1. Field of the Invention
This invention relates to heat exchangers, and more particularly to heat exchangers for cooling engines, generators, gear boxes and other heat generating sources in industrial apparatuses having fluid cooled heat sources, such as marine vessels. The invention more particularly relates to open heat exchangers (where beat transfer tubes are exposed to the ambient cooling or heating fluid, rather than being in a shell to shell container holding the cooling or heating fluid) used for cooling heat sources, where the heat exchangers are efficient, and thus have lower weight and volume compared to other heat exchangers known in the art. Alternatively, the heat exchanger according to the invention could be used as a heater, wherein relatively cool fluid absorbs heat through the heat transfer tubes. The invention relates most particularly to multiple-pass heat exchangers and to multiple systems combined heat exchangers.
2. Description of the Prior Art
Heat generating sources in industrial applications such as marine vessels are often cooled by water, other fluids or water mixed with other fluids. For example, in marine vessels used in fresh water and/or salt water, the cooling fluid or coolant flows through the engine or other heat generating source where the coolant picks up heat, and then flows to another part of the plumbing circuit. The heat must be transferred from the coolant to the ambient surroundings, such as the body of water in which the vessel is located. For small engines, such as outboard motors for small boats, ambient water pumped through the engine is a sufficient coolant. However, as the vessel power demand gets larger, ambient water pumped through the engine may continue to provide good cooling of the engine, but also serves as a source of significant contamination damage to the engine. If raw, ambient water were used to cool the engine, the ambient water would carry debris and, particularly if it is salt water, corrosive chemicals to the engine. Therefore, there have been developed various apparatuses for cooling engines and other heat sources. One apparatus for cooling the engine of a vessel is channel steel, which is basically a large quantity of shaped steel which is welded to the bottom of the hull of a vessel for conveying engine coolant and transferring heat from the coolant to the ambient water. Channel steel has severe limitations: it is very inefficient, requiring a large amount of steel in order to obtain the required cooling effect; it is very expensive to attach to a vessel, since it must be welded to the hull—a very labor intensive operation; since channel steel is very heavy, the engine must be large enough to carry the channel steel, rendering both the initial equipment costs and the operating costs very high; the larger, more powerful engines of today are required to carry added channel steel for their cooling capacity with only a relatively small amount of room on the hull to carry it; the payload capacity is decreased; the large amount of channel steel is expensive; and finally, channel steel is inadequate for the present and future demands for cooling modern day, marine vessels. Even though channel steel is the most widely used heat exchanger for vessels, segments of the marine industry are abandoning channel steel and using smaller keel coolers for new construction to overcome the limitations cited earlier.
A keel cooler was developed in the 1940's and is described in U.S. Pat. No. 2,382,218 (Fernstrum). The Fernstrum patent describes a heat exchanger for attachment to a marine hull structure which is composed of a pair of spaced headers secured to the hull, and a plurality of heat conduction tubes, each of whose cross-section is rectangular, which extend between the headers. Cylindrical plumbing through the hull connects the headers to coolant flow lines extending from the engine or other heat source. Hot coolant leaves the engine, and runs into a heat exchanger header located beneath the water level (the water level refers to the water level preferably below the aerated water, i.e. below the level where foam and bubbles occur), either beneath the hull or on at least one of the lower sides of the hull. The coolant then flows through the rectangular heat conduction tubes and goes to the opposite header, from which the cooled coolant returns to the engine. The headers and the heat conduction tubes are disposed in the ambient water, and heat transferred from the coolant, travels through the walls of the heat conduction tubes and the headers, and into the ambient water. The rectangular tubes connecting the two headers are spaced fairly close to each other, to create a large heat flow surface area, while maintaining a relatively compact size and shape. Frequently, these keel coolers are disposed in recesses on the bottom of the hull of a vessel, and sometimes are mounted on the side of the vessel, but in all cases below the water line.
The foregoing keel cooler is referred to as a one-piece keel cooler, since it is an integral unit with its major components welded or brazed in place. The one-piece keel cooler is generally installed and removed in its entirety.
