Showing papers on "Fin published in 1992"

Optimal thermal design of air cooled forced convection finned heat sinks-experimental verification

Abstract: D.B. Tuckerman and R.F.W. Pease (1981) showed that microchannels with water flow could be used to cool VLSI systems. Their work required the flow to be laminar, and the channel system, or fin array, was optimized analytically. Recently, it has been shown that, for some geometries and fluid pressure drops, a lower thermal resistance can be found if the channels are designed to allow turbulent flow. The current work uses the optimization scheme developed by R.W. Knight et al. (1991 and in this issue) to design three air-cooled aluminum finned arrays, which were built and tested experimentally. The thermal performances of the fin array designs, one containing 5 fins, one with 11 fins, and one with the predicted optimum of 8 fins, are compared. All arrays had turbulent flow and pressure drop across them, and all fins were the same length and width. The best thermal performance was obtained with the design predicted to be optimal. The scheme can be applied to a variety of heat sink design applications, including water-cooled microchannels. >

Prediction of Heat Transfer and Friction for the Louver Fin Geometry

Abstract: This paper is concerned with prediction of the air-side heat transfer coefficient of the louver fin geometry used in automotive radiators. An analytical model was developed to predict the heat transfer coefficient and friction factor of the louver fin geometry. The model is based on boundary layer and channel flow equations, and accounts for the[open quote] flow efficiency[close quotes] in the array, as previously reported by Webb and Trauger. The model has no empirical constants. The model allows independent specifications of all of the geometric parameters of the touver fin. This includes the number of louvers over the flow depth, the louver width and length, and the louver angle. The model was validated by predicting the heat transfer coefficient antifriction factor of 32 louver arrays tested by Davenport, which spanned hydraulic diameter based Reynolds numbers of 300-2800. At the highest Reynolds number, all of the heat transfer coefficients were predicted within a maximum error of [minus]14 /+ 25 percent, and a mean error of +/- percent. The high Reynolds number friction factors were predicted with a maximum error [minus]22 / + 26 percent, with a mean error of +/- 8 percent. The error ratios were slightly higher at the lowestmore » Reynolds numbers. 11 refs., 14 figs., 2 tabs.« less

Fin-tube type heat exchanger

Abstract: A fin-tube type heat exchanger has parallel heat transfer tubes and a stack of a plurality of plate fins mounted on the tubes. Heat exchange is conducted between a first fluid flowing through the tubes and a second fluid flowing through the stack across each of the fins. Each fin has flat tube-mounting portions spaced in the longitudinal direction of the fin and formed with tube-mounting holes and a louver section disposed between each adjacent pair of tube-mounting portions. The louver section has elongated slats extending longitudinally of the fin and having side edges each spaced from an adjacent side edge of an adjacent slat. The slats are classified into two groups in respect of the cross-sectional shape. The slats of one group have generally flat cross-sections to reduce the resistance of the fin to the flow of the second fluid through the stack and are disposed in planes offset from the plane of the tube-mounting portions. The slats of the other group have V-shaped or inverted V-shaped cross-sections to increase stiffness of the fin in the longitudinal direction thereof.

Locomotion, fin coordination and body form of the living coelacanth Latimeria chalumnae

Abstract: Locomotion and fin coordination of the only living crossopterygian fish Latimeria chalumnae were studied with submersibles in the fish's natural habitat at around 200 m depth off Grand Comoro, western Indian Ocean. Latimeria is a highly specialized predatory fish adapted for nocturnal drift hunting with good fast start capability. Twelve different forward movements and manoeuvres were found and described. The movements of the paired and unpaired fins were analysed. Propulsion was accomplished with downstrokes of the pectoral fins and right-left or left-right strokes of the unpaired lobed fins. The paired fins were not used for walking on the bottom. Swimming velocity, stroke amplitudes and stroke duration were analysed from films and videos taken in the wild. Stroke duration of the paired and unpaired lobed fins was similar and varies between 1.9 to 5.8 sec. Paired fins alternated synchronously. The coordination at approximately o = 180° between opposite paired fins is stable and independent of locomotory pattern and velocity. A phase deviation of about 90°–100° exists between paired and unpaired fins. A model is developed that describes the functional implication of this deviation as a method of producing a steady swimming performance which smooths recoil movements and prevents rotation of the body. The novel slow and fast swimming mode of Latimeria is named in accordance with Breder's (1926) descriptive nomenclature as ‘coelacanthiform’. This study indicates a primary swimming function for the primitive sarcopterygian fin and confirms earlier evolutionary assumptions of a more open-water life style of coelacanth fishes. Paleoethological models of the walking habits of Latimeria have to be rejected. Synchronous alternation of paired fins originating from hydrodynamic demands could be a pre-adaptation and a shared derived character in sarcopterygian fishes that facilitated the fish-tetrapod transition.

