Pin-fin Diameter Research Articles

A Review on Application of Pin-Fins in Enhancing Heat Transfer

The pin-fin is one of the main technologies in enhancing heat transfer. The accelerated flow and vortex structures are produced, which can disrupt the development of the flow boundary layer. The configuration of the pin-fin is obvious for heat transfer and flow characteristics, including its shape, size, and arrangement in the cooling channel. This work provides a detailed introduction to the application of pin-fins in enhancing heat transfer and reducing flow resistance, including the conventional shapes, improved shapes based on circular pin-fins and irregular shapes. At the same time, the influence of the diameter, height and density of pin-fins on heat transfer and flow performance is studied, and the influence mechanism is analyzed from the perspective of boundary layers. In addition, some applications that combine pin-fins with other cooling methods to further improve performance are analyzed. In terms of the optimization technology, the structure optimization for pin-fin shape and the layout optimization for pin-fin array are summarized. Therefore, this review provides a wide range of literature for the design of internal cooling channel pin-fins.

Experimental and numerical investigation on fluid flow and heat transfer behaviour of foam cladded pin fin heat sink

As technology advances, there is a growing demand for more efficient cooling solutions in electronics. Open-cell metal foams offer a unique solution, combining the strength of metals with the characteristics of foams, including being lightweight and having a high heat transfer area-to-volume ratio. Fully covering heatsinks with porous materials results in high pressure drop values, which is undesirable for electronics cooling. This study proposes a novel design that incorporates cladded aluminum foams on the pin fins within a heatsink. The hydrothermal performance of the proposed design is experimentally and numerically investigated. The results indicate that increasing the cladding thickness enhances heat transfer performance while increasing the pressure drop. For a heatsink with a pin fin diameter of 5 mm at the Reynolds number of 1121, the foam thickness of 5 mm depicts 46.5 % higher hydrothermal performance compared to a pin fin heatsink without porous while a fully porous covered heatsink depicts 38.9 % higher hydrothermal performance.

Multi‐objective optimization of a Fibonacci phyllotaxis micro pin‐fin heat sink

AbstractThere are still significant technical challenges associated with thermal management of electronic devices such as microprocessors. To improve heat dissipation performance of integrated circuits, a new Fibonacci phyllotaxis design of circular micropin fin heat sinks has been developed. To minimize both chip temperature and pumping power, a multi‐objective optimization technique was employed. The effect of design parameters such as phyllotaxis coefficient, pin fin diameter, and pin fin height on response parameters was numerically investigated using the full factorial design of the experiment. Artificial neural network was coupled with MO‐Jaya, to arrive at a Pareto frontier of optimal compromise solutions. The optimal set of design variables were found to be a height of 300 μm, a diameter of 122.6 μm, and a phyllotaxis coefficient of 130 μm with an inlet velocity of coolant 2.263 m/s. The selected optimum design was then investigated numerically, and the outcomes were compared to those predicted by the MO‐Jaya algorithm. The final confirmed response variables were a maximum temperature of 51.6°C and a pumping power of 0.191 W. The results show that the Fibonacci phyllotaxis structure of the micro pin fin heat sink has better heat‐dissipating performance.

Thermal performance of pin fin heat sinks with phase change material for electronic devices thermal management

In the present paper, an experimental and numerical study is conducted to analyze various factors affecting the thermal performance of a heat sink with phase change material (HS-PCM). In order to maintain the chip below the limit temperature of 80 °C, ZDJN-35 with a phase change temperature of 37 ∼ 45 °C is selected as the energy storage material. Under different PCM filling volume fractions, heat fluxes, and operation modes, the study evaluates the thermal performance of the HS using chip temperature and the effective time extension coefficient. The volume fractions of PCM are 0 vol%, 30 vol%, 60 vol%, and 90 vol%. Under heat fluxes of 4000 ∼ 14000 W/m2, the results indicate that under continuous operation, the HS without PCM reaches the limit temperature within 18 min at heat flux of 8000 W/m2. In contrast, the time to reach the limit temperature for HS with 30 vol% PCM, 60 vol% PCM, and 90 vol% PCM extends by 12 min, 19 min, and 26 min, respectively. Compared to the HS without PCM, the peak temperatures reduce by 4.8 %, 10.5 %, and 12.8 % for the HS with 30 vol% PCM, 60 vol% PCM, and 90 vol% PCM under intermittent operation. Moreover, under intermittent operation, temperature fluctuations decrease by 27.3 %, 36.0 %, and 37.3 %, respectively. Finally, the numerical results show that the optimization of pin fin diameter is opposite for passive and active cooling modes, and a heat dissipation unit height of 25.5 mm is recommended.

