Fin Tip Research Articles

Estimation of flow boiling heat transfer coefficient in enhanced tubes. Benchmark correlations and ANN approach

Abstract This paper addresses the critical gap in predicting the heat transfer coefficient during flow boiling in enhanced tubes, where the use of conventional correlations and predictive methods developed for smooth surfaces do not usually provide satisfactory results. For such purpose, a comprehensive database was collected from existing literature, including a wide range of operating conditions and enhanced tube geometries from several independent sources. The dataset includes mass flow rates spanning from 50 to 1000 kg/m2s, vapor qualities from the onset of boiling (x=0.0) to the dry-out occurrence and beyond (x=0.99), reduced pressures from 0.05 to 0.80, and tube diameters (measured up to the fin tip) from 0.7 to 11.9 mm, for a total amount of approximately 3000 data points. Existing flow boiling heat transfer coefficient predictive methods for enhanced tubes were implemented and tested with the present dataset, proving a limited accuracy for most of them mainly in case of testing beyond the specific parameter ranges they were developed for. Extrapolation frequently resulted in statistically poor or even non-physical outcomes. Several artificial neural network models were then developed, according to sensitivity analysis approach to look for potential input parameters and network structures. Specifically, two approaches were employed: a standard neural network model and a correlated informed neural network (CINN), integrating physical correlations into the network’s architecture, thus informing the model with physical principles that govern the heat transfer process. Despite a lower overall accuracy, the correlated informed neural network demonstrated superior reliability than standard one, resulting in an instrument to improve the accuracy of existing correlations.

Numerical Modelling and Optimization of Thermal Performance of Heat Sink with Uniform Cross - Sectional Area using Shape Optimized Al2O3 - SiC Nanoparticles in Base Fluid

This study explores the flow characteristics of proposed “Integrated hybrid nanofluid heat sink model (IHNFHSM)” with a novel mixture of Al2O3–SiC nanoparticles of various shape in base fluid. The primary objective is to evaluate the influence of various similarity parameters on the heat transfer performance of the fin structure subjected to convective and insulated tip boundary conditions. A novel combination of Al2O3–SiC hybrid nanoparticles offer a significant potential for improved dissipation of heat in engineering applications. The analysis is carried out using Darcy's model, incorporating temperature-dependent natural convection, and radiation effects. The governing energy equations are non - dimensionalized and solved using three stage Lobatto quadrature numerical technique with suitable boundary conditions. The results provide insight into the effect of similarity parameters on the thermal performance of the system under consideration. Quantitatively, the findings reveal an increase of 23% in the thermal conductivity of base fluid with hybrid nanoparticles. The heat transfer rate of convective fin tip was enhanced by an average of 17.13% at = m2 = 1 compared to an insulated fin tip. An optimal thermal performance of the model in terms of heat transfer rate was observed by an enhancement of 100% in and m2 values from 10 to 20. Additionally, dimensionless fin temperature at = 1 enhanced by 12.16% for the lamina – lamina shape combination of nanoparticles over lamina – spherical, clearly showing its dominance in the thermal performance over the rest of the combinations.

Servo System Design for Precise Fin Tip Control in Launch Vehicles Using Electromechanical Actuators

Servo System Design for Precise Fin Tip Control in Launch Vehicles Using Electromechanical Actuators

A new species of Phyllophichthus Gosline, 1951 (Actinopterygii, Ophichthidae) from Taiwan.

A unique species of the flappy-snake eel genus, Phyllophichthusdiandrus sp. nov., is described based on a single specimen (270 mm in total length) collected from Dong-gang, southwestern Taiwan. The new species possesses several characters that are distinct from the only other species in the genus, Phyllophichthusxenodontus. Phyllophichthusdiandrus sp. nov. can be easily distinguished from P.xenodontus by having two papillae inside of nasal tube (vs three in P.xenodontus), 25 branchiostegal rays (vs 29), the dorsal-fin origin positioned behind the tip of the pectoral fin (vs not behind, usually above mid-pectoral fin), and the absence of the maxillary teeth (vs present). The relationship between Phyllophichthus and Leiuranus is discussed based on generic and morphological features.

