Patent Application
20220299269
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 in
Referring now to
The spray system 16 is configured to supply a spray of water to the primary indirect HE section 12. The water moves down through the coils in the primary indirect HE section 12 as the air is drawn up by the fan 22. A water collector 24 collects the water that flows down from the primary indirect HE section 12 and deposits the collected water into the one or more hot water basins 18. The water collector 24 is shown in greater detail in
The multiple mode hybrid heat exchanger 10 is generally rectilinear in geometry having an interior space or vertical passage 30 that is of generally rectangular, uniform cross-section. The vertical passage 30 is defined by vertical front, rear walls 32, 34 and vertical side walls 36, 38, and the direct HE sections 14. The walls 32, 34, 36, and 38, extend upwardly from the basin. The side walls 32, 34 and front and rear walls 36, 38 combine to form the interior 30 within which the air passage, the hot water basin or gravity-flow intermediate basin 18, the primary indirect heat exchange assembly 12, the optional secondary indirect heat exchange assembly 46, and the direct heat exchange assembly 14 are located. The walls 32, 34, 36, and 38 provide structure, facilitate air flowing through the indirect and direct HE sections 12/14/46, and facilitate the containment of water within the multiple mode hybrid heat exchanger 10. To further limit the loss of water, the multiple mode hybrid heat exchanger 10 may, optionally, include a drift eliminator 40 disposed before an outlet from the multiple mode hybrid heat exchanger 10. In a particular example, the drift eliminator may be disposed between the spray system 16 and the fan 22. The fan 22 is preferably positioned on the top of the multiple mode hybrid heat exchanger 10 and a plenum 42 is defined by the volume between the fan 22, the drift eliminator 40, and the walls 32, 34, 36, and 38.
The walls and other structural elements that form the interior 30 and framing structure of the multiple mode hybrid heat exchanger 10 are 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 exchanger 10 is 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 exchanger 10 may freeze. In such conditions, the multiple mode hybrid heat exchanger 10 is advantageously configured to be operated in the “dry mode”. In “dry mode”, the spray system 16 is deactivated and the basins 18 and 20 may be drained of water.
Compared to all other indirect and direct hybrid evaporative cooling apparatus, the multiple mode hybrid heat exchanger 10 is configured to improve “dry mode” or “winter mode” operations by facilitating airflow up through the vertical passage 30. That is, by disposing two fill packs, one each to a side of the direct HE section 14, a greater volume of airflow may enter the vertical passage 30 in comparison to cooling towers with less airflow. With
In adiabatic mode, the spray system 16 is activated. The water may bypass the primary indirect HE section 12. Instead, by using the valve combinations (
The multiple mode hybrid heat exchanger 10 shown in
In some operations, water from the spray system valves 60, falls through the indirect heat exchange 12 and then collects in the hot water basin 18. In other operations, the hot water basin valves 58 may supply water to the hot water basin 18, for example, if water is not supplied to the indirect heat exchanger 12. It is an advantage of the multiple mode hybrid heat exchanger 10 shown in
In Table I, reference is made to opening and closing the indirect heat exchange spray valves 60, the direct heat exchange spray valves 58. the upper inlet louvers 48, and the internal dampers 44. 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.
In Table II, reference is made to opening and closing the indirect heat exchange spray valves 60, the direct heat exchange spray valves 58. the upper inlet louvers 48, and the internal dampers 44. 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.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirits and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
This application claims priority to U.S. Provisional Application No. 63/164,228, filed Mar. 22, 2021, titled MULTIPLE MODE HYBRID HEAT EXCHANGER, the disclosure of which is hereby incorporated in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63164228 | Mar 2021 | US |
