Fin Length Research Articles

Emergence of asymmetric straight and branched fins in horizontally oriented latent heat thermal energy storage units

Mobilized thermal energy storage units have a vital role in reducing energy consumption in buildings by enabling industrial waste heat to be used in buildings. High conductive fins can enhance the heat transfer performance of mobilized thermal energy storage tanks which suffer significantly from the low thermal conductivity of phase change materials. On the other hand, investment costs of the mobilized thermal energy storage tanks need to be decreased to compete with fossil fuel-driven systems in buildings. The present study numerically investigates the effect of innovative fin structures on the melting performance for fixed fin material volume to disable cost increase. Two-dimensional models with phase change were simulated for shell-and-tube heat exchangers. The shell geometry was designed sufficiently large to observe the melting growth of phase change material independent from shell walls within the given charging time. Straight and Branched type fin structures with the fin numbers of Nfin=2, 4, and 6 were simulated to uncover the effect of shape and length scale of fins on natural convection-driven melting. It was found that Straight fin type is more suited than Branched fins as they do not show significant melting enhancement with increased complexity and cost. The fin structures in all cases performed better when located at the top of the heat transfer fluid tube, even though the literature considers that top-located fins inhibit natural convection circulations. Varying the number of fins from (2-fin) to (4-fin) causes 15.8% increase in melting ratio, but further increase in the fin number (6-fin) reduces melting ratio below the (4-fin) case. Within (4-fin) structures located at the top, using distinct fin lengths yields melting ratio to increase 28.1%. Overall, the results show that heat transfer could be improved by varying the fin structure without increasing total fin volume and cost. The melting region growth shape with optimized fin structure forms the basis for the multitube arrangement of mobilized thermal energy storage units to enhance heat transfer performance with low cost.

Optimization of Fin with Rectangular and Triangular Shapes by Levenberg – Marquardt Method

The article proposes using the Levenberg – Marquardt (L – M) method to optimize the fin with the longitudinal profile. The objective in optimizing the fin shape: The fin volume achieved the minimum value, with the optimization variables being the fin's width and length. The research performed two problems about optimal design the fin with the straight profile for triangular and rectangular shapes, obtained a tiny relative error compared to the results of the published studies. Specifically, the problem with the triangular-shaped fin, the relative error of the minimum volume compared to the two published is 0.022% & 0.092%; and the problem with the rectangular-shaped fin, the relative error is 0.68% & approximately 0%, respectively.

Performance Study of the Thermoelectric Personal Cooler under Different Ambient Temperatures

In this study, a Thermo Electric Cooler (TEC) was manufactured and investigated experimentally. The heat sink, geometry, fin number, fin length, and heat sink dimensions are studied theoretically. The performance of the TEC is studied under three variables, namely: the THC power, airspeed, and ambient temperature. Two heat sinks are used for each Peltier module. The first one is for the cooling side, while the second one is for the hot side. In the theoretical part, the geometry and the dimensions of the heat sink are studied using one-dimensional heat transfer equations, as well as a theoretical simulation of the performance of a single Peltier module is achieved. The results show that the cooling capacity increases with the increase in airspeed, and the maximum cooling capacity was 180 W at an airspeed of 4 m/s and TEC power of 300 W. The maximum figure of merit of the TEC is about 0.23 when the TEC power is 350 W, at 4 m/s airspeed and an ambient temperature of 43℃. The theoretical results showed that the number of fins affected the total sink thermal resistance and that thermal resistance reduced sharply from 6.5 to about 2 m2 K/W when the fin number increased to 6. When the TEC power is 350 W, the airspeed is 4 m/s, and the ambient temperature is 28℃, the maximum TEC efficiency is 0.5%. Finally, the comparison between the current work and the other works shows the same trends in the variables under comparison.