Two-Dimensional Effects and Design Criteria for Convective Extended Surfaces

Abstract: An analysis of the thermal performance of convective extended surfaces is presented that takes into account the primary function of the fins, which is to augment the heat transfer. The measure of the heat transfer augmentation is expressed by the removal number Nr, which we proposed should be O(10). It is shown that in order to satisfy this criterion the transverse Biot number hw/k must be of the order of 0.01. Further, it is argued that the fin is fully utilized if the aspect number is O(1). These criteria, Bi; = O(0.01) and u = 0(1), offer guidelines for designing fins and are applicable to longitudinal, annular, and pin fins, of uniform thickness or tapered profile. They must substitute the criterion that is frequently used, Bi < I, which was derived from the analysis of longitudinal fins. A very important consequence of this investigation is that fins designed to meet the above criteria can be analyzed using the classical one-dimensional method without introducing any appreciable error.

Optimization of heat sink fin geometries for heat sinks in natural convection

Abstract: An approach for determining the optimum fin configurations for a given heat sink in natural convection is developed. Incorporation of minimization routines into the analysis eliminates the manual, iterative design analysis and identifies the optimum design. Optimization of fin geometry for heat sinks in natural convection with rectangular cross section fins at a constant fin spacing was implemented for steady state and intermittent duty cycle operation. The proposed algorithm allows the computer to hunt for the lowest temperature performance of a user-specified range of fin geometries. The heat transfer analysis is based on methods used in conventional heat sink analysis programs, so the results correlate well. >

Film Condensation of R-113 on Staggered Bundles of Horizontal Finned Tubes

Abstract: Film condensation of R-113 on staggered bundles of horizontal finned tubes with vertical vapor downflow was experimentally investigated. Two tubes with flat-sided annular fins and four tubes with three-dimensional fins were tested. The condensate flow and heat transfer characteristics were compared with the previous results for in-line bundles of the same test tubes and a staggered bundle of smooth tubes. The decrease in heat transfer characteristics were compared with the previous results for in-line bundles of the same test tubes and a staggered bundle of smooth tubes. The decrease in heat transfer due to condensate inundation was most significant for the in-line bundles of the three-dimensional fin tubes, whereas the decrease was very slow for both the staggered and in-line bundles of the flat-sided fin tubes. The predictions of the previous theoretical model for a bundle of flat-sided fin tubes agreed fairly well with the measured data at a low vapor velocity. The highest heat transfer performance was provided by the staggered bundle of flat-sided fin tubes with fin dimensions close to the theoretically determined optimum values.

Heat exchanger and manufacturing method

Abstract: A heat exchanger of the plate fin and tube type and a method for manufacturing such an apparatus. The heat exchanger has a curved face as may be required due to the dimensional constraints of the enclosure housing the heat exchanger. The heat exchanger is constructed with single row plate fins in those portions of the heat exchanger that will experience relative motion between adjacent tube rows during bending of the tubes to achieve the curved face. Multiple row plate fins are used in those portions of the heat exchanger where there will be no relative motion between adjacent tube rows during tube bending. A locking member affixed to one tube row receives an end of a tube in an adjacent row that is more inward, with respect to the center of curvature, during bending and secures the two tube rows together. The use of multiple row plate fins and the locking member produce a strong and rigid assembly.

Aerothermoelastic Analysis of a NASP-Like Vertical Fin

Abstract: Several aeroelastic stability analyses for a vertical fin similar to that of the National Aero-Space Plane are described. The objectives of the study were to design and obtain an experimental data base for a supersonic wind-tunnel model of the fin in order to examine the effects of thermal loading on the flutter characteristics. This paper describes the preliminary efforts to design the wind-tunnel model, including several of the geometric parameter variations that were analyzed. The dominant flutter mechanism involved a flap vibration mode and a fin bending mode. Variation of the thicknesses of flap and root flexures, used to attach the flap to the fin, and the fin to a support, significantly affected the flutter boundary. Uniform thermal loads, affecting only material properties, had little effect, as did the application of different uniform temperatures to each side of the fin. In contrast, the application of significant chord-wise thermal gradients induced stresses which reduced the flutter dynamic pressure by as much as 37 percent. For less extreme distributed loading, the low-aspect ratio fin was relatively unaffected.

