Perforated Fins Research Articles

Design of perforated branching fins in laminar natural convection

Under laminar natural convection conditions, the optimum design of a perforated branching fin for electronic cooling application is numerically investigated. Circular perforations with diameters varying between 1.1 mm and 6.6 mm are used. In this size range, the surface area of the perforated fins is less than the non-perforated fins. Two orientations of the fins are considered, namely vertical base horizontal fin (vBhF) and horizontal base vertical fin (hBvF). With a ‘single’ perforated branching fin, heat dissipation is always enhanced by making perforations in vBhF orientation, but it would diminish in hBvF orientation for certain pore sizes and distributions. The optimum values of perforation diameter, pitch and branching angle for heat transfer enhancement are determined to be d = 3.3 mm, PH = 1.05d, PL = 1.5d and α = 45o corresponding to a porosity of 40.5%. High plume velocities and low temperatures observed in 3.3 mm pores made it the optimum size. With a stack of perforated fins, heat dissipation is enhanced for every inter-fin spacing in vBhF orientation, while the enhancement in hBvF orientation is observed only at narrow spacing. Maximum total heat flux dissipated by the stack of perforated fins is 1.6 times higher in hBvF orientation due to significant contribution from convection heat transfer.

Enhance the energy and exergy performance of hydrogen combustion by improving the micro-combustor outlet in thermofluidic systems

The main reason for the heat loss of micro-combustors is the hot exhaust gases. In this study, the exit part of the conventional micro-combustor has been improved to increase the heat transfer between the hot combustion gases and the walls of the micro-combustor. For this purpose, several approaches have been applied, including porous media, perforated fins, and 24 and 8 tube outlets for outlet replacement. In these improved micro-combustors, the thermal performances of the combustion of the hydrogen-air are numerically have been investigated. The results reveal that new micro-combustors by enhancing the velocity of the exhaust gases or increasing the surface area of heat transfer or transferring the hot gases to the walls, has led to a decrease in the temperature of the exhaust gases. However, the wall temperature and its uniformity have increased in the improved micro-combustors. Raising the wall temperature and reducing heat loss have increased radiation efficiency, and reducing entropy generation and energy loss in presented geometries diminish the exergy loss and enhance the exergy efficiency. Also, results showed that micro combustor with porous media has the best energy and exergy performance. Finally, the electrical power generation of micro-combustors has been investigated by photovoltaic cells.

Boyuna Uzatılmış Yüzeylerde Dikdörtgensel Oyukların Isı Atımına Etkisi: Bir Hesaplamalı Akışkanlar Dinamiği Analizi

In this study, for three different forced convection conditions (h = 25, 50 and 100 W/m2K), heat transfer through conventional and perforated fins has been investigated by ANSYS FLUENT software, and the analyses have been repeated for various perforation levels. Aluminium has been utilised as the fin material in the analyses with a thermal conductivity of 202.4 W/mK. For the operational case, cooling of photovoltaic systems by forced convection has been considered, and in this respect, fin base temperature has been selected to be 353.15 K by taking standard test conditions (1000 W/m2 solar intensity, 298.15 K ambient temperature) into consideration. For steady-state conditions, energy equation has been solved along the fin for the convergence criterion of e=10^(-9). Reference fin profile considered in the research has a 50 mm length, 10 mm height and 1 mm width. Perforation pairs (λ) of 1 mm2 have been formed longitudinally along the fin and the heat dissipations from conventional and perforated fins have been numerically determined for each λ value. Fin efficiency has also been calculated as a function of perforation level. Numerical results have revealed that heat transfer from the fin decreases with increasing λ value, however for each convection condition, heat dissipation per fin volume from the perforated fin is greater in comparison to the conventional fin after a certain λ value. Perforation effects have been found more noticeable for the lower h values. For h = 25 W/m2K, heat dissipation from the conventional fin has been determined to be 2.5032 W whereas the heat transfer through the perforated fin has been found to be 2.6683 W. This case corresponds to an enhancement of about 6.6% in heat dissipation.

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.

Experimental and Numerical Investigation of Heat Transfer Enhancement Using Circular Perforated Fins

Experiments were done to investigate the natural and forced convection of heat transfer along a flat surface equipped with various types of rectangular aluminum fins (solid and perforated). Fins selected with dimensions of(30mm height ×30 mm width ×lmm thickness). Perforated fins have various distributed holes(2 mm dia. for 9 holes and 4 mm dia. for 5 holes). For forced convection, the air flow channel selected with a cross section area of (100×100 mm2)for (1000 mm) length. Nine Thermocouples used to recorded the temperature distributed from the fin base to its tip. Flow pattern included laminar and the air flow towards the fin lateral area of (30 mm × 30 mm). The effect of number, size and arrangement of perforated fins was studied. higher heat transfer rates observed with increasing the number of circular holes also the effectiveness were increased due to the reduction into fin’s weight. Also a numerical study was done to investigate these temperature distribution used (SOLDWORKS) simulation program. Good agreements were noted when compared between experimental and theoretical works.