It is explained in U.S. Pat. No. 2,382,218 that, according to one embodiment of the heat exchanger disclosed therein, the pair of headers at opposite ends thereof have beveled fore and aft front and rear end walls. The latter walls are respectively connected to beveled front and rear inner walls (to which the open ports of the conduction tubes are connected to the chambers of the headers) by triangular-shaped side walls. There is thus no flat lower wall (since the triangular-shaped end walls meet at a point). Each header thus essentially consists of a flat rectangular upper wall, beveled inner and end walls extending downwardly from opposite ends of the upper wall and meeting at a lower point, and triangular side walls. The coolant inlet or outlet nipple is positioned in the upper wall directly over the point where the beveled inner wall meets the beveled end wall. Since the walls beneath the nipples are beveled in opposite directions, the flow of coolant to or from the nipples is helped in one respect because the fore and aft end parts of the header assists the coolant flow between the conduction tubes and the nipple, but hindered in another respect because the beveled inner walls direct coolant flow in the opposite direction from that rebounding from the end parts of the header. The oppositely directed coolant flow in the header causes turbulence, increases pressure drop and reduces coolant flow. The lower portion of each header, where the beveled inner and end wall converge at a point, is disposed below the open ports of the conduction tubes. This further reduces the coolant flow into and out of the respective headers; in the case of coolant flowing out of a header, coolant disposed below the ports must flow upward to reach the ports, against other coolant flowing downwardly. Such upward flow contributes to turbulence in the header, and is inefficient since gravity opposes such flow. Likewise, when coolant is flowing into this type of header to exit through the nipple, some coolant flows in the direction opposite to that of the nipple and must flow against gravity, past the cross-flow of coolant from the ports of the conduction tubes into the nipple. The latter arrangement also results in turbulence in the header, an increase in the pressure drop, and reduces coolant flow. In addition, none of the open ports are located in the coolant flow path from the nipple, so there is no direct flow path between the nipple and any of the open ports.
Furthermore, the beveled end wall is not configured either to direct a substantial amount of coolant into the flow tubes, or to direct a substantial amount of coolant from the flow tubes into the nozzle. This is because part of the beveled end wall is located below the open ports to the flow tubes, and because there are significant parts of the beveled inner wall which are flat and devoid of ports to the flow tubes.
These aspects of this embodiment of the heat exchanger disclosed in U.S. Pat. No. 2,382,218 may very well have determined why it was never put into commercial production.
There are various varieties of one-piece keel coolers. Sometimes the keel cooler is a multiple-pass keel cooler where the headers and heat conduction tubes are arranged to allow at least one 180° change in the direction of flow, and the inlet and outlet ports may be located in the same header.
Even though the foregoing heat exchangers with the rectangular heat conduction tubes have enjoyed widespread use since their introduction over fifty years ago, they have shortcomings which are corrected by the present invention.
The rectangular heat exchangers of the prior art have the outward shape of a rectangular parallelepiped having headers at their opposite ends. These headers have opposing end walls which are perpendicular to the hull of the vessel and parallel to each other, and act as a barrier to ambient water flow relative to the keel cooler as the vessel with the heat exchanger travels through the water. The perpendicular header walls are responsible for the creation of dead spots (lack of ambient water flow) on the heat exchanger surfaces, which largely reduce the amount of heat transfer occurring at the dead spots. In addition, the perpendicular walls diminish the flow of ambient water between the heat conduction tubes, which reduces or diminishes the amount of heat which can be transferred between the coolant in the tubes and the ambient water.
As discussed below, the beveled header contributes to the increase of the overall heat transfer efficiency of the keel cooler according to the invention, since the ambient water is caused to flow towards and between the respective heat conduction tubes, rendering the heat transfer substantially higher than in the keel cooler presently being used. This increase in heat transfer is due at least in part to the increase in turbulence in the flow of ambient water across the forward header and along and between the coolant flow tubes.
One of the important aspects of keel coolers for vessels is the requirement that they take up as small an area on the vessel as possible, while fulfilling or exceeding their heat exchange requirement with minimized pressure drops in coolant flow. The area on the vessel hull which is used to accommodate a keel cooler is referred to in the art as the footprint. In general, keel coolers with the smallest footprint and least internal pressure drops are desirable. One of the reasons that the keel cooler described above with the rectangular heat conduction tubes has become so popular is because of the small footprint it requires when compared with other keel coolers. However, keel coolers according to the design of rectangular tubed keel coolers presently being used have been found by the present inventors to be larger than necessary both in terms of size and the related internal pressure drop. By the incorporation of the various aspects of the present invention described above (and in further detail below), keel coolers having smaller footprints and lower internal pressure drops are possible. These are major advantages of the present invention.
When multiple-pass (usually two-pass) keel coolers are specified for the present state of the art, an even greater differential size is required when compared with the present invention, as described below.
It is an object of the present invention to provide a heat exchanger for fluid cooled heat sources which is smaller than corresponding heat exchangers having the same heat exchange capability.
Another object of the present invention is to provide an improved heat exchanger for industrial applications which is more efficient than heat exchangers presently known and used.
It is yet another object of the present invention to provide an improved one-piece heat exchanger for vessels which is more efficient in heat transfer than presently known one-piece heat exchangers.
