Multiple Mode Hybrid Heat Exchanger

This application is a continuation of U.S. patent application Ser. No. 17/701,090, filed on Mar. 22, 2022, which claims priority under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 63/164,228, filed on Mar. 22, 2021, titled, “MULTIPLE MODE HYBRID HEAT EXCHANGER”, the disclosure of which is incorporated herein by reference in its entirety.

The present invention relates to a heat exchanger to cool and/or condense a heat exchange fluid. More particularly, the present invention relates to heat exchanger selectively configured to cool and/or condense a heat exchange fluid in an evaporative “wet” mode, dry mode, or adiabatic mode.

Closed circuit heat exchangers are widely used in many applications where it is necessary to cool or condense a heat transfer fluid (liquid and/or gas). While heat exchange is generally well understood, a number of different principles may be utilized in convention heat exchangers. However, a heat exchanger optimized to work well in one set of conditions may fail to operate well at another set of conditions.

The general principle of the evaporative heat exchange process involves the fluid or gas from which heat is to be extracted flowing through tubes or conduits having an exterior surface that is continuously wetted with an evaporative liquid, usually water. Air is circulated over the wet tubes to promote evaporation of the water and the heat of vaporization necessary for evaporation of the water is supplied from the fluid or gas within the tubes resulting in heat extraction. The portion of the cooling water which is not evaporated is recirculated and losses of fluid due to evaporation are replenished.

Conventional evaporative heat exchangers are presently in widespread use in such areas as factory complexes, chemical processing plants, hospitals, apartment and/or condominium complexes, warehouses and electric generating stations. These heat exchangers usually include an upwardly extending frame structure supporting an array of tubes which form a coil assembly. An air passage is formed by the support structure within which the coil assembly is disposed. A spray section is provided usually above the coil assembly to spray water down over the individual tubes of the coil assembly. A fan is arranged to blow air into the air passage near the bottom thereof and up between the tubes in a counter flow relationship to the downwardly flowing spray water. Alternatively, fans may draw air through the heat exchanger before being discharged through the fan. Heat from the fluid or gas passing through the coil assembly tubes is transferred through the tube walls to the water sprayed over the tubes. As the flowing air contacts the spray water on the tubes, partial evaporation of some of the spray water occurs along with a transfer of heat from the spray water to the air. The air then proceeds to flow out of the heat exchanger system. The remaining unevaporated spray water collects at the bottom of the conduit and is pumped back up and out through the spray section in a recirculatory fashion.

Current practice for improving the above-described heat transfer process includes increasing the surface area of the heat exchange tubes. This can be accomplished by increasing the number of coil assembly tubes employed in the evaporative heat exchanger by “packing” the tubes into a tight an array as possible, maximizing the tubular surface available for heat transfer. The tightly packed coils also increase the velocity of the air flowing between adjacent tube segments. The resulting high relative velocity between the air and water promotes evaporation and thereby enhances heat transfer.

Another practice currently employed to increase heat transfer surface area is the use of closely spaced fins which extend outwardly, in a vertical direction from the surface of the tubes. The fins are usually constructed from a heat conductive material, where they function to conduct heat from the tube surface and offer additional surface area for heat exchange.

In addition, another method currently used to increase heat exchange is the use of a direct heat exchange section in from of splash type fill structures or film type packs positioned in a vertical relationship with the coil assembly.

These current practices can have drawbacks. For example, in cold conditions, water sprayed on to the heat exchange conduits or fill media may freeze. In another example, the use of additional tubes requires additional coil plan area along with increased fan horsepower needed to move the air through the tightly packed coil assembly, increasing unit cost as well as operating cost. In addition, placement of fins between the individual tubes may make the heat exchanger more susceptible to fouling and particle build up.

Accordingly, it is desirable to provide a method and apparatus for cooling a fluid that can offer improved flexibility to function at a range of temperatures above and below the freezing point of water while improving efficiency and or without undesirably increasing the size of the unit, the manufacturing cost of the unit, and/or operating cost of the unit.

The foregoing needs are met, at least in part, by the present invention where, in one embodiment a multiple mode hybrid heat exchanger is disclosed.

