Fin Dimensions Research Articles

Methodology for determining the optimal fin dimensions in helically segmented finned tubes

Abstract Helical segmented fins of uniform profile are analyzed by means of the quasi one-dimensional fin theory coupled with the Logarithmic Mean Temperature Difference (LMTD) method from heat exchanger theory to determine the optimum fin dimensions. On one hand, the quasi one-dimensional fin theory is applied to establish the lower fin height limit, which is critical in this type of application. On the other hand, the LMTD method is used to define the optimal equilibrium point by way of the dimensionless overall heat transfer coefficient and the pressure drop. The methodology to be proposed for estimating the optimal dimensions of helical fins was applied to a bare tube with outside diameter of 50.8 mm (2 in) and a maximum transverse pitch based on a bare tube with outside diameter 2.25 larger. The computed results demonstrate that the optimal equilibrium point is affected by the lower fin height limits because it is unstable. Hence, two lower fin height limits are defined in order to determine a maximum deviation of the optimal equilibrium point, while the upper fin height limit is defined by physical–technical limiting factors. Thereby, the optimal equilibrium point predictions show a maximum deviation of 8% and a stable behavior under the influence of different thermal conditions and flow regimes associated with various helically segmented sizes, helical fin heights.

Comparative morphology of wild, farmed and hatchery-released gilthead sea bream (Sparus aurata) in western Greece

In May 2001, 60,000 individuals of gilthead sea bream (Sparus aurata) fry, originating from a common bloodstock of the Ionian coastal region, were allocated between Papas lagoon and cages of mariculture enterprises located at Western Greece. During the period of November to December 2001, a sample of 531 gilthead sea bream individuals was collected from the lagoon and the cages. The variations in 24 morphomertic characters and in two indices (condition factor and gonadosomatic index) were examined using multivariate analysis, in order to evaluate the morphological similarity/dissimilarity between hatchery-released (EN), wild (WL) and farmed (RR) individuals. Statistically significant differences were observed among the groups in mean and standard deviation values for most of the morphometric characters, a fact that can be possibly attributed to the life-history of the fish. Principal component analysis along with discriminant analysis identified that the characters of primary importance in distinguishing the three groups were those related to head, fin and lengthwise dimensions. Discriminant analysis also revealed that about 86.1% of the examined specimens could be correctly classified in the three groups. The above findings can be useful for scientific but also for commercial reasons, since the market value of the fish is highly dependant on its origin. Key words: Sparus aurata, gilthead sea bream, hatchery-release, multivariate analysis, morphometrics, lagoon

Atom-probe for FinFET dopant characterization

With the continuous shrinking of transistors and advent of new transistor architectures to keep in pace with Moore's law and ITRS goals, there is a rising interest in multigate 3D-devices like FinFETs where the channel is surrounded by gates on multiple surfaces. The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions of the device. As a result there is a need for new metrology approach/technique to characterize quantitatively the dopant distribution in these devices with nanometer precision in 3D. In recent years, atom probe tomography (APT) has shown its ability to analyze semiconductor and thin insulator materials effectively with sub-nm resolution in 3D. In this paper we will discuss the methodology used to study FinFET-based structures using APT. Whereas challenges and solutions for sample preparation linked to the limited fin dimensions already have been reported before, we report here an approach to prepare fin structures for APT, which based on their processing history (trenches filled with Si) are in principle invisible in FIB and SEM. Hence alternative solutions in locating and positioning them on the APT-tip are presented. We also report on the use of the atom probe results on FinFETs to understand the role of different dopant implantation angles (10° and 45°) when attempting conformal doping of FinFETs and provide a quantitative comparison with alternative approaches such as 1D secondary ion mass spectrometry (SIMS) and theoretical model values.

Effects of Using Fins and Carboceramics on the Solidification Characteristics of Aluminum Casting Alloys?

Recent studies have shown that using the cooling fins is one of the most appropriate methods to eliminate the shrinkage porosities in the castings. In fact, Fins play the role of heat exchangers during the solidification and their usage is the same as that of chills. The cooling effect of fins is directly related to their geometry. Also the effect of fin on decreasing the time of local freezing is a function of metal’s thermal conductivity, mould thermal conduction, superheating and fin dimensions. In this research, the effect of three types of fins on local solidification time of a casting of A356 and 6069 alloys as well as the effect of moisture content on cooling rate of sand moulds made of carboceramics have been studied. Results indicate that fin affects severely on solidification time and this influence is more severe in castings produced in moulding materials such as carboceramics which can absorb more moisture. The results show that carboceramics as a new refractory material decrease the solidification time significantly. This is particularly evident when the fins were used. Generally, using fins and carboceramics decrease the solidification time down to 45%. This is good news for casting industry in which the mechanical properties can be easily improved using simple ways.

