Rectangular Fin Arrays Research Articles

Numerical investigation of natural convection from a horizontal heat sink with an array of rectangular fins

This research focuses on the numerical analysis of a rectangular fin array with a horizontal heat sink to examine its performance in natural convection heat transfer. The study uses air as the primary working medium. Steady-state 3D modeling is carried out using the finite volume method (FVM), allowing velocity and temperature distributions to be evaluated by solving equations relating to mass conservation, fluid dynamics, turbulence, and heat transfer. This research details temperature and velocity variations as well as fluid trajectories. It also explores how the intensification of heat flow, varying from 361 W/m2 to 2527 W/m2, influences the cooling efficiency of the fins. It is observed that the increase in heat flux reduces the formation of vortices and intensifies natural convection by rising the temperature gradient between the radiator and the surrounding. The temperature increases at all parts of the heat sink fin array as heat flux increases. Besides, it is noticed that the maximum temperature is generated at the mid-region of the base plate heat sink and gradually dissipates to the surroundings through the bodies of the fins. Moreover, the study indicates that the average convection heat transfer coefficient (hav) and the average Nusselt number (Nus) increase by 86 % and 84 %, respectively, when the heat flux is increased from 361 W/m2 to 2527 W/m2. These observations are corroborated by a comparison with existing experimental data, showing an agreement of less than 9 %. The digital model is validated by comparing pre-existing data on radiators with horizontal rectangular louvers, revealing minimal deviations of less than 2 %.

Performance Optimization of Finned Surfaces Based on the Experimental and Numerical Study

Abstract This paper presents the findings of numerical and experimental investigations into the forced convection heat transfer from horizontal surfaces with straight rectangular fins at Reynolds numbers ranging from 23,600 to 150,000. A test setup was constructed to measure the heat transfer rate from a horizontal surface with a constant number of fins, fin width, and fin length under different flow conditions. Two-dimensional numerical analyses were performed to observe the heat transfer and flow behavior using a computer program developed based on the openfoam platform. The code developed was verified by comparing the numerical results with the experimental results. The effect of geometrical parameters on heat transfer coefficient and Nusselt number was investigated for different fin height and width ratios. Results showed that heat transfer can be increased by modifying the fin structure geometrical parameters. A correlation for Nusselt number was developed and presented for steady-state, turbulent flows over rectangular fin arrays, taking into account varying Prandtl number of fluids such as water liquid, water vapor, CO2, CH4, and air. The correlation developed predicts the Nusselt number with a relative root mean square error of 0.36%. This research provides valuable insights into the effects of varying Prandtl numbers on the efficiency of forced convection cooling and will help in the design and operation of cooling systems. This study is novel in its approach as it takes into account the effect of varying Prandtl numbers on the heat transfer coefficient and Nusselt number and provides a correlation for the same. It will serve as a valuable reference for engineers and designers while designing and operating cooling systems.

A study of finding empirical correlation for the Nusselt number and the factors influencing it for perforated fin array of different shapes

An experimental investigation of three-dimensional steady state forced convection heat transfer through perforated rectangular fins with three different materials were carried out. The experimental procedure has been done in turbulent region with Reynolds number range of (6200 ≤ Re ≤ 18,700) and (Pr = 0.71) and constant inlet air temperature of (Tin≈17°C) with a constant power input of (20 W ≤ Q ≤ 70 W) step 10 W. The current study used a rectangular fin array with three materials (stainless steel 430, aluminum 2014-T6, yellow brass), with various perforation shapes and patterns which includes [Rectangular, Circular, and V-shape, all (Inline, staggered)]. It is found that the mean deviation of average Nusselt number taken for previously published results to the experimental result of all specimens have been found to be ∓ 8 %. A general correlation has been derived based on average Nusselt number with an error of ± 5 % which is described with the formula (Nu¯=βRe¯αδRAFPrRAF). It is concluded that the general correlation equation derived has reasonably acceptable degree of accuracy and it’s more general and considers many materials with a wide range of RAF compared with the other equations. The average error found between the general correlation and previously published result is ± 9.8 %.

