Patent Application
20190383527
Exemplary embodiments pertain to the art of sublimator heat exchangers and, in particular, to a sublimator heat exchanger having structural members formed by an advance manufacturing technique.
A sublimator takes a fluid to be cooled and transfers the heat contained therein to a sublimate that is sublimated. A sublimator typically includes a metallic porous plate that is exposed to space vacuum on one side. It is supplied with a sublimate such as expendable feed-water on the other side. In operation, the feed-water freezes on the porous plate surface, and the vacuum side progressively sublimes water from this ice to the vacuum of space as waste heat is introduced into the plate.
Traditionally, the porous plate through which the sublimate sublimates includes plurality of fins that are individually attached to the porous plate. Depending upon the application, there can be several thousand fins that are attached to the porous plate with each fin segment being, incrementally spot welded to the porous plate in many locations. Further, the porous plate will include One, or more closure bars disposed on outer sides of the fins. The closure bars provide support to additional portions of the sublimator and may serve to define an outer boundary for the sublimate. The closure bars are also spot welded on the porous plate.
The spot welding is labor intensive and time consuming. Further, maintaining weld quality through this process requires constant tool maintenance and frequent quality inspections which increases overall manufactory cost.
Disclosed is a sublimator that includes: a porous plate having a first surface comprising a low pressure side and a second surface comprising a high pressure side such that a sublimate is configured to move through the porous plate from the high pressure side to the low pressure side, and wherein the second surface defines a primary heat transfer surface; a plurality of secondary heat transfer surfaces integrally formed on the primary heat transfer surface to facilitate flow and evenly distribute sublimate across the high pressure side of the porous plate; and one or more closure bars formed integrally formed along an outer end of the plate and formed by an advanced manufacturing technique.
In another embodiment, a sublimator is disclosed that includes: a sublimate chamber having a first side and a second side; a fluid chamber positioned on the first side of the sublimate chamber, wherein the fluid chamber is configured to receive a fluid to be cooled; and a porous plate having a first surface comprising a low pressure side and a second surface comprising a high pressure side. The high pressure side is positioned on the second side of the sublimate chamber such that sublimate is configured to move through the porous plate from the high pressure side to the low pressure side, the second surface of the porous plate defines a primary heat transfer surface, the porous plate includes a plurality of secondary heat transfer surfaces integrally formed on the primary heat transfer surface to facilitate flow and evenly distribute sublimate across the high pressure side of the porous plate, and the porous plate includes one or more closure bars formed integrally formed along an outer end of the plate and formed by an advanced manufacturing technique
In any embodiment of a sublimator previously disclosed, the advanced manufacturing technique is one of: laser-sintering, stereolithography, and fused deposition.
In any embodiment of a sublimator previously disclosed, the plurality of secondary heat transfer surfaces comprise a plurality fins extending outwardly from the primary heat transfer surface.
In any embodiment of a sublimator previously disclosed, the sublimator further includes: an intermediate plate having a first side and a second side facing opposite the first side, wherein the first side is spaced apart from the high pressure side of the porous plate and contacts the one or more closure bars to define a sublimate chamber, and wherein the second side at least partially encloses a fluid chamber configured to cool a fluid within the fluid chamber.
In any embodiment of a sublimator previously disclosed, the sublimator further includes an inlet to direct the sublimate into the sublimate chamber to flow across the primary and secondary heat transfer surfaces.
In any embodiment of a sublimator previously disclosed, the sublimator further includes a sublimate supply in fluid communication with the inlet to replenish sublimate that sublimates from the low pressure side of the porous plate into an external environment.
In any embodiment of a sublimator previously disclosed, the plurality of secondary heat transfer surfaces comprise a plurality of fins placed in a predetermined arrangement to optimize heat sink with heat flux input.
In any embodiment of a sublimator previously disclosed, a height of the plurality of secondary heat transfer surfaces is the same as a height of the one or more closure bars.
In any embodiment of a sublimator previously disclosed, the plurality of secondary heat transfer surfaces comprise a plurality of fins placed in a predetermined arrangement to optimize heat sink with heat flux input.
