Fin Efficiency Research Articles

Parametric Study on Thermal-Hydraulic Characteristics of H-Type Finned Tube Heat Exchangers

In this paper, the thermal-hydraulic characteristics of H-type finned tube banks are numerically investigated on the basis of a more accurate and convenient calculation method of fin efficiency for H-type fins. Experiments are performed to validate the numerical simulations. The variations of the Nusselt number, Euler number, and comprehensive factor with the Reynolds number and seven geometric parameters of H-type finned tube banks are obtained. The results indicate that the Nusselt number is proportional to the Reynolds number, the slit width, the fin thickness, and the longitudinal tube pitch; but, it is inversely proportional to the tube row number, the fin height, and the spanwise tube pitch. As the Reynolds number, the tube row number, the slit width, the fin pitch, and the spanwise tube pitch increase, the Euler number decreases. The factor rises with the increase of the slit width, and there exists an optimal tube row number () at which the factor is the maximum. The correlations of the heat transfer (Nusselt number) and pressure drop (Euler number) of the 10-row H-type finned tube bank, which can nearly be considered to be fully developed, are presented. The numerical results and correlations have good applicability under different fluids and show good agreement with the experimental results and correlations.

Numerical investigation of efficiency of fully wet porous convective-radiative moving radial fin in the presence of shape-dependent hybrid nanofluid

The main focus of the study is a fully wet porous fin of radial profile exposed to convective-radiative heat exchange with the hybrid nanofluid flowing past it with a constant velocity of U. In the analysis, spherical-spherical, spherical-cylindrical, and spherical-platelet shape combinations of two nanoparticles are considered. The mixture model is employed to assess all the thermophysical attributes of the hybrid nanofluid except thermal conductivity and dynamic viscosity, which are estimated by applying the nanoparticle volume fraction-based interpolation method. The fin model with the applied conditions results in an ordinary differential equation which is made dimensionless and then numerically resolved by applying the Runge Kutta Fehlberg (RKF) 4-5th ordered technique. The effect of Peclet number, wet fin parameter, thermogeometric parameter, nanoparticle volume fraction, convective parameter, radiative parameter, exponential index, empirical shape factor and ambient temperature (dimensionless) on the energy field and thermal gradient profiles of the radial fin subjected to shape-dependent hybrid nanofluid flow has been graphically analysed. Furthermore, the thermal fin efficiency has been modelled and its variation with the significant parameters has been examined. One of the major outcomes was that efficiency increases with nanoparticle volume fraction. Further, it is significantly affected by the shape factor of the nanoparticles and achieves the highest value for spherical-platelet combination. The results obtained motivate further study of nanotechnology assisted extended surface technology.

Wet-dry thermohydraulic performance comparison on fin-and-tube geometries

Condensation on the surface of a heat exchanger takes place in several engineering applications, involving important energy consumption and a shift in the thermohydraulic characteristics from those observed under dry conditions. In this study, the condensation rate of six fin-and-tube geometries is numerically determined when saturated air is conducted through these surfaces. The condensation process is enabled by programming a function at the solid–vapor interface on commercial software. A thermohydraulic performance comparison using heat transfer, condensation rate, fin efficiency, Compactness factor, Volume Goodness Factor, and pressure drop is presented to give an insight into the geometry selection. Results show that the geometry increases the heat transfer in the latent heat transfer proportion under constant inner tube surface temperature conditions. Depending on the channel blockage percentage, the water retention on the surface might significantly contribute to the pressure drop. The geometries with better performance under dry conditions show a more significant condensation rate.

