Circular Fins Research Articles

CFD studies on thermal performance augmentation of heat sink using perforated twisted, and grooved pin fins

In the present study, a numerical investigation is conducted to observe the effect of forced convection heat transfer for various innovative shaped pin fin heatsink designs by altering the effect of various parameters on the fluid domain and the solid domain. The study illustrates the possible configuration of such heat sink design implementing Twisted and Grooved shaped innovative pin fins. Different perforation shapes and alignments are applied to extend the surface area resulting in increased heat transfer rate and hydrothermal performance factor (HTPF). Navier-Stokes's equations and RANS (Reynolds Averaged Navier-Stokes) based k−ε turbulence model govern the modeling of the study. Compared to available recent literature, the HTPF has increased by about 9% for Grooved Circular perforated pin fin at Reynolds number (Re) = 21367. The results showed an improvement of the average Nusselt number (Nu) by 32%. The grooved-shaped circular perforated heat sink has been observed with an improved HTPF of about 27% from the baseline case. Also, the Cu-Diamond composite on grooved circular perforated pin fin has shown improvement in HTPF by 33% at Re = 21367. Pressure drop has also been observed to be lowest in the case of the grooved fin with circular perforations. Hence, this design significantly benefits the HTPF.

Investigation of thermal entropy generation and nanofluid flow in a new heatsink with effect of nanoparticles shape

In this paper, the entropy generation (ENT) in two novel micro heatsinks (MHSs) is investigated numerically. The HSs are two types of octagonal ones with circular and rectangular fins. Water/alumina boehmite nanofluid (NF) is used as a cooling fluid for HSs, which enters from the middle of the heatsink (HS) and exits from four side outputs. The Reynolds number (Re) varies from 300 to 1700 and the concentration of nanoparticles (NPs) changes from 0 to 6%. The shapes of NPs include platelet brick, blade, cylinder, and Oblate Spheroid (OS). A heat flux due to the operation of a microprocessor is applied to the bottom of the HSs made of copper. The finite element method is used for the simulations. The variables include pumping power (PP), ENT, ENT due to fluid friction, thermal ENT, temperature gradient contours, etc. The results of this study show that less ENT occurs in the HS with rectangular fins and less PP occurs in the HS with circular ones. Increasing the Re reduces the amount of ENT and increases the PP. The results demonstrate that the addition of NPs with high volume percentages is not suitable in terms of ENT and PP.

Effect of circular perforated pin fin on heat transfer and fluid flow characteristics of rectangular microchannel heat sink

In the present work, a numerical analysis has been performed to observe the heat transfer and fluid flow characteristics of the perforated pin fin microchannel heat sink. Six equidistant cylindrical pin fins with circular perforation at the center are entrenched at the base wall of the channel. This perforated pin fin can act as an extended surface and enhanced the heat transfer whereas the circular perforation may reduces the pressure drop and also influence the flow characteristics. The analysis has been done for the single-phase flow with Reynolds number ranges between 150 to 350 and the nondimensional diameter(α) of circular perforations considered in this study are 0.33, 0.5, 0.67 and 0.83. It is observed that the Nusslet number improves with the smallest perforation that is α = 0.33 and decreases as the diameter of perforation increases however the maximum value of overall thermal performance is associated with the perforation size of 0.5.

Micro-particle image velocimetry study on hydrodynamic characteristics of in-line and staggered micro pin fin arrays

Detailed hydrodynamics in microchannels with in-line and staggered circular micro pin fin structures over Reynolds number ranging from 50 to 700 are experimentally studied with micro-particle image velocimetry. The velocity field, vortex structure and vorticity distribution is obtained and analyzed, and differences in flow behavior in the two arrangements are examined. The result indicates a delay in the onset of vortex shedding in micro pin fin arrays as compared to their macro scale counterpart due to the confinement effect of channel walls. Flow pattern in the in-line arrangement is featured by the microchannel-like main stream between the pin rows and the double vortex wake flow behind the pins, while flow in the staggered arrangement is characterized by the wavy main stream and a pair of accelerated flow streams on two sides of the pins. Vorticity bands along the sides of the wake region intensify with the Reynolds number, diffuse further downstream, but narrow in width. Visualization and data extraction results reveal that flow behavior in the staggered arrangement differs from that in the in-line arrangement in terms of a smaller area occupied by the low-velocity wake region and a more sufficient mixing of fluid.

