Patent Application
20250085059
Airplane hydraulic oil coolers have heat exchangers embedded in fuel tanks using the fuel as coolant. However, they are not mass efficient because they do not boil the coolant. Boiling coolant is preferred for spaceflight applications to save mass. However, because boiling coolant is difficult in microgravity, a spraying architecture has been used. This latter type of cooling architecture may be performed by a water spray boiler (WSB), which was used on the Space Shuttle.
The WSB is a thermal control system that provides passive and active cooling capabilities to cool down hydraulic oil, for example, or other fluid. Cooling occurs in a heat exchanger that doubles as a container for the cooling liquid. Cooling is achieved by spraying water (or some water-based mixture) onto tubes (or channels) that contain flowing fluid to be cooled. The sprayed water generally converts to water vapor by the relatively hot tubes, and this vapor is vented to outside the space vessel.
Though the WSB has been used numerous times with success, there have also been problems. For example, because the WSB is generally operated during space flight where temperatures are very cold, freezing of coolant (e.g., the water) may occur and block flow of the coolant or vents thereof. Another problem with a WSB is its mass, which is relatively high and undesirable for repeatable and economical space flight, where mass considerations are particularly important.
The disclosure will be understood more fully from the detailed description given below and from the accompanying figures of embodiments of the disclosure. The figures are used to provide knowledge and understanding of embodiments of the disclosure and do not limit the scope of the disclosure to these specific embodiments. Furthermore, the figures are not necessarily drawn to scale.
This disclosure describes architectures for a heat exchanger system, in particular a vacuum spray boiler, for cooling a hot fluid by spray boiling a coolant in vacuum (e.g., as in space), atmospheric pressure (e.g., as on the launch pad of a space vehicle), or any pressure therebetween. As explained below, hot fluid flows in a plate-fin heat exchanger while a coolant spray apparatus, integrated with the heat exchanger, delivers coolant via spraying from nozzles. The coolant consequently phase changes from a sprayed fluid state to a boiled vapor, which is then exhausted to outside the system.
In some embodiments, a vacuum spray boiler cooling system for cooling a fluid includes a vacuum tank. In some implementations, the system need not operate in a vacuum and the “vacuum” tank need not be a tank capable of holding a vacuum. In other implementations, the vacuum tank is a chamber capable of holding a vacuum. Regardless of implementation, examples herein will recite a “vacuum” tank, though claimed subject matter is not so limited.
The vacuum tank includes an enclosed space at least partially surrounded by a casing, which may be aluminum, for example. The casing comprises sides and a lid, which includes a coolant inlet. The lid further includes a coolant spray apparatus connected to one or more nozzles, which may protrude from the lid, in the enclosed space.
A number of components are integrated with the vacuum tank such that these components and the vacuum tank are a single integrated apparatus. In other words, these components are built into the vacuum tank. These components include a fluid inlet and a fluid outlet, both penetrating the casing, for carrying the fluid through the casing. Other components integrated with the vacuum tank are the coolant spray apparatus and a heat exchanger in the enclosed space. The coolant spray apparatus is configured for spraying coolant, via one or more nozzles, onto the heat exchanger. The heat exchanger may be a plate-fin heat exchanger, which may comprise serpentine-shaped chambers to carry the fluid to be cooled. Still other components integrated with the vacuum tank are a coolant inlet and a coolant exhaust port at least partially penetrating the casing. The coolant inlet is configured for carrying the coolant to the coolant spray apparatus and the coolant exhaust port is configured for carrying vaporized coolant away from the enclosed space.
In addition to the integrated vacuum tank, the vacuum spray boiler cooling system includes an exhaust vent connected to the coolant exhaust port. The exhaust vent is in thermal contact with a portion of the components, as explained below. The exhaust vent may be configured to release the vaporized coolant from the system. Such thermal contact may allow for heating of the vented vaporized coolant, which may otherwise quickly cool to a solid state (e.g., from steam to ice) as the coolant travels toward the exterior of the space vehicle, which is generally extremely cold. Thus, such thermal contact may help maintain the vaporized coolant at a temperature above its freezing point. In other words, heat energy from at least a portion of the vacuum spray boiler cooling system may be transferred, via the thermal contact, to the exhaust vent.
