Showing papers on "Fin published in 1985"

Simulation of blunt-fin-induced shock wave and turbulent boundary-layer interaction

Abstract: The Reynolds-averaged Navier-Stokes equations are solved numerically for supersonic flow over a blunt fin mounted on a flat plate. The fin shock causes the boundary layer to separate. which results in a complicated, three-dimensional shock-wave and boundary-layer interaction. The computed results are in good agreement with the mean static pressure measured on the fin and the flat plate. The main features, such as peak pressure on the fin leading edge and a double peak on the plate. are predicted well. The role of the horseshoe vortex is discussed. This vortex leads to the development of high-speed flow and, hence, low-pressure regions on the fin and the plate. Different thicknesses of the incoming boundary layer have been studied. Varying the thicknesses by an order of magnitude shows that the size of the horseshoe vortex and, therefore, the spatial extent of the interaction are dominated by inviscid flow and only weakly dependent on the Reynolds number. Colored graphics are used to show details of the interaction flow field.

Conical similarity of shock/boundary-layer interactions generated byswept and unswept fins

Abstract: A parametric experimental investigation has been made of the class of three-dimensional shock wave/turbulent boundary layer interactions generated by swept and unswept leading-edge fins. The fin sweepback angles were 0-65 deg at 5, 9, and 15 deg angles of attack. Two equilibrium two-dimensional turbulent boundary layers with a freestream Mach number of 2.95 and a Reynolds number of 6.3 x 10 to the 7th/m were used as incoming flow conditions. All of the resulting interactions were found to possess conical symmetry of the surface flow patterns and pressures outside of an initial inception zone. Further, these interactions were found to obey a simple conical similarity rule based on inviscid shock wave strength, irrespective of fin sweepback or angle of attack. This is one of the first demonstrations of similarity among three-dimensional interactions produced by geometrically dissimilar shock generators.

Heat transfer tube having internal ridges, and method of making same

Abstract: Improved heat transfer tube and method of making same has mechanical enhancements which can individually improve either the inner or outer surfaces or which can cooperate to increase the overall efficiency of the tube The internal enhancement, which is useful on either boiling or condensing tubes, comprises a plurality of closely spaced helical ridges which provide increased surface area and are positioned at an angle which gives them a tendency to swirl the liquid The external enhancement, which is applicable to boiling tubes, is provided by successive cross-grooving and rolling operations performed after finning The finning operation, in a preferred embodiment for nucleate boiling, produces fins while the cross-grooving and rolling operation deforms the tips of the fins and causes the surface of the tube to have the general appearance of a grid of generally rectangular flattened blocks which are wider than the fins and separated by narrow openings between the fins and narrow grooves normal thereto The roots of the fins and the cavities or channels formed therein under the flattened fin tips are of much greater width than the surface openings so that the vapor bubbles can travel outwardly through the cavity and to and through the narrow openings The cavities and narrow openings and the grooves all cooperate as part of a flow and pumping system so that the vapor bubbles can readily be carried away from the tube and so that fresh liquid can circulate to the nucleation sites The rolling operation is performed in a manner such that the cavities produced will be both larger and smaller than the optimum minimum pore size for nucleate boiling of a particular fluid under a particular set of operating conditions

Natural Convection/Radiation Heat Transfer From Highly Populated Pin Fin Arrays

Abstract: Experiments were performed to determine the combined-mode natural convection/radiation heat transfer characteristics of highly populated arrays of rodlike cylindrical fins (i.e., pin fins). The fins were oriented with their axes horizontal and were attached to a vertical heated baseplate. The investigated parameters included the number of fins in the array, the fin length and diameter, the baseplate-to-ambient temperature difference, and the presence or absence of adjacent shrouding surfaces. Finning was found to be highly enhancing (up to a sixfold increase in heat transfer), and even the longest fins were highly efficient. When the number of fins was increased for fixed values of the other parameters, the heat transfer increased at first, attained a maximum, and then decreased. Arrays having different diameter fins yielded about the same performance when the surface area of the fin-baseplate assembly was held fixed. Shrouding surfaces positioned close to the array decreased the rate of heat transfer. Calculations showed that the contribution of radiation was substantial and was greatest for more populous arrays, for longer fins, and at small temperature differences.

