BACKGROUND OF THE INVENTION

The cooling tower market has steadily shifted towards fill media that is both efficient and cost-effective. Fill media, fill, fill packs or baffles are typically constructed of assemblies of polymeric sheets with flow channels or flutes formed between the connected or generally parallel arranged sheets through which air and water flow in a cooling tower. The fill media increases the surface area exposure of the flowing water and air of the cooling tower, thereby driving significant contact and interaction between the air and water in the cooling tower and, therefore, heat transfer. This interaction achieves a cooling effect of the water, mainly through mass transfer between the air and water, but may have some sensible heat transfer. Since the fill media is a critical component of a cooling tower, entities strive to have a cost-effective product with high tower performance to remain competitive in the cooling tower and fill market.

Typically, the cost of fill media can be reduced by creating a fill media product of adequate thermal performance for a given cooling tower application, which consists of fewer individual sheets to construct the fill media assembly. This reduction in sheets per unit fill volume results in a material savings and lower fill pack forming and assembly times, thereby lowering the overall product cost.

The performance of a cooling tower is usually measured by the quantity of water that the tower can cool to a specified operating temperature at specified design conditions. Most of this cooling takes place in the fill media where the water flowing through the fill media mixes with the air flowing through the fill media. The main form of heat transfer from the water to the surrounding air is though evaporation. A small quantity of water evaporates from the bulk water in the tower. This evaporating mass of water carries with it the energy equal to the heat of vaporization from the bulk water, causing the remaining water to cool. It is commonly understood that having a larger surface area within the fill media increases the rate of evaporation. Hence, a fill with more surface area per unit volume is typically more effective at cooling water flowing though the fill media or fill pack compared to a fill media or fill pack with less surface area per unit volume.

Evaporation of water into the air is limited by the moisture carrying capacity of the air. As air becomes more saturated with water vapor, the evaporation rate decreases. This means that to maintain a high rate or degree of evaporation, a high mass flow rate of air through the tower and fill media is required. In cooling towers, this is usually accomplished with the help of fans or by forcing air through the fill media or fill packs, although natural draft systems are based on currents created by a difference in air density inside and outside the tower. The air driven by the fan in the typical tower faces resistance to its motion as the forced air flows through spaces or channels within the fill media or fill packs. This resistance can be characterized by a resulting pressure drop across the fill media as the air flows from an entrance side of the fill media to an exit side of the fill media. Overcoming a relatively large pressure drop in the fill media generally requires use of a fan with a higher power when compared to a more modest pressure drop. The job of an effective fill pack is to achieve the specified cooling effect with as little pressure drop as possible. In other words, a preferred pack has high thermal performance and low pressure drop values between the air entrance side and the air exit side.

A fill media or fill pack is generally comprised of an assembly of corrugated sheets that are connected to form the fill media or fill pack. The large primary corrugations in the corrugated sheets are referred to as “flutes” or macrostructure. The flutes in a sheet increase the surface area of the sheet on which water can form a film, thereby increasing the surface area of water that is exposed to the air flowing through the corrugations or flutes. The flutes also form a channel for the air that flows though the fill pack along the flutes from an intake end to an exit end of the fill media or fill packs. For example, a flute angled at thirty degrees (30°) from a straight flow direction between the intake and exit ends, which may be a vertical direction/axis, typically in a cross-fluted fill pack, of the fill media or fill pack will cause the air to flow generally in the same direction as the flute or to generally follow along and through the flute, guided by the flute. This means that the flute geometry has an impact on the way the air flows through the pack. This feature of the flutes can be used not only to direct air where needed, but also to increase mixing of the air stream within a pair of flutes and within the fill pack; thereby avoiding stratification or channeling of the air.

Microstructure is typically added to the flutes to further increase the surface area of the fill media or fill pack upon which the water can form a film for interaction with the air flowing through the flutes. Microstructure in the flutes also keeps the film of water that flows down a flute in a state of constant flux or change such that the film of water that is closely exposed to the flowing air constantly changes to improve heat transfer. The constant mixing of the water film resulting from the microstructure increases the rate of cooling of the liquid film similar to the way stirring hot coffee cools the coffee down faster than leaving it unstirred. The microstructure also serves to maintain distribution of the water on the surface to provide a benefit for all of the available surface area provided by the flute and macrostructure geometry.

