constant cross-section along their length and are commonly cross corrugated, although may be oriented horizontally or vertically. 
     Although most of the bulk water adheres to the surface of a film fill, some of the water forms small droplets and escapes the fill through the air outlet, otherwise known as drift. Drift is undesirable, as the drift represents a loss of water or other cooling fluid from the system and the loss of water or other cooling fluid has a cost to replenish, both itself and any treatment chemicals contained within the cooling fluid. The drift may also have a deleterious impact on surrounding equipment and environments since the drift may contain chemicals, salts and bacteria present in the circulating water or fluid. For cross-flow tower film fills, drift elimination features are sometimes included on the air outlet side of the sheet to capture these drift droplets and prevent them from escaping the cooling tower, which are referred to as drift eliminators and may be comprised of integral drift eliminators (“IDs”). For cross-flow film fills, there are typically two different types of drift eliminators which may be integrated, including the tube drift eliminator and the blade drift eliminator. Generally, tube drift eliminators are angled tubes formed into the ID section of the fill by aligning drift corrugations of adjacent sheets. As water droplets enter the tubes entrained in the air stream, the momentum of the droplets causes them to impact the tube wall as the airflow changes direction while following the angled tube of the ID. A vertical channel is typically included at the inlet of the integral drift eliminator tubes to allow water collected on the surface of the integral drift eliminator to drain out of the fill into a lower catch basin, and to provide vertical structural support for bottom supported fills. One limitation of current implementations of this type of drift eliminator is introduced when water reaches the tube inlet of the eliminator. When water reaches the transition between the tube section and the drain, some water may be pushed along part of the top wall of the tube by the air before falling off into the air stream. By introducing droplets farther into the eliminator, it becomes easier for these droplets to escape out of the eliminator without impacting a wall, thereby reducing eliminator performance. Integral blade drift eliminator designs accomplish drift removal by creating a large vertically oriented ridge, near the air outlet of the fill to change the direction of airflow. The momentum of the water droplets at the integral drift eliminator inlet causes an impact with the ridge walls, eliminating the drift from the airstream. Other structural features such as ribs or spacers may be included before or after the eliminator ridge to ensure the sheets remain separated during operation and to stiffen the fill and/or sheet, as well as the assembled fill pack. 
     At the air inlet of the fill, integral louvers are sometimes included into the fill design to prevent water from splashing out of the front of the fill. These integral louvers are usually comprised of corrugations which are angled downward as they protrude into the fill, to provide a sloped surface for the water to run down, thereby preventing water or other cooling fluid from reaching the front of the fill. The corrugations on each sheet may be assembled together to form tubes or remain parallel to adjacent sheet corrugations with additional sheet spacer features added to the design. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the preferred invention is directed to a fill sheet for cooling a heat transfer fluid in a cooling tower when assembled into fill packs comprised of pluralities of fill sheets for use in a cross-flow cooling tower. The fill sheet includes an air intake end, an air outlet end positioned opposite the air intake end along a lateral axis, a top edge connecting the air intake end and the air outlet end and a bottom edge connecting the air intake end and the air outlet end. The bottom edge is positioned opposite the top edge along a vertical axis. The heat transfer fluid is configured for flowing between the top edge and the bottom edge. A plurality of flutes extends generally along the lateral axis between the air intake end and the air outlet end. An offset or transition feature provides a flat section of macrostructure and extends generally parallel to the vertical axis. A first flute of the plurality of flutes transitions from a first peak at a first side of the offset to a first valley at a second side of the offset. The offset or transition feature includes a rib extending generally parallel to the vertical axis and a spacer to provide structural support for the offset. Microstructure is preferably integrally formed into the offset and has a generally herringbone shape. The spacer is preferably comprised of a first plurality of spacers, wherein each of the plurality of flutes includes one of the first plurality of spacers positioned thereon at the offset or transition feature. The rib is preferably comprised of an intermediate rib, including a first intermediate rib and a second intermediate rib and the spacer is comprised of an intermediate column of spacers. 
     In another aspect, the preferred invention is directed to a fill sheet for cooling heat transfer fluid in a cooling tower when arranged into fill packs comprised of pluralities of fill sheets. The fill sheet includes an air intake end, an air outlet end positioned opposite the air intake end along a lateral axis, a top edge connecting the air intake end and the air outlet end and a bottom edge connecting the air intake end and the air outlet end. The bottom edge is positioned opposite the top edge along a vertical axis. A plurality of spacers extends from a heat transfer area of the fill sheet between the air intake end, the air outlet end, the top edge and the bottom edge. The plurality of spacers includes a first spacer having a first head end and a first tail end. The first head end is positioned closer to the top edge than the first tail end. The first spacer defines a first spacer axis. The first spacer axis defines a first acute spacer angle with the lateral axis. The plurality of spacers includes a second spacer having a second head end and a second tail end. The second head end is positioned closer to the top edge than the first tail end. The second spacer defines a second spacer axis. The second spacer axis defines a second acute spacer angle with the lateral axis. The first spacer axis extends at an opposite side of the vertical axis relative to the second spacer axis. 
     In yet another aspect, the preferred invention is directed to a fill pack for cooling heat transfer fluid in a cooling tower. The fill pack includes a first fill sheet having a first top edge, a first bottom edge and a first heat transfer area between the first top edge and the first bottom edge and a second fill sheet having a second top edge, a second bottom edge and a second heat transfer area between the second top edge and the second bottom edge. A first plurality of spacers extends generally perpendicularly relative to a first sheet plane from the first fill sheet. The first plurality of spacers includes a first spacer having a first head end and a first tail end. The first head end is positioned closer to the first top edge than the first tail end. A second plurality of spacers extends generally perpendicularly relative to a second sheet plane from the second fill sheet. The second plurality of spacers includes a second spacer having a second head end and a second tail end. The second head end is positioned closer to the second top edge than the second tail end. The first head end is positioned proximate the second head end in an installed configuration. A vertical axis is defined generally perpendicularly relative to the first and second top edges and the first and second bottom edges. The first tail end extends toward an opposite side of the vertical axis relative to the second tail end. 
     In a further aspect, the preferred invention is directed to a fill pack for cooling heat transfer fluid in a cooling tower. The fill pack includes a first fill sheet having a first air intake side, a first top edge, a first air outlet side and a first heat transfer area between the first air intake side and the first air outlet side and a second fill sheet having a second air intake side, a second top edge, a second air outlet side and a second heat transfer area between the second air intake side and the second air outlet side. An integral drift eliminator is associated with the first and second air outlet sides in an installed configuration. The drift eliminator defines a plurality of tubes with a drift eliminator inlet positioned proximate the first and second heat transfer areas and a drift eliminator outlet spaced away from the first and second heat transfer areas. The plurality of tubes extends generally toward the first and second top edges from the drift eliminator inlet toward the drift eliminator outlet. Each of the plurality of tubes includes a blocking structure on each of the plurality of tubes at the drift eliminator inlet configured to block a film of the heat transfer fluid at the drift eliminator inlet to promote droplet formation and direct the heat transfer fluid back into the heat transfer area. 
     In an additional aspect, the preferred invention is directed to a fill sheet for cooling heat transfer fluid in a cooling tower when assembled into fill packs comprised of pluralities of fill sheets. The fill sheet includes an air intake end, an air outlet end positioned opposite the air intake end along a lateral axis, a top edge connecting the air intake end and the air outlet end and a bottom edge connecting the air intake end and the air outlet end. The bottom edge is positioned opposite the top edge along a vertical axis. A microstructure is formed on the fill sheet. A support rib extends between the top edge and the bottom edge. The support rib includes a first support rib and a second support rib. The first and second support ribs are spaced laterally from each other along the lateral axis and extend substantially parallel to the vertical axis. The support rib has a first support rib portion having a first support rib length. The first support rib includes a first rib height and the second support rib including a second rib height. The microstructure has a microstructure height. The first rib height is less than the microstructure height in the first support rib portion and the second rib height is greater than the microstructure height in the first support rib portion. The support rib is preferably comprised of an outlet side rib positioned proximate the air outlet end. The first support rib portion preferably has a first support rib portion length. In the preferred embodiment, the first rib height may be comprised of a rib minimum height and the second rib height may be comprised of a rib maximum height with the rib height transitions between the rib maximum heights and the rib minimum heights. 