Experimental investigation of the effect of perforated fins on thermal performance enhancement of vertical shell and tube latent heat energy storage systems

A key challenge in the deployment of practical latent heat energy storage systems employing phase change materials is the inherent low thermal conductivity of these materials. The present research is motivated by the need to intensify the buoyancy-driven convection flow in the phase change material to enhance the thermal performance of the system. In this paper, for the first time, the effect of applying perforated fins on the thermal performance enhancement of a vertical shell and tube latent heat energy storage heat exchanger is experimentally investigated and the results are compared with those of the unfinned and solid finned heat exchangers as the base cases. Lauric acid as the phase change material is placed in the shell side and the water is passed through the inner tube. The shells of the heat exchangers were made of transparent Plexiglas tubes to enable the visual comparison of the melting processes. The fins and tubes were made of copper. The melting process of phase change material is studied under different inlet water flow rates (0.5 and 1 l/min) and temperatures (55 and 65 °C). The experimental results showed that the time-averaged Nusselt number of the perforated finned heat exchanger is about 30% higher than that of the solid finned heat exchanger due to the minor hindering effect of the perforated fins on the development of the convection flows. Moreover, the total melting time of the perforated finned heat exchanger is about 7% lower than that of the solid finned heat exchanger.

Improvement of heat transfer through fins: A brief review of recent developments

AbstractFins or extended surfaces are generally used in heat exchangers to enhance heat transfer between the main surface and ambient fluid. Various types of simple‐shaped fins, namely, rectangular, square, annular, cylindrical, and tapered, have been used with different geometrical combinations. To satisfy industrial demand, different trials have also been carried out for designing optimized fins. The optimization of fins can be performed either by enhancing heat dissipation at an exact fin weight or by diminishing the weight of the fin by precise heat dissipation. Recently a notable amount of work on some typical fins, like, porous fins and perforated fins, has also been carried out. This paper presents a brief review on heat transfer enhancement using fins of different types considering variable thermophysical and geometric parameters, which will also be useful for future use of geometrical modifications of extended surfaces, based on the cost and availability of space.

Numerical and Experimental Investigation of Air Cooling for Photovoltaic Panels Using Aluminum Heat Sinks

An increase in the operating temperature of photovoltaic (PV) panels caused by high levels of solar irradiation can affect the efficiency and lifespan of PV panels. This study uses numerical and experimental analyses to investigate the reduction in the operating temperature of PV panels with an air-cooled heat sink. The proposed heat sink was designed as an aluminum plate with perforated fins that is attached to the back of the PV panel. A comprehensive computational fluid dynamics (CFD) simulation was conducted using the software ANSYS Fluent to ensure that the heat sink model worked properly. The influence of heat sinks on the heat transfer between a PV panel and the circulating ambient air was investigated. The results showed a substantial decrease in the operating temperature of the PV panel and an increase in its electrical performance. The CFD analysis in the heat sink model with an air flow velocity of 1.5 m/s and temperature of 35°C under a heat flux of 1000 W/m2 showed a decrease in the PV panel’s average temperature from 85.3°C to 72.8°C. As a consequence of decreasing its temperature, the heat sink increased the open-circuit photovoltage (VOC) and maximum power point (PMPP) of the PV panel by 10% and 18.67%, respectively. Therefore, the use of aluminum heat sinks could provide a potential solution to prevent PV panels from overheating and may indirectly lead to a reduction in CO2 emissions due to the increased electricity production from the PV system.

A Numerical Research of Heat Transfer in Rectangular Fins with Different Perforations

Heat Transfer enhancement needs buoyancy force. This is to be achieved by making perforations on fin surfaces. The present paper is a study on the enhancement of heat transfer in terms of density, velocity and temperature with three different perforation geometry (parallel square, inclined square and circular). CFD was used to carry out the study of density variation, velocity and temperature drop among different perforated fins. This type of perforated fin has an improvement in heat transfer rate over its dimensionally equivalent solid fin.