Effect of Fin Spacing on the Performance of Horizontal Integral-Fin Condenser Tubes

Abstract: The dependence of heat transfer performance on fin spacing has been investigated for condensation of steam on horizontal integral-fin tubes. Thirteen tubes have been used with rectangular section fins having the same width and height (0.5 mm and 1.6 mm) and with fin pitch varying from 1.0 mm to 20.5 mm. For comparison, tests were made using a plain tube having the same inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. All tests were made at near-atmospheric pressure with vapor flowing vertically downward with velocities between 0.5 m/s and 1.1 m/s. The observed heat transfer enhancement for the finned tubes significantly exceeded that to be expected on grounds of increased area. Plots of enhancement against fin density were repeatable and showed local maxima and minima. The dependence of enhancement on fin density did not depend appreciably on vapor velocity or condensation rate for the ranges used. The maximum vapor-side enhancement (i.e., vapor-side heat transfer coefficient of finned tube/vapor-side coefficient for plain tube) was found to be around 3.6 for the tube with a fin spacing of 1.5 mm.

Vehicular air flow control device with variable angle air flow control fin

Abstract: An air flow control device for an automotive vehicle includes an air flow control fin pivotably secured near the rear end of a vehicle. The air flow control fin is pivotable to either of two angular positions with respect to the vehicle body. A manual operator is disposed within a vehicle compartment and is connected to the air flow control fin through a remote control mechanism. The air flow control fin is movable between a first spoiler position in which the fin diverts air flowing along vehicle body surface upwards so as to exert a downward force and enhance the traction of the vehicular wheels, and a second air flow guide position in which the fin guides the air flow toward a rear window surface so as to remove rain water, dust and so forth. The manual operator can be operated by a driver in the vehicle compartment to select either the first spoiler position or the second air flow guide position.

Optimum Arrays of Longitudinal, Rectangular Fins in Corrective Heat Transfer

Abstract: The theoretical basis for the least material optimization of convectively cooled arrays of longitudinal, rectangular fins is presented. The aspect ratio (fin thickness divided by fin width J of the array-optimum fin is found to be only marginally thinner than implied by the. conventional single fin optimization. Using this result, it is possible to define the geometry and thermal performance of least material, air-cooled natural convection arrays and to identify the array geometry yielding the maximum heat dissipation capability. Alternately, the added mass of a forced convection-cooled fin array is shown to be inversely related to the available pumping power and, as a consequence, no single optimum geometry could be defined. This paper includes several illustrative examples that serve to demonstrate the optimization pro cedure and to quantify the theoretical thermal performance of specific natural and forced convection air-cooled fin arrays.

Fin and tube type heat exchanger

Abstract: A fin-and-tube type heat exchanger is disclosed in which the height of each raised, slotted louver from a fin base portion continuously changes in a direction crossing at right angles both the direction of the air flow and the direction of lamination of fins, and two or three kinds of such louver pairs, each consisting of louvers symmetric with each other with respect to the fin base portion, are arranged regularly.

Lanced fin condenser for central air conditioner

Abstract: An improved fin configuration is provided for use in central air conditioning unit heat exchangers in which heat transfer takes place between a first fluid, typically a refrigerant, flowing inside a nested plurality of tubes and a second fluid, typically air, flowing between the tubes and through a plurality of heat conducting fins attached to and arrayed between the tubes. Lanced pairs of streamwise adjacent bridge-like formations, one out each side of a generally corrugated fin surface, provide numerous leading edges to generate a plurality of reforming velocity and heat transfer boundary layers which leads to an increase in flow turbulence for enhanced heat transfer between the fins and the second fluid. By strategic location of a pair of such formations between tubes, with the upstream one of the pair at a positive angle of attack to the flow, air flow is directed through the fin to mix with flow on the other side of the fin and hence the heat transfer rate is improved. The provision of a shallow conical annular fin region around each collar attaching a fin to a tube, preferably with a 6° inclination of the conical surface to a plane orthogonal to the collar axis, provides additional enhancement to the heat transfer between the fin and the second fluid.

Extension of equivalent angle-of-attack method for nonlinear flowfields

Abstract: Recent experimental results show that the control effectiveness of a missile fin in supersonic flow at moderate to high angles of attack is a strong nonlinear function of freestream Mach number, body incidence angle, fin bank angle, and fin deflection angle. Analysis of the experimental results using an Euler finite-difference computer code with flow separation, together with the equivalent angle-of-attack concept, indicates that the observed nonlinearities are due to the variation of local dynamic pressure and local Mach number around the missile body alone. The nonlinearities are shown to be a strong source of control cross-coupling for high Mach number, high angle-ofattack combinations. The analysis suggests a relatively simple yet comprehensive approach for accurately accounting for these nonlinear effects. The impact of the results on missile aeroprediction methods is discussed.