An analytical prediction for performance and optimum design analysis of porous fins

Enhancement of heat transfer rate through porous fins is one of the common choices nowadays. As the energy equation is highly nonlinear, researchers never concentrated on analyzing porous fins analytically. In the present study, an effort has been devoted to develop an analytical model for determination of the performance and optimum dimensions of porous fins with consideration of different models of predictions. Every result has been presented in a comparative way so that the merit of the models adopting in the present work can easily be understood. The optimum design analysis of porous fins has also been carried out. The influences of all the dependent parameters on the performances and optimization conditions have been studied for the selection of a design criterion of porous fins in such applications where the requirement of heat dissipation is essentially high.

Thermal performance of plate-fin vapor chamber heat sinks

Since vapor chambers exhibit excellent thermal performance, they are suited to use as bases of heat sinks. This work experimentally studies the thermal performance of plate-fin vapor chamber heat sinks using infrared thermography. The effects of the width, height and number of fins and of the Reynolds number on the thermal performance are considered. Experimental data are compared with corresponding data for conventional aluminum heat sinks. The results show that generated heat is transferred more uniformly to the base plate by a vapor chamber heat sink than by a similar aluminum heat sink. Therefore, the maximum temperature is effectively reduced. The overall thermal resistance of the vapor chamber heat sink declines as the Reynolds number increases, but the strength of the effect falls. The effect of the fin dimensions on the thermal performance is stronger at a lower Reynolds number. At a low Reynolds number, a suitable number of fins must be chosen to ensure favorable thermal performance of the vapor chamber heat sink. However, at a high Reynolds number, the thermal performance improves as the fin number increases.

고정된 휜 체적에 기준한 원관 내부반경이 변하는 환형 휜의 최적화

초록:Abstract: Optimum values of fin performance and dimensions for an annular fin with a rectangular profile anda pipe with variable inner radius are determined by using a variable separation method. The range ofambient convection characteristic number that results in optimum heat loss is listed. The optimum heat loss,corresponding optimum fin effectiveness, fin length, and fin height are presented as a function of the innerradius of the pipe, inner fluid convection characteristic number, fin volume, and ambient convectioncharacteristic number. One of the results shows that the optimum heat loss, fin effectiveness and fin lengthincrease linearly with the inner radius of the pipe when both the fin volume and fin-base radius are fixed.

Effects of channel doping concentration and fin dimension variation on self-boosting of channel potential in NAND-type SONOS flash memory array based on bulk-FinFETs

In conducting the operation of the NAND-type flash memory array, program inhibition is performed by self-boosting of the potential of the floating silicon channel. However, the high program voltage substantially affects the adjacent cells sharing either the bit-line (BL) or the word-line (WL), which results in unwanted program operation, i.e., program disturbance, in the vicinity. In this work, the dependence of self-boosting effect of the channel potential on process variables and device dimensions have been investigated by 3-D device simulation. Through a series of simulations, the process parameters and device dimensions were identified that can provide the optimum condition in self-boosting of the channel potential avoiding such disturbance. The self-boosting effect exhibited a local maximum at the channel doping concentration of 6 × 10 17 boron atoms/cm 3 when the Si fin width was 30 nm and the channel length is 100 nm. Also, it is shown that the boosted channel potential displays monotonic increase with channel length, while it decreases monotonically as the silicon fin width becomes thicker at a given channel doping level. The interpretation of these findings utilizes the graphed results with the advanced capacitance model for a FinFET-based nonvolatile flash memory device.