Effect of Perforation Shapes on the Heat Transfer Characteristic of Perforated Fins

A large number of engineering applications required rapid heat dissipation from its surface. This is achieved by the use of the fins i.e. increasing the surface area. Enhancement of heat transfer and reduction in the weight is the major criteria for designing the fins. The main objective of this project is to enhance the heat transfer through the use of perforated fin. A large number of study have been conducted on shape modification by cutting some material from fins to make holes, cavity, slots, groves or channel through the fin body to increase flow area. A rectangular fin of dimension 100 mm. x 200 mm. x 2 mm. and area of perforation is 100 mm2 was selected. The number of perforation was varied from 20, 28, 36 and 44. It was found that maximum temperature drop occurred with 44 perforations. With the same fin with 44 perforation, temperature drop and heat transfer was analysed for different shapes (circular, square, oriented square, pentagon and elliptical) of perforation. I was found that in case of different shape of perforation with same cross sectional area, weight is nearly reduced by 28.42 % for elliptical perforation (a/b>3) was most effective in which 32.20 % more temperature drop and maximum average heat flux as compared to other perforation shape.

The impact of square shape perforations on the enhanced heat transfer from fins: Experimental and numerical study

Heat sinks are widely adopted as heat transfer boosters for their role in promoting heat transfer surface area. To enhance the thermal behaviour of heat sinks under forced convection heat transfer, perforated fins are utilized. In the present investigation, the effect of utilizing the square perforation technique has been experimentally and numerically investigated. The study was conducted for different numbers of perforations, i.e. 4, 6, 9, 12, and 15; heat supplied rates of 1730, 2200, 2680, and 3150 W; and airflow velocities of 0.4, 0.7, 1.1, 1.4, and 1.8 m/s. The present numerical results were validated against the present experimental results and available data in the literature, and excellent agreements were found. Our results indicated that the perforated fin with square perforations has shown a reduction in the fin temperature up to 16 °C compared to the non–perforated one. Moreover, by increasing the number of perforations, higher heat rates were dissipated because of the rise in the flow turbulence level and the reduction in the thermal resistance between the fin surface and its surroundings. In addition, the existence of perforations reduced the friction factor around the fin and sequentially reducing the required flow pumping power, which adds another merit to the aforementioned perforation technique. Using square perforations showed a 5.9% reduction in average friction factor compared to circular perforations.

An experimental study on the air side heat transfer performance of the perforated fin-tube heat exchangers under the frosting conditions

In this paper, perforated fins were applied to enhance the air side heat transfer performance under frosting conditions for fin-tube heat exchangers with large fin pitches. The frost mass, frost thickness, heat transfer rate and heat transfer coefficient of the perforated fin-tube heat exchangers were measured and analyzed. Although, the frost mass for the perforated fin-tube heat exchangers was 46.7% more than that for the plain fin. The total heat transfer rate and the heat transfer coefficient of the perforated fin was increased by 38.9% and 31.8%. Moreover, under the same heat transfer rate, the heat exchangers with the perforated fins generated less frost mass compared with the plain fin. Two empirical correlations for predicting the j-factor and frost mass of the perforated fin-tube heat exchangers were developed respectively. The correlations were functions of the Reynold number, dimensionless fin pitch, dimensionless temperature, and humidity and Fourier number. The deviations between these predictions and the corresponding measured experimental data fell within ±15.0%.

Heat Transfer Analysis of Solid and Perforated Fins in Regular Arrangement

Extended surfaces are widely used in various applications like aerospace parts design, cooling and also in solar collectors for effective dissipation of heat. The present paper gives us an idea about the heat transfer analysis for solid pin fin and perforated pin fins that are fitted in a rectangular chamber. The rectangular chamber has a cross section area of 300 * 200 mm2. It is concluded from the experiment that perforated pin fin always works better as compared to solid pin fin in all conditions. Moreover, for lower range of Reynolds number, solid pin fin performs better whereas for higher range of Reynolds number, perforated pin fin performs better as compared to circular pin fin.

An experimental study of falling film evaporation in vertical channels with perforated fins of a plate-fin heat exchanger

In this paper, the heat transfer characteristics of falling film evaporation of pure refrigerant HCFC123 were experimentally investigated in a pilot scale plate-fin heat exchanger with perforated fins. The experiments have been carried out under the conditions that the mass flux is in the range of 23 to 49 kg/m2s, the corresponding inlet Reynolds number from 200 to 500, the heat flux from 3.2 to 9.5 kW/m2, and the evaporation pressure about 0.3 MPa. The variation laws of the local heat transfer coefficient versus the main parameters, including the inlet Reynolds number, heat flux and vapor quality were discussed. By introducing the two-phase convective multiplier F as a function of Lockhart-Martinelli parameter, a correlation for the two-phase forced convective component of the local boiling heat transfer coefficient was developed, and compared with correlations in open literature. By using a superposition method, the local boiling heat transfer coefficient that includes the contributions of forced convective boiling and nucleate boiling was analyzed. The predictions of local heat transfer coefficients were found to be in good agreement with experimental data.

