Patent Application
20090008074
The present invention relates to a tubular heat exchanger, and more particularly to a multi-pass, tubular, heat exchanger with a servicable core for marine applications.
Tubular heat exchangers are known to flow two fluid mediums of different temperatures to transfer heat from one fluid to the other. Such heat exchangers generally have an outer shell that houses a central core having a plurality of tubes for transferring heat. The first ends of the tubes are supported by a perforated first plate sealed continuously to an inward face of the shell. The opposite second ends of the tubes are supported by a perforated second plate also sealed continuously to the inward face of the shell, thus defining a mid chamber between the plates for the flow of a first fluid medium. An inlet chamber for the flow of a second fluid is defined by the first plate and a first end of the shell, and an outlet chamber is defined by the second plate and an opposite second end of the shell. The second fluid flows from the inlet chamber, through the tubes and into the outlet chamber.
The first fluid flowing through the mid chamber generally envelopes the tubes for heat transfer through the tube walls and to the second fluid flowing through the tubes. For efficient heat transfer, the tubes are typically made of copper or a copper alloy. To maintain fluid segregation, each end of each tube must be reliably sealed to the respective first and second plates. Traditionally, this seal is created by an expensive brazing procedure between the copper tubes and the plates. Because of this brazing, the first and second plates must also be of a copper alloy.
During operation of the heat exchanger, thermal expansion and contraction is known to cause stress cracks between various brazed seals causing a loss of seal integrity. Moreover, known assembly methods limit the ability to feasibly manufacture a multi-pass, tubular, heat exchanger having multiple inlet and outlet chambers, thus the ability to control cooling or heating rates as a function of multiple fluid temperatures is limited. Yet further, known brazing techniques limit or prevent cost effective maintenance and replacement of individual parts of the heat exchanger core. Such ability is particularly needed where fluids tend to be corrosive, or in marine applications that use seawater as a coolant that is not only corrosive but may encourage marine growth and sediment build-up inside the heat exchanger.
A tubular heat exchanger preferably of a multi-pass design, has a substantially cylindrical shell with open ends that are releasable covered and sealed by end caps. Located removably in the shell and axially between the end caps is a core having a plurality of outer tubes and preferably a plurality of inner tubes with each one of the inner tubes extending through a respective one of the outer tubes. A plurality of perforated plates located in the shell are sealed releasably to respective ends of the inner and outer tubes thereby forming a plurality of liquid tight chambers for the flow of a plurality of segregated mediums and the transfer of heat therebetween.
Preferably, end portions of the plurality of outer and inner tubes are supported by and sealed releasably to the respective plates. The end portions project through bores in the plates and may be sealed to the plates by at least one circumferentially continuous gasket located in a counter bore of each one of the bores for radial compression between the plate and the end portion of the tube. Each one of the plates has a peripheral circumferential surface facing radially outward that preferably defines a continuous groove for seating a circumferentially continuous gasket that compresses radially between the continuous surface and an inward circumferential face of the shell.
Objects, features and advantages of the present invention include a heat exchanger capable of operating with a wide and versatile range of heat transfer profiles and that has a removable core for maintenance and easy replacement of individual tubes and other components. Other advantages include the omission of expensive manufacturing processes such as brazing, the ability to use non-corrosive, light weight and relatively inexpensive components such as plastic, a relatively simple and robust design and a long and useful life.
These and other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and accompanying drawings in which:
Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only, and does not describe every possible embodiment of the invention because such would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention.
It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph.
Referring now to
Preferably, a coolant pump 40 positioned in an inlet leg 38 of the open loop 32 flows coolant/water from an open body of seawater to the heat exchanger 20. The pump 40 may be mechanically powered by the operating engine 24, but preferably is operated by a variable speed electric motor and a control system (not shown) that senses various parameters such as oil temperature and glycol temperature and thereby adjusts the speed of pump 40 to optimize engine performance. An outlet leg 42 of the open loop 32 preferably tees-off to flow heated seawater through respective exhaust manifolds 26, known in the marine industry, before being expelled back into the open sea.