     In a further aspect, the preferred present invention is directed to a fill sheet for cooling heat transfer fluid in a cooling tower when assembled into fill packs comprised of pluralities of fill sheets. The fill sheet includes an air intake end, an air outlet end positioned opposite the air intake end along a lateral axis, a top edge connecting the air intake end and the air outlet end and a bottom edge connecting the air intake end and the air outlet end. The bottom edge is positioned opposite the top edge along a vertical axis. A plurality of ribs positioned generally between the air intake end and the air outlet end. An intermediate rib is positioned generally between the air intake end and the air outlet end. The intermediate rib includes a first intermediate rib and a second intermediate rib. The first intermediate rib extends from a top end proximate the top edge to first end. The second intermediate rib extends from a bottom end proximate the bottom edge to a second end. The second rib includes the second end and a third end. The first end is positioned proximate the second end. An offset extends generally parallel to the vertical axis. A first flute of a plurality of flutes transitions from a first peak at a first side of the offset to a first valley at a second side of the offset. The intermediate rib is positioned at the offset. The first end of the first rib is positioned proximate the second end of the second rib. At least one of the first and second ribs are intersected by the lateral axis between the top end and the third end. The first and second ribs are preferably spaced at a lateral spacing that is between one-quarter and two inches (¼-2″). The first and second ribs of the preferred embodiments may be comprised of any one of intake side ribs, outlet side ribs or intermediate ribs. The first rib may be comprised of a first intermediate rib segment and the second rib may be comprised of a second intermediate rib segment, therein a first end and a second end are positioned proximate a middle of the fill sheet in the preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG.  1    is a front elevational view of a fill sheet in accordance with a first preferred embodiment of the present invention; 
         FIG.  1 A  is a magnified front perspective view of a portion of the fill sheet of  FIG.  1   , taken from within shape  1 A of  FIG.  1   ; 
         FIG.  1 B  is a side perspective view of the fill sheet of  FIG.  1   , taken along the line  1 B- 1 B of  FIG.  1   ; 
         FIG.  1 C  is a wireframe front perspective view of a portion of the fill sheet of  FIG.  1   , representing undulating flutes and offsets of the fill sheet; 
         FIG.  2    is a bottom perspective view of a portion of an air outlet section of the fill sheet of  FIG.  1   , taken generally rearwardly of the line  2 - 2  of  FIG.  1   ; 
         FIG.  2 A  is a front elevational view of the portion of the air outlet section of the fill sheet of  FIG.  2   ; 
         FIG.  2 B  is a cross-sectional view of a portion of the fill sheet of  FIG.  1   , taken along line  2 B- 2 B of  FIG.  2   ; 
         FIG.  2 C  is a cross-sectional view of a portion of the fill sheet of  FIG.  1   , taken along line  2 C- 2 C of  FIG.  2 A ; 
         FIG.  2 D  is a cross-sectional line view of the fill sheet of  FIG.  1   , taken along line  2 D- 2 D of  FIG.  2   ; 
         FIG.  3    is a bottom plan view of a pair of fill sheets of  FIG.  1    installed or assembled together to define a fill pack; 
         FIG.  3 A  is a cross-sectional line view of the fill pack of  FIG.  3   , taken along line  3 A- 3 A of  FIG.  3   ; 
         FIG.  3 B  is a cross-sectional line view of the fill pack of  FIG.  3   , taken along line  3 B- 3 B of  FIG.  3   ; 
         FIG.  3 C  is a cross-sectional line view of the fill pack of  FIG.  3   , taken along line  3 C- 3 C of  FIG.  3   ; 
         FIG.  4    is a magnified bottom plan view of a portion of the fill pack of  FIG.  3   , wherein spacers of the fill sheet are shown in an installed or assembled configuration; 
         FIG.  5    is a front elevational representation of the shapes of the spacers of  FIG.  4   ; 
         FIG.  6    is a front elevational representation of alternative shapes for the spacers of  FIG.  4   ; 
         FIG.  7    is a front elevational view of a fill sheet in accordance with a second preferred embodiment of the present invention, which includes an integrated drift eliminator at an air outlet side of the fill sheet; 
         FIG.  8    is a front perspective view of the fill sheet of  FIG.  7   , taken from within shape  8 - 8  of  FIG.  7   ; 
         FIG.  9    is a cross-sectional view of a portion of a pair of fill sheets installed or assembled together to define a fill pack, taken along line  9 - 9  of  FIG.  7    and generally showing a flute of a drift eliminator and connection of the drift eliminator flute to a cooling section of the fill sheets; and 
         FIG.  10    is a front elevational representation of a fill sheet in accordance with a third preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain terminology is used in the following description for convenience only and is not limiting. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. The words “right,” “left,” “lower,” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” “front” or “rear” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center or orientation of the fill sheets or fill packs and related parts thereof. The terminology includes the above-listed words, derivatives thereof and words of similar import. 
     It should also be understood that the terms “about,” “approximately,” “generally,” “substantially” and like terms, used herein when referring to a dimension or characteristic of a component of the invention, indicate that the described dimension/characteristic is not a strict boundary or parameter and does not exclude minor variations therefrom that are functionally the same or similar, as would be understood by one having ordinary skill in the art. At a minimum, such references that include a numerical parameter would include variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit. 
     Referring to  FIGS.  1 - 3 C , a fill sheet, generally designated  10 , in accordance with a first preferred embodiment of the present invention has a heat transfer section  11 , along with an air inlet portion  12 , which may include an integral louver (not shown), an air outlet portion  14 , which may include an integral drift (See  FIGS.  7 - 9   ), and/or other standard end features at the inlet portion  12  and/or the outlet portion  14 , as well as additional features, such as intermediate honeycombs. The fill sheet  10  is not limited to including the integral louver or the integral drift, neither of which are shown in the first preferred embodiment of the fill sheet  10 , and may function without the louver and drift or may include alternative features attached to, integrally formed with, positioned adjacent to or abutting the air inlet and outlet portions  12 ,  14 , such as non-integral louvers and drift that abut, but are not integrally formed with the fill sheet  10 . The air inlet portion  12  of the first preferred fill sheet  10 , which may include an integral louver, is positioned at the air intake side  10   a  of the sheet  10  and the air outlet portion  14 , which may include an integral drift, is positioned at the air outlet side  10   b  of the preferred cross-flow fill sheet  10 . 
     The heat transfer section  11  of the first preferred fill sheet  10  includes a herringbone-shaped microstructure  11   a  or the microstructure  11   a  has a generally herringbone shape to increase the surface area of the fill sheet  10  in the heat transfer section  11  and provide mixing of the air and water during operation. The microstructure  11   a  is not limited to being comprised of the herringbone-shaped microstructure and may be comprised of alternatively sized and shaped microstructure that increases the surface area of the fill sheet  10  in the heat transfer section  11  to expose additional water film area to the airflow. The microstructure  11   a  preferably has a smaller microstructure height H s  when compared to the height of the macrostructure of the preferred fill sheet  10 , wherein the macrostructure includes features such as the plurality of flutes  18 , as is described in greater detail below. In the preferred embodiments, the microstructure height H s  is three hundredths of an inch to one-half inch (0.03-0.5″) but is not so limited and may fall outside this range depending on designer preferences, microstructure type, cooling tower type, expected loading and related design considerations and preferences. The microstructure height Hs, however, of the preferred microstructure  11   a  is within the preferred range of the microstructure height H s  and is adaptable for use with the preferred fill sheets  10 . 