Enhancing Engine Cylinder Heat Dissipation Capacity Through Direct Optimization (DO) Techniques

Internal combustion (IC) engines are used widely as the primary power source for automobiles of all types, cars, motorcycles, and trucks. Because of the high combustion temperatures involved in the operation, the excess heat is removed by means of extended fins that increase the surface area for adequate cooling. Significant improvement in the heat dissipation characteristics of the engine cylinder can be achieved by optimizing the design of these fins. The aim of this study is to evaluate the thermal performance of engine cylinder fins using an analytical system of finite element analysis (ANSYS FEA) software, using a direct optimization (DO) approach to identify optimal fin design. Analysis shows that fin length and width play critical roles in improving cooling efficiency, lowering the maximum temperature within the cylinder to 549.46 K and enhancing total heat flux to 7225.31 W/m2, which is a 25.87% increase from the generic design, capable of heating removal of 5740.22 W/m2. The current fin design is effective but could be improved in heat dissipation, mainly at fin tips. To optimize thermal performance while minimizing material costs, a balanced fin dimension is recommended. Alternative materials, transient heating analysis, and experimental verification may be examined in the future to achieve a total understanding of fin geometry and behavior under real operating conditions. These insights lay a foundation to accelerate cooling systems development in the automotive, aerospace, and heavy equipment industries, where efficient heat transfer is key for performance and long-term durability.

Two new hypogean species of the genus Triplophysa (Osteichthyes, Cypriniformes, Nemacheilidae) from Guizhou Province, Southwest China, with underestimated diversity.

Two new species of the genus Triplophysa from southwestern Guizhou Province, China, are described. These are Triplophysaziyunensis Wu, Luo, Xiao & Zhou, sp. nov. and Triplophysayaluwang Lan, Liu, Zhou & Zhou, sp. nov. from Maoying Town, Ziyun County, Guizhou Province, China. Triplophysaziyunensis Wu, Luo, Xiao & Zhou, sp. nov. is distinguished from other hypogean species of the genus Triplophysa by having a combination of the following characteristics: body naked, scaleless, pigmented markings on surface of body, except ventral; eyes reduced, diameter 2.4-4.9% of head length; pelvic-fin tip extending to anus; tip of pectoral fin not reaching pelvic fin origin; anterior and posterior nostrils closely set, with anterior nostril elongated to a barbel-like tip; tip of outrostral barbel extending backward, not reaching anterior margin of the eye; lateral line complete; posterior chamber of air bladder degenerated; and fin differences. Triplophysayaluwang Lan, Liu, Zhou & Zhou, sp. nov. is distinguished from other hypogean species of the genus Triplophysa by having a combination of the following characteristics: body naked, scaleless, with irregular pale and dark brownish brown markings, except ventrally; eyes reduced, diameter 4.6-6.1% of head length; pelvic-fin tip reaching anus; tip of pectoral fin not reaching to pelvic fin origin; anterior and posterior nostrils closely set, with anterior nostril elongated to a barbel-like tip; tip of outrostral barbel extending backward, not reaching to anterior margin of the eye; lateral line complete; posterior chamber of air bladder degenerated; and fin differences. Mitochondrial Cyt b revealed relatively small genetic differences, 1.4-2.0%, between the two new species and close relatives. Nuclear gene RAG1 indicated that the two new species possessed unique haplotypes with multiple linking mutations. This study emphasizes the importance of utilizing nuclear genes to identify new species in rapidly speciation cave species, with small genetic differences due to mitochondrial introgression occurring interspecies.

Maximal heat transfer density from cross‐flow heat exchanger with tapered fins using constructal design method