Hydrodynamic swim fin

Abstract: An improved hydrodynamic swim fin utilizes a wing and a tail that are overlapped normally to provide a two-stage propulsion system. Ribs support the wing and tail and define flow channels. These ribs are parallel to each other and to the longitudinal axis of the fin whereby the effective area through which flow proceeds is uniform throughout the length of the fin. No parts of the ribs form barriers to the leading edges of the side wing segments whereby laminar flow is achieved. The fin part is maintained essentially rigid; however, the fin part is allowed limited angular movement about a defined transverse axis to achieve proper attack angle. Since the fin part is rigid, it maintains that attack angle throughout the length of the fin part. Trailing ends of the wing are individually flexible to produce greater opening for two-stage propulsion during the power downstroke, and to produce substantial closure for one-stage propulsion during the upstroke. Leading ends of the side wing segments are individually flexible to permit a truer hdyrofoil shape in response to angular movement of the fin part about the transverse axis. Deflectors prevent obstructions such as kelp from reaching the lateral wing segment flow channels. Strakes positioned parallel to the ribs along the leading ends of the wing segments and the tail also promote laminar flow through and along the fin part.

Fin swinging angle control apparatus

Abstract: The swinging angle of fins of an air conditioner or the like is controlled by control apparatus including a fin driver for swinging the fin about a pivot thereof, fin swinging angle adjusting means and an adjusting mechanism for adjusting the center of the swinging angle of the fin.

Projectile having extendable wings

Abstract: A projectile possessing extendable wings or fins which are adapted to be pivoted radially outwardly of the projectile. The wing or fin includes a flexible covering and a tensioning device; for example, a strut arrangement, and with the wing or fin being displaceable from a retracted position prior to launch of the projectile to an outwardly extended position in which the applicable covering portion is tensioned by the tensioning device so as to thereby provide a stable, predetermined aerodynamically defined wing or fin configuration.

Method of manufacturing fin-tube heat exchangers

Abstract: A method of manufacturing a fin-tube heat exchanger which includes a multiplicity of plate fins arranged in a plurality of rows disposed at a predetermined pitch in the direction of air flow, and a jointless refrigerant pipe extending through the plate fins in a zigzag manner. Pipe-receiving holes are formed in each plate fin in an offset manner relative to the center of the plate fin. The plate fins are then placed in fin-receiving grooves formed in a straight fin positioning fixture at predetermined spacings such that the same longitudinal ends of the plate fins of alternating rows appear on the same side of the fin positioning fixture and such that the pipe-receiving holes are linearly aligned. The refrigerant pipe is inserted into the pipe-receiving holes and is expanded to make tight and close contact with the plate fins. The refrigerant pipe is bent in a zigzag manner so that the straight portiions of the pipe occupy corners of rectangles and so that a predetermined spacing is provided between the plate fins of adjacent rows. Finally, a twist is imparted to the refrigernat pipe to line up the plate fins and arrange the pipe such that the straight portions of the pipe are positioned in a staggered manner, as viewed in the direction of the rows.

Recreational water craft

Abstract: A water craft includes a pair of spaced buoyant panels mounted to a substantially H-shaped frame. A pair of fins mounted along a central longitudinal member of the frame between the panels provides propulsion and steering control. Propulsion is maximized by means of a combined cam, linkage and telescoping support structure that varies the length of the aft fin so as to oscillate the fin in a substantially figure eight path. Further, the rigidity and flexibility of the fin may be controlled through a tension cable and hand actuator.

Anti-theft device for fins and surfboards

Abstract: This anti-theft device is inserted into the fin case and locked, and at the same time the fastening screw for the fin is concealed so that dismantling is no longer possible. In combination with a padlock and cable, the board and fin are protected against theft.