     The heat transfer section  11  of the fill sheet  10  also includes a spacer  16 , which may be comprised of pluralities of spacers  16 . The spacers  16  may be comprised of glue bosses, peg spacers or other similar structures or features that space the fill sheets  10 ,  9   a ,  9   b  from each other in the assembled or installed configurations. The spacers  16  preferably extend from opposing front and rear surfaces of the fill sheet  10  and mate with opposing spacers  16  on adjacent fill sheets  10 , but are not so limited and may be configured to extend from only a single surface of the fill sheet  10  or may be otherwise sized and configured to space the fill sheets  10  in the assembled configurations. The spacers  16  on the adjacent fill sheets  10  in an assembled configuration are also preferably comprised of mating glue bosses or peg spacers that facilitate spacing of the assembled fill sheets  10  relative to each other. The spacers  16  are not limited to mating glue bosses or peg spacers and may be comprised of nearly any feature of the fill sheets  10  that facilitates spacing of the adjacent fill sheets  10  relative to each other in the assembled configuration, including suspension or hanging of the fill sheets  10  next to each other at predetermined spacing intervals or distances during operation. The spacers  16  may assist in joining or bonding the adjacent fill sheets  10  together in the assembled configuration or may provide general spacing between the adjacent fill sheets  10  in the assembled configuration. The configuration and operation of the spacers  16  are described in greater detail below. The fill sheets  10  of the preferred embodiments may also include spacers  16  with alignment or connection features  19  extending therefrom. The spacers  16  preferably provide a surface for mating with a spacer  16  from an adjacent fill sheet  10  to appropriately space a first fill sheet  9   a  from a second fill sheet  9   b  in the assembled or installed configuration. The alignment or connection features  19  preferably facilitate proper alignment of the first sheet  9   a  relative to the second sheet  9   b  and/or provide for engagement or connection of the adjacent fill sheets  10  in the assembled or installed configuration. 
     The heat transfer section  11  of the fill sheet  10  further includes flutes  18  arranged thereon that generally extend parallel or substantially parallel to a lateral axis  20  of the fill sheet  10 . The lateral axis  20  extends generally horizontally in an installed configuration of the fill sheets  10  and is oriented generally perpendicular to a vertical axis  22 . The flutes  18  preferably guide the airflow through the heat transfer area  11 , generally along the lateral axis  20  from the intake side  10   a  to the outlet side  10   b.    
     The first preferred fill sheet  10  also includes an improved rib configuration for vertical and lateral rigidity and strength of the fill packs in the assembled configuration, including intake side ribs  24  and outlet side ribs  26  that extend generally parallel to the air intake side  10   a  and air outlet side  10   b , respectively. The intake side ribs  24  and the outlet side ribs  26  are preferably integrally formed in the fill sheet  10  proximate the air intake side  10   a  and the air outlet side  10   b , respectively and adjacent to the heat transfer area  11  or within the heat transfer area  11 . The intake side ribs  24  and the outlet side ribs  26  are described in greater detail below. 
     Referring to  FIGS.  7 - 9   , in a second preferred embodiment, a fill sheet  10 ′ has similar features to the first preferred fill sheet  10  and the same reference numerals are utilized to identify similar or the same features, with a prime symbol (′) utilized to distinguish the features of the second preferred embodiment from the first preferred embodiment. The second preferred fill sheet  10 ′ includes an integral drift eliminator  50  that improves upon known tube based integral drift eliminators (not shown) by introducing a blocking structure  100  to improve drift performance, as is described greater detail below. 
     Referring to  FIGS.  1  and  7   , in the first and second preferred embodiments, the fill sheets  10 ,  10 ′ are oriented in the cooling tower and configured at a forward lean or to have a pack angle Δ, Δ′ of approximately five to ten (5-10) degrees in order to offset the effects of the crossing airflow on the vertically flowing water on the fill sheet surfaces during operation. As the water flows down the sheets  10 ,  10 ′, generally parallel to the vertical axis  22 ,  22 ′, the air tends to push the water toward the air outlet side  10   b ,  10   b ′ of the fill sheets  10 ,  10 ′ due to friction at the air-water interface. The fill sheets  10 ,  10 ′, thereby lean into the direction of air flow, generally along the lateral axis  20 ,  20 ′ such that a top front corner of the fill sheets  10 ,  10 ′ near the intersection of the air intake side  10   a ,  10   a ′ and a top edge  28 ,  28 ′ is positioned closest to the air inlet of the tower. The lower front corner of the fill sheets  10 ,  10 ′ near the intersection of the air intake side  10   a ,  10   a ′ and a bottom edge  30 ,  30 ′ is the portion of the air intake side that is positioned furthest from the air inlet of the tower. 
     Referring to  FIGS.  1 - 3 C , the heat transfer area  11  of the fill sheet  10  is comprised of the herringbone-shaped microstructure  11   a  formed over the flutes  18  and covers a majority of the interior of the fill sheet  10 . The geometry of the flutes  18  is generally comprised of individual flutes  18  oriented substantially in the air travel direction or generally parallel to the lateral axis  20 . The fill sheets  10  also preferably include transition features  32 , which may be comprised of offsets  32  in the flutes  18 . The transition features  32  preferably provide a generally flat macrostructure extending generally parallel to the vertical axis  22  or pitched by the pack angle Δ, Δ′ from the vertical axis  22 . A first flute  18  of the plurality of flutes  18  transitions from the flat section of the transition feature  32  to the arcuate macrostructure spaced from the transition feature  32  (See  FIG.  1 C ). The flat section preferably includes a rib or support  38  extending generally parallel to the vertical axis  22  and a spacer  16  to provide lateral support for the rib or support  38 . The spacer  16  is preferably positioned proximate the rib or support  38  to provide lateral support for the rib or support  38  and is not limited to being positioned in the flat section or transition feature  32  but is preferably positioned proximate the rib or support  38  to provide lateral support. The spacer  16  is preferably comprised of a first plurality of spacers  16  along or at the offset  32 , wherein each of the plurality of flutes  18  is associated with or includes one of the first plurality of spacers  16  positioned thereon at the offset, flat section or transition feature  32 . The pluralities of spacers  16  of the first preferred fill sheet  10  are positioned at each of the offsets  32  proximate the air intake side  10   a , proximate the air outlet side  10   b , and proximate the intermediate vertical ribs  38 , respectively. 
     The preferred fill sheets  10  include several intermediate offsets  32  in the flutes  18  where the peaks  36  of the flutes  18  transition to valleys  34 , and vice versa, generally along the air flow direction or the lateral axis  20 . The offsets or transition features  32  are typically positioned proximate to the columns of spacers  16  such that two adjacent fill sheets  10 , such as the first and second fill sheets  9   a ,  9   b  ( FIGS.  3 - 3 C ) may be connected together or positioned next to each other to define a fill pack  8 . The first preferred fill sheets  10  and the fill pack  8  of  FIGS.  1 C and  3 - 3 C  show the transition of the peaks  36  to the valleys  34  and the valleys  34  to the peaks  36  on opposite sides of the offsets or transition features  32  in the direction of the lateral axis  20 , thereby creating a generally parallel orientation of the adjacent first and second fill sheets  9   a ,  9   b  in the heat transfer area  11 . The position of the offsets  32  in the air travel direction or generally parallel to the lateral axis  20  is staggered between the adjacent first and second fill sheets  9   a ,  9   b  for any given vertical position on the fill pack  8 . By staggering the offsets  32 , a majority of the profiles of the flutes  18  for the fill pack  8  is parallel ( FIGS.  3 C and  3 D ) to the adjacent first and second sheets  9   a ,  9   b , while short segments of the fill pack  8  between sets of offsets  32  have an opposing profile or adjacent peaks  36  to valleys  34  in the offsets  32  of the adjacent sheets  9   a ,  9   b  ( FIG.  3 B ), thereby providing a location for spacers  16  to be incorporated into the design without significantly protruding into the airstream of the flutes  18  and contributing to pressure drop. This first preferred configuration of the flutes  18  provides an advantage over prior tube-based flute arrangements by allowing the majority of the profiles of the flutes  18  of the fill pack  8  to remain generally parallel to and between the adjacent sheets  9   a ,  9   b , thereby reducing areas of restricted air flow between the peaks  36  and valleys  34  of adjacent sheets  9   a ,  9   b  of the fill pack  8 . The staggered offsets  32  also create a short tube region within the fill pack  8 , which offers structural advantages over a flute design that only consists of parallel flute profiles. By providing short segments proximate the offsets  32  where the flutes  18  are aligned into a tube configuration with the peaks  36  and valleys  34  of the adjacent sheets  9   a ,  9   b  generally aligning in the offsets  32 , the lateral stiffness of the fill pack  8  is increased, without the need for large spacer features intruding into the airflow region. In addition, the transition regions on either side of the tube structure of the offsets  32  provide a generally flat section to add vertical ribs or supports, such as intermediate vertical ribs or supports  38  without cutting through the profile of the flutes  18 . The intermediate vertical ribs or supports  38  strengthen the fill pack  8  without significantly increasing the pressure drop across the fill pack  8  between the air intake side  10   a  and the air outlet side  10   b.    