Numerical Investigation of Forced Convection Heat Transfer from Longitudinal Perforated Fins in a Horizontal Rectangular Channel

The present paper reports a numerical study to investigate the heat transfer enhancement over horizontal channel with longitudinal rectangular fin arrays by laminar forced convection heat transfer. Fins are perforated with two types of holes, square and circular with different diameters. Three-dimensional steady-state continuity, momentum and energy equations along with the Boussinesq approximation were solved by finite volume method with commercial available software ANSYS FLUENT 15.1. The bottom finned wall of the channel was supplied with constant heat flux, while the other sides are insulated. Data used in performance analysis were obtained numerically for fin arrays of material aluminum, by varying geometry, diameter and number of perforation (12, 16 and 20) mm, (10-22) respectively. In addition at different channel inclinations ( 150?> , 1590?> and 15 180?> ), as well as by varying Reynolds number from 1800 to 2300, at modified Grashof number Gr * 5 15?108> . The results show that the Reynolds number and size perforation have a larger impact on average heat transfer coefficients for the both type of Perforations. Also the channel inclination increases the removal heat from the channel. Keywords: Force convection, heat transfer, perforated fin arrays, square holes, notch fins, ordination angle. DOI : 10.7176/JNSR/9-16-05 Publication date : August 31 st 2019

Experimental and numerical study of forced convection heat transfer from array of fins with various cross perforations

In this paper, heat transfer characteristics of new types of perforated fins with cross perforations are investigated using experimental measurement and numerical simulations. Conjugate equations of turbulent flow and conduction heat transfer are solved around fins and within fins using a finite volume code. Solution includes two types of circular and square perforations and Reynolds numbers from 2×104 to 4×104 based on the fin length. From the results of nu-merical simulation, structures of flow field and heat transfer for each configuration are illustrated and discussed. For validation, comparison is made with solid fin as well as perforated fins and reasonable trend for heat transfer is ob-served. For further analysis, a series of measurements is carried out for a model of perforated fins with one streamwise opening and one cross opening. It is shown that among different perforation configurations, a fin with 1 longitudinal perforation and 3 vertical perforations shows the best heat transfer performance. In addition, it is found that the circular perforation is preferred in comparison with square perforation considering both heat transfer performance and pressure drop.

Experimental and numerical investigation of heat transfer augmentation in heat sinks using perforation technique

Extended surfaces are commonly adopted as a thermal management technique for heat transfer augmentation owing to their ability to facilitate an increment in the available surface area, and hence, the total heat dissipation. This study aims at experimentally and numerically evaluating the performance of fins with and without perforated geometry under forced convection heat transfer. The effect of the circular perforations at different perforation number and size, airflow velocity, and different input powers on the thermal and hydraulic performance of those fins, at a constant perforation area of 24 cm2, has been examined. An excellent agreement has been observed between the experimental and numerical results. The findings of this investigation show that the thermal performance of the perforated fins is superior over the non-perforated ones with a reduction in fin temperature up to 8.5 °C. Further, increasing the size and number of perforations promotes the convective heat transfer process. On the other hand, the perforated fins offer an outstanding hydraulic performance compared to the solid ones since the flow friction factor and the required pumping power will be less, particularly with the increased number of perforations. Adopting the perforation technique has been discussed in detail, as well as significant experimental and numerical information has been reported in this article.

HEAT TRANSFER AND FRICTION CHARACTERISTICS OF AN ARRAY OF PERFORATED FINS UNDER LAMINAR FORCED CONVECTION

Three-dimensional incompressible laminar fluid flow and heat transfer of a heated array of circular perforated fins are examined numerically. The Navier–Stokes and energy equations are solved by a finite volume method using the SIMPLE algorithm. The second order upwind technique is employed to discretize the momentum and energy equations. Computations were performed for a range of Reynolds numbers 100 ≤Re ≤ 350. Thermal performance and effectiveness as well as friction coefficient of perforated and solid fins are determined for the optimum porosity. The results show that the average coefficient of friction reduces with increasing the Reynolds number and the number of perforations. The heat transfer rate increases with the porosity and the Reynolds number. It is found that perforated fin effectiveness decreases with the number of peroration at constant Reynolds numbers.