Multi-objective optimization of 3D micro-fins using NSGA-II

Because of the great potential for optimization of micro-fin surfaces (< 0.5 mm tall) and the lack of any optimization work encompassing three-dimensional geometries on heat exchanger surfaces, this paper proposes a robust methodology to solve the multi-objective optimization problem with a numerical model and thereby determine the flow physics that characterize the optimal geometries. The micro-fin design variables are considered as micro-fin height, angle, thickness, pitch, length of discontinuity, and number of discontinuities per micro-fin pitch. To reduce computational time, a channel with two-sided periodic domains is presented. A parallelizable numerical model is developed based on Reynolds average Naiver-Stokes equations and a realistic k-ɛ model. The simulation procedure solves convective heat transfer and turbulent flow over micro-fins and solves heat transfer for solid conduction using a constant wall temperature condition to maintain robustness for geometries that do not yield unity fin efficiencies. This study provides a robust methodology to integrate the numerical model into a multi-objective optimization algorithm named non-dominated sorting genetic algorithm II to generate the best trade-off solutions between enhancement of Nusselt number and Fanning friction factor of a micro-fin surface to a smooth surface at two Reynold numbers (Re) of 25,000 and 49,000. This study presents a unique intersection of the drag reduction approach and heat transfer enhancement by finding unique operating geometries. For example, a particular optimal design geometry at Re = 49,000 reduced drag by 8% but was also beneficial to heat transfer increasing by 21% compared to a smooth surface. The best micro-fin surface of this study at Re = 49,000 enhanced the efficiency index by 18% compared to the highest reported efficiency index for micro-fin tubes.

Analytical fin efficiency model for open-cell porous metal fins based on Kelvin cell assumption

Open-cell porous metals are widely used to enhance convective heat transfer of thermal management devices. In this paper, the open-cell porous metal structure was represented by a polyhedron model known as the Kelvin cell, and an analytical model for the efficiency of the porous metal fin attached to an isothermal surface was derived. The forced convective heat transfer coupled with heat conduction through the ligaments of porous metal was analyzed to derive the fin efficiency model. The effects of pore diameter, ligament diameter, and porous metal fin height on the fin efficiency and heat transfer rate of porous metal fins were also investigated. The new analytical fin efficiency model based on the Kelvin cell was compared with the fin efficiency evaluated using computational fluid dynamics analysis results; good agreement was found. The proposed analytical fin efficiency model avoids the numerical calculations required for heat transfer analysis of porous metals used as extended surfaces in many engineering applications such as heat sinks and heat exchangers, and can produce simple but effective results.

Numerical investigation of transient thermal behaviour of fully wet and porous moving semi-spherical fin

A variety of engineering applications demand efficient and adaptable fin structures for the intensification of heat exchange. The semi-spherical fin structures are useful in the field of refrigeration, chemical processing systems, aerospace etc. In this regard, the present article numerically investigates the transient thermal behaviour of a fully wet semi-spherical fin. The study incorporates the Darcy model as the fin is made up of porous material. Further, the fin is exposed to convective-radiative heat exchange and is subject to uniform motion. The heat balance equation has been reduced to get a nonlinear partial differential equation (PDE) which is computed by employing the finite difference method (FDM). The dimensionless terms are grouped together and their influence on the temperature distribution in a semi-spherical fin is studied. Also, the instantaneous heat transfer rate and the transient fin efficiency have been modelled and their variations with relevant parameters have been graphically depicted. And these are found be strong functions of Peclet number, wet porous nature and dimensionless time. As a main outcome the semi-spherical fin efficiency is positively influenced by the Peclet number. Along with the fundamental point of interest the results presented benefit the fin designing purposes.

Steady State Free Convection through some Variable Fin Geometries

Thermal performances on some typical variable geometries were conducted in this work which can be reported into two phases. In the first phase of this work, fins of rectangular, cylindrical, and conical geometries having the same total surface area were studied. It is found that the cylindrical fin is the least efficient and least effective among the three. In the second phase, design modification in the form of grooves is made on cylindrical fins. Cutting grooves on cylindrical fins increase its surface area. The three grooved cylindrical fins are namely- fully grooved cylindrical fins, bottom half grooved cylindrical fins, and top half grooved cylindrical fins. All three grooved fins have the same volume. It was noticed hat, on cutting groove the on fin the quality of convective heat transfer, as well as the effectiveness, improves, but the efficiency degrades. Keywords: Finite Element Method, thermal steady state, fin effectiveness, fin efficiency, free convection