Experimental investigation on flow-induced vibrations of a circular cylinder with radial and longitudinal fins

Flow-induced vibration (FIV) of a heat exchanger tube may present both negative effects (e.g., causing fatigue damage of the tube) and positive effects (e.g., enhancing heat transfer efficiency). As a typical passive control approach, fins attached to the tube (or circular cylinder) present significant effects on its FIVs. This study carried out systematic wind tunnel tests to investigate the FIVs in the transverse direction (along with the drag forces) of a circular cylinder with various radial and longitudinal fins. For the radial group, 3 cases with spare, moderate, and dense fins were tested. For the longitudinal group, 24 cases with various fin numbers and arrangements were tested. For the longitudinal fin arrangement parallel to the flow direction (also known as a circular cylinder with single or dual splitter plates), various fin lengths were also tested. The experimental results showed that a radial finned cylinder always presents larger FIVs than a bare circular cylinder. The longitudinal fins may significantly increase or decrease the FIVs depending on the number and arrangement of attached fins. For example, a single splitter plate (placed either upstream or downstream of the circular cylinder) often increases the FIVs, while dual splitter plates with large lengths can effectively suppress the FIVs. The experimental results provide valuable guidance for selecting appropriate fin configurations to passively control the FIVs to a certain level that can enhance the heat transfer efficiency without introducing unacceptable fatigue damage.

Near Net Forming Research for Fin-Typed LED Radiator.

Pure aluminum radiator is the best choice for heat dissipation of various LED products at present. Its forming methods include common extrusion, die casting, forging, etc. Compared with other forming technologies, the LED radiator formed by cold forging has good heat dissipation performance, but there are some disadvantages in the forming process, such as uneven deformation, large material consumption and low die life. The cold forging process of pure aluminum fin-typed LED radiator is analyzed by the finite element method. The calculation results show that equal fillet structure of concave die is improper, leading to serious uneven flow velocity distribution during aluminum forging, inconsistent fin length, and warpage tendency. The gradient fillet structure of concave die is adopted. Numerical simulation and production test show that the gradient fillet structure design can significantly reduce the uneven metal flow. The extruded fins have a uniform length, which is conducive to reducing subsequent machining and production cost.

Study on thermal performance of a new optimized snowflake longitudinal fin in vertical latent heat storage

Taking the casing phase change heat storage unit filled with RT55 as the research object. According to the low thermal conductivity of phase change materials, we propose a Phase Change Material (PCM) sleeve with snowflake longitudinal fin structure to improve the melting performance of vertical latent heat storage system (LHTES), and the phase change heat transfer process is simulated by numerical simulation. We studied the enhanced heat transfer characteristics of the snowflake-shaped fin structure to the casing PCM unit, and compared with the ordinary rectangular longitudinal fin and the improved snowflake-shaped longitudinal fin. The results show that the combined mechanism of snowflake finned tube structure and local heat transfer of phase change materials can significantly shorten the charging time, which is 45.59% lower than that of traditional fin melting time. Reasonable changes in fin length, width, shape and angle structure can shorten the charging time, but reduce the heat storage. We analyzed the thermal performance of the heat storage system by taking the charging time, heat storage capacity and average heat flux as evaluation indexes, and discussed the effects of flow temperature in the tube, fin material and longitudinal fin shape on the melting performance of the system.

Melting of hybrid nano-enhanced phase change material in an inclined finned rectangular cavity for cold energy storage

The aim of this paper is to study the potential of two heat transfer enhancement techniques, namely adding fins and hybrid nanoparticle (Cu and Al2O3), for improvement of the melting process of PCM (water) in an inclined rectangular enclosure as model of cold energy storage systems. Phase change and heat transfer of PCM are modelled using an in-house built code based on Lattice Boltzmann Method, which is validated with experimental and numerical results from literature. Enhancement effect is investigated through the main parameters including number of fins, fin length ratio (W/H) and nanoparticle volume fraction (ϕ). Heat transfer and fluid flow, liquid fraction, transient evolution of melting front, required time for full melting, and thermal energy storage are analysed in detail. The results show that the melting rate is about two times higher for the fin length ratio of W/H = 0.75, compared to W/H = 0.25. Besides, nanoparticle loading further enhances the melting rate. The highest melting rate is attained in the case of 3-fins and nanoparticle concentration of ϕ = 6 vol% with a 33.5% reduction in the complete melting time. Incrementing the fin length ratio increases the thermal energy stored, and the melting time can be shortened by up to 64%.