Referring to
Referring to
The heat exchanger 20 has inlet and outlet chambers 90, 92 defined axially between respective end caps 56, 58 and respective outward plates 80, 82 for the flow of oil, inlet and outlet chambers 94, 96 defined axially between respective outward plates 80, 82 and respective inward plates 84, 86 for the flow of glycol, and a mid chamber 98 defined axially between the inward plates 84, 86 for the flow of seawater that is generally diverted by the diverter plates 88 located in the mid chamber 98. The chambers 94, 96, 98 are also defined radially by an inward face 100 of the shell 46. The ports 60, 62 communicate directly with respective inlet and outlet chambers 90, 92, and the orifices 68, 70 both communicate with the mid chamber 98, but adjacent to respective inward plates 84, 86 with the diverter plates 88 positioned axially between the orifices 68, 70.
Referring to
The core 78 has a plurality of inner tubes 110 for flow of oil of the closed loop 36. Each inner tube 110 extends through a respective outer tube 102 and through the mid chamber 98 and through the inward chambers 94, 96. Each tube 110 has opposite, distal, end portions 112 that project through respective outward plates 80, 82 and partially into respective inlet and outlet chambers 90, 92. Together, the outer and inner tubes 102, 110 define a channel 114 that has an annular cross section for the flow of coolant or glycol, and alone the inner tube 110 defines a channel 115 that has a round cross section preferably for the flow of oil.
Referring to
Referring to
The two end portions 112 of each one of the inner tubes 110 extends through a bore 138 in the respective outward plates 80, 82. Each bore 138 communicates through both the outer and inner faces 128, 130 of the plates 80, 82, and has a counter bore 140 that communicates through the inner face 128 only. The diameter of the bore 138 at the outer face 128 is substantially equal to or slightly greater than the diameter of the end portions 112 of the inner tube 110. The counter bore 140 generally seats two resiliently flexible o-rings 142, 144, a rigid spacer ring 146 and a retainer 148. The first o-ring 142 is located at the bottom of the counter bore 140. The spacer ring 146 is located axially between the two o-rings 142, 144, and the retainer 148 is located axially between the o-ring 144 and inner face 130 and press fitted to the plates 80, 82. Both the spacer ring 146 and the retainer 148 are preferably made of plastic.
Referring to
The two end portions 106 of each one of the outer tubes 102 extends through a bore 160 in the respective outward plates 84, 86. Each bore 160 communicates through both the outer and inner faces 150, 152 of the plates 84, 86, and has a counter bore 162 that communicates through the inner face 152, but not the outer face 150. The diameter of the bore 160 at the outer face 152 is substantially equal to or slightly greater than the diameter of the end portions 106 of the outer tube 102. The counter bore 162 generally seats two resiliently flexible o-rings 164, 166, a rigid spacer ring 168 and a retainer 170. The first o-ring 164 is located at the bottom of the counter bore 162. The spacer ring 168 is located axially between the two o-rings 164, 166, and the retainer 170 is located axially between the o-ring 166 and inner face 152 and press fitted to the plates 84, 86. Both the spacer ring 168 and the retainer 170 are preferably made of plastic.
A spacer member or plurality of pins 174 of the core 78 extend axially between each one of the outward plates 80, 82 and the respective inward plates 84, 86 to maintain a predetermined axial distance with respect to centerline 47. A plurality of blind bores 172 (see
Referring to
Preferably, the o-rings 126, 136, 158, 142, 144, 164, 166 are made of a resiliently flexible, rubber-like, material that is heat resistant such as viton. The inner and outer tubes 110, 102 are preferably made of metal having a high heat transfer coefficient and that is resistant to corrosion and marine growth such as copper or cupronickel. Preferably and for structural strength, the shell 46 is also made of copper or cupronickel. Unlike traditional heat exchangers, galvanic reaction concerns between various metal components is alleviated because of the plastic and o-ring components of the present heat exchanger as previously described. Moreover, any concerns with stress cracking is also alleviated because of the absence of brazing the tubes. The o-rings of the heat exchanger 20 not only provide the sealing function of traditional brazing but also permit thermal expansion and contraction between components made of different materials.