AbstractTapered fins are widely used in heat sinks cooled by forced convection. In this study, maximal forced convective heat transfer from a set of tapered fins in cross‐flow is investigated based on the constructal design method. The tapering of the fins is done for a three‐fin base‐to‐tip ratio (taper ratio). The first taper ratio is TR = 0.5 (fin base < fin tip), the second taper ratio is TR = 1 (fin base = fin tip, straight fin), and the third taper ratio is TR = 2 (fin base > fin tip). In all these cases, the fin length is constant. The fins are heated at constant surface temperature and they are cooled by cross‐flow. A constant pressure difference pushes the cross‐flow toward the fins. The Bejan number ranges from 105 to 107. The forced convective heat transfer density is maximized from the fins for the three taper ratios, and a comparison between them is carried out. The maximization is conducted by numerical and scale analysis. In the numerical analysis, the pressure‐driven flow equations (continuity, momentum, and energy) are solved by means of the finite volume method. In the scale analysis, two extremes are considered. The first extreme is for TR < 1, and the second extreme is for TR > 1. These two extremes are intersected to find the maximal forced convective heat transfer density. The results obtained from numerical and scale analysis confirmed that the maximal forced convective heat transfer density occurs for straight fins (TR = 1) in the whole range of the Bejan number. The heat transfer density from straight fins (TR = 1) is higher than that of tapered fins (TR = 2) by 45.2%, and it is higher than that of tapered fins (TR = 0.5) by 52.7% at Be = 107.

Quantitative Characterization of Zebrafish Caudal Fin Regeneration Based on Mueller Matrix OCT In Vivo.

Zebrafish serves as a valuable model for studying tissue regeneration due to their comprehensive regenerative abilities, particularly in bone tissue. In this study, a Mueller matrix optical coherence tomography (OCT) system was applied to monitor the regenerative processes of zebrafish caudal fins in vivo. The analysis focused on evaluating the thickness of the caudal fin tip and the distribution of internal bone tissue during the regenerative process. Subsequently, the effect of ectoine solution on the regeneration process was observed and discussed. Our findings revealed that the caudal fin blastema did not exhibit phase-induced polarization characteristics in the Mueller matrix OCT images. Statistical analyses indicated that the caudal fins did not fully regenerate to their original state within 21 days. Furthermore, the results suggested that ectoine solution could enhance tissue regeneration. This approach provides a method for quantifying zebrafish caudal fin regeneration and advances observation techniques for biomedical and clinical applications.

Description of a new species of the genus Oreonectes (Teleostei, Cypriniformes, Nemacheilidae) from Guangxi, China

A new loach species, Oreonectes zhangisp. nov., was identified from Xingye County, Yulin City, Guangxi, China. The species can be distinguished from all other congeners by a combination of the following characters: six branched pelvic-fin rays; a reduced posterior chamber of air-bladder; vertebrae 4 + 32; the tip of the male pelvic fin does not reach the anus. Molecular analyses using the Cyt b gene showed that the new species forms a monophyletic group and is closely related to O. damingshanensis.

Impact of stretching and shrinking on the thermal profile and efficiency of a wet and porous longitudinal fin in motion subject to convection and radiation

AbstractWe consider heat transfer with convection and radiation effect on a longitudinal wet and porous fin. The trapezoidal fin moving at a constant speed is subject to stretching and shrinking, and their influence on the fin's heat transfer rate and thermal distribution is investigated. The governing equation of the model mentioned above is nondimensionalized, and the resultant second‐order nonlinear boundary value problem is solved numerically using the Chebyshev collocation method and validated using the shooting technique. All the simulations are carried out using MATLAB software. The impact of the critical dimensionless parameters on the fin tip temperature, the thermal profile, and the base heat transfer rate are analyzed graphically. Fin efficiency is also computed, and the influence of the pertinent parameters on it is inferred. For a moving fin, the shrinking mechanism favors a faster base heat transfer, an uptick of about 9%, and the stretching fin enhances thermal distribution and efficiency by around 3% and 14%, respectively. The rise is further accelerated with the enhancement of the Peclet number. The fin tapering from that of a rectangular profile () helps achieve a faster heat transfer rate along the fin length, a gain of nearly 22%, when the fin taper ratio varies from 0 to 0.8.