Performance and optimization analysis of a constructal T-shaped fin subject to variable thermal conductivity and convective heat transfer coefficient

In the present study, an exercise has been devoted to establish an analytical model for thermal performance and optimization of a constructal fin subject to variable thermal conductivity of fin material and convective heat transfer coefficient over the fin surface. For the adaptation of these considerations, the governing energy equation for the stem as well as the flange becomes nonlinear. A new analytical scheme based on the Adomian decomposition method has been established for the solution process. As the present study is an analytic, it can be extended to the analysis for determining the optimum dimensions of fins satisfying either the maximization of rate of heat transfer for a given fin volume or the minimization of fin volume for a desired heat transfer rate. From the results, it can be highlighted that the present model predicts the fin performance always an under value in comparison with that the published results whereas the optimum heat transfer rate determined by using the present analysis gives an over value. The effect of different geometric and thermophysical parameters on both the fin performance and optimization has been studied. For a comparative study, the present and published results are executed for a wide range of thermogeometric parameters.

A simple laser photogrammetry technique for measuring Hector's dolphins (Cephalorhynchus hectori) in the field

The ability to measure and age individuals within a population has many important applications, for example, for examining growth and determining size class. We developed a simple photogrammetric system using two parallel lasers and a digital camera, in order to measure dorsal fin dimensions of free-ranging Hector's dolphins. Laser dots were projected onto the fin, providing scale, thus allowing measurement as well as simultaneous photo-ID of 34 individuals from fin nicks and other marks. Multiple measurements (≥5) were available for six individuals; these resulted in mean CVs of 3.71% for fin length and 3.76% for fin height. Errors due to variations in angle and measurement were quantified via photography of a fiberglass Hector's dolphin model. Allometric measurements and age data were collated from 233 autopsied Hector's dolphins. Using these data, fin length was found to be a better predictor of total length (females r2= 0.732, males r2= 0.678) than fin height. Gompertz age/length growth curves were fitted to these individuals. Linear regressions were used to estimate total length for 34 individuals from laser-metrically estimated fin base length. Individuals were then assigned one of three age categories. This system shows promise as a noninvasive way of measuring individuals, while allowing simultaneous photographic identification.

Thermal-fluid characteristics of plate-fin heat sinks cooled by impingement jet

This work experimentally and numerically studies the thermal-fluid characteristics of plate-fin heat sinks under impingement cooling by adjusting the impinging Reynolds number, the impingement distance, and the fin dimensions. The parameters and the ranges under consideration are the impinging Reynolds number (Re = 5000–25,000), the impingement distance ( Y/ D = 4–28), the fin width ( W/ L = 0.08125–0.15625) and the fin height ( H/ L = 0.375–0.625). The results show that the heat transferred by the heat sink increases with the impinging Reynolds number. The thermal performance can be improved significantly even at low impinging Reynolds number. However, the improvement becomes indistinct as the impinging Reynolds number increases. The thermal resistance declines as the impingement distance increases, and is minimal at Y/ D = 20 for various impinging Reynolds numbers. Additionally, the thermal resistance increases as the impingement distance increases further. Increasing the fin width can effectively reduce the thermal resistance. However, as the fin width increases beyond a particular value, the thermal resistance increases dramatically. Reducing the thermal resistance by increasing the fin height depends on a suitable impinging Reynolds number and fin width. Therefore, the effect of the fin height is weaker than that of the impinging Reynolds number or the fin width.

Approximate analytical method for prediction of performance and optimum dimensions of pin fins subject to condensation of quiescent vapor

An approximate analytic method is proposed to solve the governing equation of horizontal pin fins subject to the condensation of saturated vapor under laminar free convection. The temperature distribution and performance parameters are determined by using Adomian decomposition method. A numerical scheme followed by the finite difference method has been used to validate the present analytical result. From the results, a significant effect on the temperature distribution and performances with the variation of fin dimensions and thermophysical parameters of saturated vapor is noticed. Next, a scheme for fin optimization has been carried out in such a way that either heat transfer duty or fin volume can be taken as a constraint selected according to the requirement of a design. Finally, dependency of design variables on an optimum condition has been established which may help the designer to adopt physical conditions in a practical application.

Performance and optimum dimensions of flat fins for tube-and-fin heat exchangers: A generalized analysis

The performance of flat fins for tube-fin heat exchangers has been analyzed for both inline and staggered arrangement of tubes. In earlier published studies, regular square and equilateral triangular array tube layouts were considered. No such restriction is put in the present study. The analysis has been done by a semi-analytical technique where the boundary condition at the fin edge is discretely satisfied at a large number of points by a method of collocation. It has also been demonstrated that the approximate results obtained by the sector method closely agree with the prediction of semi-analytical technique. Finally, a generalized scheme of optimization based on Lagrange multiplier technique has been suggested which shows that irrespective of the volume and thickness of the fins, square and equilateral triangular array of tubes are the optimum layout for inline and staggered arrangements, respectively. This result was known so far only intuitively. The optimum dimensions for flat fins for other layout of tubes have also been obtained specifying the ratio of longitudinal to transverse tube pitch.