A further object is to provide an improved one-piece heat exchanger which reduces the pressure drop of coolant flowing therethrough.
A further object of the present invention is to provide an improved one-piece heat exchanger having heat conduction tubes which are rectangular in cross-section having a length which is reduced in size from the current heat exchangers due to enhanced ambient water flow across the keel cooler.
Another object is to provide an improved one-piece heat exchanger having a reduced size from present one-piece heat exchangers of comparable heat transfer capability, by reducing the length of the heat transfer tubes, the number of tubes and/or the size of the tubes.
Another object of the present invention is to provide a header for a one-piece keel cooler heat exchanger with an interior wall for improving the coolant flow between the inlet/outlet and the open ports of the keel cooler tubes.
It is yet another object to provide a header for a one-piece keel cooler with an interior wall for directing the coolant flow between the inlet/outlet and the open ports of the keel cooler tubes for reducing turbulence of the coolant in the header.
A still further object of the present invention is to provide a new one-piece heat exchanger having rectangular shaped heat conduction tubes which has enhanced durability compared to keel coolers presently on the market.
A related object of the invention is to provide an improved heat exchanger and headers thereof which is capable of deflecting debris more readily, and for presenting a smaller target to debris in the ambient water.
Another object of the present invention is to provide an improved one-piece keel cooler which is easier to install on vessels than corresponding keel coolers presently on the market.
Yet a further object of the present invention is to provide a one-piece heat exchanger and a header having a lower weight, and therefore lower cost, than corresponding one-piece heat exchangers presently in use.
Another object of the present invention is to provide a one-piece heat exchanger and headers thereof having rectangular heat conduction tubes having a lower pressure drop in coolant flowing through the heat exchanger than corresponding heat exchangers presently known.
Another object of the present invention is the provision of a one-piece heat exchanger for a vessel, for use as a retrofit for previously installed one-piece heat exchangers which will surpass the overall heat transfer performance and provide lower pressure drops than the prior units without requiring additional plumbing, or requiring additional space requirements, to accommodate a greater heat output.
It is another object of the invention to provide an improved header for a one-piece heat exchanger having rectangular coolant flow tubes.
Another object is to provide an improved header for a one-piece heat exchanger with rectangular coolant flow tubes which reduces the dead spots which have heretofore reduced the heat transfer capabilities of one-piece heat exchangers, the dead spots reducing the flow of ambient water around and between the coolant flow tubes.
A further object of the invention is to provide an improved header for a one-piece keel cooler with rectangular coolant flow tubes, by reducing the likelihood of damage to the header from striking debris and underwater objects which could damage the keel cooler.
It is still another object for the provision of a header for effecting increased turbulent flow of the ambient water flowing between and around the heat transfer tubes.
It is an additional object to provide an improved header for one-piece keel coolers which enables the anode for such keel coolers to be less likely to strike debris and underwater objects.
Another object is the provision of a keel cooler having a smaller, and more streamlined profile to reduce drag as the vessel with the keel cooler moves through the ambient water.
Another object is to provide a header for a one-piece heat exchanger which provides for enhanced heat exchange between the coolant and the ambient cooling medium such as water.
A further object to the provision of an improved multiple-pass heat exchanger.
A still additional object is the provision of an improved multiple systems combined heat exchanger.
A general object of the present invention is to provide a one-piece heat exchanger and headers thereof which is efficient and effective in manufacture and use.
Other objects will become apparent from the description to follow and from the appended claims.
The invention to which this application is directed is a one-piece heat exchanger, i.e. heat exchangers having two headers which are integral with coolant flow tubes. It is particularly applicable to heat exchangers used on marine vessels as discussed earlier, which in that context are also called keel coolers. However, heat exchangers according to the present invention can also be used for cooling heat generating sources (or heating cool or cold fluid) in other situations such as industrial and scientific equipment, and therefore the term heat exchangers covers the broader description of the product discussed herein. The heat exchanger includes two headers, and one or more coolant flow tubes integral with the header. Although keel coolers use ambient water as the cooling medium, the broader term for a cooling medium is a heat sink or a fluid heat sink.