In accordance with an embodiment of the present invention, a multiple mode hybrid heat exchanger apparatus includes a frame assembly, an indirect heat exchange section, a spray system, an intermediate distribution basin, a direct heat exchange section, a vertical passage, a lower air inlet, a cold water collection basin, and a fan. The frame assembly includes a first end wall, a second end wall that opposes the first end wall, a first side wall that extends between the first and second end walls, and a second side wall that opposes the first side wall that extends between the first and second end walls. The direct heat exchange section is disposed below the indirect heat exchange section. The vertical passage is defined by the frame and the direct heat exchange section. The lower air inlet is defined by a plurality of openings between a plurality of fill media sheets in the direct heat exchange section. The lower air inlet is configured to provide an inlet for air into the vertical passage. The cold water collection basin is disposed below the direct heat exchange section. The fan is to induce a flow of air through the lower air inlet. The multiple mode hybrid heat exchanger is selectably configured to operate in an evaporative mode, dry mode, and an adiabatic mode. The dry mode of operation includes deactivation of the spray system, air enters the vertical passage through the direct heat exchange section, and also airflow enters the upper air inlets and passes through the indirect heat exchange section. The adiabatic mode of operation includes the spray system is bypassed on the indirect heat exchange section, the direct heat exchange section is configured to facilitate a passage of water therethrough. The air enters the vertical passage through the direct heat exchange section, the air passing horizontally across a flow of water to directly cool the water. The water is collected in the cold water collection basin. The airflow then passes through the indirect heat exchange section.

In accordance with another embodiment of the present invention, a multiple mode hybrid heat exchanger apparatus includes a frame assembly, an indirect heat exchange section, a spray system, an intermediate distribution basin, a direct heat exchange section, a vertical passage, a second indirect heat exchange section, a lower air inlet, a cold water collection basin, and a fan. The frame assembly includes a first end wall, a second end wall that opposes the first end wall, a first side wall that extends between the first and second end walls, and a second side wall that opposes the first side wall that extends between the first and second end walls. The direct heat exchange section is disposed below the indirect heat exchange section. The vertical passage is defined by the frame and the direct heat exchange section. The second indirect heat exchange section is disposed in an upper portion of the vertical passage. The lower air inlet is defined by a plurality of openings between a plurality of fill media sheets in the direct heat exchange section. The lower air inlet is configured to provide an inlet for air into the vertical passage. The cold water collection basin is disposed below the direct heat exchange section. The fan is to induce a flow of air through the lower air inlet. The multiple mode hybrid heat exchanger is selectably configured to operate in an evaporative mode, dry mode, and an adiabatic mode. The dry mode of operation includes deactivation of the spray system, air enters the vertical passage through the direct heat exchange section, and also airflow enters the upper air inlets and passes through the indirect heat exchange section. The adiabatic mode of operation includes the spray system is bypassed on the indirect heat exchange section, the direct heat exchange section is configured to facilitate a passage of water therethrough. The air enters the vertical passage through the direct heat exchange section, the air passing horizontally across a flow of water to directly cool the water. The water is collected in the cold water collection basin. The airflow then passes through the indirect heat exchange section.

In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

In general, embodiments of the multiple mode hybrid heat exchanger described herein refer to a hybrid fluid cooler having crossflow film fill at the bottom and coil on the top. The recirculating water is first sprayed on the coil section. It is then collected by the collection trough and directed to hot water basins on two sides of the tower where the crossflow fill is located. There are few different ways that air flow may be directed into and through the tower. In some embodiments, air comes in from two sides through the crossflow fill. It then pass through the upper coil section. This is generally referred to as a ‘one-pass flow configuration’.

In other embodiments, air flow is selectively controlled to enter the tower via the top coil section and/or bottom fill section. If air is controlled to enter via the top coil section, air enters from two side in the collection trough area. This can be referred to as a ‘two-pass flow configuration’. Yet another embodiment is a variation of the two-pass flow configuration with an added section on top or below of the water collection section to allow air to enter from all four sides. In still yet another embodiment, an interior damper may control airflow to selectively bypass the primary upper coil section. As described herein, the various dampers may be open and closed to selectively operate in a wet (e.g., evaporative’) mode, dry mode, or adiabatic mode. In some or all of the embodiments, the fill can be sloped at different angles. For example, the fill may be sloped at 12 degrees as shown incompared toin which the fill is sloped at 5.5 degree. Optional dampers may be added at the upper air inlet section in, and-. This helps to achieve the optimal air split ratio during different mode of operation. For example, dampers at the upper inlet section can be closed during the adiabatic mode to pre-cool of the ambient air. An optional secondary indirect finned heat exchange may also be included as shown in. If included, the optional secondary indirect finned heat exchange may improve dry mode performance, for example. A supply of heat transfer fluid (e.g., water as liquid or vapor) is provided to the multiple mode hybrid heat exchanger by supply piping, removed by outlet piping, and controlled via a pump and a plurality of valves.

