Rectangular Fins Research Articles

An experimental and numerical study of forced convection heat transfer from rectangular fins at low Reynolds numbers

This paper presents an experimental and numerical study of forced convection heat transfer from straight rectangular fins on a horizontal surface at low Reynolds numbers ranging from 2600 to 6800. Heat transfer for a fixed number of fins, fin spacing, and length was measured in a wind tunnel for varying inlet air velocity and heat input. Three-dimensional conjugate heat transfer simulations were also conducted to characterize important features of heat transfer and flow of the fin array and the effects of fin channel length on heat transfer. A maximum relative error of about 4.28% was found between the experimental and the numerical results for the average Nusselt number. The experimental results showed that forced convection heat transfer is characterized by an approximately linear relationship between the Nusselt and Reynolds numbers, which also agreed reasonably well with the available correlations for fully developed turbulent convective heat transfer for tubes with uniform heat flux. Further investigations of the effects of fin geometry were made numerically. Shorter fin channels, where the flow is thermally and hydrodynamically developing, were more effective in heat transfer than longer ones, where the flow approaches or reaches full development. It is shown that heat transfer rate per channel decreases linearly with the increase in channel length, but remains approximately constant with the increase in number of fins. It is also shown that the contributions of natural convection and radiation were negligible for the specific fin design and the range of inlet flow conditions and maximum fin temperature investigated here.

Intensification of turbulent heat transfer in a circular tube by inserting different configuration of finned converging-diverging nozzles turbulators

In this paper, an experimental study has been conducted to show the influence of insertion converge-diverge conical turbulators fitted with rectangular fins inside a circular test tube on Nusselt number, the friction and the overall performance. The air is utilized as working fluid for Reynolds number varied 10000 to 50000. In this investigation, two improvement devices of turbulent heat transfer are utilized. One is the nozzle conical used as turbulators and fixed in the circular tube with three different values of pitch ratio (P.R=1, 1.5 and 2) and the another is rectangular fins placed at the inner surface of the conical turbulators. The conical turbulators fitted with rectangular fins are tested at pitch ratio P.R=1.0 with three different area ratios of the rectangular fins Ar=0.064, 0.106 and 0.149. The experimental results appeared that the heat transfers by using combined the conical nozzle turbulators and the rectangular fins is enhanced by about 234 % for the largest area ratio (Ar =0.149). Also, the optimal thermal performance is obtained to be larger as compared with plain tube case and the conical turbulators alone.

Effect of heat sink design on the thermal characteristic in computational fluid dynamics analysis

The thermal management in the electronic device or system using the heat sink is important to ensure the device or system operating under the allowable temperature. The present study aims to investigate the thermal characteristic (i.e., temperature distribution) of the various heat sink designs via computational fluid dynamics (CFD) analysis. The electronic cooling process of the heat sink is carried out via CFD software. The temperature distribution of the various heat sink designs (i.e., plate fin, circular pin fin and rectangular fin) was analyzed and compared. The CFD analysis revealed the plate fin heat sink has lowest temperature distribution on the fin region. High temperature distribution was observed on the pin fin heat sink. The non-uniform temperature distribution was attributed by the direction of inlet airflow, whereas the low temperature was found in the region that close to the inlet airflow. Thus, the research findings indicated the design of heat sink significantly affects the temperature distribution during the electronic cooling process.

Temperature Distribution in Porous Fins, Subjected to Convection and Radiation, Obtained from the Minimization of a Convex Functional

This work proposes a convex functional endowed with a minimum, which occurs for the solution of the thermal radiation and natural convection heat transfer problem in a rectangular profile porous fin with a fluid flowing through it. The minimum principle ensures the (mathematically demonstrated) uniqueness of the solution and allows the problem simulation by employing a minimization procedure. Darcy’s law with the Oberbeck–Boussinesq approximation simplifies the momentum equation. The energy equation assumes thermal equilibrium between the porous matrix and fluid, allowing comparisons with previous authors’ models, which accounts for the effects of a porosity parameter, a radiation parameter, and a temperature ratio on the temperature. Results for very long fin and finite-length fin with insulated tip were successfully compared with previous works. Closed-form exact solutions for two limiting cases (no convection and no thermal radiation) are also presented.