The Role of Pin Fin Array Configurations and Bubble Characteristics on the Pool Boiling Heat Transfer Enhancement

Pool boiling surface modification by pin fin array has demonstrated a practical but effective cooling enhancement. Whilst the main challenge is to determine the best configuration of the pin fin dimensions and positioning, it is known that the result varies among the working conditions. To obtain a more general formulation, it is utterly vital to obtain a deep understanding of the pool boiling mechanism during the phase-change process. This study aimed to analyze the role of pin fin array configuration on the pool boiling phenomenon by generating visualization and non-dimensional analysis. The results illustrated three different regimes occurring during the boiling process: natural convection, isolated bubble, and merged bubble. For all regimes, the average heat transfer performance was enhanced as the fin gap rose to 17% and 63% for circular and rectangular pin fins, respectively. Furthermore, Grashof (Gr) and Bond (Bo) numbers were calculated to quantitatively describe the effect on the bubble dynamics. From these approaches, it was found that the insulated bubble regime provides a better means of cooling by around 60% due to the better bubble dynamics.

Performance Development and Evaluation of Solar Air Collector with Novel Phase Change Material

Experiments were carried out on an evacuated tube solar air collector connected to intrinsic thermal power storage to provide warm air unless solar radiation was available. As a phase change material, stearic acid was employed (PCM). Water has been used as a base fluid for converting sunlight into electricity gain to warm air, and the solar collector’s manifold was connected to the intrinsic thermal energy store. The most significant temperature variation between warm air and ecologic air was 38°C and 22°C, respectively, during direct and indirect solar radiation. A circular fin arrangement was used to achieve a flow rate of 0.020 kg s-1. The efficiency of minimum airflow rates (0.020 kg s-1) was 0.08–0.48 times that of maximum airflow rates (0.04 kg s-1). Because of the PCM’s better heat-storing capability, this system has a benefit over sensible storage systems in that it may be used after sunset.

Impact of utilizing hollow copper circular fins and glass wool insulation on the performance enhancement of pyramid solar still unit: An experimental approach

Desalination of salt and contaminated water, which is widely used in remote areas, is difficult due to high construction and maintenance costs. So, solar still units by using a free energy source are more economical than other desalination technologies. The current article aims to model the impact of copper fins, and insulation on the accomplishment of a solar unit. Hence, three different scenarios have been introduced, and the tests were done from August to September of 2020 in Shahriar-Iran. In each of the scenarios, a conventional solar still with pyramid-shaped compared with an enhanced pyramid-shaped unit. The scenarios were designed in order to evaluate the efficacy of increasing fins number and insulation on the solar still unit productivity. The outcomes revealed that the maximum daily productivity is about 5.33 L/m2 which demonstrated a 62.5% enhancement in freshwater productivity compared with traditional pyramid solar still units. Also, the daily efficiency of first, second, and third modified pyramid solar stills is estimated to be 39.64, 43.3, and 48.12% respectively. The economic analysis revealed that using hollow circular copper fins, and glass wool insulation diminishes the cost of producing freshwater from the first, second, and third modified pyramid-shaped solar still by 12.76, 16.68, and 27.33% respectively.