Heat transfer enhancement in multijet micropin fin heat sink

The thermal performance of tiny heat sinks with liquid cooling is being studied in order to solve the issue of electronics cooling. Increasing thermal performance while lowering pressure drop and maintaining a constant substrate temperature is a difficult task. The purpose of this study is to harvest the useful features of combination of microjet and micropin fins and explore the influence of geometrical features on fluid structures and heat transfer. To comprehend and assess the performance of a multijet heat sink with a micropin fin, three-dimensional numerical simulation is used in this inquiry. The three parameters under consideration are, the ratio of the jet diameter to the pin fin diameter (α), which ranges from 1.5 to 6.0; the ratio of the jet diameter to the jet standoff distance (β), which ranges from 0.75 to 1.5; and the pin fin pitch is determined by the ratio of the pin fin diameter to the pitch length (λ), which ranges from 0.1 to 0.8. The grid independence test is done to ensure accuracy in numerical results. The numerical scheme is validated by comparing numerical results with that of experimental results from literature. The results obtained from numerical simulation are analyzed. It has been found that improving heat transfer is not just caused by expanding the contact surface area; fluid structure vortex generation also affects overall thermal performance. Better overall performance is produced at lower values of α, β and higher values of λ. The ideal design parameters are α = 1.99, β = 1.431, and λ = 0.699, according to the optimization of geometrical parameters using a radial basis neural network surrogate model and particle swarm optimization. The jet Reynolds number is found to have no significant impact on the overall performance.

Fluid flow and heat transfer behavior of a liquid based MEMS heat sink having wavy microchannels integrating circular pin-fins

MEMS heat sink having wavy microchannels integrating circular pin-fins for cooling of microelectronic chips is proposed and analyzed in this work; the pin-fins are placed at the valleys and peaks of the wavy structure. The pumping power and thermal resistance of the proposed MEMS heat sink is higher and lower than that of MEMS heat sink having straight microchannels. At Reynolds number of 250, the maximum temperature of the microelectronic chip, generating 106 W/m2, when using the proposed MEMS heat sink is only 0.77 of that when using MEMS heat sink having straight microchannels; this ratio lowers to 0.6 at Reynolds number of 1250. The thermal resistance of the proposed MEMS heat sink is only 0.72 and 0.43 of that of the MEMS heat sink having straight microchannels at Reynolds numbers of 250 and 1250, respectively. Regarding the pumping power of the proposed MEMS heat sink, it is higher than that of the MEMS heat sink having straight microchannels by 2 and 3.7 at the lowest and highest Reynolds numbers, respectively. This work also analyzes the contribution of geometric features on the behavior of the proposed MEMS heat sink in terms of maximum temperature of the microelectronic chip, thermal resistance, and pumping power as well as that of microchannel employed in the proposed MEMS heat sink in terms of Poiseuille and Nusselt numbers. Maximum temperature of the microelectronic chip and thermal resistance decrease along with increase in pumping power with increase in amplitude, diameter of pin-fins, and hydraulic diameter of microchannel as well as with decrease in wavelength. Poiseuille and Nusselt numbers increased with rise in amplitude, diameter of pin-fins, and hydraulic diameter as well as decrease in wavelength. In addition, experiments have been conducted on two designs of the proposed MEMS heat sink to generate data for purposes of validating the model. The experimental data are compared with data from simulations and the difference between the two are within the uncertainty of experimental data thereby validating the model.

Deposition Characteristics of Particles with Different Diameters in an Impingement-Effusion Structure with a Double-Wall Blade

Ingestion and deposition of fine particles on the surface of the coolant passage degrade the blade’s cooling performance. This paper proposes a deposition model to investigate the complex deposition characteristics of fine particles during repeated collision, adhesion, rebound, and removal events in the small space inside a typical impingement-effusion structure with a double-wall blade. The results show that the particles rarely collide with the wall and escape directly from the film hole outlet when the particle diameters are smaller than 0.5 μm. Most particles with diameters of 0.5 to 1.0 μm are deposited after the first collision around the stagnation point in an area 0.35 times the pin-fin diameter. Some particles with diameters of 1.0 to 3.0 μm are deposited in the stagnation region, but most are deposited between the two pin fins and near the film hole after the second collision. Particles with diameters larger than 3.0 μm are mainly deposited on the region enclosed by the adjacent pin fins and film holes after multiple collisions, and the escape rate of particles is higher than 30%. The escape rates of particles with diameters of 0.5 to 1.0 μm and 1.0 to 3.0 μm have the same trends, exhibiting a decrease followed by an increase with the increasing particle diameter. The particles entering the impingement-effusion structure, especially those with diameters of 0.7 -0.8 μm and 1.4 -2.4 μm, are primarily deposited on the target surface, resulting in the cooling performance degradation of double-walled blade.