Numerical investigation of using helical fins for the enhancement of the charging process of a latent heat thermal energy storage system

This paper is focused on the enhancement of the thermal performance of a vertically oriented shell and tube latent heat thermal energy storage (LHTES) system by using helical fins. In order to see the improvement made by using the helical fin in a LHTES unit, the performance of the helically finned LHTES system has been compared with those of axially finned LHTES system, and no finned LHTES system. The length of the helical fin in the helically finned LHTES system is considered equal to the total length of the four axial fins used in the axially finned LHTES system and the net volume of the PCM is supposed to be identical for all studied cases. Three different temperatures of 345 K, 355 K, 365 K have been considered for the inner tube wall. Results revealed that for the helically finned TESS, the total melting time of the PCM can be reduced up to 18.25%, 21.5% and 16.75% in comparison with axially finned LHTES system for the inner tube wall temperatures of 345, 355 and 365 K, respectively. The presence of a helical fin causes the penetration of the heat into the core of the PCM inside the container and the motion of the molten PCM will be affected by the result of the buoyancy forces and the centrifugal force. Thus, there will be both transverse convection and longitudinal convection for the helically finned LHTES system. Besides, for the helically finned LHTES system, the PCM receives the needed heat for its full melting (charging) in less time compared to the axially finned LHTES system. This is due to the helicity of the molten PCM and also the formation of the vorticities due to the existence of the helical fin which contributes to deeper penetration of the heat and melt front.

Melting performance assessments on a triplex-tube thermal energy storage system: Optimization based on response surface method with natural convection

The low thermal conductivity of phase change materials significantly affects the heat storage and release performance for a phase change energy storage system. To alleviate this issue, a novel triplex-tube latent heat thermal energy storage system is designed and the melting behavior of phase change materials is studied numerically. On the premise of a fixed total volume of phase change material, the multi-parameter optimization design of the system is carried out by the response surface method. The fluid-structure coupling function of each parameter is fitted. Compared with the original model for the triplex tube, the melting performance of the optimized model is improved by 23.87%. The internal temperature fluctuation is found by dynamic temperature response, and the mechanism is explained by dynamic flow rate study. The improvement of melting performance by natural convection after optimization is also studied. The influences of the physical parameters (fin length, initial temperature of phase change material, inner and outer tube wall temperature, and fin material) of the optimization model on the melting performance of the system are quantified, as well. The effect of fin length (30-35-40 mm) on melting performance is found to be less than 11.47% and the effect of thermal conductivity of fin on the melting process is not obvious.

Efficacy of angled metallic fins for enhancing phase change material melting

Research on enhancing phase change material (PCM) heat transfer is concentrated in latent heat thermal energy storage (LHTES) field, especially with utilization of metallic fins. One interesting fin parameter that was less explored for a rectangular PCM system, is the metal fin's inclined angle. This research aims to experimentally validate the hypothesis and evaluate the efficacy of angled metallic fins enhancing PCM melting in a sidewall heated cuboid LHTES system. Experiments indicate that three-dimensional PCM melting in the LHTES unit can be characterized as two dimensional. The angled fins considerably influence temperature evolution of local solid PCM around fins. Compared to the horizontal fin, positive inclined fins with angles of +30° and +15° prolong the PCM melting time by 4.0% and 3.8% respectively, while the downward tilted inclined fins at −15° and −30° promote PCM melting by up to 5.2% melting fraction difference. Extending simulations with seven fin angles and three fin lengths explicate the substantial effect on PCM heat storage, melting time, and temperature uniformity. Particularly, the longest fin at the downward angle of −15° reduces the PCM melting time most. The study shows feasibility of utilizing downward angled fins to enhance PCM transient melting in the LHTES unit.