The Experimental Impact of Convective Heat Transfer Improvement from Numerous Perforated Shape Fin Array

The current work explores a trial forced convective heat move from rectangular blades on an upward surface at low Reynolds numbers. The heat removal for a proper number of punctured and non-punctured fins, fin dividing, and length was estimated in an upward air stream for fluctuating inlet air speed and some way or another low info heat power somewhere in the range of 20W and 70W. The characteristics are investigated for rectangular, circular, and V-shape perforated fin array against non-perforated one. The impact of different boundaries, like heat input with various liquid stream speed on average coefficient of heat transfer (h) improvement has been considered. The impact of the Nusselt numberand Reynolds number, were practically examined. The heat loss has been improved by increasing the heat transfer coefficient between the fin total surface and its encompassing, through increasing the area of heat to remove all out surface through fin perforations. The trial relations have been differentiated by correlating Nu and Re for non-punctured plate heat sink, the reach 6*103 £ Re £ 19*103, and Pr @ 0.7 with error ±7%, and punctured finned plate heat sink with the reach 6*103 £ Re £ 20*103, and Pr @ 0.7 with a deviation factor R2=0.995.

Melting Characteristics of Hybrid Nano Enhanced Phase Change Material in a Finned Circular Tube

In this study, the melting characteristics of hybrid nano-enhanced phase change material in a finned circular tube were studied by using the Finite volume method. This setup of circular tubes with a phase change material is used as cooling systems in automotive industries, air-conditioning, refrigerators, and other applications of cooling systems. There is a need for enhancing the specific heat capacity of this system to ensure that the system works even at high temperatures. As the current problem includes many design parameters and boundary constraints, the finite volume method has been performed to obtain a detailed report and data to examine the deformation of the hybrid nanoparticles and heat transfer rate on the corresponding surface. The current paper reviews and focuses mainly on the high-temperature PCM. And the suitable PCM has been selected based on its limitations and properties. To ensure the increased specific heat capacity, a salt-based phase change material, i.e., a mixture of NaNO3-KNO3 (60:40 ratio) binary salt. This PCM could hold a temperature up to 334◦C before melting to change its phase. In addition to spherical-shaped nanoparticles of silica (SiO2) in this binary salt, it tends to have a significant potential for enhancing the thermal storage characteristics of the NaNO3-KNO3 binary salt. On an extended surface, Finns are used on the peripheral of the circular tube to increase the surface area, which leads to an increase in frictional resistance resulting in a reduced airflow rate in the vicinity of the finned surface. From case studies, it has been found that the optimum fork-shaped fin array with two branches gives higher heat dissipation than the optimum rectangular fin. In the majority of the cases, the optimum fork-shaped fin array gives a 59.9% higher heat transfer rate compared to the rectangular fin array. Thus, the melting characteristics of the hybrid of NaNO3- KNO3 with nanoparticles of silica are studied when placed in a circular tube containing fork-shaped fins.

The effect of fin height on forced convection heat transfer from rectangular fin array

In this research, experimental investigation of the coefficient of the heat transfer has been conducted for a set of rectangular fins with different fin height, 0.27, 0.47 and 0.67 m at air velocity test points of 1.1, 1.3, 1.5, 1.7 and 2 m/s, to meet the Reynolds number (Re). Thirty samples from the two cases with changing fin positions were studied to verify the thermal performance of the system. The study was conducted based on the cross-sectional diameter of 21167, 25016, 28864, 32713, and 38486. Total heat flux in all tubes has been settled as 26.3, 58, and 88.7 W/m 2 . The experimental results showed that the temperature difference between the surface of the block and flowing air increases with increasing Reynolds number for all heat flow states.

Characteristics of thermal plume from an array of rectangular straight fins with openings on the base in natural convection

Straight rectangular fins with openings in the base surface in natural convection exhibit greater heat transfer than rectangular fins without openings in the base. In this paper, thermal plume arising from such fin configuration used as a heat sink for natural convection cooling of light-emitting diode (LED) grow lights is investigated using three-dimensional conjugate laminar flow simulations. Understanding of plume characteristics is crucial in optimizing the cooling performance as well as optimal placement of grow lights from ceilings and walls in proximity. A prototype LED grow light was designed and experimentally measured to assess the cooling performance, and numerical simulations were conducted to investigate the plume structure. The results showed that openings in the base enhanced vertical draft of air, mixing, and overall heat transfer rate. It was found that local pressure gradient is proportional to the degree of mixing of ambient air into the plume. Low pressure regions around the fins and channels showed upward convection of plume mass and a high pressure region below the fins indicated higher concentration of denser air mass. High pressure gradients were observed in the openings, which further justifies the significance of openings in improving mixing of ambient air with the plume to enhance heat transfer.