Performance analysis of variable thickness longitudinal fin with functionally graded material in dry and fully wet conditions

PurposeWhen the temperature of an air conditioning unit’s fin surface goes below its dew point temperature, condensation forms on the unit’s surface. As a result, the cooling coil’s performance is compromised. By altering the cross-section and heat conductivity of the fins, the performance of such systems can be improved. This study aims to analyze the thermal performance of longitudinal fins made up of a variable thickness (assuming constant weight) and functionally graded material.Design/methodology/approachDifferent grading parameters are considered for an exponential variation of thermal conductivity. The humidity ratio and the corresponding fin temperatures are assumed to follow a cubic relationship. The Bvp4c solver in MATLAB® is used to solve the differential heat transfer equation resulting from balancing heat transfer in a small segment.FindingsValidation of the methodology is provided by previous research presented in this area. For different combinations of grading parameters, geometry parameters and relative humidity, the normalized temperature distribution along the fin length and fin efficiency contours are plotted, and the results are very promising.Originality/valueWhen compared to the efficiency of an isotropic homogenous rectangular longitudinal fin with optimal geometry and grading parameters, a 17% increase in efficiency under fully wet conditions is measured. When it comes to fin design, these efficiency contour plots are extremely useful.

Thermo-Hydraulic Analysis of Slightly Inclined Finned Channel under Natural Convection

The influence of slight inclination, ‘α’ (i.e., 10°, 15°, and 20°) of the channel comprised of shrouded vertical rectangular non-isothermal fin array has been computationally investigated. Simulations are performed to obtain the convective coefficient of heat transfer for the different dimensionless fin spacing (S*= 0.2, 0.3, 0.5), non-dimensional fin tip to shroud clearances (C*= 0.1, 0.2 and 0.3), Grashof numbers (Gr= 1.08×105, 4.42×105 and 11.5×105), fin lengths (L= 0.25m and 0.5m) and fin heights (H= 0.025m, 0.04m, and 0.055m). Hydrodynamic behavior of the fluid indicates that a significant amount of flow reversal occurs near the entrance of the channel at very low inclination which vanishes with the increase in inclination. Further, at higher length, reverse flow is found to occur only in the clearance zone. An increase in the value of ‘α’ from 10° to 20°, results in enhancement of convective coefficient up to a maximum of 161%. An increase in the value of fin spacing from 0.2 to 0.5 results in the enhancement of the convective heat transfer coefficient. At α= 15° and 20°, the heat transfer is enhanced by 84.1% and 101.6%, respectively, while at α=10°, the same is reduced by 33.3%. At lower fin spacing (S*<0.3) increase in C* tends to reduce the efficiency. Further, the efficiency of the finite conductive fin is found to reduce by almost 8% with an increase in Grashof number.

A Numerical Investigation of Laterally Loaded Steel Fin Pile Foundation in Sand

Pile foundations are often subjected to lateral loadings. By adding steel plates (fins) to the side of the pile, steel fin pile foundations (SFPFs) can improve the lateral load capacity of piles. Existing numerical studies using elastic–perfectly plastic models (e.g., Mohr–Coulomb model) for soil behavior may result in unrealistic load response when modeling soil–pile interaction in dense sand due to the lack of consideration of strain-hardening/softening behavior. In the present study, finite-element analyses were conducted to understand the effect of fin geometry on the lateral load capacity of SFPFs. The prepeak hardening and postpeak softening soil behavior was accounted for by varying soil strength parameters with plastic shear strain based on a modified Mohr–Coulomb model. The developed model was calibrated and validated against well-documented experimental and field tests in the literature. The validated model was subsequently used to conduct a parametric study to understand the effect of fin geometry on the response of SFPFs subjected to lateral loading at the pile head. The behavior of SFPFs at different displacement levels and load levels was studied. The effect of the relative density of soil on the performance of SFPFs was also investigated. Based on the numerical simulation results, the optimal fin width and length values for mobilizing soil resistance were suggested and the underlining mechanisms affecting the efficiency of fins were discussed.