Investigation on the Contribution of Large-Scale Fluctuation and Small-Scale Disturbance of Coolant to Heat Transfer Enhancement in a Rectangular Channel With Pin Fins

Abstract The flow field in a channel with staggered pin-fin array was measured using time-resolved Particle Imaging Velocimetry (PIV). The distributions of flow field statistics were compared with those of Nusselt number on the endwall measured by thermochromic liquid crystal (TLC) of the same geometry. Lower-order large-scale fluctuation and higher order small-scale disturbances were examined separately using Proper Orthogonal Decomposition (POD) to study the flow field characteristics and their individual effect on the heat transfer enhancement. Pin fins with circular and square cross-section geometries were studied at Reynolds numbers of 10,000 and 20,000. Results indicate that for circular pin fins, the distribution of lateral/transverse velocity fluctuations or turbulent kinetic energy from large-scale vortex shedding resembles that of local Nu, and the heat transfer augmentation downstream of the recirculation zone is dominant, while the heat transfer enhancement is limited in the shear layer on both sides of recirculation where disturbances are small scale. However, for square pin fins, heat transfer augmentation in the shear layer is as strong as that downstream of recirculation, while large-scale fluctuations downstream is much weaker than small scale disturbances in the shear layer. Compared to small-scale disturbances, large-scale fluctuations are found to contribute more efficiently to endwall heat transfer enhancement both for circular and for square pin fins. Large-scale fluctuation, as well as heat transfer enhancement, weakens with the increase in Reynolds number, while smaller-scale disturbance grows stronger at the same time.

Heat and Flow Study of the Internally Finned Tubes with Different Fin Geometries

Heat and flow enhancement is a critical weapon for the design of highly efficient, compact, and cost-effective devices. The objective of this analysis is the detailed examination of the implementation of different fin shapes on the internal side of a tube aiming the heat and flow enhancement. The reference empty tube is examined, while the use of circular, rectangular, and triangular fins is also studied. Different simulations were conducted with a developed computational fluid dynamic model, and the results were expressed in heat and flow terms. The developed model was validated by comparing the results with the theoretical expressions for the Nusselt number, as well as for the friction factor. The obtained results were evaluated by calculating the heat convection coefficient, the pressure drop, the Nusselt number, the friction factor, the pump work, the mean wall temperature, and the Bejan number. According to the calculations, the use of rectangular fins is the best solution; the use of triangular fins is the second choice, while the less efficient improvement method is the use of circular internal fins. Regarding the heat transfer enhancement, the rectangular fins lead to 36% enhancement, circular fins to 25%, and triangular fins to 23% compared to the reference tube.

Study of Impingement Cooling Technology by Using Circular Pin Fins and Mist/Air Methods in Gas Turbine Combustor

The gas turbine is an indispensable part of technology and it is commonly used in electric power, aviation and marine mechanical. However, the gas combustion temperature was higher than the melting point of metal, which prevents further increase in efficiency in a gas turbine. To enhance the turbine inlet temperature greatly, an advanced cooling technology has been essentially required to protect the material of high thermal components. The final numerical results are compare with each other and show the characteristics of heat transfer and pressure drop. In these investigations, different cases evaluate that the adiabatic cooling effectiveness (ηc ) indicates a downward curvature in the following descending order: circular pin fin with mist case = circular pin fin only case > normal with mist cooling case > normal with air only case. Mist/air impiangement cooling with circular pin fins not only maintain the superiorities of air cooling jets, but more effective than pin fins technique. Accordingly, renewing the air impingement cooling systems with pin fins and mist cooling seems to be more attractive. The inspire application of the circular pin fins and mist/air impingement cooling will make it a reference for designing a new cooling structure in marine gas turbine combustor.

Numerical simulation of dimensions and arrangement of triangular fins mounted on cylindrical lithium-ion batteries in passive thermal management

This paper examines a battery pack consisting of three cylindrical lithium-ion batteries in an enclosure saturated with Phase Change Material (PCM) using COMSOL software. A two-dimensional longitudinal section of the enclosure is evaluated transiently. There are 6 circular fins on the batteries, which are triangular in two dimensions. The temperature of the battery cells, the liquid volume fraction of PCM, and the heat transfer coefficient (HTCO) are studied using two fin arrangements on the battery. The FEM is used to solve the equations. The results show that the use of a fin with a width of 1 cm to 4 cm reduces the maximum temperature (Tma) of the battery pack by 2.04 and 2.15, respectively, for models F1 and F2. Also, using a 1-cm wide fin instead of a 4-cm one enhances the HTCO for models F1 and F2 by 20% and 19.4%, respectively. However, the use of a fin with a width of 4 cm compared to 1 cm intensifies the amount of liquid PCM at different times. The values of battery temperature (TBa), the amount of liquid PCM, and the amount of HTCO are intensified with time.

