Porous Heat Sink Research Articles

Thermohydraulic performance optimization of integrated porous pin fins in microchannel heat sink using shape optimization coupled with NSGA

Micro porous heat sink (MPHS) with enhanced heat transfer performance faces higher pressure drop challenges than conventional heat sinks. Practical applications of MPHS are recently investigated focusing on basic structures. But explorations on complex structures and their performance enhancement are limited. Moreover, the heat conductivity along channel height direction needs further enhancement. To address the problems and extend porous fin designs, we propose a brand-new bionic integrated porous pin fin in MPHS. Procedures of shape optimization coupled with NSGA are applied to the porous fin design. The objective is chosen as figure of merit (FOM) regarding integrated pin fin spacing, solid sub pin fin spacing, and porous zone diameter. This novel method in MPHS investigation helps to find the optimal geometric parameter combination and counter-intuitive design. Then, a detailed performance comparative analysis for the optimized structure is conducted. The results show improvement ratio ranges of FOM are 18.79–––21.65%, 71.84–––108.72%, and 212.7–––231.5%, compared to non-optimized, partially-filled, and fully-filled structures, respectively. This work indicates that the innovative design attains significant energy efficiency improvement, and the novel method is feasible for comprehensive optimization.

A facile design of porous heat sink optimized thermodynamically for thermo-hydraulic performance

Implementing active cooling through micro-channel heat sinks integrated with printed circuit heat exchangers demands a simultaneous enhancement of thermal and hydraulic performance, all while avoiding complex designs for ease of fabrication. We propose a porous wall embedded double-layered micro-channel heat sink, aiming to decrease the necessary pumping powers while maintaining a minimal impact on the heat transfer rate. Additionally, this design simplifies geometric complexities, enhancing ease of fabrication. We assessed the feasibility of different porous embedded double-layered micro-channel heat sink configurations by evaluating their thermal and hydraulic performance. Our analysis uniquely integrates the principles of the second law of thermodynamics with traditional first law analysis, providing novel insights into heat sink design. We discovered that configuring porous walls solely in the top layer of the double-layered micro-channel heat sink is the only viable option. Furthermore, our analysis reveals that embedding porous walls exclusively in the top layer reduces irreversibility due to frictional losses by 9.13 %, with a slight increase in irreversibility due to heat transfer by 1.55 %, in comparison to the solid double-layered micro-channel heat sink at a flow rate of 1000 ml/min. Moreover, at the same flow rate, compared to configuration with porous walls in both layers, the top layer configuration exhibits improved thermal performance by 17.28 %. Next, we demonstrate that while the first law analysis indicates the viability of the top porous configuration, the second law analysis limits its viability to a certain coolant flow rate range. Finally, we optimize the heat sink design and coolant flow rates, proposing a viable design by simply incorporating porous walls in only the top layer of double layered micro-channel heat sink, which otherwise proved to be non-viable.

Concentrated solar photovoltaic cell equipped with thermoelectric layer in presence of nanofluid flow within porous heat sink: Impact of dust accumulation

Solar cell performance has been enhanced by means of a cooling system involving nanofluid jet impingement. A thermoelectric module has been located beneath the Tedlar layer resulting in greater electrical output. MWCNT nanoparticles were added to water as a testing fluid. The nanoparticles were concentrated up to a maximum value of 0.036, to achieve a homogenous mixture. To scrutinize the influence of dust accumulation on the performance of the unit, the transmissivity of glass was calculated based on dust density. Different concentration ratios (CR) were examined to assess their influence on the system's performance using Fresnel lenses in the setup. To further enhance the performance, the unit was tested both without (1) and with (2) pin fins. With the increase of CR from 2 to 14, the PV efficiency reduces by around 26.15% and 25.31% for cases 1 and 2, respectively. The value of TE efficiency for case 2 with CR=14 is 4.16 times greater than that with CR=2. The thermal efficiency of case 1 enhances by 4.8% with the growth of CR. For case 1, the improvement in PV, TE and thermal efficiencies is about 1.42%, 8.48% and 0.91%, respectively, with applying porous zones. Also, the temperature uniformity contributes a further 8.05% improvement. Thermal, TE and PV efficiency decrease respectively by about 7.69%, 12.11% and 26.47%, with an increase in dust density from 0 to 7.2 for case 2.

