Thermal performance of a carbon fiber composite material heat sink in an FC-72 thermosyphon

This study analyzes the use of a carbon fiber epoxy heat sink for evaporator surface enhancement in a FC-72 thermosyphon. The pin-fin heat sink features 945 small-cross-section (1.27 mm by 0.965 mm) fins fabricated with an integral base plate. These fins have a high thermal conductivity (500 W/m K) along the length of the fin. The influence of heat load, thermosyphon fill volume, and condenser operating temperature on the overall thermal performance is examined. The results of this experiment provide significant insight into the possible implementation and potential benefits of carbon-fiber heat sink technology in two-phase flow leading to significant improvements in thermal management strategies for advanced electronics.     

Controllability of nonlinear systems

In this paper we obtain global controllability of a semilinear system involving monotone nonlinearities of both Lipschitzian and non-Lipschitzian types.     

Recursion operator for coupled KdV equation

The recursion operator for the infinitesimal transformations about solutions of the coupled KdV is obtained as a 2 × 2 matrix.     

Variation in hyperfine field with atomic order in FeCo and FeNi3

The variation in hyperfine field with long range order parameter is estimated both in FeCo and FeNi₃ with the help of an emperical relation connecting field and magnetic moments. The agreement is good with the available experimental values.     

Heat transfer between an impinging jet and a continuously moving flat surface

Experiments have been carried out to determine heat transfer rates from a continuously moving belt to an air jet impinging normally. The parameters that were varied included the jet velocity (4 < V_N < 40 m/s), the jet width (4.8 < B < 19 mm), the nozzle-to-plate distance (3 < H/2B < 11) and the belt speed (0. 15 < V_B < 5. 5 m/s). An infrared thermometer was used for the measurement of temperature of the moving belt. The average heat transfer coefficients increase with belt speed steeply initially to a maximum value and then remain almost constant for all higher belt speeds. The maximum heat transfer coefficients are about 1.5 to 2.0 times higher than those predicted for the stationary surface. The present data on continuously surface in still air and in impinging jet flow are well compared with the data on rotating cylinders reported in the literature.

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Wärmeübergang zwischen einem senkrecht auftreffenden Strahl und einer bewegten Oberfläche

Zusammenfassung Experimentell bestimmte Wärmeübergangskoeffizienten für Düsengeschwindigkeiten zwischen 4 m/s und 40 m/s, sowie Düsenbreiten zwischen 4,8 mm und 19 mm lagen bei Bandgeschwindigkeiten zwischen 0, 15 m/s bis 5, 5 m/s ca. 50 % bis 100 % höher als bei unbewegtem Band. Die gemessenen Daten bei bewegtem wie bei unbewegtem Band schließen gut an bekannte Werte aus der Literatur an.

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Nomenclature A Heat transfer area - B Width of the nozzle - D Diameter of the cylinder or equivalent diameter of the flat surface (D=L/) - k Thermal conductivity - Gr Grashof number - h Heat transfer coefficient - H Height of the nozzle from the surface - i Number of nozzles - L Heat transfer length of a flat surface - Nu_D Nusselt number hD/k - Re_DB Belt Reynoldsnumber, DV_B/ - Re_DN Nozzle Reynolds number, DV_N/ - Re_SN Nozzle Reynolds number, SV_N/ - S Hydraulic diameter of the nozzle, 2B - V_B Belt velocity or circumferential velocity of a cylinder - V_N Nozzle celocity - Kinematic viscosity     

Re-radiation of acoustic waves from the A0 wave on a submerged elastic shell

We consider evacuated thin semi-infinite shells immersed in a fluid, which may be either of cylindrical shape with a hemispherical shell endcap, or formed two-dimensionally by semi-infinite parallel plates joined together by a semi-cylinder. The connected shell portions are joined in a manner to satisfy continuity but with a discontinuous radius of curvature. Acoustic waves are considered incident along the axis of symmetry (say the z axis) onto the curved portion of the shell, where they, at the critical angle of coincidence, generate Lamb and Stoneley-type waves in the shell. Computations were carried out using a code developed by Cao et al. [Chinese J. Acoust. 14, 317 (1995)] and was used in order to computationally visualize the waves in the fluid that have been re-radiated by the shell waves a the critical angle. The frequency range was below that of the lowest Lamb wave, and only the A0 wave (and partly the S0 wave) was observed to re-radiate into the fluid under our assumptions. The results will be compared to experimental results in which the re-radiated waves are optically visualized by the Schardin-Cranz schlieren method.