     Referring to  FIGS.  3  and  4 - 6   , in addition to the improved geometry of the flutes  18  in the fill pack  8  of the first preferred embodiments used in the cross-flow fill design, improvements have been made to the spacers  16  used to space the adjacent fill sheets  9   a ,  9   b  apart to define the fill packs  8 . The first preferred embodiment of the spacers  16  has a generally angled teardrop or raindrop shaped spacer  16 , at least in the heat transfer area  11  where the microstructure  11   a  is formed on the fill sheets  10 . In an installed configuration, a first spacer  16   a  of the first fill sheet  9   a  mates with and is joined, positioned in facing engagement or positioned proximate to a second spacer  16   b  on the second, adjacent fill sheet  9   b  to space the first and second fill sheets  9   a ,  9   b  at a predetermined distance from each other and may facilitate joining or connection of the adjacent fill sheets  9   a ,  9   b . The preferred fill sheets  9   a ,  9   b  have a plurality of spacers  16  that extend from both opposing faces of the fill sheets  9   a ,  9   b  to mate with adjacent fill sheets  9   a ,  9   b ,  10  in the installed configuration. As a non-limiting example, the first preferred fill sheets  9   a ,  9   b ,  10  have three columns of fourteen (14) spacers  16  proximate a middle of the fill sheets  9   a ,  9   b ,  10  along the offsets  32  and the air intake and air outlet sides  10   a ,  10   b , respectively. The fill sheets  9   a ,  9   b  also include pluralities of spacers  16  positioned adjacent the air intake and air outlet sides  10   a ,  10   b  with the alignment or connection features  19  thereon. The three columns of spacers  16  include an intermediate column of spacers  15   b , an air intake side column of spacers  15   a  and an air exit side column of spacers  15   c . In the first preferred embodiment, the air intake side column of spacers  15   a  is positioned at an air intake side offset  32 , the intermediate column of spacers  15   b  is positioned at an intermediate offset  32  and the air exit side column of spacers  15   c  is positioned at an air exit side offset  32 . The intermediate column of spacers  15   b  is positioned between a first intermediate rib  38   a  and a second intermediate rib  38   b  at the intermediate offset  32 . The first intermediate rib  38   a  is positioned between the intermediate column of spacers  15   b  and the air intake side  10   a  and the second intermediate rib  38   b  is positioned between the intermediate column of spacers  15   b  and the air exit side  10   b . The fill sheets  9   a ,  9   b ,  10  are not limited to including the fourteen (14) spacers  16  in each of the columns of spacers  15   a ,  15   b ,  15   c  or to the specific locations shown in the preferred embodiments and may include more or less spacers  16 , depending on the size of the fill sheets  9   a ,  9   b ,  10 , the expected loading on the fill sheets  9   a ,  9   b ,  10 , the expected environment, designer preferences and related factors. The fill sheets  9   a ,  9   b ,  10  may include nearly any number of spacers  16  that facilitate spacing or joining of the adjacent sheets  9   a ,  9   b ,  10  together in the installed configuration, are able to withstand the normal operating conditions of the spacers  16  and perform the functions of the spacers  16 , as described herein. 
     In the first preferred embodiment, each of the spacers  16  includes a generally wider and relatively semi-circular shaped head end  40  and a narrower tail end  42 . The first spacer  16   a  includes a first head end  40   a  and a first tail end  42   a  and the second spacer  16   b  includes a second head end  40   b  and a second tail end  42   b . The head ends  40  and the tail ends  42  define the teardrop or raindrop shape of the spacer  16 , wherein the tail ends  42 ,  42   a ,  42   b  are generally rounded, particularly in comparison to a traditional teardrop or raindrop shape. In the installed configuration, the head ends  40  of adjacent spacers  16  generally mate and provide surfaces for joining the spacers  16  and the tail ends  42  extend away from each other in the installed configuration, generally to opposite sides of the vertical axis  22 . The tail ends  42  of the first preferred embodiment extend away from the head ends  40  along a spacer axis  17 . In the first preferred embodiment, the first spacer  16   a  includes a first spacer axis  17   a  and the second spacer  16   b  includes a second spacer axis  17   b . The first and second spacer axes  17   a ,  17   b  preferably define first and second acute spacer angles Ωa, Ωb, respectively, with the lateral axis  20  that are approximately ten to eighty degrees (10-80°), but are not so limited and may take on nearly any acute angle that facilitates performance of the functioning of the spacers  16  and withstands the normal operating conditions of the spacers  16 , such as within the range of approximately twenty to fifty degrees (20-50°) or approximately thirty-five degrees (35°). The first spacer axis  17   a  preferably extends at a first side of the vertical axis  22  and the second spacer axis  17   b  preferably extends at a second, opposite side of the vertical axis  22 , such that the first and second spacer axes  17   a ,  17   b  extend at opposite sides of the vertical axis  22 . This extension of the first and second spacer axes  17   a ,  17   b  at opposite sides of the vertical axis  22  results in the first and second tail ends  42   a ,  42   b  being spaced from each other in an installed configuration such that cooling fluid generally does not collect at and bridge between the first and second tail ends  42   a ,  42   b , particularly if they were to substantially mate. The first spacer axis  17   a  preferably extends from a central portion of the first head end  40   a  through a central portion of the first tail end  42   a  and the second spacer axis  17   b  preferably extends from a central portion of the second head end  40   b  through a central portion of the second tail end  42   b , even if the first and second spacers  16   a ,  16   b  have some curvature to the tail ends  42   a ,  42   b  and is not necessarily straight or uniformly shaped. The first and second spacer axes  17   a ,  17   b  also preferably define a separation angle μ measured between the first and second acute spacer angles Ωa, Ωb across the vertical axis  22 . The separation angle μ is preferably between approximately twenty and one hundred sixty degrees (20-160°), preferably approximately one hundred twenty degrees (120°). The separation angle μ plus the first and second spacer angles Ωa, Ωb preferably sum to one hundred eighty degrees (180°). 
