Longitudinal Fins Research Articles

Comparison of solidification performance enhancement strategies for a triplex-tube thermal energy storage system

• The comprehensive application of fins and multistage inner tubes in TTES system is studied. • The difficult solidification zone of the system is found by dynamic temperature response. • The optimum position of multistage inner tubes and fins is explored by response surface method. • The ternary mixed molten salts of Li 2 CO 3 - K 2 CO 3 - Na 2 CO 3 ( 32 - 35 - 33 w t % ) is used as PCM. To enhance the solidification performance of phase change material in a triplex-tube thermal energy storage system, a two-dimensional model is established in this paper. The solidification performance of the system is studied by numerical simulation, and the method of adding multistage inner tubes and longitudinal fins is proposed to strengthen the solidification. Firstly, the size of eight fins in the initial model is studied to select the most suitable model, and the most difficult solidification area of the system is found through the study of dynamic temperature response at the position points. Then, multiple inner tubes and T-shaped fins are added to the area and a response surface method is used to optimize the design. The solidification performance of the system can be improved by 50.19% when the diameter of the multistage tube is 4 mm in the best position. The results show that enhancement of solidification property of phase change material by multistage inner tube is better than that by fin. The effects of physical parameters such as multistage inner tubes diameter, cold fluid temperature, and fin structure on solidification performance are also discussed. Finally, the effect of natural convection on the solidification process of phase change material is analyzed.

Effect of fin number on the melting phase change in a horizontal finned shell-and-tube thermal energy storage unit

This paper studies the enhanced heat transfer of adding longitudinal fins in a horizontal shell-and-tube heat storage unit. A two-dimensional numerical model is established and validated through comparing with experimental data in literature. Under the same ratio of fin volume to phase change materials (PCMs), the melting thermal performance is optimized by changing the fin thickness, interval and the number. Results demonstrate that adding longitudinal fins is a simple and effective method to enhance the thermal energy storage efficiency. The number of fins greatly affects the complete melting time, and the maximum time difference caused by the number of fins is as high as 72.85% under the same phase change material (PCM) filling mass. At the same time, increasing the number of fins will weaken the local natural convection. In this paper, the optimal number of fins in the limited research range is given, and the effectiveness of longitudinal fins in improving melting speed is quantified, which has certain practical significance for the engineering application research of phase change energy storage. • Optimal number of fins is given in a horizontal finned thermal energy storage unit. • Melting time can maximally be saved as high as 72.85% by increasing fin number. • Blindly increasing fin numbers cannot further improve the energy storage speed. • Heat conduction plays a leading role in paraffin melting process for a finned TES application.

Effects of stretching/shrinking on the thermal performance of a fully wetted convective-radiative longitudinal fin of exponential profile

Effects of stretching/shrinking on the thermal performance of a fully wetted convective-radiative longitudinal fin of exponential profile

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.

Parametric investigation of a rectangular microchannel utilizing the internal longitudinal fins to enhance its hydraulic and thermal characteristics

A comprehensive study on the hydraulic and thermal behaviors of a microchannel with internal longitudinal fins under an H2 boundary condition has been done, and it has been tried to improve its performance via geometric optimization. The conjugate method was utilized to simulate the heat transfer in both fluid and solid domains through the finite volume method, and the Figure of Merit (FOM) was used to compare the thermal and hydraulic performances. The optimization process has multiple steps, and in each step, the impact of the geometric parameters of the internal fins on convective heat transfer coefficient, pressure drop, and FOM was investigated. During the optimization process, the optimal value of the area fraction of fins, its corresponding aspect ratio, and the number of fins have been investigated step by step, and they have been determined as 26%, 0.5, and 16, respectively. At the end of this study, the performance of the microchannel improves by more than 50%. Also, the hydraulic and thermal responses of the microchannel to Reynolds number were studied, and it was proved that the total hydro-thermal performance of the system decreases by increasing the Reynolds number.