Experimental investigation and multi-objective optimization of ice thermal storage device with multichannel flat tube

A novel plate-shaped ice thermal storage device is constructed with multichannel flat tube. The different temperatures and flow rates of heat transfer fluid (HTF) on the variations in the internal temperature and the store/release power are experimentally investigated. Results indicate that the reduction in temperature of cold HTF from −3 °C to −4 °C is notably to shorten the super-cooling process, reduced the freezing time by 35.04% and increased the average storage power by 24.9%, its effect gradually weaken with decrease in temperature. Furthermore, numerical simulation and response surface method are adopted to gain predictive models of four response indices for estimating the behavior of the device in terms of five different design parameters, and the interaction effects of design parameters on responses are investigated. Finally, the multi-objective joint optimization is developed based on an efficient storage device with goals of excellent thermal performance and thermodynamic perfection, while its manufacturing cost is low. The optimization results recommend the fin height, number and thickness are 30.1 mm, 10, and 0.5 mm, respectively, temperature and flow rate of cold HTF are −4.01 °C and 0.2 m3/h, respectively, to maximize ice formation rate, exergy efficiency, and fin efficiency and minimize the metal consumption.

CFD analysis andheat transfer characteristics of printed circuit heat exchanger

This paper aims to investigate the cubical fins and the thermal-hydraulic characteristics in a Printed Circuit Heat Exchanger (PCHE). The working fluid is considered a supercritical LNG. The outcomes show that the thermal-hydraulic performance is enhanced using the cubical fins comparing it to the straight channel. The maximum and minimum difference of N_u/E_u between the cubical fins channel and the straight channel were 71.7 % and 64.8 % respectively. It is noticed that the pressure drop and Heat Transfer coefficient are increasedsimultaneously with increasing the mass flux.Using Ansys Fluent 15.0, numerical optimization isperformed to examine and analyzethe influence of the sparser staggered arrangement. The computed results show that this type of arrangement improves the thermal-hydraulic efficiency of the cubical fins in a PCHE. A comparison between the straight fins arrangement and the staggered fins arrangement is reported.It has been noticed that the velocity of the LNG flow in the cubical fins channel is increased along the length of the PCHE,and decreased byincreasing the vertical separationL_V. The side effect of the vertical separation L_V on the PCHE’s efficiency was more evident than that of the staggered arrangementL_S. Finally, afeasibility study is performed to inspect the power consumption of the new design.

Numerical investigation on the performance and environmental aspect of roll bond photovoltaic thermal unit condenser incorporating fins on the absorber

To contribute to the sustainable energy production, the current paper proposed and numerically solved a model of roll bond photovoltaic thermal (RB-PVT) condenser with fins by using ANSYS Sotfware18. First, the effect of four different fin shapes and number was analyzed to determine the fin shape and number best suit for the study. Last, on the basis of RB-PVT unit condenser with 3 fins of straight rectangular shape, a sensitivity was conducted considering fin length and width in the range of 0.2–0.7 mm, and 195⁰-255⁰ and 345⁰-285⁰ for the position of fin on left and right side of the fixed one, respectively. The highest average values in heat dissipation flux, pressure drop and overall fin efficiency were respectively obtained to be 1792.693 W/m2, 86.471 kPa and 79.767% when varying fin(s) width and angle. In addition, the average refrigeration coefficient of performance (COP) of 5.079 and which is higher than that of previous studies was achieved. Meanwhile, the maximum average of 258.07 united state dollars (USD) would be saved to capture and store 8.603 tons of emissions (CO2), after every 5 years. RB-PVT unit with fins not only can improve the system performance but also can help achieving a clean environment.