During assembly of the heat exchanger 20, the o-rings 164, 166, spacer ring 168 and retainer 170 are premounted in the counter bores 162 and the o-ring 158 is preferably preseated in the groove 152 of the inward plates 84, 86. Similarly, the o-rings 142, 144, spacer ring 146 and retainer 148 are premounted in the counter bores 140 and the o-ring 136 is preferably preseated in the groove 124 of the outward plates 80, 82. The ends 176 of the spacer member or pins 176 may then be press fitted into respective blind bores 172 in the plates 84, 86.
The mid portion 104 of the outer tubes 102 are then inserted through and generally seated to the diverter plates 88. The end portions 106 of the outer tubes 102 are then inserted through the bores 160 with the inner surfaces 152 of the plates 84, 86 opposing one-another. During this insertion, the o-rings 164, 166 resiliently compress about the end portions 106 for a liquid tight seal. This insertion preferably ceases when the annular stops 108 abut or come in near contact with the respective retainers 148.
The inner tubes 110 are then inserted through each respective one of the outer tubes 102 and the end portions 112 are of the inner tubes 110 are then inserted through the bores 138 with the inner surfaces 130 of the outward plates 80, 82 opposing one-another. During this insertion, the o-rings 142, 144 resiliently compress about the end portions 112 for a liquid tight seal. This insertion generally ceases when the distal ends 178 of the spacer pins 174 abut the inner surfaces 130 of the outward plates 80, 82.
With the core 78 preassembled, it may then be slid axially into the shell 46 from either of the openings defined by the ends 48, 50. Preferably, the ends 48, 50 are flared radially outward for easy insertion of the core 78. When the core 78 is axially moved into the shell 46, the o-rings 136, 158 are first cleared by either of the open ends 48, 50 and then compress against the inner face 100 of the shell 46. Because of the symmetrical design of the core 78, rotationally indexing the core 78 with respect to the centerline 47 and with respect to the shell 46 is not required. With the core 78 axially centered in the shell 46, the end caps 56, 58 with the preseated o-rings 126 are press fitted to the respective ends 48, 50. Contact of the annular surface 119 of the end caps 56, 58 with the outer face 128 of the respective outward plates 80, 82 assures that the core 78 is properly centered.
The angular position of the nozzles 52, 54 may then be independently adjusted by rotating the respective end caps 56, 58 about the centerline 47. Once adjusted, a plurality of threaded fasteners 180 are inserted through holes in the ends 48, 50 of the shell 46 and threaded into the end caps 56, 58. With the fasteners 180 engaged, the end caps 56, 58 are prevented from shifting axially. One skilled in the art, however, would now know that the end caps may releasably engage the shell 46 in a variety of ways. For instance, the caps 56, 58 may carry threads that threadably engage threads carried by the shell 46, thus fasteners would not be required. In this embodiment, the o-rings 126 can be compressed axially as oppose the illustrated radial compression. In yet another modification, the caps may be clamped to the shell 46.
During disassembly of the heat exchanger 20 for inspection and maintenance reasons, both end caps 56, 58 may be removed. With both ends of the shell 46 open, the core 78 can be pushed at one end and pulled out from the other. This technique is particularly advantageous if sediment build-up has occurred within the heat exchanger 20 that may otherwise make pulling of the core 78, from one end alone, difficult.
While the forms of the invention herein disclosed constitute a presently preferred embodiment, many others are possible. For instance, although the heat exchanger is generally described as a cooler, it could also function as a heater. Moreover, the liquid coolants (e.g. glycol and seawater) and oil may be any other form of a flowable medium and is not limited to liquids alone. Yet further, although the embodiment described entails three flowing mediums, the same novel aspects can be applied to heat exchangers having two, four or more flowing mediums. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.
