A ferrofluid seal for a shaft comprising several sealing gaps concentrically arrayed about a shaft. Each gap is filled with ferrofluid liquid through a bore-hole. Each of the bore-holes is sealed and hydraulically isolated from the other bore-holes.

There is disclosed a novel high heat flux liquid cooled semi-conductor heat sink of modular construction suitable for semi-conductor chips such as IC's, hybrids, lasers, and power semi-conductors, said modular heat sink containing inserts with chip substrates made of metals, such as tungsten or molybdenum, said substrate including at least one surface suitable for bonding one or more semi-conductor chips in intimate thermal relationship thereto, and including a heat exchange surface on the interior surface thereof, said module providing means for enclosing said heat exchange surface in a liquid tight manner and including means for providing a flow of coolant liquid to remove heat from said heat exchange surface by formation of nucleate vapor bubbles on said heat exchange surface, the improvement wherein said heat sink module comprises individual heat sink inserts upon which semi-conductor chips are intimately bonded, said heat sink element being provided with means to electrically isolate each heat sink element from all other heat sink elements mounted on said heat sink module, said heat sink elements having their corresponding liquid cooled surface directly opposing said semi-conductor chip, the heat transfer characteristics of said liquid cooled surface being unobstructed by said electrically isolating means.

A self-cooling ferrofluid seal includes a housing having a housing case and an external pole piece integrally connected to the housing case where the housing case has a plurality of heat dissipating surfaces, a magnetic circuit within the housing formed in conjunction with the external pole piece, a rotatable shaft having one or more fan blades where the rotatable shaft is coaxially aligned within the housing, and a quantity of magnetic fluid between the rotatable shaft and the external pole piece forming a ferrofluid seal.

The present approach pertains to colloidal chemistry and methods of manufacturing magnetic fluid such as ferrofluid. In particular, the present approach is directed to methods of manufacturing magnetic fluid that is resistant to aggregation and clumping, and is more stable over time. The process according to the present approach comprises sedimentation of magnetic particles; mixing the magnetic particles with an aqueous acetic acid solution, a surface-active agent and a polarizing composition; applying pulsed magnetic fields; removing excess surface-active agents and polarizing composition; ferrite desalination; and peptization of the surface-active agent in a non-polar, dispersing fluid. Magnetic fluids made according to the process of the present approach can be used, e.g., for ferrofluidic seals, inclinometers, accelerometers, or as magnetic lubricants.

A magneto-fluidic seal includes a shaft; a sleeve surrounding the shaft; a housing made of soft magnetic material surrounding the sleeve; a magnet conducting a magnetic flux to the sleeve; and a magnetic fluid in a gap between the sleeve and the shaft, and/or in a gap between the sleeve and the housing. Optionally, the sleeve includes a channel on a longitudinal side, and wherein the magnet is positioned in the channel. The channel can be substantially circular or polyhedral. The magnet is preferably offset from a bottom of the channel, and oriented radially. Preferably, the magnet includes a plurality of segments, or flat plate-shaped magnets, arranged substantially evenly and circumferentially around the shaft.