Evaluations of corrugated macro-structure porous heat sinks for the combined heat dissipation and noise reduction performance

In compact air convection cooling applications, it is desirable to satisfy noise reduction and heat dissipation within same functional space. Designing a solution for such application need to consider thermal, acoustic and flow aspects. The corrugated arrangement of porous material is utilized for the combined thermal-acoustic function, as it is known to offer a lesser mean-flow pressure drop than other geometries such as block shape, wedge shape. It consists of air channels separated by porous walls which conduct the heat away from base of the heat sink. The porous walls are considered to be consisting of a periodic foam material. The effect of higher-than-ambient temperatures on the acoustic performance of the corrugated arrangement is observed experimentally using a custom-built test setup. Two designed, additively manufactured corrugated porous heat sink samples with octet truss periodic foam are tested within the heat sink operating conditions observed typically in electronics cooling applications (<70 °C). A coupled thermal-acoustic model is presented to predict and study the performance of the corrugated porous heat sinks for the combined application. The relevant performance parameters are pressure drop, overall thermal resistance and transmission loss (TL). Using this model, a simple parametric design study is enabled with variations in porosity and different macro-geometric parameters of the corrugated arrangement.

EXPERIMENTAL INVESTIGATION ON TWO-PHASE HEAT AND FLUID FLOW IN POROUS HEAT SINKS

The current paper presents a novel experimental study on flow boiling in heat sinks with rectangular cross-section parallel microchannels fabricated by conventional powder metallurgy process. The dimensions of microchannel heat sinks are 20 mm &amp;#215; 20 mm. Porosities of heat sinks produced by sintering vary between 13.9&amp;#37; and 21.3&amp;#37;. A pure (nonporous) copper heat sink was also produced to compare the experimental data with each other. Channel sizes and numbers of all heat sinks used in the tests are identical. Flow boiling tests were carried out with deionized water at a flow rate of 238.2 kg/m&lt;sup&gt;2&lt;/sup&gt; s and 430.32 kg/m&lt;sup&gt;2&lt;/sup&gt; s. The fluid enters the heat sink at 80&amp;#176;C, completely liquid. The tests were carried out under constant heat flux conditions and the heat fluxes are 46.5 W/cm&lt;sup&gt;2&lt;/sup&gt; and 61.5 W/cm&lt;sup&gt;2&lt;/sup&gt;. Experimental studies have shown that the heat transfer coefficients in the heat sink with the highest porosity are from 28&amp;#37; to 33.3&amp;#37; higher than in the pure copper heat sink. Experimental heat transfer coefficients increase with increasing flow rate and decrease with increasing heat flux and vapor quality. On the other hand, the pressure drop values of the heat sink sample with the highest porosity were measured to be one and half times more than that of the pure copper heat sink. The imaging technique was used during the experiments. With the imaging technique, it was determined that the fluctuations in the pressure values were caused by the reverse steam flow. Additionally, the heat transfer coefficient values obtained experimentally were compared with the existing correlations in the literature. Experimental results showed that pure heat sinks are more compatible with the results given in the literature than porous heat sinks.

Experimental Study of Thermal and Pressure Performance of Porous Heat Sink Subjected to Al2O3-H2O Nanofluid

With the developing technology, the dimensions of electronic systems are becoming smaller, and their performance and the amount of energy they need increases. This situation causes the electronic components to heat up more and the existing cooling systems to become inadequate. In this study, instead of the fins used in existing systems, 10 PPI and 40 PPI PHS were placed inside a water block, and the Al2O3-H2O nanofluid at a mass fraction of 0.1% was used as the cooling fluid. Experiments were carried out under constant heat flux of 454.54 W/m2 and 1818.18 W/m2, with volumetric flow rates varying between 100 mL/min and 800 mL/min. The heat transfer results were compared with the results obtained from the base fluid and the empty surface. The results showed that the nanofluid reduced the surface temperatures compared to the base fluid. Especially when PHSs were used together with the nanofluid, a significant increase in heat transfer occurred compared to the empty surface. The highest heat transfer was observed when both the nanofluid and 40 PPI PHS were used together. In addition, the highest thermal performance value was determined as 1.25 times compared to the empty surface when the nanofluid and 10 PPI PHS were used together.