Dynamic phase change materials with extended surfaces

Phase change materials (PCMs) present opportunities for efficient thermal management due to their high latent heat of melting. However, a fundamental challenge for PCM cooling is the presence of a growing liquid layer of relatively low thermal conductivity melted PCM that limits heat transfer. Dynamic phase change material (dynPCM) uses an applied pressure to pump away the melt layer and achieve a thin liquid layer, ensuring high heat transfer for extended periods. This paper investigates heat transfer during dynPCM cooling when the heated surface has extended features made from high thermal conductivity copper (Cu). Using experiments and finite element simulations, we investigate the heat transfer performance of dynPCM paraffin wax on finned Cu surfaces. A total of 102 transient temperature measurements characterize the performance of dynPCM with extended surfaces and compare the performance with other cooling methods including hybrid PCM and air cooling. The study examines the effects of fin geometry, applied power (20–65 W), and pressure (0.97–12.5 kPa). For dynPCM on a finned surface and a heating power of 65 W, the thermal conductance is 0.45 W/cm2-K, compared to 0.22 W/cm2-K for dynPCM on a flat surface and 0.10 W/cm2-K for hybrid PCM. The heat transfer is highest at the fin tips where the melt layer is thinnest, providing valuable design guidelines for future high performance dynPCM cooling technologies.

Simulation of the effect of the structure and location of non-closed droplet microchannel on flow/ thermal performance

In order to investigate the effects of geometric parameters and flow modes on the fluid flow morphology, resistance and heat transfer effect in the non-closed droplet pin fin array, in this manuscript, a numerical simulation has been conducted under Re = 100–700 with different pin fin heights (Hp = 0.3 mm, 0.5 mm, 0.7 mm) and pin fin densities (β = 0.046, 0.059, 0.072), with different flow directions under heat flux (10 W/cm2 – 50 W/cm2) studied as well. It is discovered that increasing the height and density of the non-closed droplet pin fin increases the interference with the fluid, resulting in a greater flow resistance phenomenon. However, the enhancement of turbulence not only exacerbates the flow instability in microchannels, but also further promotes the mixing of hot and cold fluids, making the internal temperature distribution more uniform. In which way, the effect of optimizing heat transfer performance achieves. In addition, as q > 20 W/cm2, the overall heat transfer capacity of flow direction B (the tip of the pin fin as upstream fluid direction) is better than that of flow direction A (the cavity of the pin fin upstream as upstream fluid direction). When q = 30 W/cm2, there is a process transferring from single-phase flow to two-phase flow along with the direction of working fluid flow in the microchannel. Under this condition, the local maximum heat transfer coefficient is 15,502.4 W/(m2·K) in flow direction A and 16,094.8 W/(m2·K) in flow direction B. Furthermore, the comprehensive evaluation concludes that the channel flow/thermal performance is the best with Hp = 0.7 mm, β = 0.046.

Numerical and experimental investigation on boiling heat transfer and flow attributes for the exterior of smooth tubes and T-fin tubes

Experiments and numerical analyses of saturated pool boiling have been carried out on the outer surfaces of horizontal smooth tubes and T-fin tubes. Using a computational model that closely matches the experimental results, the study examined the dynamics of the bubbles as well as the boiling heat transfer coefficients in both the circumferential and axial orientations of the T-fin tubes. For the first time, comprehensive information on the process of high-performance external tube boiling has been made available. The findings demonstrate that an increase in fin density on the surface of the T-fin tubes leads to an abundance of bubble nuclei, with the escaping bubbles exhibiting both increased size and accelerated velocity. Due to the distinctive configuration of the T-fin tube, the local heat flow is lowest at the root fin and highest at the fin tip, indicating that heat transfer is inhibited in the narrow cavity between the two lateral fins. The optimal fin density, which corresponds to the maximum overall heat transfer coefficient has been identified. This states that the enhanced heat transfer mechanism within the T-fin tube is a symbiotic effect of both the increase in heat transfer area and the subsequent degradation of heat transfer fostered by the bubbling of the tube.