Comparative study on the thermal-hydraulic performance of a shell and plate particle-SCO2 moving packed bed heat exchanger with various channel configurations

This article proposes a predictive static model to evaluate the thermal-hydraulic performance of a shell and plate particle-SCO2 moving packed bed heat exchanger, with consideration of pressure drop, radiation and property variations. The results reveal that convection resistance on the SCO2 straight channel side occupies a large part of total thermal resistance in most design and off-design cases. A three-dimensional model inheriting conclusions from the static model is raised, which demonstrates that extremely short entrance region in the x-y plane hinders the overall heat transfer behavior of the SCO2 straight channel. Deservedly, suppressions of the development of thermal layers in the y direction will contribute to improving the thermal-hydraulic performance of the shell and plate particle-SCO2 moving packed bed heat exchanger. Four different fin configurations on SCO2 channel side are presented, analyzed and compared via the static model at the design-point case. Offset rectangular fins configuration behaves the best heat transfer enhancement in total heat transfer rate and overall heat transfer coefficient when compared with the original channel, followed by zigzag fins configuration, offset airfoil fins configuration and s-shaped fins configuration. Zigzag fins-modified channel expresses the worst hydraulic behavior, of which the pressure drop is nearly four times that of original straight channel. The pressure drop of channel with s-shaped fins nearly equals to that of the unmodified channel. Introduction of fins on SCO2 channel side reduces the ratio of convection resistance as a result of apparently increased SCO2 convection coefficients.

ASSOCIATED EFFECT OF PERFORATION POSITION AND DIAMETER ON THERMAL PERFORMANCE OF PLANE FIN UNDER NATURAL CONVECTION ENVIRONMENT

The fin perforation represents an efficient way to reduce fins weight and enhance its thermal performance. In this study, rectangular plane fins were designed and fabricated aiming to experimentally investigate the effect of the perforation, perforations position and diameter on the solid fins thermal performance under natural convection heat transfer conditions. The experiments were conducted at a wide range of the supplied heat fluxes, and also covered three perforations positions (bottom, middle, top) and perforations diameters (3, 5, 7) mm. At all the used diameters, results showed that the middle position for perforations performed the best in terms of the Nusselt number and mean surface temperature. The maximum Nusselt number and mean surface temperature were 662.08 and 71.95 oC respectively when the heat flux was 4181.82 W/m2, and the perforation diameter was 3.0 mm. The thermal performance of the top-perforated fins was slightly smaller than that of the middle-perforated fins. Besides, the bottom perforated fins demonstrated the worst thermal performance in terms of Nusselt number and the mean surface temperature. Regarding the effect of the perforation diameter, the 3.0 mm showed superior thermal performance compared with 5.0 mm, and 7.0 mm regardless of the perforation’s positions.

Enhancement of the Thermal Performance Characteristics of an Electrical Power Transformer

A 3D numerical simulation was conducted to test the effects of the geometrical and operational parameters on the cooling performance of a three-phase electrical distribution transformer (250 kVA oil natural air natural (ONAN)). The geometric parameters include the shape of the transformer (rectangular, circular, and hexagonal), fins shape (rectangular, semicircular, and trapezoidal) as well it arrangement (asymmetric fin heights and perforated fins). Both of oil temperature and thermal load have been used as boundary conditions. In order to verify the reliability of the numerical model, comparison between numerical results and experimental finding has been done. The results have indicated that the circular and hexagonal shapes reduced the average oil temperature by 3.4% and 4.7%, respectively, compared to the traditional transformer shape (rectangular). Furthermore, the lowest average oil temperature was observed for the trapezoidal fin, followed by the rectangular and semicircular fins. Additionally, it has been noticed that the asymmetric fin heights of the trapezoidal and perforated trapezoidal fins been contributed to the improvement of the cooling performance of the transformer. Furthermore, the best thermal performance was obtained with the trapezoidal perforated fin to compared other arrangement of fins. Finally, the highest reduction in oil has been obtained by the use of hexagonal transformer with a perforated trapezoidal fin approximately by 12% compared to traditional rectangular transformer. Hence, it can be concluded that the shape of the transformer and fins play an important role in thermal performance of such systems.