Incorporating flutes and microstructures in the flutes of a fill pack, however, may cause an undesired effect of increasing the resistance to the air flow, thereby increasing pressure drop between the entrance or intake end and the exit end of the fill pack. It would be desirable to design, develop and deploy fill sheets assembled into fill packs that improve thermal efficiency and limit pressure drop in the typical operating conditions of a cooling tower. The preferred present invention addresses shortcomings of prior art fill sheets and related fill pack assemblies by arranging the fill sheets in the fill packs relative to each other to improve the heat transfer between the water flowing through the fill packs and the air flowing along the flutes.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, a fill pack includes a first fill sheet defining an air intake edge, an air exit edge and an airflow axis extending between the air intake edge and the air exit edge. The first fill sheet defines a first flute section having a first inlet end and a first outlet end. The first flute section also includes a first peak and first and second valleys extending between the first inlet end and the first outlet end. A second fill sheet defines a second flute section having a second inlet end, a second outlet end and a second peak extending between the second inlet end and the second outlet end. The first inlet end is positioned proximate the second inlet end and the first outlet end is positioned proximate the second outlet end. The first peak, the second peak, the first valley and the second valley define a first flute airflow portion. A cross-sectional shape of the first flute airflow portion constantly changes along the first flute airflow portion. The cross-sectional shape of the first flute airflow portion for any given flute is generally comprised of an area of a plane drawn substantially perpendicular to the airflow axis between a pair of adjacent or stacked fill sheets, bounded by the first sheet flute macrostructure corrugation and a flute line connecting two flute valleys. In the preferred embodiments, the peak of the second fill sheet extends into the adjacent flute airflow portion and constantly changes position relative to the first fill sheet peak along its length to constantly change the cross-sectional shapes in the flute airflow portion between rows of spacers or connectors at the inlet end and outlet end of the flute section. The first peak extends relative to the second peak such that the flute airflow portion continuously changes between the first and second inlet ends and the first and second outlet ends or throughout all flute segments between connection or spacer locations throughout the flute path.

In another aspect, a preferred embodiment of the present invention is directed to a fill sheet for cooling a medium flowing over the sheet. The fill sheet includes a top edge and a plurality of projections. The plurality of projections includes a first peak projection proximate the top edge having a first base. An upper plateau is defined adjacent the first base. The upper plateau defines an upper sheet plane. A plurality of flutes extends from the top edge toward a bottom edge of the fill sheet. A longitudinal axis extends through the top edge and the bottom edge and a lateral axis extends substantially perpendicular to the longitudinal axis and parallel to the upper sheet plane. The plurality of flutes include a first flute having a first top flute end proximate the first peak projection. Microstructure comprised of bands is formed on the flutes. The microstructure defines a microstructure peak between the top edge and the bottom edge on the first flute. The upper plateau and the microstructure peak define an upper offset distance.

In a further aspect, a preferred embodiment of the present invention is directed to a fill sheet for insertion into a cooling tower to cool a cooling medium flowing over the sheet. The fill sheet includes an air intake edge, an air exit edge positioned opposite the air intake edge and a plurality of flutes extending from the air intake edge toward the air exit edge. An airflow axis extends through the top edge and the bottom edge and a lateral axis extends substantially perpendicular to the airflow axis. The plurality of flutes includes a first flute section. The first flute section includes a first arc extending at a first side of the airflow axis and a second arc extending at a second opposite side of the airflow axis. The fill sheet also includes a plurality of spacer rows. The spacer rows include an air intake spacer row and an intermediate spacer row. The air intake spacer row is positioned at the air intake edge and the intermediate spacer row is positioned between the first arc and the second arc. The fill sheet also includes microstructure formed on the plurality of flutes. The microstructure defines a microstructure angle relative to the lateral axis.