Improvement of labyrinth seal performance using the partial honeycomb lands

In this study, a partial honeycomb land was proposed for improving the sealing performance of a labyrinth seal which has been widely applied to the low-pressure section of a gas turbine. The partial honeycomb land in this experiment is distinguished by a solid strip under the fin of the honeycomb land labyrinth seal. The tested fin front angle of the labyrinth seal was 60°, and the clearance size ranged from 1.15 to 2.82 times the fin tip thickness. The honeycomb cell diameter was 4 times the fin tip thickness, and the honeycomb cell depth was 10.58 times the fin tip thickness. The experiments were conducted under pressure ratios ranging from 1.1 to 2.5, and it was confirmed that the application of the partial honeycomb land resulted in a maximum 39.4 % reduction in the discharge coefficient. Computational Fluid Dynamics (CFD) analysis revealed that the application of the partial honeycomb land altered the flow of leakage, leading to a decrease in the effective clearance. It was confirmed that, for the honeycomb labyrinth seal with smaller clearance, the sealing performance degradation for the conventional honeycomb land case due to the weakened vortex inside the fin cavity was not observed for the case with partial honeycomb land. Therefore, the improvement in sealing performance of the labyrinth seal with partial honeycomb land was attributed not only to the reduction in the effective leakage flow area, but also to the maintained vortex size, which induced resistance to the leakage flow even in smaller clearance conditions.

The Effect Of Pitch Ratio On Screw Turbine Performance With Tip Fin

A water turbine is an energy conversion machine that converts water head into shaft movement. In screw-type turbines, performance is influenced by several parameters including outer diameter, inner diameter, rotor length, head angle, number of blades, and pitch distance. This research uses a screw turbine type with a tip fin. The research aims to determine the performance of screw turbines with tip fins on mechanical power and efficiency. The research independent variables consist of pitch ratio and flow rate. The pitch ratio variations used are 1.2; 1.4 and 1.6 while the variations in flow rate used are 3 l/s, 3.5 l/s, and 4 l/s. The method used in this research is experimental. This study's data analysis employed the two-way Anova method with an alpha (α) of 5%. Anova's results show that the P-value of the interaction of the two independent variables, pitch ratio and water discharge, is <0.05, meaning that the independent variables have a significant influence on the performance of the screw turbine. The highest turbine performance results were at a pitch ratio of 1.4 at a water flow rate of 4 l/s resulting in an efficiency value of 34.91% and a mechanical power value of 6.82 watts at a rotational speed of 125 RPM. The lowest turbine performance results at a pitch ratio of 1.2 with a flow rate of 3 l/s resulting in an efficiency of 22.64% and a mechanical power of 3.32 watts at a rotational speed of 56 RPM.

Aerodynamic Characterization of a Generic High-Speed Projectile Configuration

A combined experimental and numerical study was conducted on a generic projectile configuration with low-aspect-ratio fins. The main objectives of this study were to characterize the aerodynamic behavior and validate numerical simulations for a range of Mach numbers (0.4–4) to facilitate an understanding of major flow features such as forebody and fin-generated shock waves, crossflow shear layer vortex, and fin vortex interactions. Measurements included forces and moments, surface oil flow visualization, and high-speed shadowgraph imaging. Numerical simulations were performed using the CFD++ solver. The results showed an excellent match between the experimental and numerical force and moment data. Pressure contours obtained using numerical simulations were integrated to obtain the contributions of individual components toward the total normal force on the body. Flow visualization results show a few complex and interesting flow features, such as shear layer roll-up, crossflow and fin tip vortex interactions, and shock-wave–boundary-layer interactions. The effects of vortex strength and location were analyzed to determine their contributions to the overall forces on the model. The database generated will be very useful for further validation of the numerical tool and a better understanding of vortex-dominated supersonic flows.

Numerical analysis of stretching/shrinking fully wet trapezoidal fin

<p>The purpose of fins or extended surfaces is to increase the dissipation of heat from hot sources into their surroundings. Fins like annular fins, longitudinal fins, porous fins, and radial fins are used on the surface of equipments to enhance the rate of heat transfer. There are many applications of fins, including superheaters, refrigeration, automobile parts, combustion engines, electrical equipment, solar panels, and computer CPUs. Based on a wide range of applications, the effects of stretching/shrinking on a fully wet trapezoidal fin with internal heat generation is investigated. The shooting approach is used to calculate the trapezoidal fin's thermal profile, tip temperature, and efficiency. It is observed that with an increase in the shrinking and wet parameter, the temperature distribution decreases and efficiency increases. On the other hand, when stretching increases, the temperature distribution increases and efficiency diminishes. Using the computed results, it is concluded that shrinking trapezoidal fins improves the effectiveness and performance of the system.</p>

Early ontogenetic development of Cynodon gibbus (Characiformes: Cynodontidae) in the Amazon River basin