Referring now toof the drawings, a multiple mode hybrid heat exchanger, generally designated, is illustrated in accordance with an embodiment of the present invention. Generally, the multiple mode hybrid heat exchangerincludes a tower frame or structure having a primary indirect heat exchange (“HE”) section, an optional secondary indirect HE section, and a direct HE section. The primary indirect HE sectionincludes any suitable heat exchanger. Examples of heat exchangers suitable for use as the primary indirect HE sectioninclude: various plate style heat exchangers; various coil type heat exchangers such as a serpentine, single or multi-circuit coil indirect heat exchange for evaporative fluid cooling or condensing; and the like. The direct HE sectionincludes a fill media such as polymer film sheets to increase the wetted surface area and cool the water via the air flowing through the wet fill media. The multiple mode hybrid heat exchangerincludes a cooling liquid distribution assembly or spray system, one or more hot water collection basins, and a cold water collection basin. The multiple mode hybrid heat exchangeralso includes a fanthat moves or generates a stream or current of air into the multiple mode hybrid heat exchangervia one or more lower air inlets. The fanmay include more than one fan and the size may vary depending upon multiple mode hybrid heat exchangersize and application.

The spray systemis configured to supply a spray of water to the primary indirect HE section. The water moves down through the coils in the primary indirect HE sectionas the air is drawn up by the fan. A water collectorcollects the water that flows down from the primary indirect HE sectionand deposits the collected water into the one or more hot water basins. The water collectoris shown in greater detail in.

The multiple mode hybrid heat exchangeris generally rectilinear in geometry having an interior space or vertical passagethat is of generally rectangular, uniform cross-section. The vertical passageis defined by vertical front, rear walls,and vertical side walls,, and the direct HE sections. The walls,,, and, extend upwardly from the basin. The side walls,and front and rear walls,combine to form the interiorwithin which the air passage, the hot water basin or gravity-flow intermediate basin, the primary indirect heat exchange assembly, the optional secondary indirect heat exchange assembly, and the direct heat exchange assemblyare located. The walls,,, andprovide structure, facilitate air flowing through the indirect and direct HE sections//, and facilitate the containment of water within the multiple mode hybrid heat exchanger. To further limit the loss of water, the multiple mode hybrid heat exchangermay, optionally, include a drift eliminatordisposed before an outlet from the multiple mode hybrid heat exchanger. In a particular example, the drift eliminator may be disposed between the spray systemand the fan. The fanis preferably positioned on the top of the multiple mode hybrid heat exchangerand a plenumis defined by the volume between the fan, the drift eliminator, and the walls,,, and.

The walls and other structural elements that form the interiorand framing structure of the multiple mode hybrid heat exchangerare preferably formed from mill galvanized steel, but may be composed of other suitable materials such as stainless steel, hot dipped galvanized steel, epoxy coated steel, and/or fiber reinforced plastics (FRP).

The multiple mode hybrid heat exchangeris configured to be selectable between a “evaporative mode”, a “dry mode”, and an “adiabatic mode” of operation. Depending upon the ambient temperature and humidity, and the system heat load, the three operation modes can achieve energy or water consumption saving. It can also avoid otherwise undesirable affects for example such as the spray water in the multiple mode hybrid heat exchangermay freeze. In such conditions, the multiple mode hybrid heat exchangeris advantageously configured to be operated in the “dry mode”. In “dry mode”, the spray systemis deactivated and the basinsandmay be drained of water.

Compared to all other indirect and direct hybrid evaporative cooling apparatus, the multiple mode hybrid heat exchangeris configured to improve “dry mode” or “winter mode” operations by facilitating airflow up through the vertical passage. That is, by disposing two fill packs, one each to a side of the direct HE section, a greater volume of airflow may enter the vertical passagein comparison to cooling towers with less airflow. With, all of the air stream passes through the primary indirect HE section (in all three modes), regardless whether it is one-pass flow configuration or two-pass flow configuration. No other hybrid indirect/direct products have this design.

In adiabatic mode, the spray systemis activated. The water may bypass the primary indirect HE section. Instead, by using the valve combinations (), the spray water is directed to the hot water basin which in turn cascades over and then through the direct HE section.