The fundamental components of a heat exchanger system for a water-going vessel are shown in
A keel cooler 17 according to the prior art is shown in
Turning to
Referring also to
In the discussion above and to follow, the terms “upper”, “inner”, “downward”, “end”, etc., refer to the heat exchanger, keel cooler or header as viewed in a horizontal position as shown in
Each exterior side wall of header 19 is comprised of an exterior or outer rectangular tube, one of which is indicated by numeral 60 in
Still referring to the prior art header 19 shown in
Still referring to
Referring next to
Considering specifically cut away
The angle of beveled wall 216 is an important part of the present invention. As discussed herein, the angle, designated as θ (theta), is appropriately measured from the plane perpendicular to the longitudinal direction of coolant flow tubes 202 and located at the part of the closed end portion of header 204 spaced furthest from the set of open ends or ports 227 of tubes 206, i.e. from end wall 214, to beveled wall 216. Angle θ is described as an exterior angle, since it is exterior to end wall 214 and beveled wall 216; it is measured from a plane perpendicular to the longitudinal axes of the flow tubes 202 and roof 210, and it is along end wall 214 at the beginning of beveled wall 216. The factors for determining angle θ are to maintain the center-to center distance of the nozzle spacing, to maintain the overall length of the keel cooler, to provide vertical drop beneath the roof of the header so that the header can hold the anode insert, to keep the anode assembly from extending longitudinally beyond wall 214, and to allow for the maximum length of heat transfer tubing (and the associated reduction of the length of the header). Angle θ could be affected by the size of orifice 220, but generally the other factors limit angle θ before the orifice would affect it.
Another important aspect to beveled wall 216 is the manner in which it directs the flow of ambient water over and between the exterior walls of coolant flow tubes 202, to increase the heat transfer between the coolant inside the tubes and the outside ambient water. It will be recalled that under the prior art as shown in
Referring to
It can be seen that outer exterior surfaces 230 define an envelope transverse to the longitudinal direction of the keel cooler. The envelope has a height equal to the exterior height of exterior tubes 208, and a width equal to the distance between outer exterior surfaces 230. Header 204 thus has an exterior width equal to the width of the envelope and an interior height defined by the interior surfaces of upper wall 210 and lower wall 217, and therefore of the envelope.
So far, only single-pass keel cooler systems have been described. In two-pass systems, the inlet and outlet nozzles are both disposed in one header, and coolant flows into the header via an inlet nozzle, through a first set of tubes from the first header into the second header (with no nozzles), and then back through a second set of tubes at a lower pressure—and finally out from the header via an outlet nozzle. Referring to
For space limitations or assembly considerations, sometimes (as noted above) it is necessary to remove the inner wall or a section of the inner tube instead of one or the other of the orifices. Other times, a separator plate is used and the standard angle interior tubes are used instead of separator tubes.
Keel cooler 300 has one set of coolant flow tubes 302 for carrying hot coolant from header 306 to header 308, where the direction of coolant flow is turned 180° by header 308, and the coolant enters a second set of tubes 304 for returning the partially cooled coolant back to header 306. Thus, coolant under high pressure flows through tubes 302 from header 306 to header 308, and the coolant then returns through tubes 304, and subsequently through nozzle 312 to the engine or other heat source of the vessel. Walls 334 and 336 (shown in
The keel cooler system shown in
Another aspect of the present invention is shown in
There can be one or more single-pass systems and one or more double-pass systems in combination as shown in
The keel coolers described above show nozzles for transferring heat transfer fluid into or out of the keel cooler. However, there are other means for transferring fluid into or out of the keel cooler; for example, in flange mounted keel coolers, there are one or more conduits such as pipes extending from the hull and from the keel cooler having end flanges for connection together to establish a heat transfer fluid flow path. Normally a gasket is interposed between the flanges. There may be other means for connecting the keel cooler to the coolant plumbing system in the vessel. This invention is independent of the type of connection used to join the keel cooler to the coolant plumbing system.
Keel coolers according to the invention are used as they have been in the prior art, and incorporate two headers which are connected by an array of parallel coolant flow tubes. A common keel cooler according to the invention is shown in
The keel coolers described above show nozzles for transferring heat transfer fluid into or out of the headers. However, there are other means for transferring fluid into or out of the headers; for example, in flange mounted keel coolers, there are one or more conduits such as pipes extending from the hull and from the keel cooler having end flanges for connection together to establish a heat transfer fluid flow path. Normally a gasket is interposed between the flanges. There may be other means for connecting the keel cooler to the coolant plumbing system in the vessel. This invention is independent of the type of connection used to join the keel cooler to the coolant plumbing system.
The invention has been described with particular reference to the preferred embodiments thereof, but it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains.
This is a continuation of U.S. Ser. No. 10/119,412 filed Apr. 9, 2002, which itself is continuation-in-part of U.S. Ser. No. 09/427,565 which was filed on Oct. 26, 1999, now abandoned.
Number | Date | Country | |
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Parent | 10119412 | Apr 2002 | US |
Child | 11434622 | May 2006 | US |
Number | Date | Country | |
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Parent | 09427565 | Oct 1999 | US |
Child | 10119412 | Apr 2002 | US |