Patent Number: 048658022
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 therein is depicted a schematic of a power system for use in a substantially zero gravity environment, such as an orbiting satellite or a spacecraft. The system includes a reactor 12 for heating a primary coolant fluid, a conduit 14 and a pump, typically an electromagnetic pump 16, for inducing a flow of heated primary fluid to a heat exchanger 18. A conduit 20 provides for return of the primary fluid to reactor 12. A working fluid is passed in indirect heat exchange relationship with the primary fluid via conduits 22 and 24 which circulate the working fluid through a power conversion system 26. Power conversion system 26 converts the heat in the working fluid to electrical energy for use, for example, as the source of power for data acquisition and transmission devices on an oribiting satellite. The primary fluid flowing through reactor 12 may range in temperature by as much as 1,000K during normal operation. This temperature differential results in either thermal expansion or contraction of the fluid, thus it is essential there be provided means for accommodating such expansion and contraction. As depicted, this is accomplished by an accumulator 28 which is in fluid communication with conduit 20. It will be appreciated that the precise location is not critical and accumulator 28 could be placed in fluid communication with the primary fluid at any point in the system. Referring now to FIG. 2, therein is depicted in cross-section a schematic of accumulator 28. In the preferred embodiment shown, accumulator 28 comprises a closed vessel 30 provided at an end thereof with a conduit 32. Located within vessel 30 is a grid plate 34 which is surrounded by and in sealing engagement with the walls of vessel 30. Grid plate 34 is provided with a plurality of openings, one for each tube, for receiving and supporting a plurality of tube members 36. Each of tube members 36 is provided with an internal passageway which provides the sole means of fluid communication between a liquid zone 38 and a gas zone 40. The apparatus further includes a body of liquid in liquid zone 38 which extends at least partially into each of tubes 36 wherein it is contained by capillary action. The surface tension of the liquid forms a meniscus in each tube which acts as a gas-liquid interface 42 forming a barrier to the body of gas contained in gas zone 40 and an upper portion of each of tubes 36. Alternatively, the body of gas may be contained within each individual tube by sealing an end 37 of the tube 36. Given the direction and intent of the present invention the precise size of the passageways within each of tubes 36 is readily determinable by the artisan. For the containment of the liquid metal in a substantially zero gravity environment, tubes 36 will typically have an internal diameter within the range of from about 0.5 to 10 millimeters. In selecting the precise size, consideration must be given of course, to the acceleration forces to which the apparatus will be exposed during operation as well as the direction of such forces. In a similar manner, the length and nubmer of tubes will be determined by the volume of liquid which must be accommodated. In addition, in some instances, to assist the apparatus in withstanding higher acceleration loadings, a screen could be placed beneath grid member 34. When a screen is used, it will typically have a size of from about 30.times.30 to 500.times.500 mesh standard sieve size. The operation of the device depicted in FIG. 2 will be described with reference to a particularly preferred application, namely, accommodating the thermal expansion of a primary coolant for a nuclear reactor required to operate in a substantially zero gravity environment. Typically, the coolant for such a reactor will be a liquid metal such as sodium, potassium, lithium or a mixture of sodium and potassium. Conduit 32 is placed in fluid communication with the primary coolant loop. Upon thermal expansion of the coolant, it will flow into liquid zone 38 displacing that coolant previously there and compressing the gas in gas zone 40. Generally the gas will be one of more of the inert gases from group VIIIa of the Periodic Table of the Elements. The more common gases for such use are helium and xenon or mixtures thereof. When the reactor output power is reduced, the coolant temperature will decline and the volume of coolant contract. At that time, the gas in gas zone 40 will expand pushing the liquid back through conduit 32 and back into the system from which it was drawn. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.