Patent Application
20190101334
The devices, systems, and methods described herein relate generally to plate and frame heat exchange. More particularly, the devices, systems, and methods described herein relate to plate and frame exchangers with variable chamber sizes.
Plate and frame heat exchangers are used in most industries as they are compact and cheap to make. However, they are very inflexible in operation, due to their rigidity and lack of moving parts. This prevents varying of various flow parameters during operations inside the exchanger. A plate and frame heat exchanger that overcomes these limitations is needed.
Devices, systems, and methods for a heat exchanger and operation of a heat exchanger are disclosed. The heat exchanger comprises a chamber with a plurality of fluid inlets and a plurality of fluid outlets. The chamber comprises one or more plates, the one or more plates being parallel and defining fluid plenums between each of the one or more plates. The fluid plenums define a fluid flow path, wherein each of the fluid plenums are aligned with one of the plurality of fluid inlets, one of the plurality of fluid outlets, a fluid path between at least two of the fluid plenums, or a combination thereof. The one or more plates are mounted on guides perpendicular to a plane of the one or more plates. The one or more plates move along the guides due to changes in pressure in the fluid plenums, application of an external force to the one or more plates, or a combination thereof.
The heat exchanger may further comprise spacers that limit movement of the one or more plates. The spacers may be mounted on the guides. The spacers may also be mounted on the one or more plates. The spacers may also limit the movement of the one or more plates such that the fluid plenums aligned with each of the plurality of fluid inlets and each of the plurality of fluid outlets do not change.
The one or more plates comprising the heat exchanger may also be sufficiently rigid that the one or more plates moves when an even force is applied to the plate.
The one or more plates may comprise silicone, aluminum, steel, copper, bronze, plastic, or combinations thereof. The one or more plates may also flex such that solids deposited on the one or more plates break off.
The one or more plates may also be pre-tensioned to buckle when a pressure differential between sides of the one or more plates exceeds a limit. The one or more pre-tensioned plates flex such that solids deposited on the one or more plates break off.
The one or more plates may be prevented from moving when a temperature limit is reached by a mechanical locking mechanism, temperature-induced expansion or contraction of the one or more plates, temperature-induced expansion or contraction of the chamber, or combinations thereof.
The one or more plates comprise an electroactive material that flexes or deforms when a charge is applied to the one or more plates.
The heat exchanger may further comprise one or more pressure sensors, one or more temperature sensors, or a combination thereof.
The one or more plates may be vibrated to break off solids deposited on the one or more plates.
The external force applied to the one or more plates may be provided by a piston, gears, electromagnets, or combinations thereof.
The fluid flow paths may be counter flow, co-current flow, cross flow, or combinations thereof.
The one or more plates may comprise dimples or grooves. The dimples or grooves may comprise spacers that limit movement of the one or more plates.
In order that the advantages of the described devices, systems, and methods will be readily understood, a more particular description of the devices, systems, and methods briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the described devices, systems, and methods and are not therefore to be considered limiting of its scope, the devices, systems, and methods will be described and explained with additional specificity and detail through use of the accompanying drawings, in which:
It will be readily understood that the components of the present devices, systems, and methods, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the present devices, systems, and methods, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of certain examples of presently contemplated embodiments in accordance with the described devices, systems, and methods.
Cryogenic heat exchangers operate at temperatures low enough that normally benign gases desublimate, condense, freeze, deposit, or combinations thereof out of fluids onto surfaces in a solid form, termed foulant. Foulant builds up on the various surfaces in the heat exchanger, but most especially on heat transfer surfaces. This causes increased pressure drops across the heat exchanger, increasing operating expenses for the heat exchanger while also decreasing heat exchange efficiency. Various solutions have been attempted, most occurring after shutdown.
The devices, systems and methods herein prevent or remove foulant during operations. The change in pressure caused by foulant deposition is used to solve the foulant deposition. Rather than brazing plates into the typical rigid form of traditional plate and frame heat exchangers, the devices, systems, and methods described herein are designed to allow the plates to move or float depending on the changes in pressure of the fluids or other applied mechanical forces. As foulant deposits within the process side of the heat exchanger, pressures in the process flow path increase. The pressure differential thus formed versus the coolant flow path across the plates pushes outward on the plate, constricting the flow of the coolant, increasing the back-pressure on the coolant flow path until the pressures equalize. The movement of the plates breaks up the solids that have built up in one or more ways. First, the movement itself can cause fracturing of foulant, allowing it to be stripped off the plates. Second, the coolant now has less volume to move through, but the same incoming flow. The increased flow velocity through the coolant flow path means cooling of the process side decreases, and so the foulant will be warmed by the process fluid, melting, desublimating, or dissolving into the process fluid.
These “floating” plates also provide control benefits for operation of the heat exchanger. Controlling the pressure of one fluid can control the pressure of both fluids. Dropping fluid flow into the coolant flow path drops pressure in the coolant flow path such that the plates move to increase the volume of the process flow path until pressures are equalized.
The floating plate also allows for a pressure impulse to be sent through either fluid to abruptly move the plates and break up any foulant before the foulant causes a sizable pressure drop and a loss of efficiency.