Heat transfer augmentation of triplex type latent heat thermal energy storage using combined eccentricity and longitudinal fin

The universe has shifted its focus from non-renewable to renewable energy sources from the last decade. The limited availability of fossil fuels and pollution is the reason behind the utilization of renewable sources. A major renewable energy source, solar energy, requires efficient thermal energy storage due to its intermittent nature. Phase change material (PCM) can store a large amount of heat by changing its phases. However, the low thermal conductivity of PCM makes its usage very limited. Hence, PCM's heat transfer augmentation technique using eccentricity and fin is studied in the present research. First of all, positive (lower displacement of the inner tube) and negative eccentricity (upper displacement of the inner tube) are studied in triplex type latent heat thermal energy storage (TTLHTES). Among the eccentricities of -15 mm to +15 mm, the eccentricity of +10 mm is found most effective in melting with a 27.63% reduction in melting time, while -3 mm eccentricity is found most effective in solidification with a 12.82% reduction in solidification time. The combination of fins with eccentricity is examined for melting and solidification enhancement. The combination of fin and eccentricity efficiently reduces melting time, with a maximum decrement of 67.37% with +3 mm eccentric TTLHTES with four fins. However, the only fin without any eccentricity is found more effective in solidification enhancement. The solidification time is reduced maximum by 46.15% using four longitudinal fins and no eccentricity. It can be concluded that fin and eccentricity must be coupled when melting time is required to enhance. However, only fin must be utilized when solidification is more critical.

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.

Experimental Investigation of the Heat Transfer between Finned Tubes and a Bubbling Fluidized Bed with Horizontal Sand Mass Flow

The sandTES technology utilizes a fluidized bed counter current heat exchanger for thermal energy storage applications. Its main feature is an imposed horizontal flow of sand (SiO2) particles fluidized by a vertical air flow across a heat exchanger consisting of several horizontal rows of tubes. Past international research on heat transfer in dense fluidized beds has focused on stationary (stirred tank) systems, and there is little to no information available on the impact of longitudinal or helical fins. Previous pilot plant scale experiments at TU Wien led to the conclusion that the currently available correlations for predicting the heat transfer coefficient between the tube surface and the surrounding fluidized bed are insufficient for the horizontal sand flow imposed by the sandTES technology. Therefore, several smaller test rigs were designed in this study to investigate the influence of different tube arrangements and flow conditions on the external convective heat transfer coefficient and possible improvements by using finned tubes. It could be shown that helically finned tubes in a transversal arrangement, where the horizontal sand flow is perpendicular to the tube axes, allows an increase in the heat transfer coefficient per tube length (i.e., the virtual heat transfer coefficient) by a factor of 3.5 to about 1250 W/m2K at ambient temperature. Based on the literature, this heat transfer coefficient is expected to increase at higher temperatures. The new design criteria allow the design of compact, low-cost heat exchangers for thermal energy storage applications, in particular electro-thermal energy storage.

Effect of internal heat source and non-independent thermal properties on a convective–radiative longitudinal fin

In the current research, the mixed convection and radiation heat transfer for a longitudinal fin with a constant velocity and considering heat source is analytically investigated. Two effective analytical methods called Method of Moments (MOM) and Least Square Method (LSM) will be employed to analyze the problem. However, using weighted residual methods creates an economical way in solution time and there is no need for grid generation difficulties. After attaining the dimensionless governing equations and solving them by MOM and LSM, the precision of results is tested by comparing with numerical solutions, and a reasonable accuracy is demonstrated. It can be drawn from the results that increasing the M, NR and Pe causes a decrease in temperature profile, but with rise of β the dimensionless temperature enhances.

Analytical solution for temperature equation of a fin problem with variable temperature-dependent thermal properties: Application of LSM and DTM-Pade approximant

Temperature variation through a longitudinal fin with linear and nonlinear temperature-dependent thermal conductivities and heat transfer coefficient, subject to radiative heat flux and convective heat transport is explained in the present examination. For the radiative heat flux, the Rosseland approximation is incorporated and convection mode of energy transmission is accounted on the fin's surface. The associated physical problem is developed in such a manner that the steady-state heat transmission problem is governed with the help of dimensionless variables signified by a second order differential equation (ODE). To solve this equation, an analytical approach, DTM-Pade, and the LSM are implemented. Moreover, the consequence of a few non-dimensional factors on the temperature field are depicted graphically. The investigation's main findings illustrate that a significant decline in the thermal field is caused by an increment in the convection and the radiation mechanism. The internal development of heat affects the thermal distribution in the fin.