Utilize mechanical vibration energy for fast thermal responsive PCMs-based energy storage systems: Prototype research by numerical simulation

For commercialisation of PCMs (liquid-solid phase change materials) based energy storage systems, the biggest challenge is to improve the thermal responsive rate of PCMs. In the present authors’ latest study, it is found mechanical vibration may be utilized to address the challenge as most engineering systems work under vibration conditions. However, to utilize mechanical vibration more efficiently, it is critical to accelerate melting speed of solid PCMs in the beginning of charging processes. In the present study, a fin is introduced for the purpose. Here comprehensive numerical simulation is conducted to reveal the effectiveness of the new combination of a fin and mechanical vibration. So far there is no open research on feasibility of this new combination. The present work bridges the gap. The present research shows the integration of a fin and mechanical vibration can provide an effective way to maintain a sustainable high thermal responsive rate for PCMs during charging processes. The fin and mechanical vibration are complementary: the fin can improve thermal responsive rate of PCMs significantly in the early period of the charging process but its influence will become weak; on the contrary, the enhancement effect of mechanical vibration is slight in the beginning but later will become strong. The effects of vibration frequency, vibration amplitude and fin length are investigated numerically. It is found a low/moderate vibration frequency can accelerate charging processes more effectively and the optimal vibration frequency range is around 0–200. And there is also an optimal range for fin length. If the ratio of fin length to side length of the cubic tank is more than 3/4, the benefit by introducing a fin will become slight, which indicates the length of fin is not the longer the better. The present work proposes a new way to develop commercial PCMs-based energy storage systems. The findings can serve as guides for realistic engineering applications.

Experimental and numerical analyses of thermal-hydraulic characteristics of aluminium flying-wing fins

• In general, the flying-wing fin performs better than the wavy fin at the same Re . • The field synergy of the flying-wing fin is much better than that of the wavy fin. • There exist the butterfly-shaped low velocity zones perpendicular to the streamwise direction. • The heat transfer coefficient on the obtuse-angled side of the fin is larger. • Both fin length and fin thickness have little effect on the performance of the fin. The secondary heat transfer surface of the shovel-cut finned tube, called the flying-wing fin, eliminates the thermal contact resistance. In the present study, the thermal-hydraulic characteristics of the flying-wing fin at Reynolds number range of 1500–3000 were studied, including overall quantitative analysis and three-dimensional thermophysical field analysis. It was found that the ratio of Nu · η 0 / f 1/3 of the flying-wing fin (Case A1) is about 8.6% larger than that of the wavy fin (Case B3). The fundamental reason is that the flying-wing fin has a smaller average field synergy angle than the wavy fin. There is a butterfly-shaped low-velocity zone at the root of the wave trough of the monitoring section on the acute-angled side of the flow channel. In addition, along the fin height direction, the influence range of this low-velocity zone on the flow field is less than around 1.34 mm. Similarly, there are butterfly-shaped zones for the temperature and field synergy angle distributions. The average value of the convective heat transfer coefficient on the left side of the flying-wing fin is greater than that on the right side. In general, the promising flying-wing fins show better thermal-hydraulic performances than the wavy fins with similar geometric parameters, which deserve further promotion and engineering application.

Thermal performance and multi-objective optimization of thermosyphon heat sinks with rectangular radial fins for high power LED lamps cooling

The thermosyphon heat sinks with rectangular radial fins are presented for heat dissipation of high power LED lamps in this paper. The thermosyphon is made of copper, which includes the evaporator with 60 mm length and condenser with 180 mm length. The rectangular radial fins with 2 mm thickness and 180 mm height are connected to the external surface of the condenser. The influence of fin number (10–50) and fin length (30–90 mm) on the thermal performance is revealed by the partial derivative of temperature to mass. A multi-objective optimization of the thermosyphon heat sink considering the thermal performance and mass is performed to obtain the Pareto optimal thermal performance using Response Surface Methodology and non-dominated sorting genetic algorithm II. The results show that the effects of the fin length (30–60 mm) and fin number on the thermal performance and the mass are significant, respectively. The Pareto optimal solution is obtained of the maximum temperature (67.7 °C), thermal resistance (0.45 K/W) and mass (1.74 kg) corresponding to the number of fins (23) and fin length (59 mm), which releases the heat of 92 W. It provides further guidelines for designing thermosyphon heat sinks in high power LED lamps cooling.