A Novel Learning Approach for Different Profile Shapes of Convecting–Radiating Fins Based on Shifted Gegenbauer LSSVM

The purpose of this paper is to introduce a novel learning approach to solve the heat transfer problem from convecting-radiating fin model. This model is a nonlinear differential equation in which different boundary conditions cause different profile shapes including rectangular, triangular, trapezoidal and concave parabolic. We consider one-dimensional, steady conduction in the fin and neglect radiative exchange between adjacent fins and between the fin and its primary surface. Our method is based on using the quasilinearization method to linearize the nonlinear models and applying shifted Gegenbauer polynomials as new kernel in least squares support vector machines method. The results of fin efficiency and heat transfer rate of the problems which compared with available previous results indicate better efficiency and accuracy of the proposed approach.

Thermal Management Effectiveness and Efficiency of a Fin Surrounded by a Phase Change Material (PCM)

Extended surfaces, also known as fins are used commonly for heat transfer enhancement in energy storage and thermal management problems. A fin may improve the rate of heat transfer by offering greater surface area. While the performance of a fin in a single-phase ambient such as air is well-understood, relatively lesser work is available on fin performance, including parameters such as fin effectiveness and efficiency, when embedded in a phase change material (PCM). A key theoretical challenge in such analysis is the transient nature of the phase change problem that must be combined with transient diffusion and phase change in the fin. This work presents theoretical analysis of phase change heat transfer between a base wall and a PCM in presence of a fin. The processes of thermal diffusion in the fin, thermal diffusion and phase change in the PCM are combined using perturbation analysis of a problem with time-dependent boundary condition. Results are found to be in good agreement with numerical simulations. Expressions for fin effectiveness and fin efficiency as functions of time are derived. The impact of various problem parameters such as fin geometry, material and the Stefan number on fin performance is analyzed. Expressions for efficiency and effectiveness of an array of equally-spaced fins are also derived. It is shown that while a fin provides additional surface area for enhanced melting of the PCM, transient diffusion in the fin may limit the benefit of the fin, especially at small times. On the other hand, fin performance at large times is limited by slow phase change in the PCM. Results presented here improve the fundamental understanding of PCM and fin based thermal management. Expressions for fin effectiveness and efficiency derived in this work offer useful tools for designing and improving the performance of practical fin and PCM based thermal management systems.

Strouhal Number Measurement for Novel Biomimetic Folding Fins Using an Image Processing Method

The aim of the paper is to present the parameters of new biomimetic folding fins measured using image processing. Tests were carried out for different types of folding biomimetic fins and compared to the most popular fins on the market. A noninvasive image processing method was used to estimate divers’ velocities in the vertical and horizontal directions and the frequency and the amplitude of the fin trailing edge, and as a result, the Strouhal number was calculated. These tests are a continuation of studies conducted in a water tunnel, where fin efficiency was measured as the ratio of generated thrust to electrical energy consumption, taking into account the mechanical efficiency of the leg manipulator as well as the water velocity. The Strouhal number helped us to analyse the parameters of the fin–diver–water system taking into account the properties of the fins, in particular the newly designed biomimetic folding fins.

Exploration of Temperature Distribution through a Longitudinal Rectangular Fin with Linear and Exponential Temperature-Dependent Thermal Conductivity Using DTM-Pade Approximant