     In the first preferred embodiment, adjacent spacers  16 , such as the first and second spacers  16   a ,  16   b , are oriented with their tail ends  42   a ,  42   b  extending in opposite directions or to opposite sides of the vertical axis  22 , thereby forming an upside down V-shape when viewed from the front or rear ( FIGS.  5  and  6   ). This mis-alignment of the tail ends  42 ,  42   a ,  42   b  allows water, which hits the head ends  40 ,  40   a    40   b  of the pair of spacers  16 ,  16   a ,  16   b , to run down the sloped side surfaces of each of the spacers  16 ,  16   a ,  16   b  and separate near the tail ends  42 ,  42   a ,  42   b  of the spacers  16 ,  16   a ,  16   b . In contrast, prior art glue bosses that fully align and have generally the same size and shape result in the water or other cooling fluid flowing over the prior art glue bosses and forming a film of water below the connection, which spans between the two associated fill sheets and impedes airflow. The inverted V shape formed by the tail ends  42 ,  42   a ,  42   b  of the adjacent spacers  16 ,  16   a ,  16   b  is the preferred shape to provide a contact surface to space adjacent fill sheets  10 ,  9   a ,  9   b  and to prevent water sheeting, while minimizing the height of the spacer profile between the adjacent fill sheets  10 ,  9   a ,  9   b  of the fill packs  8  in the waterflow direction or generally parallel to the vertical axis  22 . The preferred spacers  16  have the teardrop or raindrop shape, but this shape is not limiting. For example, in an alternative preferred embodiment, the spacers  16  may have a generally rectangular shape ( FIG.  6   ), or any shape which forms a contact feature with an adjacent spacer feature near the top of the connection, and slopes downward and away from the adjacent spacer  16  relative to the vertical axis  22 . The adjacent spacers  16 ,  16   a ,  16   b  are preferably glued or otherwise secured together, such as by ultrasonic welding or mechanical joining, at the mating surfaces in the installed configuration to connect the fill sheets  10 ,  9   a ,  9   b  together, thereby forming the fill packs  8 . The spacers  16 ,  16   a ,  16   b  are not limited to being glued or otherwise joined together in the installed configuration and may act exclusively as spacers to space the adjacent fill sheets  10 ,  9   a ,  9   b  relative to each other in the installed configuration, such as when the fill sheets  10 ,  9   a ,  9   b  hang from a rail adjacent to each other in the tower, but are not otherwise joined or connected at the spacers  16 ,  16   a ,  16   b . In addition, the spacers  16 ,  16   a ,  16   b  may include connection features that secure the spacers  16 ,  16   a ,  16   b  together in the installed configuration or may be otherwise connected or joined together in the installed configuration, such as by ultrasonic welding, mechanical deformation, fastening or otherwise securing the mating spacers  16 ,  16   a ,  16   b  together in the installed configuration. 
     Referring to  FIGS.  1 - 3 C , structural support is provided to the first preferred fill sheets  10 ,  9   a ,  9   b  and fill packs  8  by the intake side ribs  24 , the outlet side ribs  26  and the intermediate vertical ribs or supports  38 , as well as the remaining body of the fill sheets  10 ,  9   a ,  9   b . Each of the intake and outlet side ribs  24 ,  26  and the intermediate ribs  38  is preferably comprised of two substantially vertical support ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  extending along the height of the fill sheet  10 ,  9   a ,  9   b , generally parallel to the air intake side  10   a  and the air outlet side  10   b . In the first preferred embodiment, the support ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  are not fully vertical, but are oriented substantially parallel to the air intake and air outlet sides  10   a ,  10   b  of the fill sheets  9   a ,  9   b ,  10 , such that the support ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  are oriented generally at the pack angle Δ, Δ′ of approximately five to ten (5-10) degrees relative to the vertical axis  22 , but are not so limited and may be otherwise oriented and configured. The microstructure  11   a  of the heat transfer area  11  of each of the fill sheets  10 ,  9   a ,  9   b  is preferably comprised of angled bands of microstructure  11   a  in the herringbone arrangement, extending between at least the first structural intake and outlet side ribs  24   b ,  26   a , respectively, in the heat transfer area  11 . The preferred support ribs  24 ,  26 ,  38 , including the intake side ribs  24 ,  24   a ,  24   b , the outlet side ribs  26 ,  26   a ,  26   b  and the intermediate ribs  38 ,  38   a ,  38   b , extend generally vertically along the fill sheet  10 ,  9   a ,  9   b  in the installed configuration. The ribs  24   a ,  24   b ,  26   a ,  26   b , vary in height in an alternating pattern as they extend along the fill sheet  10 ,  9   a ,  9   b  from and between the top edge  28  and the bottom edge  30 . In the preferred embodiment, the intake and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  alternate between a maximum height H x  and a minimum height H n . The pairs of first and second intake side ribs  24   a ,  24   b  of the intake side rib  24 , the first and second outlet side ribs  26   a ,  26   b  of the outlet side rib  26 , and the first and second intermediate supports  38   a ,  38   b  of the intermediate support  38  are designed such that there is preferably at least one rib or support  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  with a height, such as the rib maximum height H x  extending past or being greater than the microstructure height H s  of the microstructure  11   a  on any given position along the lengths of the individual ribs or supports  24 ,  26 ,  38  on the fill sheets  10 ,  9   a ,  9   b.    
     In the first preferred embodiment, the first and second air intake ribs  24   a ,  24   b  are configured such that while the first air intake rib  24   a  has the maximum height H x  that extends past or is greater than the microstructure height H s  of the microstructure  11   a  and the second air intake rib  24   b  extends below or has the rib minimum height H n  that is less than the microstructure height H s  of the microstructure  11   a . Similarly, the first and second outlet side ribs  26   a ,  26   b  are configured such that while the first outlet side rib  26   a  has the rib maximum height H x  that extends past or is greater than the microstructure height H s  of the microstructure  11   a , the second outlet side rib  26   b  has the rib minimum height H n  that dips below or is less than the microstructure height H s  of the microstructure  11   a . The first and second intermediate ribs or supports  38   a ,  38   b  are similarly configured in the first preferred embodiment in that the first and second intermediate ribs  38   a ,  38   b  are laterally spaced, but are differently configured in that the first intermediate rib  38   a  substantially ends at a height where the second intermediate rib  38   b  begins. There may be sections where both of the first and second inlet side ribs  24   a ,  24   b , the first and second outlet side ribs  26   a ,  26   b  and the first and second intermediate ribs or supports  38   a ,  38   b  are taller than the surrounding microstructure  11   a  to provide additional support at the base of the fill sheets  10 ,  9   a ,  9   b  and fill packs  8 , such as where the fill pack  8  meets the supporting structure underneath the fill pack  8  in an assembled configuration in the tower. The air intake and outlet ribs  24 ,  26  are, however, preferably configured such that when one of the pair of first and second ribs  24   a ,  24   b ,  26   a ,  26   b , respectively, is at its greatest height relative to the microstructure  11   a , the adjacent one of the pair of first and second ribs  24   a ,  24   b ,  26   a ,  26   b , respectively, is at its smallest height or is generally below the height of the microstructure  11   a  and is substantially embedded in the microstructure  11   a . The first and second ribs  24   a ,  24   b ,  26   a ,  26   b , therefore, have alternating tapers between the top edge  28  and the bottom edge  30 . 
     The intake side rib  24  and the outlet side rib  26  are not limited to extending from the top edge  28  to the bottom edge  30 . The intake side rib  24  and the outlet side rib  26  may extend proximate to the top and bottom edges  28 ,  30  and may include some interruptions along their length, but the intake and outlet side ribs  24 ,  26  preferably extend to the top and bottom edges  28 ,  30  and are comprised of the alternately extending pairs of first and second ribs  24   a ,  24   b ,  26   a ,  26   b  that alternatively taper relative to each other. The intake and outlet side ribs  24 ,  26  extend to and between the top and bottom edges  28 ,  30  in the preferred embodiments. The intake and outlet side support ribs  24 ,  26  include the pairs of first and a second support ribs  24   a ,  24   b ,  26   a ,  26   b . The first and second support ribs  24   a ,  24   b ,  26   a ,  26   b  are spaced laterally from each other along the lateral axis  20  and extend substantially parallel to the vertical axis  22  or the intake and outlet sides  10   a ,  10   b . The intake and outlet side ribs  24 ,  26  have a first support rib portion  33  having a first support rib length or first support rib portion length L r1 . The first support ribs  24   a ,  26   a  include a first rib height and the second support ribs  24   b ,  26   b  include a second rib height. The first rib height is less than the microstructure height in the first support rib portion  33  and the second rib height is greater than the microstructure height in the first support rib portion  33 . The intake and outlet side ribs  24 ,  26  of the first preferred embodiment also have a second support rib portion  35  having a second support rib length or second support rib portion length L r2 . The first rib height is greater than the microstructure height in the second support rib portion  35  and the second rib height is less than the microstructure height in the second support rib portion  35 . 