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.

Numerical simulation of the thermal performance of a wavy fin configuration for a straight fin array

Fins over the years have been used as heat exchangers for exchanging heat generated in engineering machines or systems, between the system surface and the ambient air. However, the challenge of thermal design for the best geometry of heat fin prompted the study, to determining the performance of a wavy and straight fin projecting vertically from a horizontal base, by comparing their rate of heat transfer. In this study a free convection steady state numerical analysis was carried out using Solidworks 2018 flow simulation application, which is based on finite volume method of Computational Flow Dynamics (CFD). The numerical analysis was carried out on three different fin array configurations, all of the same fin spacing or separation distance. The three fin array modeled includes the straight and wavy fin of fin height, 35mm and spacing, 14.2mm respectively. The third fin was a straight fin of height, 50mm equivalent of the effective wavelength of the wavy fin, but of same fin spacing. Aluminum metal was selected as the material, and the simulation was done using air as the fluid, of temperature, and convective heat coefficient, 27°C and 20W/mK respectively. Simulation was carried out at different temperatures for each geometry, ranging from 45°C – 120°C. The results showed that the difference in the rate of heat transfer for the wavy fin and straight fin were close at low temperatures, but significantly increased to about 28% at higher temperatures in favor of the wavy fin. The third fin had an insignificant 9% heat transfer rate higher than the wavy fin but with 43% additional height, thereby occupying more space. It is established from this study that wavy fin array possesses higher convection heat transfer performance than the straight rectangular fin array. Therefore, in a bit to achieve high performance heat transfer with limited space, a wavy fin array is recommended.

Computational Investigation on Natural Convection Heat Transfer in Vertical Plate Fin Arrays

Objectives: To perform computational studies on different combinations of plate fin arrays of different shapes for studying their performance in natural convection heat transfer. To compare the heat transfer performance of uniform notched fins with hybrid notched fins and also performance of normal notched fins with inverted notched fins. Methods: SolidWorks Flow Simulation software is used for the present computational studies. Three types of vertical plate fin arrays viz. plain rectangular fin, rectangular fin with square notch and rectangular fin with semi-circular notch are used with their seven combinations. These fin array combinations are: plain rectangular, rectangular square notched, rectangular semi-circular notched, rectangular inverted square notched, rectangular inverted semi-circular notched, hybrid rectangular square-semi-circular notched and hybrid rectangular inverted square-semi-circular notched. Findings: The highest average heat transfer coefficient of 7.82 W/m2K is found to be for inverted hybrid square-semicircular notched fin array. This value of heat transfer coefficient is about 8% higher than compared to that with plain rectangular plate fin array (7.25 W/m2K) subjected to same operating conditions. Average heat transfer coefficients for inverted plate fin array combinations are high as compared with the non-inverted combinations. Also, hybrid plate fin arrays, whether inverted or not, show higher heat transfer coefficient values as compared with uniform notched fin arrays. Novelty : Seven types of plate fin array combinations are studied computationally. SolidWorks Flow Simulation software is used very effectively for this 3D CFD analysis. The behaviour of fluid i.e. air during natural convection flow is studied using air flow velocity trajectories. Surface contours are effectively used for studying variation in surface temperature and heat transfer coefficient at all locations of fin arrays. Keywords Natural convection, plate fin array, heat transfer coefficient, CFD, heat transfer enhancement