In any embodiment of a sublimator previously disclosed, a height of the plurality of secondary heat transfer surfaces is the same as a height of the one or more closure bars.
In one embodiment a method of making a sublimator is disclosed. The method includes: providing a porous plate having a first surface comprising a low pressure side and a second surface comprising a high pressure side such that sublimate is configured to move through the porous plate from the high pressure side to the low pressure side, and wherein the second surface defines a primary heat transfer surface; and integrally forming at least one closure bars on the porous plate by using an additive manufacturing.
In one embodiment, any method previously disclosed further includes integrally forming with an additive manufacturing process a plurality of secondary heat transfer surfaces on the primary heat transfer surface to facilitate flow and evenly distribute sublimate across the high pressure side of the porous plate.
In one embodiment, in any method previously disclosed the additive manufacturing process is one of: laser-sintering, stereolithography, and fused deposition.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
The fluid chamber 18 comprises an area that is enclosed by a housing 32 that includes an intermediate plate portion 34 that is located between the sublimate chamber 12 and the fluid chamber 18. While a single fluid chamber 18 and a single sublimate chamber are shown, it should be understood that there could be additional fluid chambers 18 and additional sublimate chambers 12. This will be discussed in greater detail below.
In one embodiment, the closure bars 52 contact the intermediate plate 34 and define outer boundaries of the sublimate chamber 12.
The sublimator 10 includes an inlet 40 to direct the sublimate 28 into the sublimate chamber 12 to flow across the primary and secondary heat transfer surfaces. A sublimate supply 42 is in fluid communication with the inlet 40 to replenish sublimate that sublimates from the low pressure side Lp of the porous plate 22 into an external environment E, such as outer space for example. A header 44 fluidly connects the inlet 40 to the sublimate chamber 12.
The sublimator 10 is used with a sublimate 28 that has a triple point where equilibrium of vapor, liquid, and solid will occur at a predetermined temperature or pressure and there is available an environment at or below this condition in one example, the sublimate 28 comprises water: however, other types of sublimate could also be used. The sublimate 28 is directed into the sublimate chamber 12 from the pressurized supply 42. The sublimate 28 then passes through the porous material that forms the porous plate 22 and freezes when exposed to the low pressure side Lp to form a layer of ice 50 that blocks further sublimate 28 from exiting the low pressure side Lp of the porous plate 22.
The sublimate 28 sublimates into the external environment E as heat is conducted to the porous plate 22 due to the heat exchange between the fluid 20 to be cooled and the sublimate 28 in the sublimate chamber 12. As the sublimate 28 sublimates away from the porous plate 22 and the solid sublimate becomes depleted, more sublimate is automatically used to replenish the porous plate 22.
In one example, the porous plate 22 is comprised of a stainless steel material having a pore size of approximately 0.5 microns. Other types of porous materials could also be used: however, the material needs to have a porous characteristic that facilitates formation of the necessary layer of ice 50 for sublimation. Each pore essentially becomes plugged with ice that has a surface exposed to the outer space environment E. As sublimation occurs at this surface, the thickness of the layer of ice 50 is reduced until it can no longer support the internal pressure within the chamber 12 and the sublimate will begin to pass into the external environment E. When the sublimate is exposed to this lower pressure level below its triple point, the sublimate freezes and reforms the ice.
In the example shown, the entire high pressure side Hp of the porous plate 22 is overlaid on the sublimate chamber 12 to provide maximum exposure. The fins 30 formed on the porous plate further enhance flow and improve distribution across and through the porous plate 22. This allows the formation of a uniform sheet of ice 50 across the low pressure side Lp of the porous plate 22. The fluid 20 that is to be cooled transmits heat through the intermediate plate portion 34 and through the sublimate 28 and eventually into the porous plate 22. The heat sublimates the ice at a rate that is directly proportional to the heat load and the fluid 20 to be cooled is discharged at a temperature that is lower than when the fluid entered the fluid chamber 18.
As discussed above, while only a single fluid chamber or passage 18 is shown in
With reference now to
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The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