The present study elaborates on the thermal distribution and efficiency of a longitudinal rectangular fin with exponentially varying temperature-dependent thermal conductivity and heat transfer coefficient concerning internal heat generation. Also, the thermal distribution of a fin is comparatively studied for both exponentially varying temperature-dependent thermal conductivity and linearly varying temperature-dependent thermal conductivity. Further, the thermal distribution of a longitudinal fin is examined by using ANSYS software with different fin materials. Many physical mechanisms can be explained by ordinary differential equations (ODEs) with symmetrical behavior, the significance of which varies based on the perspective. The governing equation of the considered problem is reduced to a non-linear ODE with the assistance of dimensionless terms. The resultant equation is solved analytically using the DTM-Pade approximant and is also solved numerically using Runge-Kutta Fehlberg’s fourth-fifth (RKF-45) order method. The features of dimensionless parameters influencing the fin efficiency and temperature profile are discussed through graphical representation for exponentially and linearly varying temperature-dependent thermal conductivity. This study ensures that the temperature field enhances for the higher magnitude of thermal conductivity parameter, whereas it diminishes for diverse values of the thermo-geometric parameter. Also, greater values of heat generation and heat transfer parameters enhance the temperature profile. Highlight: Thermal distribution through a rectangular profiled straight fin is examined. Linear and non-linear thermal properties are considered. The combined impact of conduction, convection, and internal heat generation is taken for modeling the energy equation of the fin. Thermal simulation is performed for Aluminum Alloy 6061 (AA 6061) and Cast Iron using ANSYS.

Results for the heat transfer of a fin with exponential-law temperature-dependent thermal conductivity and power-law temperature-dependent heat transfer coefficients

Abstract In this article, thermal behavior analysis of nonlinear fin problem with power-law heat transfer coefficient is studied to determine temperature distribution. This new supposition for the thermal conductivity, exponential-law temperature dependent, makes it to be nonlinear that is a general case in some sense. It is shown that the governing fin equation, that is, a nonlinear second-order differential equation, is exactly solvable with proper boundary conditions. To this purpose, the order of differential equation is reduced and then is converted into a total differential equation by multiplying a proper integration operant. An exact analytical solution is given to advance physical meaning, and the existence of unique solution for some specific values of the parameters of the model is demonstrated. The results are shown graphically. It is observed that fin efficiency is decreasing with respect to the power-law mode for heat transfer.

Variable transform-based semi-analytical methods for solving convective straight fins problem with temperature-dependent thermal conductivity

This paper presents effective algorithms to approximate solutions of nonlinear fin problem with temperature dependent thermal conductivity and heat transfer coefficient. We propose new approximate semi-analytical techniques, namely the Laplace homotopy variable transform method (LHVTM) and the differential variable transform method (DVTM), to obtain expressions for generalized convective straight fins problem. The linear dependence of thermal conductivity on temperature is considered, and fin efficiency and effectiveness are evaluated. We further analyzed the effects of the model parameters on surface heat loss, and the results are presented in tables and with graphical illustrations.

RETRACTED: Thermal analysis of an annular fin under multi-boiling heat transfer coefficient using differential transform method with Pade approximant (DTM-Pade)

The convective heat transfer between the object and surrounding environment can be improved by increasing the surface area. This can be done by mounting an annular/radial fin to a cylindrical surface and thus enormous heat is transferred by the annular fin. Motivated by this fact, the temperature distribution and thermal stresses of an annular fin with internal heat generation under multi-boiling heat transfer are examined using the differential transform method (DTM)-Pade approximant. The governing equation and corresponding boundary conditions are transformed into a highly nonlinear ordinary differential equation (ODE) by introducing suitable non-dimensional terms. The resultant transformed ODE is solved analytically using DTM-Pade approximant. The results achieved from DTM-Pade and Runge-Kutta Fehlberg fourth-fifth (RKF-45) technique are compared for numerical validation and are found to be close to each other. The performance of the fin and aspects of dimensionless temperature profile has been elucidated graphically with the impact of dimensionless parameters. Furthermore, the results of this scrutiny manifest that the temperature profile of the fin increases with the impact of thermal conductivity parameter and heat generation parameter whereas it decreases for thermo-geometric parameter. Fin efficiency varies significantly with the impact of prescribed parameters under multi boiling heat transfer cases. The radial and tangential stress distribution are more in the case of radiation heat transfer compared to other cases.