The multiple mode hybrid heat exchangershown inis similar to the multiple mode hybrid heat exchangershown inand thus, for the sake of brevity, those elements already described with reference to, may not be described again.

is a cutaway view through the side of the multiple mode hybrid heat exchangerthat is narrower in comparison to the multiple mode hybrid heat exchangerdepicted in. As shown in, the dimensions and/or aspect ratio of the height to the width of the multiple mode hybrid heat exchangermay be modified while staying within the purview of the various embodiments of the invention.

is a cutaway view through the side of the multiple mode hybrid heat exchangerthat includes a more steeply angled fill pack in comparison to the multiple mode hybrid heat exchangerdepicted inand includes upper air inlets. The multiple mode hybrid heat exchangershown inis similar to the multiple mode hybrid heat exchangershown inwith the exception of the fill media being raked at a higher angle in the direct HE section.

is a cutaway view through the side of the multiple mode hybrid heat exchangerthat includes a secondary indirect finned heat exchanger. The secondary indirect finned heat exchangershown inis configured to provide improved dry mode heat transfer.

is an orthogonal projection of the water collection assemblyfor the multiple mode hybrid heat exchangerof. As shown in, the water collection assemblyincludes a plurality of water collecting vanes. Each water collecting vaneincludes a sloped faceconfigured to redirect a flow of water falling down from above. At the lower edge of each water collecting vaneis a channeldefined by the intersection of the sloped facewith a vertical face. The water collection assemblyis raised along a central line in comparison to the sides of the water collection assemblyso that collected water runs along the channels and into the hot water basin. In this manner, the flow of air is allowed to flow up through the water collection assemblywhile the water is redirected and collected to be distributed onto the direct HE section.

is a cutaway view through the side of the multiple mode hybrid heat exchangerthat includes internal dampersand a vertical passage extending up through an indirect heat exchange section. As shown in, the internal dampersare configured to rotate or swing to modulate the flow of air through the vertical passage. As described in greater detail herein, rotation of the dampersis configured to modulate the airflow in the multiple mode hybrid heat exchangerso that less or more of the airflow passes through the indirect HE section. In this manner, the multiple mode hybrid heat exchangermay be selectively controlled and optimized to operate in “dry mode”, “adiabatic mode”, or “evaporative mode”. In addition, the multiple mode hybrid heat exchangerincludes hot water basin valves, spray system valvesand a recirculating pump. The hot water basin valvesare configured to control a flow of water to the hot water basin. The spray system valvesare configured to control a flow of water supplied to the indirect heat exchanger. The recirculating pumpis configured to pump water up from the cold water basinto the hot water basin valvesand spray system valves.

In some operations, water from the spray system valves, falls through the indirect heat exchangeand then collects in the hot water basin. In other operations, the hot water basin valvesmay supply water to the hot water basin, for example, if water is not supplied to the indirect heat exchanger. It is an advantage of the multiple mode hybrid heat exchangershown inthat the multiple mode hybrid heat exchangeris operable to selectively operate in each of the operational modes shown inand thus, may be optimized to operate in a variety of environmental conditions. Table I below summarizes the operating modes of the multiple mode hybrid heat exchangeraccording to:

In Table I, reference is made to opening and closing the indirect heat exchange spray valves, the direct heat exchange spray valves. the upper inlet louvers, and the internal dampers. For the purpose of this disclosure, it is to be understood that the term, “open” is defined as facilitating the flow of fluid (air, water, or the like) therethrough and that the term, “closed” is defined as restricting the flow of fluid. For example, valves, louvers, and dampers may leak fluid when ‘closed’. Additionally, even partially open, valves, louvers, and dampers may allow suitable flow to provide sufficient cooling.

is a cutaway view through the side of the multiple mode hybrid heat exchangerofin an evaporative mode with vertically closed internal dampers and open inlet louvers. In this orientation, the internal dampersform a vertical passage extending up through an indirect heat exchange section. As shown in, the internal dampersare configured to rotate or swing to modulate the flow of air through the vertical passage. As described in greater detail herein, rotation of the dampersis configured to modulate the airflow in the multiple mode hybrid heat exchangerso that less or more of the airflow passes through the indirect HE section. In this configuration, the spray system valvesare activated, and spray is applied to the indirect HE section, and reapplied to the direct HE systemthough fluid initially collected in the Hot Water Basin. In this manner, the multiple mode hybrid heat exchangermay be selectively controlled and optimized to operate in evaporative or “wet mode”.