Artificial intelligence-based entropy generation investigation of two-phase nanofluid flow in a heatsink with pin fins

It is crucial to assess the efficiency of using entropy generation (EYG) in energy-consuming devices. In this article, a study is done on the EYG of laminar water/alumina nanofluid (NFD) in a heatsink (HTK) with circular pin fins. The NFD enters the middle of the HTK and exits around it and passes through the pin fins. The bottom portion of the HTK is subjected to a steady flux, and the temperature of the HTK is lowered by the cold NFD. By changing the diameter and height of pin fins and their distance, the values ​​of thermal EYG (TEYG), frictional EYG (FEYG), and total EYG (TOEYG) are estimated and the contours of temperature and NFD flow are presented. An optimization is performed on the results by using the response surface method (RSM) in the range of the studied variables to obtain minimum amounts of EYG and HTK temperature. The finite element method (FEM) and the two-phase mixture method are utilized to simulate the NFD flow. The findings show that increasing the height of the pin fins decreases thermal and TOEYG while increasing FEYG. Enhancing the distance between the pin fins, leads to a slight decrease in thermal and TOEYG.

The effect of short pin fin aspect ratio on thermal characteristics of intermittent impinging jet; An experimental and numerical study

BackgroundPin fins are secondary surfaces extending from an object to enhance the heat transfer rate. Pin fin is one of the most effective practical techniques used in many industrial applications and thermal treatments especially for cooling electronic devices. Also, Pulsating flow is extremely used in the machinery industry and it can improve the heat transfer. Therefore, pulsating flow is combined with an extended surface to enhance the heat transfer efficiency. MethodsThe current paper investigates numerically and experimentally the intermittent impingement flow and consequence heat transfer characteristics in the presence of a pin-fin array over a flat plate. The RNG k − ɛ model is employed to simulate unsteady three-dimensional turbulent flow using CFD software. The influences of jet Reynolds number, pulsation frequency, jet-to-surface distance, and aspect ratio on the distribution of the area-time averaged Nusselt number are studied. 36 elliptical pin-fins considered at three rows on the surface, placed at r/ D = 3, 5, and 7 (36, 60, and 84 mm) from the central point of the jet. Considering the influence of the aspect ratio on the streamline and temperature patterns of the flow, numerical simulations were conducted in various pin-fin diameters of 4–12 mm. Significant findingsFrom the experimental data, the results indicated that there is a specific frequency that the heat transfer increases for Reynolds numbers in the range of 10,000–20,000. The results illustrated that the rate of heat transfer is reduced with rising the diameter of the pin fin for AR>1, whereas it is enhanced for AR<1. The area-time averaged Nusselt number is enhanced with rising aspect ratio at various pin fin heights. For Re=10,000, the heat transfer rate decreases with increasing the jet-to-surface distance in steady state while it increases for pulsating flow. Also, the maximum value of turbulent kinetic energy appears nearby the pin-fin owing to the formation of a horseshoe vortex. The vortex structures are strengthened and grow downstream, as the frequency increases.

Multi-objective design of laminated cooling configuration applied in gas turbine based on fuzzy grey relational analysis

Laminated cooling is a compound system consisting of different cooling units that can provide effective protection to the hot components in next generation gas turbines. In the present work, using validated numerical simulations, the influential levels of geometrical parameters in laminated cooling configuration (film hole diameter, pin-fin diameter, impingement hole diameter and film hole inclined angle) on multi-objective functions (overall cooling effectiveness, friction loss and temperature uniformity) are calculated and ranked by fuzzy grey relational analysis (FGRA). The FGRA results indicate that the film hole diameter is the primary influence factor on the overall cooling effectiveness and temperature uniformity, but insensitive to the friction loss. Based on this finding, two novel laminated cooling configurations with revised film-hole shapes, i.e., fan-shaped film holes and discrete rectangular film slots, are proposed to meet the multi-objective requirement. Through calculations, it is proved that the overall cooling effectiveness of the discrete film slots with a width of 0.5 mm can be increased by approximately 20%, whereas the additional friction loss is negligible (the increase of flow resistance coefficient is only 0.06 at mass flow ratio equals to 1.19%). Meanwhile, the acceptable temperature uniformity along with high overall cooling effectiveness, low friction loss can be obtained with the design of the fan-shaped film holes. The present work provides a novel analytical method for the multi-influence-factor problem and multi-objective design of complex laminated cooling system in gas turbine application.