     The intermediate rib  38  is alternatively constructed such that the first intermediate rib  38   a  extends from the top edge  28  approximately to a middle of the vertical height of the fill sheet  10  where the first intermediate rib  38   a  substantially ends and the second intermediate rib  38   b  starts and extends to the bottom edge  30 . The ribs  24 ,  26 ,  38  are not limited to having these configurations and may be otherwise designed and configured to provide strength and stiffness to the fill sheet  10 , such as switching the general configurations of the air intake and outlet ribs  24 ,  26  and the intermediate ribs  38  or configuring each of the ribs  24 ,  26 ,  38  substantially the same. 
     By alternating the height or positioning of the pairs of first and second ribs  24   a ,  24   b ,  26   a ,  26   b  of the inlet side and outlet side ribs  24 ,  26  and the intermediate ribs  38  so that the localized height of at least one of the pair of first and second ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  is preferably greater, specifically at the maximum height H x , than the microstructure height H s  of the microstructure  11   a  for any position along the length of the ribs  24 ,  26 ,  38  on the fill sheets  10 ,  9   a ,  9   b , it is ensured that each side of the fill sheet  10 ,  9   a ,  9   b  has at least one functioning stiffening member or rib  24 ,  26 ,  38  for all vertical positions along the air intake side and the air outlet side  10   a ,  10   b , respectively, as well as in the intermediate area or offset  32  between the intake and outlet sides  10   a ,  10   b , thereby limiting weak points or sections where the fill sheets  10 ,  9   a ,  9   b  may buckle. Additionally, the lower peak height sections of the pairs of first and second ribs  24   a ,  24   b ,  26   a ,  26   b  of the intake and outlet side ribs  24 ,  26 , wherein the maximum height H x  is present, allow the bands of overlapping microstructure  11   a  to stiffen the fill sheet  10 ,  9   a ,  9   b  in the air travel direction or generally parallel to the lateral axis  20  by creating minor corrugations which resist bending moment in the plane perpendicular to the applied force at the intake and outlet side ribs  24 ,  26 . This configuration increases the rigidity of the fill sheets  10 ,  9   a ,  9   b  for handling and shipping. The configuration of the intake and outlet side ribs  24 ,  26  and the intermediate rib  38 , wherein the full height rib sections or sections with the maximum rib height H x  overlap before transitioning to the lower height rib sections or sections with the minimum rib height H n  of the first and second ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b , respectively, where load is transferred between the pairs of first and second ribs  24   a ,  24   b ,  26   a ,  26   b ,  38   a ,  38   b  of the intake and outlet side ribs  24 ,  26  and the intermediate ribs  38  strengthens and also adds support at the intake and outlet sides  10   a ,  10   b  and the intermediate portion of the fill sheets  10 ,  9   a ,  9   b.    
     In the preferred embodiments, the maximum rib height H x  is approximately four hundredths of an inch to three-quarters of an inch (0.04-0.75″) or approximately one hundredth of an inch to one-quarter of an inch (0.01-0.25″) greater than the microstructure height H s . The maximum rib height H x  of the stiffening members or ribs  24 ,  26 ,  38  is not limited to these particular heights and may be otherwise sized and configured based on the expected loading of the stiffening member ribs  24 ,  26 ,  38 , external loading factors, designer preferences, size of the fill sheet  10 , type of cooling medium employed and other design considerations. The maximum height H x  of the support ribs  24 ,  26 ,  38 , however, preferably falls within the preferred range such that the maximum height H x  is greater than the microstructure height H s  in desired sections or segments while the minimum rib height H n  is less than the microstructure height H s  and the maximum rib height H x . In the preferred embodiments, the minimum rib height H n  is approximately zero to one-half inch (0-0.5″) or smaller than the microstructure height H s  of the particular fill sheet  10 . The minimum rib height H n  of the stiffening members or ribs  24 ,  26 ,  38  is not limited to these particular heights and may be otherwise sized and configured based on the expected loading of the stiffening member ribs  24 ,  26 ,  38 , external loading factors, designer preferences, size of the fill sheet  10 , type of cooling medium employed and other design considerations. The minimum rib height H n  preferably falls within the preferred range such that the minimum rib height is less than the microstructure height H s  in desired sections or segments. For example, the minimum rib height H n  is about half or less than half of the microstructure height H s  and the microstructure height Hs is slightly greater than half the maximum rib height H x  in the first preferred embodiment (See  FIG.  2 D ). The minimum rib height H n  may also be approximately zero, as is shown at the lower portion of the first intermediate rib  38   a  and the upper portion of the second intermediate rib  38   b  of the first preferred fill sheet  10  (See  FIG.  1   ). 
     In the first preferred embodiment, the first intermediate rib  38   a  includes a top intermediate rib end  39   a  and a first intermediate rib end  39   b  and the second intermediate rib  38   b  includes a second intermediate rib end  39   c  and a third intermediate rib end  39   d . The first intermediate rib end  39   b  is positioned proximate the second intermediate rib end  39   c  on the fill sheets  10 ,  9   a ,  9   b . The first intermediate rib  38   a  or the second intermediate rib  38   b  is intersected by the lateral axis  20  between the top intermediate rib end  39   a  and the third intermediate rib end  39   d , meaning the first intermediate rib  38   a  or the second intermediate rib  38   b  are intersected by the lateral axis  20  at generally any location along the height of the fill sheets  10 ,  9   a ,  9   b  between the top intermediate rib end  39   a  and the third intermediate rib end  39   d . In the first preferred embodiment, the lateral axis  20  preferably intersects the first intermediate rib  38   a  or the second intermediate rib  38   b  at any location between the top edge  28  and the bottom edge  30 , as the first intermediate rib  38   a  generally extends from the top edge  28  to a central portion of the fill sheet  10 ,  9   a ,  9   b  and the second intermediate rib  38   b  generally extends from the central portion of the fill sheet  10 ,  9   a ,  9   b , where the first intermediate rib end  39   b  is positioned proximate the second intermediate rib end  39   c , to the bottom edge  30 . The first and second intermediate ribs  38   a ,  38   b  are not limited to this preferred configuration and the first and second intermediate ribs  38   a ,  38   b  may be separated into multiple segments, preferably such that at least one of the segments of the first and second intermediate ribs  38   a ,  38   b  is intersected by the lateral axis  20  at generally any location along the height of the fill sheets  10 ,  9   a ,  9   b , as is described in further detail below with respect to the intake and outlet side ribs  24 ,  26 . 