is a cutaway view through the side of the multiple mode hybrid heat exchangerofin an adiabatic mode with horizontally closed internal dampersand closed inlet louvers. As shown in, with the dampersrotated to close the vertical passageup from the direct HE section, substantially all of the airflow may be drawn through the indirect HE section. The water from the spray systembypasses the indirect HE sectionand is directed only to the direct HE sectionvia activation of the Hot Water Basin valves. In this configuration, the multiple mode hybrid heat exchangeris operating in adiabatic mode.

is a cutaway view through the side of the multiple mode hybrid heat exchanger ofin a dry mode with horizontally closed internal dampersand open inlet louvers. As shown in, with the dampersrotated to close the vertical passageup from the direct HE section, substantially all of the airflow may be drawn through the indirect HE section. The spray systemis deactivated so that no water passes down through the indirect HE sectionor on the direct HE section. In this manner, the multiple mode hybrid heat exchangeris operating in dry mode. Of note, although in ‘Dry Mode’, the process water flowing through the heat exchange conduits of the multiple mode hybrid heat exchangermay always be circulating.

is a cutaway view through the side of the multiple mode hybrid heat exchangerofin an evaporative-dry mode with horizontally closed internal dampersand open inlet louvers. As shown in, with the dampersrotated to close the vertical passageup from the direct HE section, substantially all of the airflow may be drawn through the indirect HE section. This allows the hybrid heat exchanger to operate in two modes simultaneously. On one side of the multiple mode hybrid heat exchanger, water from the spray systempasses down through one side of the indirect HE sectionand on to the direct HE section. In addition, the other side of the indirect HE sectionmay have the spray deactivated and be closed off with an option damper door. In this configuration the multiple mode hybrid heat exchangeris operating in evaporative-dry mode.

is a cutaway view through the side of the multiple mode hybrid heat exchangerofin an evaporative-adiabatic mode with horizontally closed internal dampersand partially closed inlet louvers. As shown in, on one side of the hybrid heat exchanger with the dampersrotated to close the vertical passageup from the direct HE section, substantially all of the airflow may be drawn through the indirect HE section. The water from one side of the spray systempasses down through the indirect HE sectiondisposed below, collects in the hot water basin, and on to the direct HE section. For example, each of the valvesand each of the valvesof the spray systemmay be independently controlled. As shown in, the valveon the left is closed while the valveon the right is in the open position. The valveon both the left and right are in the open position. In addition, the other side of the indirect HE sectionmay be closed off with an option damper doorand the inlet louverson the opposite side may be closed to increase draw through the direct HE. In this configuration of the dampers, the multiple mode hybrid heat exchangeris operating in evaporative-adiabatic mode.

is a cutaway view through the side of the multiple mode hybrid heat exchangerofin an adiabatic-dry mode with horizontally closed internal dampersand partially closed inlet louvers. As shown in, with the dampersrotated to close the vertical passageup from the direct HE section, substantially all of the airflow may be drawn through the indirect HE section. The spray system valvesare closed to stop the flow of water from the spray systemand water is supplied to the hot water basinvia opening the hot water basin valve. In addition, the other side of the indirect HE sectionmay be closed off with an option damper doorand the inlet louverson the opposite side may be closed to increase draw through the wetted direct HE. In this configuration the multiple mode hybrid heat exchangeris operating in adiabatic-dry mode.

is a plan view showing inlet and outlet piping, hot water basin valves, spray system valves, heat exchanger valves, and recirculating pumpof the multiple mode hybrid heat exchangerof. As shown in, each of the valves-may be operated independently and systems to each side of the multiple mode hybrid heat exchangermay be operated independently from the other side.

is a cutaway view through the side of a multiple mode hybrid heat exchangerwith internal dampers, inlet louvers, and a secondary finned heat exchanger. The dry finned coilsis disposed in the vertical passageand may augment cooling from the indirect HE section. In this regard, the dry finned coilsmay be connected in series or parallel with the coils of the indirect HE section. It is an advantage of the multiple mode hybrid heat exchangershown inthat the multiple mode hybrid heat exchangeris operable to selectively operate in each of the operational modes shown inand thus, may be optimized to operate in a variety of environmental conditions. Table II below summarizes the operating modes of the multiple mode hybrid heat exchangeraccording to:

In Table II, reference is made to opening and closing the indirect heat exchange spray valves, the direct heat exchange spray valves. The upper inlet louvers, and the internal dampers. For the purpose of this disclosure, it is to be understood that the term, “open” is defined as facilitating the flow of fluid (air, water, or the like) therethrough and that the term, “closed” is defined as restricting the flow of fluid. For example, valves, louvers, and dampers may leak fluid when ‘closed’. Additionally, even partially open, valves, louvers, and dampers may allow suitable flow to provide sufficient cooling.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin evaporative mode with vertically closed internal dampersand open inlet louvers. In this orientation, the internal dampersform a vertical passageextending up through an indirect heat exchange section. As shown in, the internal dampersare configured to rotate or swing to modulate the flow of air through the vertical passage. As described in greater detail herein, rotation of the dampersis configured to modulate the airflow in the multiple mode hybrid heat exchangerso that less or more of the airflow passes through the indirect HE section. As shown in, with the dampersrotated to open the vertical passageup from the direct HE section, a greater amount of airflow may be drawn in through the direct HE sectionand this flow of air is then drawn through the secondary finned heat exchanger. The water from the spray systempasses down through the indirect HE sectionand on to the direct HE section. In this manner, the multiple mode hybrid heat exchangermay be selectively controlled and optimized to operate in evaporative or “wet mode”.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin adiabatic mode with partially closed internal dampersand closed inlet louvers. As shown in, with the dampersrotated to partially close the vertical passageup from the direct HE section, a portion of the airflow may be drawn through the indirect HE sectionand this portion may be varied in response to the rotation of the dampers. The spray system valveare closed to stop the flow of water through the indirect HE section. The hot water basin valvesare opened to provide water to the direct HE section. In this configuration of the dampers, multiple mode hybrid heat exchangeris operating in adiabatic mode with the increased heat exchange via the finned HE.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin dry mode with vertically closed internal dampersand open inlet louvers. As shown in, with the dampersrotated to open the vertical passageup from the direct HE section, the airflow may redirected away from and between the indirect HE section. This redirected airflow is directed up through the secondary indirect finned HE. The spray systemis deactivated so that no water passes down through the indirect HE sectionand the direct HE sectionis also dry. The multiple mode hybrid heat exchangeris operating in dry mode.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin evaporative-dry mode with vertically closed internal dampersand open inlet louvers. As shown in, with the dampersrotated to open the vertical passageup from the direct HE section, substantially all of the airflow may be drawn up through the secondary indirect finned HE section. The inlet louversare open to allow a flow of air into the multiple mode hybrid heat exchangerbelow the indirect HEand this airflow is then drawn through the indirect HE section. The water from the spray systempasses down through one side of the indirect HE sectionand on to the direct HE section. Optionally, the hot water basin valvemay supply water to the hot water basinon the second side. The multiple mode hybrid heat exchangeris operating in evaporative-dry mode.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin evaporative-adiabatic mode with partially closed internal dampersand partially open inlet louvers. As shown in, with the dampersrotated to partially close the vertical passageup from the direct HE sectionon a first side to allow some of the air passing through the direct heat exchangerto be drawn through one side of the indirect HE section. On a second side, the water from the spray systempasses down through one side the indirect HE sectionand on to the direct HE sectionwhile the inlet louverare open to allow air through the wetted indirect HE. In addition, on the first side of the indirect HE section, the inlet louversmay be closed to increase draw through the direct HE. In this configuration of the dampers, the multiple mode hybrid heat exchangeris operating in evaporative-adiabatic mode.

is a cutaway view through the side of the multiple mode hybrid heat exchangeraccording toin dry-adiabatic mode with partially closed internal dampersand partially open inlet louvers. As shown in, with the dampersrotated to partially close the vertical passageup from the direct HE sectionon a first side to allow some of the air passing through the direct heat exchangerto be drawn through one side of the indirect HE section. On both sides, the spray system valvesare closed to prevent water from falling through the indirect HE. On the second side, the inlet louverare open to allow air through the dry indirect HE. In addition, on the first side of the indirect HE section, the inlet louversmay be closed to increase draw through the direct HE. In this configuration of the dampers. the multiple mode hybrid heat exchangeris operating in adiabatic-dry mode.

is a plan view showing inlet and outlet piping, hot water basin valves, spray system valves, heat exchanger valves, and recirculating pumpof the multiple mode hybrid heat exchangerof. As shown in, each of the valves-may be operated independently and systems to each side of the multiple mode hybrid heat exchangermay be operated independently from the other side. The piping diagram ofis similar to the piping diagram ofexcept that the piping diagram ofincludes a third heat exchanger valveand configured to selectively control a flow of water to the secondary indirect finned HE. It is an advantage of the embodiment shown inthat the multiple mode hybrid heat exchangeris configured to perform a Pre-Cooling feature by circulating the process water through the secondary indirect finned HE.