Thermal-Hydrodynamic Behavior and Design of a Microchannel Pin-Fin Hybrid Heat Sink.

A three-dimensional convective heat transfer model of a microchannel pin-fin hybrid heat sink was established. Considering the non-uniform heat generation of 3D stacked chips, the splitting distance of pin-fins was optimized by minimizing the maximum heat sink temperature under different heat fluxes in the hotspot, the Reynolds numbers at the entrance of the microchannel, and the proportions of the pin-fin volume. The average pressure drop and the performance evaluation criteria were considered to be the performance indexes to analyze the influence of each parameter on the flow performance and comprehensive performance, respectively. The results showed that the maximum temperature of the hybrid heat sink attained a minimum value with an increase in the splitting distance. The average pressure drop in the center passage of the microchannel first increased and then decreased. Furthermore, the optimal value could not be simultaneously obtained with the maximum temperature. Therefore, it should be comprehensively considered in the optimization design. The heat flux in the hotspot was positively correlated with the maximum heat sink temperature. However, it had no effect on the flow pressure drop. When the Reynolds number and the pin-fin diameter increased, the maximum heat sink temperature decreased and the average pressure drop of the microchannel increased. The comprehensive performance of the hybrid heat sink was not good at small Reynolds numbers, but it significantly improved as the Reynolds number gradually increased. Choosing a bigger pin-fin diameter and the corresponding optimal value of the splitting distance in a given Reynolds number would further improve the comprehensive performance of a hybrid heat sink.

Energy analysis of a phase change material embedded heat exchanger for air conditioning load reduction in different Indian climatic zones

Air conditioning (AC) systems for tropical countries like India account for sixty percent of the total energy needs of a building. With the onset of COVID-19, the increase of fresh air ventilation rate has been recommended by various guidelines for indoor spaces which increase the load on the AC system. The present study attempts to reduce this burden through retrofitting a phase change material (PCM) embedded pin fin heat exchanger into an air-conditioning system. The heat exchanger is designed to cater to the peak load fluctuations for cities in three hot climatic zones of India, viz., Jaisalmer, Kolkata, and Delhi. Dodecanol with a melting temperature of 24 °C, is chosen as the appropriate PCM material for these locations. The optimal pin fin diameters are estimated through an entropy generation minimization analysis for the three locations. A heat transfer analysis of the PCM embedded heat exchanger is further presented through an analytical approach to estimate the PCM mass requirement and energy savings potential. The masses of the PCM estimated for Jaisalmer, Kolkata, and Delhi are 11.36 kg, 22.42 kg, and 19.35 kg, respectively for their respective peak load fluctuations of 0.25 kW, 0.28 kW and 0.48 kW. Energy savings of up to 4.7 % for Delhi, 2 % for Kolkata, and 2.75 % for Jaisalmer are identified with the PCM embedded heat exchanger incorporation. The results show the potential of such PCM thermal storage in reducing the peak energy demands of buildings amidst various environmental and health concerns.

Influence of pin-fin height and diameter on flow and cooling characteristics of three-layer porous laminates: An experimental study

ABSTRACT Pin-fins play a very important role in heat-transfer enhancement in engine combustor liners. In this engineering-scale experimental study, the flow and cooling characteristics of two- and three-layer porous laminates with pin-fins were compared. The influence of the diameter and height of the pin-fin on the flow and cooling characteristics of three-layer porous laminates was also investigated. Adding a third (impingement) layer to the two-layer porous laminate in the study increased the heat-transfer coefficient by 66.00% and the cooling efficiency by 5.90%; both performance factors were further improved as the pin-fin diameter and height in the three-layer laminate were reduced. An empirical expression for the Nusselt number of a three-layer porous laminate was obtained, with a prediction error below 5%.