Abstract Knowledge regarding the early life history of neotropical fish, although incipient, is crucial for the accurate identification of larvae collected from the natural environment. Such details are important for defining spawning, drift, and nursery areas as well as the reproductive periods of species. Herein, the larval development of Cynodon gibbus was described using morphological, meristic, and morphometric characteristics. Specimens were collected from open water limnetic zones and under macrophyte stands in the Amazon basin from 2010 to 2023. Forty-eight larvae with standard lengths ranging from 5.73 to 21.57 mm were studied. The larvae have a long to very long body, small eyes, and a small head, which progresses to a moderate size in the preflexion stage. Furthermore, the larvae had ample mouths with numerous conical teeth, an oval-triangular swim bladder, overlapping dorsal and anal fins, and the tip of the pectoral fin not reaching the swim bladder. Pigmentation pattern comprised two punctate pigments above the fontanelle, the rectum, and at the lower and upper ends of the caudal peduncle. Various body parts exhibited predominant allometric relationships, reflecting differential developmental rates among them in response to fundamental ecological requirements for survival. The C. gibbus larvae can be identified by a combination of the position of dorsal, anal and pectoral fins, pigmentation pattern, swim bladder shape, and the total number of myomeres (51 to 53).

Heat transfer in a wet porous moving inclined longitudinal fin exposed to convection and radiation in the presence of shape-dependent hybrid nanofluid: Adomian decomposition Sumudu transformation approach

This research paper investigates the thermal examination of a non-integer-ordered mobile fin situation with a hybrid nanofluid flowing past it at an unceasing speed U. The combination approach is utilized to evaluate the physical and thermal characteristics of the hybrid nanofluid, excluding the thermal conductivity and dynamic viscosity. This governing equation is transformed into a dimensionless form and the Adomian Decomposition Sumudu Transform method is employed to solve the conundrum of a moving fin immersed in a hybrid nanofluid. The reliability of this research has been confirmed by verifying the results through a comparison with numerical simulations. The influence of diverse factors on the thermal overview for varying noninteger values alpha is analyzed and presented in graphical representations. Moreover, the analysis reveals that the highest heat flux occurs in the scenario where nanoparticles with spherical-platelet shapes are combined. This is succeeded by the spherical-cylindrical combination, and finally, the spherical-spherical pairing, in terms of heat flux magnitude. Here, we discovered that the temperature at the fin tip decreases by 11.19141 % for s-s shaped nanoparticles, 10.45649 % for s-c shaped nanoparticles and 10.21162 % for s-p shaped nanoparticles as the wet parameter (m2) increases by a factor of 400, and also when the radiation parameter is increased by 400 %, the temperature of the fin tip drops by 13.11313 % for s-s shape nanoparticles, 11.97076 for s-c shape nanoparticles and 11.653899 % for s-p shape nanoparticles.

Semianalytical investigation on heat transfer in porous fins with temperature‐dependent thermal conductivity via the homotopy perturbation Sumudu transform approach

AbstractA unique investigation has been undertaken to analyze the heat transmission by convective and radiative mechanisms in a fully saturated penetrable fin of a longitudinal structure positioned on a leaning surface. This study introduces the fusion of the realms of Homotopy perturbation and Sumudu transform techniques to address a previously unexplored problem involving a moving fin with temperature‐dependent thermal conductivity. In prior research papers, the Homotopy Perturbation Sumudu Transform Method (HPSTM) was utilized to obtain analytical solutions for fins featuring temperature‐dependent thermal conductivity. However, in our current study, we employ the HPSTM to tackle a novel problem involving a moving porous fin. This fin exhibits temperature‐dependent thermal conductivity and is subjected to convection and radiation effects. Through a comparison with numerical results, the present study has validated the dependability of its findings. The dimensionless temperature profile has been investigated by studying its relationship with several parameters. Here we observed that when the Peclet number is augmented by 400%, there is a corresponding 1.11% increase in thermal outline at the fin's extremity. Enhancing the value of radiation parameter by 400% declines the temperature of the fin tip by 14.079%. This study encourages the application of the Homotopy perturbation Sumudu transform technique in more complex fin problems.