Enhancement of the Thermal Performance Characteristics of an Electrical Power Transformer

A 3D numerical simulation was conducted to test the effects of the geometrical and operational parameters on the cooling performance of a three-phase electrical distribution transformer (250 kVA oil natural air natural (ONAN)). The geometric parameters include the shape of the transformer (rectangular, circular, and hexagonal), fins shape (rectangular, semicircular, and trapezoidal) as well it arrangement (asymmetric fin heights and perforated fins). Both of oil temperature and thermal load have been used as boundary conditions. In order to verify the reliability of the numerical model, comparison between numerical results and experimental finding has been done. The results have indicated that the circular and hexagonal shapes reduced the average oil temperature by 3.4% and 4.7%, respectively, compared to the traditional transformer shape (rectangular). Furthermore, the lowest average oil temperature was observed for the trapezoidal fin, followed by the rectangular and semicircular fins. Additionally, it has been noticed that the asymmetric fin heights of the trapezoidal and perforated trapezoidal fins been contributed to the improvement of the cooling performance of the transformer. Furthermore, the best thermal performance was obtained with the trapezoidal perforated fin to compared other arrangement of fins. Finally, the highest reduction in oil has been obtained by the use of hexagonal transformer with a perforated trapezoidal fin approximately by 12% compared to traditional rectangular transformer. Hence, it can be concluded that the shape of the transformer and fins play an important role in thermal performance of such systems.

A Numerical and Experimental Study of a Novel Heat Sink Design for Natural Convection Cooling of LED Grow Lights

Light-emitting diode (LED) grow lights are increasingly used in large-scale indoor farming to provide controlled light intensity and spectrum to maximize photosynthesis at various growth stages of plants. As well as converting electricity into light, the LED chips generate heat, so the boards must be properly cooled to maintain the high efficiency and reliability of the LED chips. Currently, LED grow lights are cooled by forced convection air cooling, the fans of which are often the points of failure and also consumers of a significant amount of power. Natural convection cooling is promising as it does not require any moving parts, but one major design challenge is to improve its relatively low heat transfer rate. This paper presents a novel heat sink design for natural convection cooling of LED grow lights. The new design consists of a large rectangular fin array with openings in the base transverse to the fins to increase air flow, and hence the heat transfer. Numerical simulations and experimental testing of a prototype LED grow light with the new heat sink showed that openings achieved their intended purpose. It was found that the new heat sink can transfer the necessary heat flux within the safe operating temperature range of LED chips, which is adequate for cooling LED grow lights.

Performance analysis and optimization of rectangular fin arrays used in plate-fin heat exchangers

This paper deals with longitudinal rectangular fin arrays used in plate-fin heat exchangers. The temperature distribution and rate of heat transfer were obtained using 1-D and 2-D solutions. The ranges of independent parameters within which the 1-D solution was within 1% from the 2-D solution were determined. Simple analytical solutions were determined for the rate of heat transfer, fin effectiveness, and augmentation factor. The aspect ratio at which the rate of heat transfer reached a maximum was determined, as well as the corresponding effectiveness and augmentation factor.

Solidification characteristics of phase change material in a rectangular finned spherical capsule

This work investigates the solidification characteristics of deionized water in a stainless steel spherical capsule fitted with rectangular fins immersed in a constant temperature bath. Experiments are carried at three different bath temperatures (-6,-9, and -12°C). Four rectangular fins of size 20.6mm length, width 10.6 mm, and 1mm thick made of copper are fixed on the inner surface of the spherical capsule. Results indicated that fin had a significant reduction in total solidification time. A reduction of 13% in total solidification duration is achieved at -9 and -12°C. However a decrease of 87-90 % in freezing duration is observed while considering 50% of PCM mass at bath temperatures of -6°C,-9°C, and -12°C. It is concluded that fins can be employed in CTES systems at lower bath temperatures to achieve expected energy savings of 9-12% under the partial charging method.

Calculating the Efficiency of Complex Shaped Fins

In the calculation of heat exchangers with individual finned tubes or continuous fin heat exchangers, i.e., plate-fin and tube heat exchangers (PFTHEs), it is necessary to determine the efficiency of complex fins. Usually, these are circular or rectangular fins mounted on circular, elliptical, or oval tubes as well as flattened tubes. In case of PFTHEs, the continuous fin is divided into virtual fins, which are rectangular for an inline pipe layout or hexagonal for a staggered pipe arrangement. This paper presents a procedure based on the finite element method for determining the efficiency of fins of any shape placed on tubes of any shape. The article shows examples of calculating the efficiency of virtual fins in most commonly used PFTHEs. The research also assesses the accuracy of determining the efficiency of complex-shaped fins using approximated methods such as the equivalent circular fin method (Schmidt’s method) and the sector method. The efficiency of a fin as a function of heat transfer coefficient for four different, most common geometries in PFTHEs was depicted. An example of determining the efficiency of a hexagonal fin using various methods for air velocities measured at the exchanger inlet was presented.