Performance analysis and optimization of a novel cooling plate with non-uniform pin-fins for lithium battery thermal management

• Cold plate with varying-diameter pin-fins is proposed for battery thermal management. • Heat generation rate of lithium battery cell is evaluated with experiment method. • The impacts of varying diameter pin-fins on cold plate performance are studied. • Optimization is performed to search the optimal varying pattern of pin–fin diameter. • The pump work, weight and T sd are reduced by 29.8%, 29.0% and 17.4%, respectively. The structure of the flow path has significant impacts on the performance of cooling plate for battery thermal management. This paper aims at improving the temperature uniformity, power consumption and weight performance by proposing a novel cooling plate with non-uniform pin-fins. Experimental method is employed to obtain the battery heat generation rate at 5C discharge rate. Then the performances of cooling plates with fixed diameter and varying diameter pin-fins are evaluated based on CFD method. To explore the best varying pattern of the pin–fin diameter, multi-objective optimization with multi-island genetic algorithm considering the maximum temperature (T m ), temperature standard deviation (T sd ), power consumption (P) and mass of cooling plate (m) is performed. Then numerical simulation is employed to compare the optimized design with the traditional parallel mini-channel design. The result shows that optimized design with non-uniform pin fins can reduce the power consumption, weight and temperature standard deviation by 29.84%, 29.00% and 17.43%, respectively. The maximum temperature is also reduced by 1.04 °C.

Parametric Studies of Laminated Cooling Configurations: Overall Cooling Effectiveness

Combing the advantages of film cooling, impingement cooling, and enhanced cooling by pin fins, laminated cooling is attracting more and more attention. This study investigates the effects of geometric and thermodynamic parameters on overall cooling effectiveness of laminated configuration, and model experiments were carried out to validate the numerical results. It is found that the increases in film cooling hole diameter and pin fin diameter both result in the increase in cooling effectiveness, but the increases in impingement hole diameter, impingement height, and spanwise hole pitch degrade the cooling performance. The increase of the coolant flow rate causes the increase in cooling efficiency, but this effect becomes weaker at a high coolant flow rate. The coolant-to-mainstream density ratio has no obvious effect on cooling effectiveness but affects wall temperature obviously. Moreover, based on the numerical results, an empirical correlation is developed to predict the overall cooling efficiency in a specific range, and a genetic algorithm is applied to determine the empirical parameters. Compared with the numerical results, the mean prediction error (relative value) of the correlation can reach 8.3%.

Multi-optimization of a specific laminated cooling structure for overall cooling effectiveness and pressure drop

The structural optimization of a specific laminated cooling structure is conducted under gas turbine combustor representative aero-thermal conditions, with the aim at improving its overall cooling effectiveness. The optimization procedure is realized by using conjugate heat transfer CFD analysis and radial basis function neural network (RBFNN) surrogated model. For this specific laminated cooling structure, both the thickness of impinging plate (ti) and the thickness of film cooling plate (tf) are all fixed as 0.5 mm. The other geometric parameters including impinging-hole diameter(di), pin-fin diameter(dp), film-hole diameter (df), inner height of double walls (H), streamwise hole-to-hole pitch (S) and spanwise hole-to-hole pitch (P) are selected as the design variables. Two geometric constrains are considered that the total thickness of laminated cooling structure is not bigger than 2 mm, and the minimum clearance between adjacent fins should be bigger than 0.5 mm. By using the current CFD-based optimization methodology, the optimized laminated cooling structures are presented from the given range of possible geometric variables. An optimized laminated cooling structures makes the maximum spatially-averaged overall cooling effectiveness approach to 0.9, and the other for minimum relative total pressure drop can reach 0.17%. Moreover, it is found that the thermal stress has a regularity with the overall cooling effectiveness.

On the heat transfer characteristics of a Lamilloy cooling structure with curvatures with different pin fins configurations

PurposeThe pin fin is applied into a Lamilloy cooling structure which is broadly used in the leading edge region of the modern gas turbine vane. The purpose of this paper is to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge region of a turbine vane.Design/methodology/approachA numerical method is applied to investigate effects of the layout, diameter and shape of pin fins on the flow structure and heat transfer characteristics in a newly improved Lamilloy structure at the leading edge of a turbine vane. The diverse locations of pin fins are Lp = 0.35, 0.5, 0.65. The diameter of the pin fins varies from 8 mm to 32 mm. Three different ratios of root to roof diameter for pin fins are also investigated, i.e. k = 0.5, 1, 2. The Reynolds number ranges from 10,000 and 50,000. Results of the flow structures, heat transfer on the target surface and pin fin surfaces, and friction factor are studied.FindingsThe heat transfer on the pin fin surface gradually decreases and then increases as the location of the pin fins increases. Increasing the diameter of the pin fins causes the heat transfer on the pin fin surface to gradually increase, while a lower value of the friction factor occurs. Besides, the heat transfer on the pin fin surface at a small root diameter increases remarkably, but a slight heat transfer penalty is found at the target surface. It is also found that both the Reynolds analogy performance and the thermal performance are increased compared to the baseline whose diameter and normalized location of pin fins are set as 16 and 0.5 mm, respectively.Social implicationsThe models provide a basic theoretical study to deal with nonuniformity of the temperature field for the turbine vane leading edge. The investigation also provides a better understanding of the heat transfer and flow characteristics in the leading edge region of a modern turbine vane.Originality/valueThis is a novel method to adopt pin fins into a Lamilloy cooling structure with curvature. It presents that the heat transfer of the pin fin surface in a pin-fin Lamilloy cooling structure with curvature can be significantly increased by changing the parameters of the pin fins which may lead to various flow behavior. In addition, the shape of the pin fin also shows great influence on the heat transfer and flow characteristics. However, the heat transfer of the target surface shows a small sensitivity to different layouts, diameter and shape of pin fin.