Three-dimensional analysis of heat transfer and entropy production of jet impingement hybrid nanofluid cooling a porous media-filled heat sink

ABSTRACT In this study, a numerical assessment was carried out on heat transfer and entropy production of a three-dimensional heat sink exposed to an impinging jet, where the area between the heat sink fins is filled with aluminum foam saturated with A L 2 O 3 − C u / w a t e r hybrid nanofluid. Darcy-Brinkman-Forchheimer’s model with the local thermal equilibrium was considered. The effects of various important parameters such as Reynolds number 400 ≤ R e ≤ 1600 , volumetric concentrations 1 % ≤ φ h n f ≤ 5 % , Darcy number 10 − 5 ≤ D a ≤ 10 − 1 , porosity 0.1 ≤ ε ≤ 0.6 , and the diameter of nanoparticles 20 n m ≤ d n ≤ 60 n m on fluid flow, heat transfer, drop pressure, and entropy generation were investigated. A finite-volume approach with SIMPLE algorithm was employed to solve continuity, momentum, energy, and entropy equations with the help of the Ansys-Fluent 14.5 program. Regarding the validation of the computational approach used in this paper, a strong consensus has been reached with other findings available in the literature. Outcomes indicated that boosting Darcy number D a and porosity ε of the used porous material helps increase the heat exchange rate by up to 72 % and 40 % , respectively. On the other hand, we obtained a 7 % enhancement in the heat transmission rate when using nanoparticles with a diameter d n of 20 n m instead of nanoparticles with a diameter of 60 nm. Furthermore, it has been demonstrated that boosting D a , ε and d n minimize drop pressure by various proportions. Based on the entropy production analysis, it is possible to infer that entropy due to heat transfer is more dominant than other types of entropy with all parameters analyzed. Also, it can be deducted that as the values of ε and D a grow and the values of d n decline, the total entropy production ( S p , t ) rises up to 55 % , 75 % and 3 % , respectively. The same findings were reached with the Bejan number B e , but different percentages. Finally, three correlations of Nusselt number with several variables with an error not exceeding 15 % have been suggested. The proposed study’s findings may be utilized to define appropriate process factors for improved thermodynamic efficiency of heat sinks using hybrid nanofluids and porous media.

Research on thermal characteristics of tapered laser chip

The tapered laser with high power and high beam quality is one of the research hotspots in the field of laser. The thermal effect of the tapered laser will reduce the thermal saturation current and produce thermal deformation, which will lead to the decrease of output power. Therefore, the thermal effect of the tapered laser is the main cause of failure. In order to investigate the thermal characteristics of the tapered laser chip, this paper simulates the tapered laser by using COMSOL Multiphysics. The changes of thermal stress under different ridge widths and tapered angles are simulated, and the thermal stress distributions in the ridge and tapered regions are obtained. In addition, a porous heat sink is designed. The simulation results of ordinary radiator and porous radiator are compared, which can be seen that porous heat sink has better heat dissipation capacity than ordinary heat sink. Through the simulation of tapered laser, this paper does research on the thermal characteristics of tapered laser, which can be a useful reference to improving the performance of tapered laser.