Convection in a differentially heated cavity with a conducting fin attached at the bottom and ceiling

The flow and heat transfer within a differentially heated convective cavity, whose bottom and ceiling are attached with a conducting thin fin, are investigated with numerical simulations in this study. Rayleigh number from 5 × 107 to 1.84 × 109, and fin length from 1/6 to 1/2 are examined and analysed. The numerical results demonstrate that plume flow, which is similar to the extensively studied Rayleigh-Bénard convection, separates intermittently from the horizontal thin fin and it subsequently causes strong oscillations in the entire vertical thermal boundary layer. It is also found that the Rayleigh number and fin length distinctly impact the origination and development of the plume flow, as well as the interaction between the plume and its downstream vertical boundary layer. The present simulation results demonstrate that the integral absolute horizontal velocity on the cavity centreline Q is remarkably enhanced by 175.3% in the early stage and it is improved by 467.1% in the fully-developed stage at Ra=1.84 × 109 and s = 1/2. It is further revealed that heat transfer across the convective cavity increases with fin length and a maximum enhancement factor 71.05% is achieved at Ra=1.84 × 109 and s = 1/2. Nevertheless, it also demonstrates that compared to the Nusselt number in a non-finned cavity, heat transfer through the heated sidewall is depressed in the present finned cavity owing to a lower temperature difference adjacent to the heated sidewall.

Hydrodynamic performance of an unconstrained flapping swimmer with flexible fin: A numerical study

Flexible tail fins are commonly found in undulatory swimmers which can propel freely in omni-direction with flapping-wing-based propulsion. In this work, the hydrodynamic performance of an unconstrained flapping foil equipped with a flexible tail fin at different length is investigated numerically. As the fin length Lfin changes from 0.2c to c with c being the cord length, the propelling speed of the system first increases and then decreases after maximum propelling speed is achieved when the fin length is 0.8c. There are two kinds of wake vortical structures observed with bending stiffness kb = 2.0: (i) the regular reverse Bénard–von Kármán vortex configuration for foil with short fin and (ii) the aligned vortices with two-layered street at downstream for foil with long fin (Lfin≥ 0.6c). Control volume analysis reveals that for both types of vortical structures, the time-averaged thrust force is mainly related to the momentum flux contribution from the downstream face. Besides, the wake symmetry of a pitching foil with flexible tail fin is sensitive to the vertical phase velocity of vortices, where it can be used to predict whether the wake symmetry of the unconstrained system is preserved. Moreover, the bending stiffness effectively affects the hydrodynamic performance, and the breaking of wake symmetry greatly reduces the propulsive efficiency. The results obtained shed some new light on the role of flexible structures in the self-propulsive biological system and furthered our understanding of flexible self-propulsion system.

Heuristic technique for multi-objective optimisation of engine cylinder fins

In this paper, we perform an analysis of an engine fin array, of the conventional circular type, for both heat dissipation and fin material cost. The set of designs proposed are non-dominated in nature and serves both objectives reasonably. The Non-dominated Sorting Genetic Algorithm (NSGA-II) is used to optimise the factors affecting the heat transfer and the material cost. The bore radius, fin thickness, fin length, number of fins, and velocity of air around the fins are taken as parameters for the multi-objective optimisation. The Steady State Thermal module of ANSYS 19.0 software is used to compute the fitness function, which is an integral part of GA. This work aims at developing an integrated solution technique by combining the ANSYS software with Genetic Algorithm (GA) which will increase the accuracy and speed in obtaining the results. The results attained show that the proposed method offers an efficient and robust optimisation technique.