Method for making heat exchange tubes

Abstract: Improved method and apparatus for making finned tubing from difficult to work materials such as titanium and stainless steel uses spaced sets of finning discs on a plurality of arbors to form a tube against a mandrel having different diameters under each set of discs. By forming the tube fin tips to their final O.D. in a first disc set and by depending their roots to bring the fins to their final height in a second disc set, tubes with higher fin counts and/or higher fin heights can be achieved than were formerly possible. The process of separately cold working the tips and roots also permits tubes to be made which are dimensionally identical to prior art tubes but with higher quality and productivity since tube stresses are greatly reduced. An improved titanium tube is also disclosed which has at least 26 fins per inch, a fin height of at least 0.034" and an outside to inside surface area ratio of at least 3.0.

Laminated type heat exchanger

Abstract: PURPOSE: To increase the exchange heat amount to improve the heat exchanger performance by using multi-entry type inner fins to set the fin pitch in a specific range. CONSTITUTION: Plate-like tube elements 1 and corrugated fins 2 are alternately and vertically laminated in a plurality of stages. Each of tube elements 1 has at its intermediate portion a heat exchange medium passage 1a and at its both ends tank parts 1b communicating with the passage 1a and a relatively large expansion height. Further, multi-entry type inner fins 6 having a size extending the full part of a heat medium passage 1a in the inner part thereof are loaded therein so that the flow direction is along a direction of connecting the tank parts 1b and 1b. The multi entry type inner fins 6 are formed by folding a single plate continuously in a U-shape. The fin pitch fp of the inner fins 6 is set to 3.0W0.6mm. By this organization, the heat transfer property with respect to the circuit apparatus wall is high by the remarkable turbulence effect of the heat exchanger. COPYRIGHT: (C)1986,JPO&Japio

Fin stock material for use in plate fin heat exchanger adapted for superhigh pressure service

Abstract: Fin stock materials adapted for use in superhigh pressure service heat exchanger fabricated by brazing are made of aluminum alloys consisting essentially of, in weight percentages, 0.6 to 1.5% of Mn, 0.1 to 1.0% of Cu, 0.1 to 0.75% of Mg, and 0.05 to less than 0.30% of Si, and the balance being aluminum and incidental impurities, the Fe in said impurities being controlled up to 0.8%. The aluminum alloy fin stock materials contain optionally at least one component selected from the group consisting of 0.05 to 0.25% of Zr, 0.01 to 0.25% of Ti, 0.05 to 0.25% of Cr and 0.01 to 0.25% of V. The fin stock materials have a combination of advantageous properties, particularly a high prevention effect of excessive silicon diffusion of brazing materials into the fins, good strength and formability, whereby give good utility particularly in plate fin heat exchangers for use in superhigh pressure applications.

Manufacture of fin tube type heat exchanger

Abstract: PURPOSE: To prevent the collapse and wrinkle of U-shape bent section of refrigerant pipe as well as the increase of refrigerant side pressure loss by a method wherein a round pipe is bent into U-shape and, thereafter, the parts of the pipe, which are to be inserted into the holes of plate fins, are formed into elliptical form. CONSTITUTION: The refrigerant pipe 13, made by bending a round pipe 13a into U-shape and forming the parts 13' thereof which are to be inserted into the holes of the plate fins 12 into elliptical shape, is penetrated through the mounting holes 11 of the plate fins 12, having the mounting holes 11 for the elliptical refrigerant pipe and arranged in parallel with predetermined spaces, thereafter, the penetrating parts 13" of the refrigerant pipe 13 are expanded under keeping the elliptical shapes thereof to adhere and fix to the plate fins 12. Thereafter, the opening ends 15 of the refrigerant pipes 13 are formed into round opening ends 15', 15'... while bends 14 are inserted into and fixed to the round opening ends. According to this method, the connecting sections of the bends 14 are located at one side of the heat exchanger only, therefore, man-hours may be reduced. On the other hand, collapse and wrinkle will never be generated in the U-shape bent section 13' and the section of the pipe is round, therefore, the sectional area of refrigerant path is large enough and refrigerant side pressure loss may be reduced. COPYRIGHT: (C)1986,JPO&Japio

Finned tube contact conductance: Characterizing the integrity of the mechanical bond