PERFORMANCE OF RECTANGULAR PIN-FIN HEAT SINK SUBJECT TO AN IMPINGING AIR FLOW

The heat sink is used to enhance heat rejection from heated surface to air. The seize and the geometry of the heat sink with the shape of the extended surfaces have a great influence on the heat transfer coefficient. The first step to get the optimal design is to predict the heat transfer by conduction in solid walls of heat sink and then by convection between the solid and air flow. The purpose of the present study is to predict the effectiveness of closely spaced parallel rectangular fin array arrangement. The electronic processor was represented by the copper heat sink base with thermal conductivity of 401 W/m.K. The 72 fins with the geometry above mentioned were exposed to heat transfer with conduction and convection along all the boundaries except the bottom from which heat flow toward air flow domain. Mesh generation at a specific cells, number of element and number of nodes were taken under temperature difference validation. The experiments were done under impinging air flow rate with Reynolds number ranged between 4000-16000. The flow was turbulent so the k-Ԑ turbulence model needed to simulate mean flow characteristics. Constant heat fluxes boundary conditions were proposed with range between 10000-70000 kW/m2. The Results of temperature contour lines depicted a heat trend from the hot base through the extended surfaces to the fin tips. The fins were aligned in the core of heat sink showed higher temperature gradient compared with the fins existed in lines surrounded the core. The thermal resistance decreased as the Reynolds number increased and the Nusselt number increased as the Reynolds number increased and also when the heat flux increased. The Reynolds number depicted increasing as the Nusselt number increased and so the heat rejected from the heat sink base increased. There is a good agreement between the experimental and simulating results at error percentage not exceed 2%.

Experimental Enhancement of Mixed Convection Heat transfer in Hot Base Rectangular Channel

This paper presents an experimental study to enhance the flow and heat transfer enhancement over horizontal and orientation channel with hot base by laminar mixed convection heat transfer. The hot base is fitted with the longitudinal rectangular fin arrays as a finned wall. The study covered the following range: modified Grashof number varied (3× 101 - 8× 108), Reynolds number in range 1800-2300, and Pyrantel number 0.71. The bottom finned wall of the channel was supplied with constant heat flux, while the other sides are insulated. The experiment part includes a suitable test rig that was built to get accurate decisions. A good mechanism was created to get the orientation angles at (90°,120°, 150 °and 180°) then to analysis this effect on heat transfer for laminar flow force convection. Three different cases are investigated: the effect of modified Grashof number and orientation angles on fluid particles flow and heat removal will be an enhancement. The experiment results show that the average heat transfer coefficient increased with Reynolds number and an increase of the Grashof number for all orientation angles due to increases buoyancy forces, thus causes a detach with the secondary layer flow. The average heat transfer coefficient and fins effectiveness are enhanced to 25% at highest longitudinal orientation angles.

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.

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.

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.

Laminar entry region mixed convection heat transfer from an inclined rectangular fin array

Purpose The paper aims to investigate the influence of the angle of inclination on mixed convection heat transfer from rectangular plated shrouded fin array computationally. This study has got applications in the various thermal field such as cooling, solar thermal and so on. Design/methodology/approach A computational study is made to evaluate the thermal performance in an inclined channel. Findings Increase in clearance from 0.01 to 0.25 results in an increase of local Nusselt number by is as high as 15% near the exit. At a higher value of Gr with an increase in C* from 0.10, Nu is found to increase by 5.5%. Increase in Gr by 1.37 times results in enhancement of Nu by a maximum of 25-30%. Around 10% increase in overall Nu value is observed with an increase in inclination (i.e. from 30° to 60°). Practical implications This study has got applications in the various thermal field such as cooling, solar thermal and so on. Originality/value Entry region mixed convection in a shrouded inclined finned channel is performed.

Fork-shaped constructal fin array design a better alternative for heat and mass transfer augmentation under dry, partially wet and fully wet conditions

In actual practical situations, the evaporator fins of refrigeration and air-conditioning apparatuses may operate under dry, fully wet or partially wet conditions. Thus in the present study, the optimum design of an array of constructal fork shaped fins operating under partially wet conditions has been determined by using a linear variation of the humidity ratio of saturated air with the corresponding fin surface temperature. The point of separation between the dry and wet portions may be located either in the stem or branch part of the fin and hence, two cases having different governing equations and boundary conditions are analysed in the current study. The optimisation study is done by maximising the total heat transfer rate of the fin array and un-finned surface and the constraints are imposed in such a way that fin material limitations, minimum fin gap requirements as well as space limitations in the radial direction are taken into account. For obtaining the optimum condition, a swarm based meta heuristic algorithm called Firefly algorithm has been employed. Arrays of fork-shaped fin having two and three numbers of branches are analysed in the present study and a comparative study is done with the rectangular fin array. For more compact evaporators, it would be more preferable to select the fin array that results in larger optimum heat transfer rate as well as that having a smaller total length of each fin. An important finding is that the array of fork–shaped fins with two branches give higher optimum heat transfer rate than that from the rectangular fin array in all the cases of different operating conditions. However, no advantage with respect to either higher optimum heat transfer rate or smaller fin length is obtained when the number of branches of fork shaped fins is increased from two to three.