Referring now to the Figures,
In one exemplary embodiment, process fluid 130 is pentane with dissolved carbon dioxide. Coolant 132 is liquid methane. As the pentane is cooled across plates 106, a portion of the dissolved carbon dioxide desublimates out of solution and forms solid carbon dioxide on the surface of plates 106. This carbon dioxide restricts flow of pentane through process plenum 116, resulting in an increase in pressure in process plenum 116. As the pressure in process plenum 116 exceeds the pressure in coolant plenum 114, plates 106 begin moving 118 such that process plenum 116 gains volume and coolant plenum 114 loses volume. This movement may remove a portion of the solid carbon dioxide from the surface due to fracturing of the solid carbon dioxide. Restriction of the liquid methane into coolant plenum 114 results in less cooling across plates 106, such that the pentane doesn't become as cold, and can sublimate, melt, and dissolve the solid carbon dioxide back into solution.
Referring to
The heat exchanger 206 comprises shell 208, process inlet pipe 232, process outlet pipe 234, coolant inlet/outlet pipe 236, coolant internal pipe 238, and plates 214. Shell 208 comprises box 242, head plate 212, and tail plate 210. Head plate 212 and tail plate 210 are fixed in place. Coolant inlet/outlet pipe 236 comprises coolant inlet 218, coolant outlet 222, slits 244 and 246, separators 252, and spacers 240. Coolant internal pipe 238 comprises slits 248 and 250, separators 252, and spacers 240. Process inlet pipe 232 comprises process inlet 216, spacers 240, slits 258 and 260, separators 252. Process outlet pipe 234 comprises process outlet 220, spacers 254 and 256, slits 236, and separators 252. The plenums between plates 214 and between plates 214 head and tail plates 212/210 alternate as ascending-coolant plenum 224, descending-process plenums 228, descending-coolant plenum 226, ascending-process plenum 230, and then repeats the pattern.
Process fluid 270 enters process inlet 216 and is forced by a separator 252 to pass through a first slit 258 into the first descending-process plenum 228. Process fluid 270 then passes through a first slit 254 into process outlet pipe 234 and is forced by a separator 252 to pass through the next slit 256 into ascending-process plenum 230. Process fluid 270 reenters process inlet pipe 232 through a slit 260. This pattern repeats until process fluid 270 passes out process outlet 220.
Coolant 280 enters coolant inlet 218 and is forced by a first separator 252 to pass through a slit 244 into the first ascending-coolant plenum 224. Coolant 280 then passes through a slit 250 into coolant internal pipe 238, and is forced by a separator 252 to pass through the next slit 248 into descending process plenum 226. Coolant 280 then passes through a slit 246, reentering coolant inlet/outlet pipe 236. This pattern repeats until Coolant 280 passes out coolant outlet 222.
Plates 214 conduct heat between process fluid 270 and coolant 280. Plates 214 can move perpendicular to the plane of the plates. Pipes 232, 234, 236, and 238 serve as guides for plates 214, limiting the movement of the plate to the perpendicular. They are also a path for fluid flow, a mount for spacers, and as a structural support of the heat exchanger. Pipes 232, 234, and 238 are mounted to head or tail plate 212/210 for rigidity and structural support where pipes 232, 234, and 238 do not pass through both head and tail plate 212/210. This mounting is not shown for clarity of drawings.
Plates 214 can move side to side between spacers 240 due to pressure differences between coolant and process plenums. The spacers 240 limit the maximum travel distance of plates 214. Spacers 240 also keep plenums 224, 226, 228 and 230 aligned with their corresponding slits. By placing the spacers where they are, the openings 230 and 232 are locked to the correct plenum. This arrangement allows the fluid to flow through plenums 224, 226, 228, and 230 without backflow or mixing of process fluid 270 with coolant 280.
Referring to
In some embodiments, the spacers are mounted on the guides. In some embodiments, the spacers are mounted on the one or more plates. In some embodiments, the spacers limit the movement of the one or more plates such that the fluid plenums aligned with each of the plurality of fluid inlets and each of the plurality of fluid outlets do not change.
In some embodiments, the one or more plates are sufficiently rigid that the one or more plates move when an even force is applied to the plate.
In some embodiments, the one or more plates comprise silicone, aluminum, steel, copper, bronze, plastic, or combinations thereof.
In some embodiments, the one or more plates flex such that solids that deposit on the one or more plates are broken off. In some embodiments, the one or more plates are pre-tensioned to buckle when a pressure differential between sides of the one or more plates exceeds a limit. In some embodiments, the one or more plates flex such that solids that deposit on the one or more plates are broken off.
In some embodiments, the one or more plates are prevented from moving when a temperature limit is reached by a mechanical locking mechanism, temperature-induced expansion or contraction of the one or more plates, temperature-induced expansion or contraction of the chamber, or combinations thereof.
In some embodiments, the one or more plates comprise an electroactive material that flexes or deforms when a charge is applied to the one or more plates.
In some embodiments, the heat exchanger comprises one or more pressure sensors, one or more temperature sensors, or a combination thereof.
In some embodiments, the one or more plates are vibrated to break off solids deposited on the one or more plates.
In some embodiments, the external force applied to the one or more plates is provided by a piston, gears, electromagnets, or combinations thereof.
In some embodiments, the fluid flow paths are counter flow, co-current flow, cross flow, or combinations thereof.
In some embodiments, the one or more plates comprise dimples or grooves. In some embodiments, the dimples or grooves comprise spacers that limit movement of the one or more plates.
This invention was made with government support under DE-FE0028697 awarded by the Department of Energy. The government has certain rights in the invention.