Design and Analysis of the IGBT Heat Dissipation Structure Based on Computational Continuum Mechanics.

With the trend of high integration and high power of insulated gate bipolar transistor (IGBT) components, strict requirements have been placed on the heat dissipation capabilities of the IGBT devices. On the basis of traditional rectangular fins, this paper developed two new types of heat-dissipating fins to meet the high requirements of heat dissipation for the IGBT devices. One is the rectangular radiator with a groove length of 2.5 mm and a width of 0.85 mm, the other is the arc radiator with the angle of 125 arc angle, 0.8 mm arc height, and 1.4 mm circle radius. After theoretically calculating the IGBT junction temperature, numerical simulations have been implemented to verify the theoretical result. The commercial CFD software, STAR-CCM+, was employed to simulate the heat dissipation characteristics of the IGBT module under different wind speeds, power, and fin structures. By analyzing the temperature field and vector field of the IGBT module, the analysis results demonstrate that the error between the simulation result and the theoretical calculation is within 5%, which proves the feasibility of the newly designed heat-dissipating fins. When the wind speed is 12.5 m/s, the power is 110 W, the fin height is 31.2 mm, and the fin thickness is 2.3 mm, the rectangular radiator can achieve the best heat dissipation performance.

Geometric optimization of a lid-driven cavity with two rectangular intrusions under mixed convection heat transfer: A numerical investigation motivated by constructal design

The present work aims at the geometric optimization, by means of constructal design and exhaustive search, of two rectangular fins inserted in a lid-driven cavity subjected to unsteady, incompressible, laminar, two-dimensional mixed convective flow with stable stratification. The main purpose is to maximize the dimensionless heat transfer rate (q˜′) and time and spatial-averaged Nusselt number (NuH¯). The domain presents three constraints: cross-sectional areas for each fin and total area of the cavity. Two degrees of freedom are investigated, height/length ratios of the left and right rectangular fin (H1/L1 and H2/L2), considering three different fraction areas for fins and two different Richardson numbers Ri = 0.1 and 1.0, representing two conditions for mixed convective flow. All cases have constant Reynolds and Prandtl numbers (ReH = 400 and Pr = 6.0). The conservation equations of mass, momentum, and energy are solved using the Finite Volume Method. Recommendations for fins shapes were strongly affected by the performance indicators chosen. Results also indicated that asymmetric configurations for the fins with different fraction areas for each fin led to the best thermal performance. Moreover, the optimal shapes and the effect of degrees of freedom over performance indicators were also affected by the Richardson numbers investigated.

Dual solutions of the nonlinear problem of heat transfer in a straight fin with temperature-dependent heat transfer coefficient

Purpose In this paper, a numerical scheme is provided to predict and approximate the multiple solutions for the problem of heat transfer through a straight rectangular fin with temperature-dependent heat transfer coefficient. Design/methodology/approach The proposed method is based on the two-point Taylor formula as a special case of the Hermite interpolation technique. Findings An explicit approximate form of the temperature distribution is computed. The convergence analysis is also discussed. Some results are reported to demonstrate the capability of the method in predicting the multiplicity of the solutions for this problem. Originality/value The duality of the solution of the problem can be easily predicted by using the presented method. Furthermore, the computational results confirm the acceptable accuracy of the presented numerical scheme even for estimating the unstable lower solution of the problem.

Investigation of thermal performance of modified vertical rectangular fin array in free convection using experimental and numerical method

Heat transfer by free convection from fin array is influenced by modification in size and shape of the fins as well as interruption in fluid flow. The objective of heat sink is the thermal management of electronic devices by removing excessive heat and improve the lifespan of the device. The paper investigates the thermal performance of free convection heat transfer with vertical heat sink by providing slits along the vertical surface of the fins. For the evaluation purpose two different arrangements viz. plain fin and slitted fin are selected. Fins are made from high thermal conductivity aluminium material and five dissimilar heat inputs are selected for study. The experimental and numerical findings are confirmed using the theoretical correlations available from the literature.The effect of number of slits and width of slits is investigated on convective heat transfer coefficient. Numerical study is used to understand the flow patterns around the vertical fin surface. It has been observed that the presence of slits on the surface appreciably improves the thermal performance of vertical fin array.