Electrical Circuit Modeling and Validation of Through-Silicon Vias Embedded in a Silicon Microfluidic Pin-Fin Heat Sink Filled With Deionized Water

This article presents the electrical circuit model of signal-ground through-silicon vias (TSVs) in a silicon microfluidic pin-fin heat sink in which the pin-fins are surrounded by deionized water. Such TSVs are asymmetric vertically because the TSVs are partially embedded in cylindrical pin-fins as well as in a rectangular silicon base. In this article, we propose a circuit model that segregates the asymmetric geometry into two symmetric segments: one segment for a silicon base and the other segment for cylindrical silicon pin-fins surrounded by deionized water, which we refer to as “a pin-fin segment.” Specifically, the pin-fin segment is modeled using two-dielectric coaxial-line formulas to represent the double layers of silicon dioxide and silicon that surround the copper vias. Using the developed circuit model, this article quantitatively analyzes the impact of fluidic designs, such as the diameter and height of pin-fins on the electrical characteristics of TSVs. Following circuit model validation using high-frequency electromagnetic field simulations, the modeling results are compared with measured data.

Experimental study of free-stream turbulence intensity effect on overall cooling performances and solid thermal deformations of vane laminated end-walls with various internal pin–fin configurations

Experimental investigations of mainstream turbulence intensity (Tu) effect on conjugate heat transfer performances, total pressure loss and solid thermal deformations of vane laminated cooling end-walls (LCEs) have been carried out under two engine-near mainstream-to-coolant temperature ratios of 1.4 and 2.0. Influences of parameters of internal elements of LCEs were discussed. A servicing film cooling end-wall (FCE) was chosen as a reference. Two typical Tus were designed, 2.2% and 10.1% (in the engine range). Measurements of fluid-thermal-solid coupling characteristics of cooled end-walls were implemented in a hot wind tunnel based on matched engine Biot number under three mass flow ratios. Generally, the elevated Tu exhibited a negative influence on overall cooling effectiveness and component reliability of cooled end-walls, total pressure loss in cascade and slight thermal deformations of LCEs. Moreover, the elevated Tu displayed a negative effect on the remarkable benefit of LCEs over FCE. The shape and diameter of pin-fins and the impingement-hole size played complex roles on overall effectiveness, surface thermal gradient, aerodynamic loss and component weight. However, the Tu effect on the aforementioned roles was slight. Overall, the LCE with diamond-shaped pin-fins and large impingement-holes was the most optimal design.

Heat Transfer Characteristics in a Pin Finned Channel With Different Dimple Locations

A numerical simulation is conducted to investigate effects of dimple locations on the flow structure and heat transfer in a dimpled-pin finned channel. Pin fins are arranged with a staggered layout on the endwall surface. The dimple print diameter is the same as the pin fin diameter. Five different dimple locations are investigated in this study. All results are acquired at Reynolds numbers ranging from 8,500 to 60,000. The results show that the dimple locations have remarkable effects on the flow structure and heat transfer in a dimpled-pin finned channel. The Nusselt number of the dimpled-pin finned channel is only increased by 3.52%, while the friction factor is increased by 1.81% compared to the pure pin finned channel when the dimple is located in the wake region. The wake and reversed flow are responsible for this low heat transfer augmentation. When the dimple is located in between the two pin fins, the counter-rotating vortex and impingement within the dimple produce the highest Nusselt number and the lowest friction factor among the tested dimple locations. In this case, the Nusselt number is increased by 20.94% and the friction factor is decreased by 1.69% compared to the pure pin finned channel.