Numerical study on thermal-hydraulic characteristics of flattened microfin tubes

Abstract The thermal-hydraulic characteristics and performance of the circular and flattened straight tubes with longitudinal inward microfins are studied with isothermal wall condition and Reynold numbers (Re) between 10,000 and 30,000. The geometric models with fins (8, 12, and 16 fins) and three flattening ratios (1.4, 2, and 3.4) are considered for the simulation. The results indicate that the longitudinal microfins have a limited effect on the improvement of heat transfer, but the application of microfins increases the pressure drop significantly. Furthermore, an increase in Reynolds number increases the heat transfer characteristics. Therefore, a discriminative use of longitudinal microfins for circular tubes to improve thermal performance is advised. Flattening the microfin tubes has shown a significant increase in heat transfer coefficient and friction factor compared to circular cross-section tubes with microfins. The percentage gain in heat transfer with the flattening ratio of 3.4 is about 52% compared to the circular fin tube at Re = 30,000. A 61% increase in centreline velocity is observed at Re = 10,000. Area-based Enhancement Factor (AEF) and performance evolution factor (PEF) are more than 1 for flattened tubes with microfins. It shows an improvement in the overall thermal-hydraulic characteristics of tubes.

Topology Optimization and Material Selection of Cooling Fin Structure in Submarine Data Center

The optimization of fin heat dissipation structure has always been an interesting topic, and a good heat dissipation structure is conducive to the full function of electronic devices. In order to obtain the best heat dissipation structure, the COMSOL density penalty method and heat conduction model are adopted to study the topology optimization model of heat dissipation structure. On the basis of circular fins, the material types of fins are kept unchanged, and the optimized fins are obtained after topology optimization under various working conditions. The contact area and average temperature of the topological fin and circular fin are compared. The simulation results show that the topology fin has better heat dissipation performance when the heat source power and ambient temperature are similar. Compared with the circular fin profile, the contact length of the topological fin increases by 48%, and the average temperature is reduced by 14.7K. After obtaining the best heat dissipation structure, the entropy weight method is adopted to select the best heat dissipation material of heat dissipation fins and determine that the best heat dissipation material is lead.

Study the mechanical properties of epoxy resin reinforcement by ziziphus spina-christi powder

The mixed convection investigation of various design parameters utilizing finned pipes in the cylindrical enclosure has been investigated computationally. Various geometries of fins are used (circular and longitudinal). The effect of fins number (12-16), aspect ratio (1.83-2.7), radius ratio (2-3) and fins geometry have been introduced within the present study. The observations show that when Richardson number=0.5 and 5.5 , the heat transfer decreases by 12.22% and 7.777%.,. Values of the Nusselt number rise as the number of fins increases. While, when the Rayleigh number is high, no noticeable variations in the numbers of fins (12 and 14). The purpose of using fins is to increase the surface area of heat transmission. The highest heat transfer improvement is shown to be 4.2 percent, when log (Rayleigh)=7.342 and 16 fins are utilized. The radius ratio does not affect Nusselt number throughout the whole Richardson and Rayleigh in both hot and cold locales. The turbulence sub-layer does not affect the free stream behaviour for different Richardson number. In the case of high Richardson number, the geometry does not influence the Nu. Longitudinal fins do not have dead zones, unlike circular fins, which have channelling generated by geometrical arrangement. To reach thermal equilibrium in a cold environment, the Nu in rectangular fins was reduced by 18% as compared to circular fins with a low Richardson number. Flow development would increase the impact of channelling. The heat transfer improvement decreases as the number of fins increases, as illustrated in temperature and velocity profiles for various values