In some embodiments, because spray nozzles of the coolant spray apparatus are integrated with, and relatively close to, a relatively warm heat exchanger inside the enclosed space of the vacuum tank, these spray nozzles may remain relatively warm. This situation, e.g., thermal contact between the heat exchanger and the spray nozzles, allows for prevention of coolant freezing at the nozzles, which could otherwise occur in the extreme cold temperature of space.
Coolant spray apparatus 110 may include nozzles 122 that substantially direct coolant, such as water, toward cooling chambers 124 of heat exchanger 116. In this way, coolant spray apparatus 110 is configured for spraying coolant onto heat exchanger 116. Coolant inlet 118 may receive coolant from a reservoir tank (e.g., from which the coolant may be moved via a pump, though a pump may not be necessary, wherein coolant may move via residual pressure in the tank) and carry the coolant to coolant spray apparatus 110. In some implementations, at least a portion of the coolant may be sourced from recirculated coolant. Generally, upon contact with cooling chambers 124, which are relatively hot, coolant sprayed onto these chambers will phase transition from liquid to a vapor. Coolant exhaust port 120 is configured for carrying the vaporized coolant away from enclosed space 106.
In addition to the vacuum tank and its integrated components, a cooling system that includes vacuum spray boiler 102 may also include an exhaust vent 126 connected to coolant exhaust port 120. The exhaust vent may be configured to release vaporized coolant from the system. For example, vaporized coolant may be released into space from the vehicle carrying the cooling system. The exhaust vent may be in thermal contact, indicated by dashed double arrow 128, with a portion of the components. As mentioned above, such thermal contact may help maintain the vaporized coolant at a temperature above its freezing point. Thus, heat energy from at least a portion of vacuum spray boiler 102 may be transferred, via the thermal contact, to exhaust vent 126. Such thermal contact may arise via conduction heating from heat exchanger 116 to exhaust vent 126. In some implementations, inlet tubing (not shown) may be connected to fluid inlet 112 to carry hot fluid (to be cooled) from a source such as machinery or an engine, for example, to vacuum spray boiler 102. In this case, the thermal contact may arise via conduction, convection, and/or radiation heating, based on ambient conditions surrounding the system (e.g., conduction and/or radiation heating in space, and convection heating in air), from the fluid in the inlet tubing to the exhaust vent.
Vacuum spray boiler 202 includes a vacuum tank 204 having an enclosed space, such as 106 in
A coolant spray apparatus, such as 110, may be included in lid 210 in the form of channels for coolant to flow from coolant inlet 216 to spray nozzles, such as 122, which may substantially direct the coolant toward cooling chambers (e.g., 124) of a heat exchanger (e.g., 116). Inside casing 206, and not visible in
Also illustrated in
A plate-fin heat exchanger, such as 402, provides a number of advantages for use in space vehicles. For example, it is relatively compact with a high heat-transfer-surface-area to volume ratio. Heat exchanger 402 may be fabricated from aluminum or aluminum alloy (e.g., a brazed aluminum heat exchanger), or other metals, such as stainless steel.
Heat exchanger 402, which may be the same as or similar to, heat exchanger 116 of
Plate-fin heat exchangers may incorporate any of several types of fins. For example, a plain configuration has a straight-finned triangular or rectangular design. A herringbone configuration has fins that are placed sideways to provide a zig-zag path. A serrated and perforated configuration has cuts and perforations in the fins to augment flow distribution and improve heat transfer. A serpentine configuration, such as 504, has fins that are sinuous, as illustrated in
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the disclosure. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the systems and methods described herein. The foregoing descriptions of specific embodiments or examples are presented by way of examples for purposes of illustration and description. They are not intended to be exhaustive of or to limit this disclosure to the precise forms described. Many modifications and variations are possible in view of the above teachings. The embodiments or examples are shown and described in order to best explain the principles of this disclosure and practical applications, to thereby enable others skilled in the art to best utilize this disclosure and various embodiments or examples with various modifications as are suited to the particular use contemplated. It is intended that the scope of this disclosure be defined by the following claims and their equivalents.