Study on Efficiency of Fully Wet Porous Trapezoidal Fin Structures in the Presence of Convection and Radiation

The thermal behaviour of fully wet porous trapezoidal profiled longitudinal fin structures in the presence of natural convection and radiation has been scrutinized in the present analysis. The rectangular and trapezoidal profiles have been comparatively analysed. The Darcy’s law has been incorporated to study the solid-fluid interactions. Further, the internal heat generation has been assumed to be a linear function of temperature. The obtained non-linear second order ordinary differential equation has been reduced and evaluated numerically. The impact of fully wet condition, porous nature, internal heat generation and other relevant parameters on the thermal profile and efficiency of trapezoidal and rectangular fin profiles has been interpreted graphically and discussed. It has been derived that the rectangular fin profile is more efficient than the trapezoidal profile.

Increment of heat transfer by graphene-oxide and molybdenum-disulfide nanoparticles in ethylene glycol solution as working nanofluid in penetrable moveable longitudinal fin

The main interest of the current research study is, on the one hand, to increase heat transfer of the base and mixture fluids by using hybrid nanoparticles. By considering two types of boundary conditions such as insulated and convective tips, to explore numerically and analytically the simultaneous impacts of the thermal radiative and free convective flow of hybrid nanofluid via a moving porous longitudinal fin. This investigation employs Darcy’s model and the mixture base fluid H2O (50%)–C2H6O2 (50%). The governing equations have been solved by utilizing Runge–Kutta–Fehlberg 4th–5th order technique (RKFT45) with shooting-scheme and analytically via Duan–Rach Approach (DRA). It is found that the nondimensional temperature is a decreasing function of a wet porous number and convective parameter for both insulated and convective tips, and as an increasing function of ambient temperature , Peclet number Pe and power index n. It is also found that the thermal profile presents a decrease for all considered shape factors in the cases of insulated and convective tips boundary conditions. Computational results and those obtainable in the previous works have been used to verify and strengthen the results gained by the analytical DRA technique.

Heat Transfer Enhancement of Latent Heat Storage Using Novel Quadruple Helical Fins

A novel fin configuration which is of quadruple helical geometry is proposed to augment the heat transfer performance of latent heat thermal energy storage systems. The thermal characteristics of paraffin wax under the influence of quadruple helical fins and longitudinal fins are analyzed through three-dimensional numerical formulation employing enthalpy-porosity approach. The impact of these two fin geometries on the natural convection during melting is also investigated. The numerical results are validated against experimental results. The quadruple helical fins are found to be superior to conventional longitudinal fins in accelerating phase change rates as they provide higher heat transfer surface despite occupying same volume. Hence, the melting time was reduced by 85% with quadruple helical fins as compared to system without fins and longitudinal fins could exhibit 80% reduction in melting time. The reduction in solidification time is found to be 68% (quadruple fins) and 63% (longitudinal fins). Further, quadruple fin arrangement can generate vortex flow in liquid phase change material during melting and hence, enhanced natural convection is observed when compared to longitudinal fin system. The role of heat transfer fluid in altering the phase change rate is pronounced only in the finned systems.

Effect of electromagnetic field on the thermal performance of longitudinal trapezoidal porous fin using DTM–Pade approximant

AbstractThe heat transfer and thermal distribution through porous fins have gotten a lot of attention in recent years due to their extensive applications in the manufacturing and engineering field. In porous fins, the impact of magnetic field aids in improved heat transfer enhancement. Also, the combination of an electric effect and a magnetic field considerably enhances heat transfer. In this direction, the thermal distribution through a convective–radiative longitudinal trapezoidal porous fin with the impact of an internal heat source and an electromagnetic field is discussed in the present analysis. The governing heat equation is nondimensionalized with nondimensional terms, and the transformed nonlinear ordinary differential equation is solved analytically using the DTM–Pade approximant algorithm. Furthermore, the graphical discussion is presented to explore the impact of various nondimensional parameters, such as convection‐conduction parameter, fin taper ratio, thermomagnetic field, radiation–conduction parameter, internal heat generation parameter, and thermoelectrical field on the temperature gradient of the fin. The investigation's key findings disclose that as the magnitude of the convection–conduction parameter, fin taper ratio, and radiation–conduction parameter increase, the thermal distribution through the fin reduces. The thermal distribution inside the fin increases for the heat‐generating parameter, thermoelectric, and thermomagnetic fields.