Numerical study of the heat sink with un-uniform fin width designs

The thermal performances of the heat sink with un-uniform fin width designs with an impingement cooling were investigated numerically. The governing equations are discretized by using a control-volume-based finite-difference method with a power-law scheme on an orthogonal non-uniform staggered grid. The coupling of the velocity and the pressure terms of momentum equations are solved by the SIMPLEC algorithm. The well-known k − ε two-equations turbulence model is employed to describe the turbulent structure and behavior. The parameters include the five Reynolds number ( Re = 5000–25000), three fin heights ( H = 35, 40, 45 mm), and five fin width designs (Type-1–Type-5). The objective of this study is to examine the effects of the fin shape of the heat sink on the thermal performance. The results show that the Nusselt number increases with the Reynolds number. The increment of the Nusselt number decreases gradually with the increasing Reynolds number. Furthermore, the effects of fin dimensions on the Nusselt number at high Reynolds numbers are more significant than that at low Reynolds numbers. It is also found that there is potential for optimizing the un-uniform fin width design.

Effect of Absorptive Coating of the Hot Fluid Passage of a Heat Exchanger Employing Exergy-Optimized Pin Fins in High Temperature Applications

Abstracts An expression for the optimum pin fin dimension is derived on exergy basis for a high temperature exchanger employing pin fins. The present result differs from that obtained by Poulikakos and Bejan (1982, “Fin Geometry for Minimum Entropy Generation in Forced Convection,” ASME J. Heat Transfer, 104, pp. 616–623) for a low temperature heat recovery application. Also, a simple relation is established between the amounts the base temperature of the optimized pin fin is raised for a range of absorptive coating values. Employing this relation, if the absorptivity of the coating, the plate emissivity, the number of protruding fins, and some area and fluid parameters are known, the corresponding value for the base temperature of the fin is immediately obtained. The analysis shows that the thermal performance of the exchanger improves substantially with a high absorptivity coating hence can be seen as a heat transfer enhancement feature of the exchanger operating with radiation dominance.

Modelling and parametric study of modular undulating fin rays for fish robots

Abstract Biomimetic robots borrow their senses and structure from animals, such as insects, fish and birds. Development of underwater vehicles is one of the areas where biomimetic robots can potentially perform better than conventional robots. In this paper, the biomimetic design and the workspace study of undulating fin propulsion mechanisms are considered and discussed. We are interested in fish with long and/or wide undulating body/fin – especially those of anguilliform, amiiform, rajiform, and gymnotiform. Two major mechanism layouts developed to mimetic fin undulations of real fish are compared and discussed. Various kinematics expressions of fin waves are presented and the model’s limitation is also discussed. For a parametric study, the geometry of a single fin segment of the assembled fin mechanisms and the fin wave generated are first developed. Next, the fin workspace of the single fin segment is derived based on a defined area ratio. By virtue of the obtained fin dimensions, a gymnotiform robot, Nanyang knifefish (NKF-II), has been designed and constructed. With the fin-ray linkages with sliders connecting in series, the fish robot is able to generate arbitrary undulating waveforms. The robot’s maneuvering and its depth control have also been achieved by the integration of a buoyancy tank with the undulating fin mechanisms. Initial pool testing has been conducted to demonstrate the basic performance of the fish robot underwater.

An approximate analytical prediction about thermal performance and optimum design of pin fins subject to condensation of saturated steam flowing under forced convection

An approximate analytical method has been suggested for solving the governing equation for horizontal pin fins subject to condensation while saturated steam flowing over its under laminar forced convection. Adomian decomposition method is used for determination of the temperature distribution, performance and optimum dimensions of pin fins with temperature dependent thermal conductivity under the condensation of steam on the fin surface. From the results, a significant effect on the temperature distribution in the fin and its performances are noticed with the variation in fin-geometric parameters and thermo-physical properties of saturated vapor. Next, a generalized scheme for optimization has been demonstrated in such a way that either heat-transfer duty or fin volume can be taken as a constraint. Finally, the curves for the optimum design have been generated for the variation of different thermo-physical and geometric parameters, which may be helpful to a designer for selecting an appropriate design condition.