Design and numerical investigations of natural convection heat transfer of a new rippling fin shape

In the present work, a new fin shape is proposed to improve the convective heat transfer in heat sinks and to reduce their weight. The problem under consideration is a natural convection with air as the working fluid. Three-dimensional numerical simulations are carried out using FLUENT 19.0, to solve the continuity, momentum, turbulence, and energy equations to predict the flow and temperature field for different fins on a vertical base. Five configurations of rippling fins are considered with two aspect ratios and different heat flux inputs. The numerical results are compared to previous data available in the literature for a vertical rectangular finned plate (reference case) to validate the model. For each configuration, the heat sink temperature field and the natural convection driven air flow are discussed. The heat flux is varied from 519.396Wm2 to 4674.565Wm2. The overall thermal performance is characterized by the heat dissipation rate per unit mass. By comparison to conventional rectangular fin, the proposed fin geometry can reduce the temperature at the heat sink base by up to 18.35 K, increase the mass specific heat transfer coefficient by up to 101.41%, and decreases the thermal resistance by 9.81%. Within the scope of this study. The case with one ripple provides the best thermal performance. The results also showed that, the flow and heat transfer enhancements are a decreasing function of Rayleigh number. Overall, the heat transfer enhancement is better with rippling fins than with the rectangular fins, with a maximal mass reduction of 47%. The proposed models provide a practical alternative to the widely adopted plate fin heat sinks, which very promising for future thermal developments.

Numerical investigation of natural convection behavior of molten PCM in an enclosure having rectangular and tree-like branching fins

Abstract In phase-change applications, once the melting process is completed, the natural convective heat transfer of liquid material may be promoted or degraded by the fins, which is the main motivation of this research. For this reason, the natural convection heat transfer inside a PCM container that can be a representative model for PV/PCM systems is numerically investigated in this study by considering three aspect ratios (AR = 1, 2 and 4), three Rayleigh numbers (Ra = 104, 105 and 106), two types of fins as rectangular and tree-like branching fin, and three different length-to-height ratio of rectangular fin (w/H = 0.3, 0.4 and 0.5). The rates of increment and decrement are presented taking the finless enclosure as the reference case. The computed results revealed that the natural convection is promoted up to 20%, depending on Ra and fin length by the inclusion of fins when the AR = 1, while it is degraded down by 5.5% for AR = 4. Interestingly, at AR = 2, the percentage increase and decrease of mean Nu numbers are slighter compared to other aspect ratios. Besides, it is also noticed in this study that utilizing a tree-like branching fin is not as effective as a rectangular fin with the same mass.

An unsteady thermal investigation of a wetted longitudinal porous fin of different profiles

The unsteady thermal behavior of a porous longitudinal fin in a fully wet circumstance in the existence of convection as well as radiation effect is modeled in the present analysis. The thickness of the fin is assumed to vary with the length of the fin. Therefore, different profiles of the fin such as rectangular, convex, as well as triangular-shaped fin have been considered. Darcy’s model is imposed to study porous nature. The derived nonlinear partial differential equation is non-dimensionalized and solved numerically with the help of Maple software by the Finite Difference Method. The transient thermal response and fin efficiency for diverse values of the significant parameters have been discussed graphically. A comparative analysis of three different shaped fins has been performed. It is found that the temperature drop rate is faster in triangular fin and efficiency is higher in rectangular fin.

Heat Transfer Enhancement in a Double Pipe Heat Exchanger Using Different Fin Geometries in Turbulent Flow

Heat transfer enhancement is widely used for improving heat exchanger performance in industrial processes. This is accomplished by increasing the surface area of the heat exchange surface by using fins or inserts of different geometries. The present work is an experimental study of heat transfer when using different fin geometries for the heat exchange surface in a double pipe heat exchanger. The fin geometries included interrupted rectangular fins, circular fins and helical ribs. The heat transfer coefficient and pressure drop were experimentally determined for a range of Reynolds numbers of hot and cold fluids. The results showed that extending the surface using different fin geometries enhanced the heat transfer coefficient, but was dependent on the Reynolds number of both fluids. The maximum heat transfer enhancement was obtained for a rectangular fin and the minimum was for a circular fin. In the case of the finned tubes, the lowest pressure drop was observed for the circular fin and highest for the rectangular fin.