Convective heat transfer from an inclined isothermal fin array: A computational study

Miniaturization of electronic devices and continuous evolution in new compact devices always seeks for the higher heat-releasing system. The use of rectangular fin is gaining popularity due to its ease of production and seeks an effort to analyze different configurations. In the present study, a computational analysis of shrouded rectangular fin array in an inclined channel is performed. The conservation equation of mass, momentum, and energy are solved by using finite volume method. For a range of inclination of 30°, 45° and 60° with non-dimensional spacing (S* = 0.2, 0.3 and 0.4) and clearance (C* = 0.1, 0.25 and 0.4) results are obtained. Also, the Reynolds number (Re) is varied from 640 to 1707 along with the Grashof number (Gr = 1.4 × 105 to 3.32 × 105), the effect on axial pressure defect and the non-dimensional bulk temperature is presented at each inclination. The increase of C* from 0.1 to 0.25 results in a maximum of 6.5–8% increase in the coefficient of heat transfer (h) at an inclination of 60°. Increase in Re enhances the heat transfer by about 12% and increase the pressure drop by about 30%, at a higher inclination. In general, higher inclination provides better heat transfer.

A novel optimum constructal fork-shaped fin array design for simultaneous heat and mass transfer application in a space-constrained situation

The present study deals with the design and analysis of an array of constructal fork-shaped fins adhered to a circular tube and operating under fully wet conditions. Fork-shaped fin arrays with two and three numbers of branches are considered in the current work. The mass transfer process is calculated by using a cubic relation between the humidity ratio of saturated air and the corresponding fin surface temperature. The governing equations are highly non-linear and hence they are solved by using a semi-analytical technique called Homotopy Perturbation method. The optimisation is done by maximising the net heat transfer rate of the fin array and un-finned surface and by imposing certain constraints. The constraints are taken such that the radial space limitations fin material limitations, as well as the minimum fin gap considerations, are taken into account. As the present problem involves a large number of design parameters as well as the interrelated constraints, a bio-inspired metaheuristic algorithm called the Firefly Algorithm has been employed for obtaining the optimum condition. The analysis has been performed for different operating conditions and the results have been compared with the corresponding rectangular fin array. From the study, it has been seen that the heat transfer rate from the optimum fork-shaped fin array with two branches is higher than that from the optimum rectangular fin array. However, in a few cases, it has been found that there is marginal difference in heat transfer rate between the optimum fork-shaped fin array with two branches and the rectangular fin array but the total length of each fin for the former case is found to be smaller and hence fork-shaped fin array with two branches would be a better selection than the rectangular fin array. However, increasing the number of branches of the fork-shaped fins from two to three does not provide any benefit in terms of either lower fin length or higher heat transfer rate.

Optimum Arrangement of Fins in a Free Convection-Based Solar Air Heater

Abstract In this paper, the details of a numerical study performed for the optimum fin arrangement in a solar air heater with a rectangular fin array attached to the bottom side of the absorber plate have been presented. Results have been presented for various fin sizes and spacing between the fins, while the heat transfer and fluid flow are directed by natural convection. An inclined rectangular channel similar to the dimensions of a typical solar air heater has been considered. Three different fin configurations, namely, continuous long fins for the whole length of the channel, in-line interrupted and staggered interrupted arrangements of fins, have been studied. The present analysis aims to identify the optimum configuration of the fin array for enhanced heat transfer. The spacing between the fins and the height of the fins are varied to obtain an optimum configuration. The numerical simulations are performed for heat flux (q″) ranging from 250 to 750 W/m2 on the absorber plate. The inclination angles of the channel (θ) have been maintained at 15 deg, 30 deg, and 45 deg from the horizontal plane. The results show that with the spacing between fins, S = 5.4 cm performs better in the case of longitudinal continuous fin arrangement. However, a fin spacing of 4.75 cm shows a higher heat transfer in the case of staggered fin configuration. In comparison with nine long uninterrupted fins, using the staggered arrangement with 15 × 10 fins saves up to 33% of fin material.