Wing-loading, stability and morphometric relationships in flying fish (Exocoetidae) from the North-eastern Atlantic

Abstract: ‘Four-winged’ flying fish (in which both pectoral and pelvic fins are hypertrophied) reach greater maximum sizes than ‘two-winged’ forms in which only the pectoral fins are enlarged. Exocoetus obtusirostris shows negatively allometric growth in relation to standard length in terms of body mass (b =2·981), and lateral fin area (b =1·834). In consequence, wing-loading rises in positive allometric fashion with standard length (b =l·236). Pectoral fin length cannot be greater than 78–79% of standard length or swimming will be impaired, so the requirement for increased flying speed resulting from increased wing-loading during growth means that lift:drag ratios have to be improved by relatively narrowed wings and tapered wing tips; features which in turn increase wing-loading. Evidence is presented to show that hypertrophied pelvic fins in four-wingers are required to solve problems of stability in pitch, rather than to decrease wing-loading. The ‘non-flying’ flying fish, Oxyporhamphus micropterus , has very high wing-loadings, but the main reason that it cannot fly is that the centre of gravity of the fish is so far behind the pectoral fins that stalling on take-off would be inevitable. Flying fish possess reasonable quantities of red axial musculature, but no more than are used for cruising in fast-moving pelagic fish such as mackerel; it seems probable that acceleration to take-off speed in flying fish requires use of anaerobic white muscles.

Tube and fin circular heat exchanger

Abstract: A heat exchanger is disclosed comprising a pair of laterally spaced fluid conducting tanks operatively interconnected by a plurality of elongated fluid conducting tubes having sector shaped cross sections and arcuately spaced from one another in a circular pattern to present parallel interfacing sides. A plurality of elongated corrugated fins or air centers each having convolutions of substantially constant height and width to have spaced lines of contact along the width and length of each of the sides of the tubes for maximizing heat transfer and so that the tubes will be optimally supported to provide increased resistance to pressure ballooning and burst. These air centers are standard corrugated rectilinear components that reduce complexity and cost of this circular heat exchanger. This heat exchanger can be arranged in a parallel relationship with a transverse automotive engine and a cooling fan operatively mounted within the heat exchanger can be directly driven by the engine. An annular oil cooler and air conditioner condenser can also surround the heat exchanger.

Interaction Between Crossing Oblique Shocks and a Turbulent Boundary Layer

Abstract: A numerical study of the three-dimensional interaction between crossing shocks generated by symmetric sharp fins and a flat-plate turbulent boundary layer is presented. The full mean compressible Navier-Stokes equations, incorporating a turbulent eddy-viscosity model, are solved. Computed results for the flow past (11 deg, 11 deg) symmetric fins at a freestream Mach number Mw = 2.95 and Reynolds number Re^ = 2.5 X 10s (based on the undisturbed boundary-layer thickness 600) show general agreement with experimental measurements for flatplate surface pressure and surface flow visualization. Analysis of the computed flowfield reveals a complex interaction involving the "collision" of two slowly counter-rotating vortical structures generated by the initial shock/boundary-layer interaction due to each fin. Associated with the streamline structure of the interaction is the formation and growth of a region of low energy near the centerline, downstream of the crossed shocks. A "first look" at the shock structure of the interaction is provided.