Optimization and Thermal Performance Assessment of Pin-Fin Heat Sinks

In this work, the heat transfer and fluid flow analyses are employed to optimize the geometry of the pin-fin heat sinks. An entropy generation minimization method is employed to optimize the overall thermal performance and behavior of pin-fin heat sinks. The performance of the heat sinks is determined by its thermal resistance and pressure drop, since they significantly influence the thermal resistance during forced convection cooling. The optimum design of heat sink for in-line and staggered alignments with circular, square, rhombus, rectangular, and elliptical configurations are investigated, and the thermal behavior is compared. The entropy generation rate is developed using mass, energy, and entropy balance over the control volume. The formulation for the dimensionless entropy generation rate due to heat transfer and due to fluid flow (pressure drop) is obtained in terms of fin geometry, thermal conductivity, pin-fin alignment, Reynolds, and Prandtl numbers. Using an energy balance equation over the same control volume, the average heat transfer coefficient for heat sink is developed, which is a function of the heat sink material, fluid properties, fin geometry, pin-fin alignment. The selected materials are plastic, aluminum, and copper. Thermal and hydrodynamic analysis of pin-fin heat sink are performed using parametric variations of each design variable, including pin diameter or side, pin height, approach velocity, number of pin-fins, and thermal conductivity of the material. Optimization of heat sink designs and parametric behavior are presented and compared based on the selected pin-fin configurations, alignment, and material property. The results indicate that geometries of circular and elliptical shapes provide more favorable conditions for heat transfer than that of square, rectangular, and rhombus shapes. In all cases, optimum size of staggered alignment is better than in-line alignment. In a particular pin-fin configuration, entropy generation rate is comparatively elliptical < circular < rhombus < rectangular < square pin-fins. The optimum entropy generation rate moves down as the thermal conductivity of the fin material increases. Copper fin gives the best performance, and if the weight of the heat sink is a constraint, the aluminum fin would be preferable. However, the optimum diameter for the selected materials is almost the same. The optimum entropy generation rate moves down again with the thermal conductivity of the fin material, which shows the best performance of copper fins for the same approach velocity. Also, the optimum approach velocity for the selected materials is almost the same. The entropy generation rate decreases with the increase in thermal conductivity for the same number of fins and under the same operating conditions. Also, the optimum fin length increases with thermal conductivity of fin materials. The results enable the designer to quickly and easily access the merits of pin-fin geometries for specific design conditions and for selecting the optimal dimensions of fin and material.

Heat Transfer and Thermal Design of Finned Frames for TEFC Variable-Speed Motors

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper addresses the evaluation of the heat transfer capability of a finned frame for different velocities of the cooling fan and different numbers and dimensions of the fins. As the heat transfer is highly dependent on the air speed and turbulence, separate evaluations are done in four axial sectors of four different frames. For each frame, each sector is thermally isolated and evenly heated by an internal cylindrical heater with controlled losses. The experimental results allow computing the local transfer coefficient on each axial sector in terms of the fin dimensions and cooling air velocity, and using these empirical coefficients, it is possible to evaluate the thermal capability of the frames and/or to compute the temperature gradient needed to dissipate certain losses. Based on these results, a simple and accurate method to size finned frames is proposed. </para>

Performance and optimum design analysis of convective fin arrays attached to flat and curved primary surfaces

A model has been developed analytically to carry out the performance and optimum design analysis of four fin arrays, namely, longitudinal rectangular fin array (LRFA), annular rectangular fin array (ARFA), longitudinal trapezoidal fin array (LTRA) and annular trapezoidal fin array (ATFA) under convective cooling conditions. The performance parameters such as fin efficiency, fin effectiveness and augmentation factor are evaluated for a wide range of design variables. It has been observed that the conduction through the supporting structure and the convection from the interfin spacing have a pronounced effect on the performance of a fin array. The optimum fin dimensions in a fin assembly have been determined by consideration of the constant total height of the fin assembly and interfin spacing. From the results, it can be highlighted that the optimum fin dimensions in fin arrays differ from that of the individual fins.