Numerical investigation of the impact of various design parameters of finned-pipes on mixed convection

The mixed convection investigation of various design parameters utilizing finned pipes in the cylindrical enclosure has been investigated computationally. Various geometries of fins are used (circular and longitudinal). The effect of fins number (12-16), aspect ratio (1.83-2.7), radius ratio (2-3) and fins geometry have been introduced within the present study. The observations show that when Richardson number=0.5 and 5.5, the heat transfer decreases by 12.22% and 7.777%.,. Values of the Nusselt number rise as the number of fins increases. While, when the Rayleigh number is high, no noticeable variations in the numbers of fins (12 and 14). The purpose of using fins is to increase the surface area of heat transmission. The highest heat transfer improvement is shown to be 4.2%, when log (Rayleigh)=7.342 and 16 fins are utilized. The radius ratio does not affect Nusselt number throughout the whole Richardson and Rayleigh in both hot and cold locales. The turbulence sub-layer does not affect the free stream behaviour for different Richardson number. In the case of high Richardson number, the geometry does not influence the Nu. Longitudinal fins do not have dead zones, unlike circular fins, which have channelling generated by geometrical arrangement. To reach thermal equilibrium in a cold environment, the Nu in rectangular fins was reduced by 18% as compared to circular fins with a low Richardson number. Flow development would increase the impact of channelling. The heat transfer improvement decreases as the number of fins increases, as illustrated in temperature and velocity profiles for various values.

The effect of using circular fins with a V-shaped cut on the weight reduction and the overall performance of a finned tube heat exchanger

In this work, we have investigated the use of circular fins with a V-shape cut in place of regular circular fins. This study was carried out numerically in a natural convection heat transfer in order to understand the effect of creating a V-shape cut on circular fins. We performed this study for a 3D model in a laminar flow containing a single finned tube heat exchanger. The result of this study shows us that, using circular fins with a V-shape cut instead of regular circular fins can significantly improve weight reduction. For fins with a large diameter and a high thermal conductivity, the weight reduction can reach up to 27.8%. On the other hand, for the same fin weight, we can improve the total heat transfer rate by up to 41.6% by using fins with a V-shaped cut in the place of regular ones.

Pool Boiling Heat Transfer Performance and Bubble Dynamics from Pin Fin-Modified Surfaces with Geometrical Shape Variation

In this paper, an experimental study investigating the effect of the geometrical shape of the circular and rectangular pin fins on the heat transfer performance and the boiling phenomenon is presented. A pool boiling experiment in the HFE-7100 dielectric working fluid under atmospheric pressure was conducted. Boiling curves and boiling heat transfer coefficients of different test cases were plotted to evaluate the heat transfer performance as well as the captured images of the boiling phenomenon on the test samples. Two quantities, flow resistance and wetted perimeter, were calculated to understand the behaviour of the boiling physics due to variation of fin geometrical shape and, hence, their effect on the heat transfer performance. It was found that the cooling performance of the rectangular pin fins was higher than that of the circular pin fins, despite having a slightly higher flow resistance of 4% and 7%, respectively. This is believed to be the result of the longer wetted perimeter up to 27%, whereby the nucleation site has a higher probability of generating more bubbles in the same boiling surface area. For the tested modified boiling surface with 196 and 144 pin fins, the average heat transfer performances were found to have differences of up to 3.54 and 1.58 times larger, respectively.

On the performance of an innovative electronic chipset thermal management module based on energy storage unit concept utilizing nano-additive phase change material (NPCM)