Effect of Trailing-Edge Ejection on Local Heat (Mass) Transfer in Pin Fin Cooling Channels in Turbine Blades

Abstract: Experiments are conducted to study the local heat transfer distribution and pressure drop in a pin fin channel that models the cooling passages in modern gas turbine blades. The detailed heat/mass transfer distribution is determined via the naphthalene sublimation technique for flow through a channel with a 16-row, staggered 3 × 2 array of short pin fins (with a height-to-diameter ratio of 1.0, and streamwise and spanwise spacing-to-diameter ratios of 2.5) and with flow ejection through holes in one of the side walls and at the straight flow exit (to simulate ejection through holes along the trailing edges and through tip bleed holes of turbine blades). The pin fin heat/mass transfer and the channel wall heat/mass transfer are obtained for the straight-flow-only and the ejection-flow cases

Interference flows past cylinder-fin-sting-cavity assemblies

Abstract: A computer code, VISCC, is developed to solve the three-dimensional, Reynolds-aver aged, unsteady, compressible, and complete Navier-Stokes equations. The equations are solved by an implicit, fully vectorized, finite-volume, upwind-biased, approximately factored, and multigrid method. A hybrid domain decomposition method is developed to utilize the combined advantages of overlapped grids, zonal grids, and block-structured grids. An algebraic turbulence model is developed to represent the Reynolds stresses. The store considered here for simulation is a missile configuration with four tail fins and an L-shaped offset sting. The missile is placed first directly above the opening of a rectangular box cavity, then submerged completely inside the cavity. These two cases represent two distinct and important interference characteristics for an internal store carriage and a subsequent separation. The freestream Mach and the unit Reynolds numbers are 2.75 and 2.97 million per foot, respectively. The results of the time-accurate computations depict these complex flows and help understanding the interference effects between the store and the cavity. These effects are more pronounced when the store is placed inside the parent body. The time-averaged surface pressures compare well with the wind-tunnel data.

Modal S-matrix design of metal finned waveguide components and its application to transformers and filters

Abstract: Optimized all-metal E-plane finned waveguide components are designed with the rigorous method of modal field expansion into the ridged eigenmodes, which includes both the higher order mode interaction between the step discontinuities and the finite thickness of the fins. The design, which combines the advantage of constant fin thickness with that of the optimum matching potential of different waveguide inner cross-section dimensions and fin heights, achieves very broadband transformers and evanescent-mode filters with improved performance. Computer optimized data demonstrate the efficiency of the method by typical design examples: compact transformers for WR112, WR42, WR15, and WR12 input waveguides to E-plane finned waveguides, corrugated lowpass filters designed for a cutoff frequency in the waveguide Ku and U bands, and an evanescent-mode bandpass filter with unequal fin heights. The theory is verified by available measurements. >

Heat transfer from convecting-radiating fins of different profile shapes

Abstract: A finite difference method is used to predict the performance of convecting-radiating fins of rectangular, trapezoidal, triangular, and concave parabolic shapes The analysis assumes one-dimensional, steady conduction in the fin and neglects radiative exchange between adjacent fins and between the fin and its primary surface For the range of thermal and geometrical parameters investigated, the variation of heat transfer rate and the fin efficiency with other profile shapes was found to be within 11 percent of the rectangular shape The effect of profile shape is most pronounced when the Biot number,Bi, and radiation number,Nr, are small compared to unity Because of several limiting assumptions, the results would be used only for preliminary analysis and design particularly when a fin assembly is involved rather than an individual fin

Circuit pack layout with improved dissipation of heat produced by high power electronic components

Abstract: Dissipation of the heat produced by the operation of electronic circuitry may be improved by a heat sink which comprises a flat base from which a number of vertical fins extend. The fins are parallel to one another and define a number of parallel channels into which coolant flow is directed. The thermal resistance of the heat sink is optimized by setting fin thickness and channel width parameters to appropriate values. The heat sink may be attached in a heat conductive manner to a heat producing electronic component. One or more of these heat sinked components may be laid out in an in-line or staggered arrangement on a support in the form of a circuit pack. Cooling fluid is delivered to the circuit pack in a variety of ways to cool the heat sinked components. A method of determining the optimum fin thickness and channel width parameters involves determining a relationship between total thermal resistance of the heat sink and combinations of fin thickness and channel width parameters. A contour plot is produced in accordance with the relationship referred to above. The contour plot shows regions of optimum heat dissipation for heat sinks in accordance with the geometry identified here.

Prediction of Condensation Heat Transfer Coefficient in Horizontal Integral-Fin Tube Bundles

Abstract: A method of predicting the condensation heat transfer coefficient in horizontal integral-fin tube bundles with negligible vapor shear is proposed and compared with experimental results. This method is based on an analytical model talcing the condensate inundation effect into account, where the condensation heat transfer coefficient decreases due to a decrease in effective fin area as condensate flows through the interfin spaces. Heat transfer measurements were carried out in eight-row tube bundles consisting of integral-fin tubes with 35, 26, and 16 fins/in. Refrigerants Rll and R114 were used as test fluids. The proposed method was able to predict the condensation heat transfer coefficient with enough accuracy to enable condensers to be designed without the need for complex calculations.