Abstract: Thermal contact conductance of expanded tube joints is dependent upon the interfacial pressure between the mating parts. A review of the literature indicates that very little work has been done towards relating the joint stresses to the dimensional parameters for mechanically expanded plate finned-tube heat exchangers, commonly called fin coils. This paper presents an experimental testing technique to investigate the fin-to-tube mechanical bond based upon the axial pull strength of the joint. Typical coils from two manufacturers were used in this investigation. They were fabricated from 3/8 in. copper tubes and plate aluminum fins. The coils tested had fin spacings of 6, 7, 8, 12, and 20 fins per inch, fin thicknesses of 0.008 and 0.0055 in. Tube thicknesses of 0.015 and 0.016 in. and diametrical interferences of 0.001, 0.006, and 0.010 in. The maximum force attained during a tube pullout was found to be descriptive of the bond. Plots of this force versus fin number and net interference are presented that illustrate the sensitivity of this force to the fin thickness, fin number, and net interference. These plots show that the fin thickness has the predominant effect on the pullout force and, in turn, the bond between the finmore » collar and the tube.« less

Titanium heat exchange tubes

Abstract: Improved method and apparatus for making finned tubing from difficult to work materials such as titanium and stainless steel uses spaced sets of finning discs on a plurality of arbors to form a tube against a mandrel having different diameters under each set of discs. By forming the tube fin tips to their final O.D. in a first disc set and by deepening their roots to bring the fins to their final height in a second disc set, tubes with higher fin counts and/or higher fin heights can be achieved than were formerly possible. The process of separately cold working the tips and roots also permits tubes to be made which are dimensionally identical to prior art tubes but with higher quality and productivity since tube stresses are greatly reduced. An improved titanium tube is also disclosed which has at leasts 26 fins per inch, a fin height of at least 0.034" and an outside to inside surface area ratrio of at least 3.0.

Modelling of three-dimensional shock wave turbulent boundary layer interactions

Abstract: The accuracy of numerical computations of the three-dimensional sharp fin flow field using the Reynolds-averaged Navier-Stokes equations is examined. Computed flows are compared with a set of benchmark experiments at Mach 3 for two different Reynolds numbers. A detailed comparison is performed between experimental data and separate computational results for the three-dimensional sharp fin for a 10 deg fin angle in order to examine the accuracy of two different turbulence models. The computed surface pressure for the fin at a 20 deg angle is compared with recent experimental data. The computed yaw angle profiles are shown to be sensitive to the turbulence model. In the immediate vicinity of the surface, the calculated results using the Baldwin-Lomax (1978) model are in better agreement with the data than the Jones-Launder (1972) model. Within the inner portion of the boundary layer, both models tend to underpredict the yaw angle.

Wound heat exchanger, in particular for heat pumps or refrigerating plants

Abstract: The invention relates to a wound heat exchanger, in particular for condensation and/or evaporation in heat pumps or refrigerating plants The heat exchanger consists of a jacket tube (1) consisting of at least one externally finned internal tube (2) arranged therein and having fins (3) running round in the shape of a helix, and of fittings (9) arranged at the end face and provided with openings (10, 11) In order to improve output and the degree of compactness while maintaining the previous advantages with regard to erosion and corrosion, according to the invention the heat exchanger is constructed in such a way that the fins (3) of the internal tube (2) run round in a T-shape which remains constant in the fin cross-section, the smooth ends (6) of the fins (3) being situated on an imaginary cylindrical face coaxial with the central axis of the tube, and the ends (6) approaching one another accompanied by the formation of narrow grooves (7)

Inner fin of heat exchanger

Abstract: PURPOSE:To improve heat exchanging efficiency and restrict pressure loss by a method wherein the pitch, the height and the ratio of segmental length to the pitch of the inner fin, accommodated in the flow path of fluid, are determined so as to be in specified relations in the heat exchanger for a supercharger. CONSTITUTION:An intercooler for the supercharger is formed by a method wherein the plates 1, made of aluminum, are bonded and the flow path 2 of fluid is formed in the set of bonded aluminum plates 1 while the set of plates 1 are piled sequentially while arranging a fin 3 between the sets of the plates 1. The inner fin 8 of rectangular waveform is inserted into the flow path 2 of fluid so that walls 8a are arranged in parallel to the flow of supercharging air while the inner fin is designed so that relations of 3<=P<=7mm, 3<=B<=6mm and 0<2L/P<=3 are kept in the fin pitch P, the height B of fin and the segmental length L of the fin and the inner fins are bonded to the plates 1 by brazing. Thus, the heat exchanging rate between gasses may be improved and the pressure loss may be minimized without changing the profile dimension or the shape of the heat exchanger.