     The first and second inlet and outlet side ribs  24   a ,  26   a ,  24   b ,  26   b  of the first preferred embodiment are comprised of a plurality of rib segments  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d , wherein the first inlet side rib  24   a  is comprised of a first inlet side rib segment  70   a  and a third inlet side rib segment  70   b , the second inlet side rib  24   b  is comprised of a second inlet side rib segment  70   c  and a fourth inlet side rib segment  70   d , the first outlet side rib  26   a  is comprised of a first outlet side rib segment  80   a  and a third outlet side rib segment  80   b  and the second outlet side rib  26   b  is comprised of a second outlet side rib segment  80   c  and a fourth outlet side rib segment  80   d . The first inlet side rib segment  70   a  includes a top end  71   a  and a first end  71   b  and the third inlet side rib segment  70   c  includes a fourth end  71   e  and a fifth end  71   f . The second inlet side rib segment  70   b  includes a second end  71   c  and a third end  71   d  and the fourth inlet side rib segment  70   d  includes a sixth end  71   g  and a seventh end  70   h . The first outlet side rib segment  80   a  includes a top end  81   a  and a first end  81   b  and the third outlet side rib segment  80   c  includes a fourth end  81   e  and a fifth end  81   f  The second outlet side rib segment  80   b  includes a second end  81   c  and a third end  81   d  and the fourth outlet side rib segment  80   d  includes a sixth end  81   g  and a seventh end  80   h . The inlet side rib  24  and outlet side rib  26  are configured such that at least one of the pluralities of segments  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d  is intersected by the lateral axis  20  at any position between the top ends  71   a ,  81   a  and the seventh ends  71   h ,  81   h , respectively. In contrast to the first and second intermediate ribs  38   a ,  38   b , the rib segments  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d  somewhat overlap in the height direction or the water flow direction, such as between the third and fourth ends  71   d ,  81   d ,  71   e ,  81   e  and the first and second ends  71   b ,  81   b ,  71   c ,  81   c , for example. The rib segments  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d  are not so limited and may be configured without the overlaps in the height direction and may include additional or less segments, although preferably such that at least one of the rib segments  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d  of each of the inlet side rib  24  and the outlet side rib  26 , respectively, is intersected by the lateral axis  20  at any position between the top and bottom edges  28 ,  30 . The inlet side ribs  24 , the outlet side ribs  26  and the intermediate ribs  38 , including the respective rib segments  38   a ,  38   b ,  70   a ,  70   b ,  70   c ,  70   d ,  80   a ,  80   b ,  80   c ,  80   d , extend generally parallel to the vertical axis  22  or the intake and outlet sides  10   a ,  10   b  in the first preferred embodiment, but are not so limited and may be otherwise oriented and configured to provide strength and stiffness to the fill sheets  9   a ,  9   b ,  10 . 
     In the preferred embodiments, the inlet side rib  24 , the outlet side rib  26  and the intermediate rib  38  include the adjacent first and second inlet side ribs  24   a ,  24   b , the first and second outlet side ribs  26   a ,  26   b  and the first and second intermediate ribs  38   a ,  38   b , respectively. The pairs of the first and second inlet side ribs  24   a ,  24   b , the first and second outlet side ribs  26   a ,  26   b  and the first and second intermediate ribs  38   a ,  38   b  are spaced at a lateral spacing S L  that is preferably between one-quarter and two inches (¼-2″). The lateral spacing S L  is not limited to being between one-quarter and two inches (¼-2″) and may be otherwise sized and configured based on fill sheet  10  loading, external loading factors, designer preferences, size of the fill sheet  10  and other design considerations. The lateral spacing S L  of the first and second outlet side ribs  26   a ,  26   b  is shown in  FIG.  2    and the first and second inlet side ribs  24   a ,  24   b  and the first and second intermediate ribs  38   a ,  38   b  are also similarly designed and configured to have the lateral spacing S L . 
     The inlet side rib  24  and the outlet side rib  26 , including first and second inlet and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  and have variable heights between the top and bottom edges  28 ,  30 . As a non-limiting example, the outlet side rib  26  and, specifically, the second outlet side rib  26   b  includes the second outlet side rib segment  80   b  and the fourth outlet side rib segment  80   d  with a reduced height portion or portion with the minimum rib height H n  of the second outlet side rib  26   b  extending between the second outlet side rib segment  80   b  and the fourth outlet side rib segment  80   d  between the top edge  28  and the bottom edge  30 . The second outlet side rib segment  80   b  preferably has the rib maximum height H x  in the second outlet side rib segment  80   b  and the fourth outlet side rib segment  80   d  has the rib minimum height H n  in a portion between the second and fourth outlet side rib segments  80   b ,  80   d . The second outlet side rib  26   b  of the preferred embodiment also includes transition portions  110  where the second outlet side rib  26   b  transitions between the rib maximum height H x  and the rib minimum height H n  along the length of the second outlet side rib  26   b . Each of the intake side ribs  24 ,  24   a ,  24   b  and the outlet side ribs  26 ,  26   a ,  26   b  are preferably similarly configured to the second outlet side rib  26   b , with the rib segments or portions having the rib maximum height H x , portions or segments having the rib minimum height H n  and the transition portions  110  between the segments with the rib maximum and minimum heights H x , H n . In addition, the pairs of intake side ribs  24   a ,  24   b  and outlet side ribs  26   a ,  26   b  preferably have the transition portions  110  at generally the same lateral positions along the lateral axis  20  and opposing rib maximum and minimum heights H x , H n  along the lateral axis  20  for the adjacent intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b , respectively. As a non-limiting example, the second outlet side rib segment  80   b  preferably has the rib maximum height H x  along the lateral axis  20  while the adjacent portion or segment of the first outlet side rib  26   a  has the rib minimum height H n . 
     The microstructure  11   a  in the heat transfer section  11  of the preferred embodiment has a microstructure height H s . The minimum height or first rib height H n  is less than the microstructure height H s  in a first rib support portion, such as along the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  wherein the ribs  24   a ,  24   b ,  26   a ,  26   b  have the minimum height H n . The maximum height H x  is, conversely, greater than the microstructure height H s  in a second rib support portion, such as along the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  wherein the ribs  24   a ,  24   b ,  26   a ,  26   b  have the maximum height H n . The ribs  24   a ,  24   b ,  26   a ,  26   b  are not so limited and may have consistently smaller or greater heights than the microstructure height Hs, depending on design and requirement considerations of the particular fill sheet  10 . The ribs  24   a ,  24   b ,  26   a ,  26   b  are not limited to the described configuration with the alternating maximum and minimum heights H x , H n  with the transition portions  110  therebetween and the microstructure height H s  being between the maximum and minimum heights H x , H n  and may be otherwise designed and configured to support the fill sheets  10  based on designer preferences, loads being carried by the fill sheet  10 , external factors of the operating environment or other factors that may drive the design and configuration of the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b . The intermediate rib  38  may be similarly designed and configured as the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  with the maximum and minimum heights H x , H n  and the microstructure height H s  sized therebetween, but is similarly not so limited, as is described herein. In addition, in the preferred embodiments, the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  and the intermediate rib  38  has a generally arcuate-shaped cross-section. The intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  and the intermediate rib  38  are not limited to having the arcuate-shaped cross-section and may have alternative cross-sectional shapes, such as solid, squared, triangular or other shapes, as long as the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  and the intermediate rib  38  are able to perform the preferred functions and withstand the normal operating conditions of the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  and the intermediate rib  38 , as is described herein. 
     The preferred intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  include the transition portions  110 , which has a substantially consistent first taper, therein the intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  transition from the minimum or first rib height H n  to the maximum or second rib height H n . The transition portions  110  are not limited to having the substantially consistent first taper and may have staged, stepped, sudden or otherwise inconsistent tapers between various heights along their length, but the preferred intake side and outlet side ribs  24   a ,  24   b ,  26   a ,  26   b  have the relatively consistent first taper to assist in transitioning loads, for manufacturability, to limit stress concentrations and for additional design considerations. 
     Referring to  FIGS.  7 - 9   , in the second preferred embodiment, the fill sheet  10 ′ includes the integral drift eliminator  50 . The integral drift eliminator  50  of the second preferred embodiment is comprised of an angled tube integral drift eliminator type, with a blocking structure or rib  100  at a drift eliminator inlet  102  where air flow enters the drift eliminator  50  from the heat transfer area  11 ′ of the fill sheet  10 ′ in the fill pack  8 ′. The blocking structure  100  is substantially comprised of a rib or wall in the preferred embodiment. The drift eliminator  50  is not limited to including the blocking rib  100  or to the blocking structure  100  being oriented generally vertically or to being a rib or wall. The blocking structure or rib  100  may be comprised of nearly any structure that provides an impediment or block for cooling fluid flowing directly into the drift eliminator  50  and facilitates drip formation at the inlet  102 , preferably on or proximate to the blocking structure  100  so that the cooling fluid drips do not form deep into the drift eliminator  50 . The cooling fluid is then able to drain back into the heat transfer area  11 ′ before exiting the drift eliminator  50  and being lost from the cooling tower. 