Numerical Studies of a Compact Fin-Tube Heat Exchanger

Abstract: A numerical scheme has been developed to compute the flow field between neighboring fins of a compact fin-tube heat exchanger. Exemplary computations show that at low Reynolds number (~ 400) the Nusselt number in the neighborhood of the second tube of a two-tube in-line configuration is close to the Nu given by the periodically fully developed flow.

Heat exchanger and air conditioner using same

Abstract: PURPOSE:To obtain an air conditioner capable of uniformly supplying water over the surface of a refrigerant condenser. CONSTITUTION:A container 36 where drain water from an evaporator is stored is installed above a condenser 30. Holes 40 are provided on the bottom of the container 36 in the same number as that of fins 44 which forms the condenser 30. As drain water is supplied to the upper parts of the fins 44 through the holes 40, the drain water is transferred downward along each fin 44, so that water is evenly supplied to all the fins 44.

Natural convection heat transfer coefficients for a horizontal cylinder with vertically attached circular fins

Abstract: Experiments were performed to investigate the natural convection heat transfer characteristics of a vertically finned horizontal isothermal cylinder. The apparatus was designed so that the fin spacing, fin length, and the cylinder Rayleigh number could be varied within limits of practical interest. The Rayleigh number (based on the cylinder diameter) ranged from 105 to 5 × 107. It was found that the interaction of the fin boundary layer with the cylinder brought about a reduction of the cylinder Nusselt number relative to that for the classical case of the long isolated horizontal cylinder. The reduction was strong at Rayleigh numbers below the critical value and at spacing ratios less than 0.125. However, at Rayleigh numbers beyond the critical, the Nusselt number was quite insensitive to the fin spacing and length, with the typical data spread being in the 5–8% range.

Anti-skid device for flat-bottomed boats

Abstract: A pair of pivotally attached fins depend into the water below the hull of the boat. When turning maneuvers are executed the tendency of the boat to skid sideward is resisted by the downwardly engaged fin panels. The device provides improved steering control to all boats so equipped, but especially to outboard jet powered boats traveling in shallow water. When underwater objects or the bottom of a body of water are encountered, the leading edge of the fins strike the object(s), causing the fins to pivot upward to clear the obstacle(s) and then return automatically to the water to provide an extra measure of boating safety.

Heat exchanger with fin

Abstract: PURPOSE:To prevent scattering of condensed water to a fan and the circumference, and to prevent damage of the fan, etc., due to icing by collecting the water to be passed through a heat exchanger. CONSTITUTION:A heat exchanger has plate type fins 10 in which many fin plates 1 are arranged in parallel at a predetermined interval and air streams flow through gaps of the plates 1, and heat transfer tubes 1 which are passed perpendicularly to the films 10. Then, superheated vapor or high temperature refrigerant flows to heat transfer tubes 6 disposed at the edge 10A of the gas flow-out side of the fins 10.

The One-Dimensional Analysis of Oscillatory Heat Transfer in a Fin Assembly

Abstract: Studies of the transient heat transfer within extended surfaces have so far considered the fins in isolation. The isolated fin model is not representative of the physical boundary conditions within an extended surface heat exchanger since it does not account for the thermal effects of the supporting interface. The aim of this study is to extend the work on transient heat transfer within finned surfaces by incorporating the supporting wall in the problem. A mathematical one-dimensional solution for harmonic oscillatory heat transfer in a fin assembly is derived. It is concluded that, unlike steady-state situations, the transient heat transfer in a fin assembly can only be found by considering both the wall and the fins simultaneously.

Head radiating fin and semiconductor integrated circuit device

Abstract: PURPOSE:To effectively cool a semiconductor integrated circuit device during operation CONSTITUTION:Heat radiating fins 1a made of a shape memory alloy subjected to shape memory alloy treatment are fitted on the top face of a package body 4 so that the surface area of fins 2b may be increased by heat during operation of a semiconductor chip encapsulated in the package body 4 which constitutes a semiconductor integrated circuit device 3