Effect of Fin Length and Angle on the Melting Process of Phase Change Materials in Vertical Latent Heat Storage Unit

Effect of Fin Length and Angle on the Melting Process of Phase Change Materials in Vertical Latent Heat Storage Unit

Experimental Investigation of the Variable Fin Length on Melting Performance in a Rectangular Enclosure Containing Phase Change Material

Experimental Investigation of the Variable Fin Length on Melting Performance in a Rectangular Enclosure Containing Phase Change Material

Relationship between miR-203a inhibition and oil-induced toxicity in early life stage zebrafish (Danio rerio)

Dysregulation of microRNA (miRNA, miR) by environmental stressors influences the transcription of mRNA which may impair organism development and/or lead to adverse physiological outcomes. Early studies evaluating the effects of oil on developmental toxicity in early life stages of fish showed that reductions in expression of miR-203a were associated with enhanced expression of downstream mRNAs that predicted altered eye development, cardiovascular disease, and improper fin development. To better understand the effects of miR-203a inhibition as an outcome of oil-induced toxicity in early life stage (ELS) fish, embryonic zebrafish were injected with an miR-203a inhibitor or treated with 3.5 µM phenanthrene (Phe) as a positive control for morphological alterations of cardiovascular and eye development caused by oil. Embryos treated with Phe had diminished levels of miR-203a at 7 and 72 h after injection. Embryos treated with the miR-203a inhibitor and Phe exhibited a reduced heart rate by 48 h post fertilization (hpf), with an increased incidence of developmental deformities (including pericardial edema, altered eye development, and spinal deformities) and reduced caudal fin length by 72 hpf. There were significant reductions in lens and eye diameters in 120 hpf miR-203a-inhibitor and Phe-treated fish, as well as a significantly reduced number of eye saccades, determined by an optokinetic response (OKR) behavioral assay. The expression of vegfa, which is an important activator during neovascularization, was significantly upregulated in embryos receiving miR-203a inhibitor injections by 7 and 72 hpf with increased trends in vegfa expression in 72 hpf larvae treated with Phe. There were decreasing trends in crx, neurod1, and pde6h expression by 72 hpf in miR-203a inhibitor and Phe treatments, which are involved in photoreceptor function in developing eyes and regulated by miR-203a. These results suggest that an inhibition of miR-203a in ELS fish exhibits an oil-induced toxic response that is consistent with Phe treatment and specifically impacts retinal, cardiac, and fin development in ELS fish.

Influence of longitudinal fin arrangement on the melting and solidification inside the triplex tube latent heat thermal storage system

A two-dimensional melting/solidification model of Phase Change Material (PCM) is developed. The present research has studied the novel PCM based Triplex Tube Latent Heat Storage System (TTLHSS). The primary target of this research is to establish the effect of longitudinal fins on the performance of both melting and solidification rate of PCM. Initially, melting and solidification enhancement with four longitudinal fins are studied, and 60% and 46.15% reduction are observed in melting and solidification time. Then, the arrangement of fins inside TTLHSS is studied, and it is found that TTLHSS with three fins in the bottom portion can be more effective for melting enhancement. However, three fins in the bottom portion are not found beneficial for solidification enhancement. Then, instead of straight fins, l-shaped longitudinal fins are studied and found almost similar enhancement in melting as straight fins. At the same time, a 2–5% reduction in solidification time is observed with l-shaped fins. For further improvement, a greater number of fins with small lengths are examined. The fin volume remains the same in this case of eight fins and found good improvement in the melting and solidification processes. In short, three different parameters, fin arrangement, fin shape, and a number of fins are studied in current research. The case with a greater number of fins with reduced length is found maximum effective. The arrangement with eight fins (in which bottom fin length is increased with compensation of reduced side fin length) is found most effective with a 60.77% reduction in combined melting-solidification duration.