     The blocking structure  100  preferably provides a block to drift, typically comprised of cooled water droplets or cooling fluid, or formation of cooling fluid drips at the inlet  102  so that the cooling fluid does not flow deep into the drift eliminator  50 . Formation of drips at the inlet  102  generally prevents the fluid from flowing deep into the drift eliminator  50 , potentially escaping into the drift eliminator  50  and out of the heat transfer area  11 ′. The cooling fluid captured at the inlet  102  of the drift  50  is preferably, ultimately maintained in the heat transfer area  11 ′ for further dissipation of heat and eventually into a catch basin (not shown) below the fill pack  8 ′ or the individual fill sheets  9   a ,  9   b ,  10  in the tower (not shown). To prevent the cooled water or cooling fluid film that is flowing through the fill pack  8 ′ from travelling up and out of the tubes  104  of the drift eliminator  50  and out of the air outlet side  10   b ′ of the fill pack  8 ′, the blocking structure  100  is added at the drift eliminator inlet  102  which acts as a barrier for the water film and a drip formation area to limit flow of the cooling fluid deep into the drift  50 . As the water or cooling fluid film reaches the blocking structure  100 , the film forms drips which enter the airstream near the drift eliminator inlet  102 , rather than farther into the drift eliminator tube  104  toward the air outlet side  10   b . This change in the location of drip formation at the drift eliminator inlet  102  on the blocking structure  100  causes the droplet or drip to be introduced to the air stream in a location earlier in the transition of airflow direction, thereby causing the droplet or drip to impact a bottom tube wall of the drift eliminator tubes  104 . The drip from the drift eliminator inlet  102  is thereby removed from the airstream to improve performance and effectiveness of the drift eliminator  50  and the fill pack  8 ′, because the potentially lost cooled water or other cooling fluid film is blocked at the blocking rib  100  to facilitate drip formation at the inlet  102  to be captured by the drift eliminator tubes  104 . The water or cooling fluid, therefore, flows back into the heat transfer area  11 ′ through a drainage structure  106  for further dissipation of heat and eventually into the catch basin below the fill pack  8 ′ during operation. In the second preferred embodiment, the blocking structure  100  is comprised of a pair of rounded ribs or walls measuring from approximately five hundredths of an inch to two tenths of an inch (0.05″-0.2″) in height and one tenth to one-half inch (0.1″-0.5″) in width. The blocking structure or ribs  100 , which are formed at the drift eliminator inlets  102  of each of the fill sheets  10 ′,  9   a ′,  9   b ′, align generally adjacent the top walls of each of the drift eliminator inlets  102  of the tubes  104  to act as a barrier for the water film to generally limit the water or other cooling fluid drift from moving into the tubes  104  or facilitate formation of drips to limit flow of the cooling fluid deep into the drift  50 . 
     The second preferred embodiment of the fill sheet  10 ′ also includes drainage structures  106  ( FIG.  8   ) positioned inwardly toward a center of the sheet  10 ′ relative to the drift eliminator  50 . The drainage structures  106  provide a flowpath for the water or cooling fluid blocked by the blocking structure  100  to flow back into the heat transfer area  11 ′ for further dissipation of heat. The second preferred fill sheet  10 ′ is not limited to inclusion of the drainage structure  106  and may include alternatively configured features to direct the captured water or other cooling fluid back into the heat transfer area  11 ′ or no features without significantly impacting the structure and operation of the second preferred fill sheet  10 ′. 
     Referring to  FIG.  10   , in a third preferred embodiment, a fill sheet  10 ″ has similar features compared to the first and second preferred fill sheets  10 ,  10 ′ and the same reference numerals are utilized to identify similar or the same features, with a double prime symbol (″) utilized to distinguish the features of the third preferred embodiment from the first and second preferred embodiments. The third preferred fill sheet  10 ″ includes an intermediate rib  38 ″ including first, second and third intermediate ribs  38   a ″,  38   b ″,  38   c ″. Each of the first, second and third intermediate ribs  38   a ″,  38   b ″,  38   c ″ are laterally spaced from each other and include intermediate rib segments  90   a ,  90   b ,  90   c ,  90   d ,  90   e ,  90   f ,  90   g  that extend generally vertically or parallel to the vertical axis  22 ″ to provide strength and stiffness to the third preferred fill sheet  10 ″. 
     In the third preferred embodiment, the first intermediate rib  38   a ″ includes first and third intermediate rib segments  90   a ,  90   c , the second intermediate rib  38   b ″ includes second, fourth and fifth intermediate rib segments  90   b ,  90   d ,  90   e  and the third intermediate rib  38   c ″ includes sixth and seventh intermediate rib segments  90   f ,  90   g . The first intermediate rib segment  90   a  includes top and first ends  91   a ,  91   b  and the second intermediate rib segment  90   b  includes second and third ends  91   c ,  91   d . The first end  91   a  of the first intermediate rib segment  90   a  is positioned proximate the second end  91   c  of the second intermediate rib segment  90   b  such that at least one of the first and second intermediate ribs  90   a ,  90   b  is intersected by the lateral axis  20 ″ between the top end  91   a  and the third end  91   d , meaning there is generally not an interruption of the first and second intermediate rib segments  90   a ,  90   b  where the lateral axis  20 ″ would not intersect either the first or the second intermediate rib segment  90   a ,  90   b  between the top end  91   a  and the third end  91   d . All of the plurality of intermediate rib segments  90   a ,  90   b ,  90   c ,  90   d ,  90   e ,  90   f ,  90   g  are similarly arranged and configured such that the lateral axis  20 ″ intersects at least one of the plurality of intermediate rib segments  90   a ,  90   b ,  90   c ,  90   d ,  90   e ,  90   f ,  90   g  between an end of the intermediate rib segment that is closest to the top edge  28 ″ of the fill sheet  10 ″, which is a tenth end  91   k  of a sixth intermediate rib segment  90   f  in the third preferred embodiment, and an end of the intermediate rib segment that is closest to the bottom edge  30 ″, which is a fifth end  91   f  of a third intermediate rib segment  90   c  in the third preferred embodiment. In the third preferred embodiment, the third intermediate rib segment  90   c  includes a fourth end  91   e  and a fifth end  91   f , the fourth intermediate rib segment  90   d  includes a sixth end  91   g  and a seventh end  91   h , the fifth intermediate rib segment  90   e  includes an eighth end  91   i  and a ninth end  91   j , the sixth intermediate rib segment  90   f  includes a tenth end  91   k  and an eleventh end  91   l  and the seventh intermediate rib segment  90   g  includes a twelfth end  91   m  and a thirteenth end  91   n . To maintain strength and stiffness of the third preferred intermediate rib  38 ″ the tenth end  91   k  is positioned proximate the top end  28 ″, the eleventh end  91   l  is positioned proximate the eighth end  91   i , the ninth end  91   j  is positioned proximate the top end  91   a , the first end  91   b  is positioned proximate the second end  91   c , the third end  91   d  is positioned proximate the twelfth end  91   m , the thirteen end  91   n  is positioned proximate the sixth end  91   g , the seventh end  91   h  is positioned proximate the fourth end  91   e  and the fifth end  91   f  is positioned proximate the bottom edge  30 ″. The third preferred intermediate rib  38 ″, therefore, extends generally vertically or parallel to the vertical axis  22 ″ or to the intake and outlet sides  10   a ,  10   b  such that the lateral axis  20 ″ intersects at least one of the plurality of intermediate rib segments  90   a ,  90   b ,  90   c ,  90   d ,  90   e ,  90   f ,  90   g  between the tenth end  91   k  and the fifth end  91   f . The sixth intermediate rib segment  90   f  and the third intermediate rib segment  90   c  are spaced from the top and bottom edges  28 ″,  30 ″, but are not so limited and may extend to the top and bottom edges  28 ″,  30 ″ or closer to the top and bottom edges  28 ″,  30 ″, respectively. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed but is intended to cover modifications within the spirit and scope of the present invention as defined by the present disclosure.