Thermal performance of a radial heat sink with longitudinal wavy fins for electronic cooling applications under natural convection

Thermal performance of a radial heat sink with longitudinal wavy fins for electronic cooling applications under natural convection

Influence of Fins Number and Frosting on Heat Transfer through Longitudinal Finned Tubes of LNG Ambient Air Vaporizers

The use of cryogenic liquefied gasses in industry is constantly increasing both for process purposes and for power supply needs. The liquefied natural gas (LNG) is stored at cryogenic temperature and its immediate use in gaseous form requires its evaporation. The heat needed to cause a phase change is usually delivered by means of vaporizers. This paper presents a numerical analysis of the influence of the fins number and frost accumulated within the fins surface on the heat transferred through the aluminum finned tubes of LNG ambient air vaporizers. The calculations were carried out applying finite element thermal analysis within Ansys software as well as using an analytical approach. As a result, the heat rate per unit length of the finned tube was obtained. The results were compared for different numbers of longitudinal fins both without frost and for total frosting of the tubes.

Experimental analysis of the heat transfer rate of phase change material inside a horizontal cylindrical latent heat energy storage system

Latent heat thermal energy storage system can help in the smooth operation of energy supply and demand. In the present work, experimental study was performed to analyze the heat transfer rate of phase change material inside an annulus. A copper pipe (centrally loaded) runs the length of a cylindrical container during both discharging and charging modes. The overall heat transfer rate is enhanced during phase change process by adding longitudinal fins with the copper pipe. These longitudinal fins were tilted at an angle of 120⁰. Paraffin wax is used as phase change material. The main objective of the experiment is to analyze the heat transfer rate during the solidification and liquefaction of PCM. Also, the effect of mass flow rate and inlet temperature of heat transfer fluid was analyzed. Conduction was found to be the primary heat transfer mechanism during the initial stages of charging. Once the PCM get liquefied inside the system, natural convection gets dominated. During the solidification of PCM conduction heat transfer get dominated. Also, it was observed that melting duration is strongly affected by the inlet temperature of HTF while the flow rate slightly affects the melting duration.

Analysis of Longitudinal Finned Pipes in Cross-Flow Heat Exchanger

In this case, the recovery of excess heat in the steel-making process becomes challenging to save energy effectively and efficiently. One way to help the process of heat recovery in the steel-making process is with a heat exchanger. This heat exchanger maximizes the production process work. However, in the application, the heat exchanger developed to date can still work optimally. Based on the literature study that has been done previously for the design of the heat exchanger, in this study, the addition of four longitudinal fins variations with the cross-flow flow was carried out. This research compares the heat exchanger performance finned pipes with pipes without fins design, where liquid and airflow rates are varied. This study evaluated whether the longitudinal fins configuration and the fluid flow rate affect the cross-flow heat exchanger performance. The results show that fins addition on the copper pipes increases the value of Nusselt number 2.56% in liquid fluid and 16.57% in air fluid and increases the NTU value of its effectiveness by 24.77%.

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.

Analytical and numerical solution of the longitudinal porous fin with multiple power‐law‐dependent thermal properties and magnetic effects

AbstractThe present study is concentrated on the application of electric and magnetic fields on the longitudinal porous fin with power‐law‐dependent heat transfer coefficient, surface emissivity, and heat generation. The porosity parameter controls the amount of empty spaces or voids in the porous fin and its practical value lies in the range . In industrial application, the heat transfer coefficient is governed by a power law and its specific value defines a certain heat transfer process. The heat generation and surface emissivity of the longitudinal porous fin are assumed to be varied according to the power law and the whole fin is under the influence of an external electric field. The resulting nonlinear equation is solved by the classical Adimian decomposition method (ADM) and the obtained solutions are verified further by the finite difference method (FDM). It has been found that both ADM and FDM are in good agreement for lower values of thermophysical parameters. The effects of power index of heat generation, surface emissivity, and heat transfer coefficient parameter on the temperature distribution, heat flux, and efficiency are analyzed at different values of the porosity parameter comprehensively.