Due to size minimization and increment in the frequency of electronic devices, efficient and reliable methods for thermal management are required to reduce operating temperature, enhance stability, increase lifetime and user comfort. To prevent the damages of leakage and corrosion which occur in conventional heat sinks, proposing innovative thermal management methods has always been welcomed. Regarding these issues and based on the energy storage unit concept, in this study, a passive heat sink (HS) is fabricated and characterized for electronic chipset cooling with heat fluxes of 2000 to 4000 W/m2 utilizing phase change material (PCM) and nano-additive PCM (NPCM). The presented cooling module has two separate parts of a conventional HS and energy storage unit which are linked together with horizontal circular copper fins; thus, this design provides indirect contact between PCM and electronic chipset. To elucidate the cooling ability of various cases, chipset and PCM temperatures in the transient and steady-state conditions, as well as thermal efficiency, are selected as the comparison criteria. In addition to this, image processing is carried out to visualize the PCM/NPCM melting behavior. The results indicate that the steady-state and transient temperatures decrease about 10 °C and 12 °C, respectively, in the case of innovative cooling module (PCM filled energy storage unit) compared to that of the conventional one (PCM filled heat sink). The maximum reduction in the chipset transient temperature is equal to 22 °C which can be achieved when the storage unit is filled with PCM/ZnO. At a heat flux of 3000 W/m2, the chipset experiences 60 °C after 19 min; while by the aid of a storage unit with 50, 90, 110, and 130 ml of PCM, this time increases to 34, 45, 50, and 53 min, respectively.

Experimental and Numerical Study of the Turbulent Flow and Heat Transfer in a Wedge-Shaped Channel With Guiding Pin Fin Arrays Under Rotating Conditions

Abstract Experiments and numerical simulations under stationary and rotating conditions have been conducted to investigate turbulent flow and heat transfer characteristics of innovative guiding pin fin arrays in a wedge-shaped channel, which models the internal cooling passages for modern gas turbine blade trailing edge. The Reynolds number range is 10,000–80,000, and the inlet rotation number range is 0–0.46. With the increase of Reynolds number, the enhancement of heat transfer performance of the channel with guiding pin fin arrays is significantly higher than that of the channel with conventional circular pin fin arrays. At the highest Reynolds number of Re = 80,000, the overall Nusselt number of the channel with guiding pin fin arrays is about 33.7% higher than that of the channel with circular pin fin arrays under the stationary condition and is about 23.0% higher than the latter under the rotating conditions. At the highest inlet rotation number of Ro = 0.46, the heat transfer difference between the trailing side and leading side of the channel is significantly lower with the guiding pin fin arrays than with the circular pin fin arrays. Through both the experiments and numerical simulations, it is found that the heat transfer uniformity of the endwall is significantly improved by the guiding pin fin arrays, and the rotation presents appreciably less influence on the heat transfer distribution with the guiding pin fin arrays than with the circular pin fin arrays. Moreover, the novel guiding pin fins provide more reasonable flow distribution in the wedge-shaped channel and produce obviously higher heat transfer performance in the tip region of the channel, which is significantly advantageous for a better design of gas turbine blade trailing edge internal cooling.

Improved Melting of Latent Heat Storage Using Fin Arrays with Non-Uniform Dimensions and Distinct Patterns.

Employing phase-change materials (PCM) is considered a very efficient and cost-effective option for addressing the mismatch between the energy supply and the demand. The high storage density, little temperature degradation, and ease of material processing register the PCM as a key candidate for the thermal energy storage system. However, the sluggish response rates during their melting and solidification processes limit their applications and consequently require the inclusion of heat transfer enhancers. This research aims to investigate the potential enhancement of circular fins on intensifying the PCM thermal response in a vertical triple-tube casing. Fin arrays of non-uniform dimensions and distinct distribution patterns were designed and investigated to determine the impact of modifying the fin geometric characteristics and distribution patterns in various spatial zones of the heat exchanger. Parametric analysis on the various fin structures under consideration was carried out to determine the most optimal fin structure from the perspective of the transient melting evolution and heat storage rates while maintaining the same design limitations of fin material and volume usage. The results revealed that changing the fin dimensions with the heat-flow direction results in a faster charging rate, a higher storage rate, and a more uniform temperature distribution when compared to a uniform fin size. The time required to fully charge the storage system (fully melting of the PCM) was found to be reduced by up to 10.4%, and the heat storage rate can be improved by up to 9.3% compared to the reference case of uniform fin sizes within the same fin volume limitations.