Fanless, porous graphene-copper composite heat sink for micro devices

Thermal management in devices directly affects their performance, but it is difficult to apply conventional cooling methods such as the use of cooling liquids or fans to micro devices owing to the small size of micro devices. In this study, we attempted to solve this problem by employing a heat sink fabricated using copper with porous structures consisting of single-layer graphene on the surface and graphene oxide inside the pores. The porous copper/single-layer graphene/graphene oxide composite (p-Cu/G/rGO) had a porosity of approximately 35%, and the measured pore size was approximately 10 to 100 µm. The internal GO was reduced at a temperature of 1000 °C. On observing the heat distribution in the structure using a thermal imaging camera, we could observe that the p-Cu/G/rGO was conducting heat faster than the p-Cu, which was consistent with the simulation. Furthermore, the thermal resistance of p-Cu/G/rGO was lower than those of the p-Cu and pure Cu. When the p-Cu/G/rGO was fabricated into a heat sink to mount the light emitting diode (LED) chip, the measured temperature of the LED was 31.04 °C, which was less than the temperature of the pure Cu of 40.8 °C. After a week of being subjected to high power (1000 mA), the light intensity of p-Cu/G/rGO decreased to 95.24%. However, the pure Cu decreased significantly to 66.04%. The results of this study are expected to be applied to micro devices for their effective thermal management.

The Thermohydraulic Characteristics and Optimization Study of Radial Porous Heat Sinks Using Multi-Objective Computational Method

AbstractThe use of porous media (PM) to improve conductive heat transfer has been at the focus of interest in recent years. Limited studies, however, have focused on heat transfer in radial heat sinks (RHSs) fully and partially saturated porous media with a different arrangement. As a development of the above-mentioned investigations, this research, therefore, addresses the ability of radial porous heat sink solutions to improve the thermohydraulic characteristics and reduce the effect of the second thermodynamics law. The response surface methodology (RSM) technique with ansysfluent-cfd is utilized to optimize the thermohydraulic features and the total entropy generation by the multi-objective optimum design for different design parameters such as porosity (Ø), inlet temperature (Tin), and applied heat flux (Q) simultaneously after achieving the optimum porous media arrangement related to the flow direction. The results show that, in terms of the flow direction, the optimum radial porous heat sink of the 100%PM model is recognized as providing the best results and the best option (fully saturated porous media). Moreover, a significant agreement between the predicted and numerical simulation data for the optimum values is also seen. The optimum and undesirable designs of the thermohydraulic features, the total entropy generation, and the optimum thermal management are detected in this investigation.

INVESTIGATIONS ON HEAT TRANSFER CHARACTERISTICS OF POROUS TYPE COPPER HEAT SINK WITH BIFURCATIONS

The lotus type porous copper heat sink has a higher heat transfer capacity as compared to micro channel heat sink for same size. Many studies on this heat sink show that its heat transfer capacity can be further improved by improving design of heat sink. This study investigates the heat transfer and flow characteristics of porous heat sink with different designs of internal bifurcations under both laminar &amp;amp; turbulent flow and studies the effect of such bifurcations on heat transfer of heat sink. The results of heat sink with bifurcations are compared with that of heat sink without bifurcations which show that for case of both laminar &amp;amp; turbulent flow, the heat sink with bifurcation showed better thermal performance as compared to heat sink without bifurcations.

Numerical optimization of a new concept in porous medium considering thermal radiation: Photovoltaic panel cooling application

Temperature is one of the most important factors of solar photovoltaic panel (PV) efficiency. İncreasing the temperature causes serious damage to the solar panel. In this research, the effect of the new model of the porous fin as rows of connected spheres on surface temperature was investigated. For achieving this target, the rigid fins and this model of porous fin were compared. Thermal radiation was also examined to increase accuracy in the calculations. After validation and grid study, two models of heat sink with distinct vertical layers and two horizontal layers of connected spheres have been investigated to cool down the PV panel. After that, the new concept of porous heat sink was optimized based on sensitivity analysis (SA) and Differential Evolution (DE) optimization algorithm. A combination of numerical modeling and D.E optimization can improve the final efficiency and increase heat transfer. In this study, by considering the porosity range between (0–70%), we try to find the optimal value of porosity. The results show that by using the special form of porosity on the back layer of the P.V panel, the heat transfer can be increased up to 15%. It’s also indicated that the optimization process can improve the Nu and reduce calculation cost. This optimization algorithm is 34 times much faster than another optimization process in CFD method.

Non-uniformity of flow rate in a unidirectional porous heat sink and its control

Non-uniformity of flow rate in a unidirectional porous heat sink and its control

Heat transfer and entropy generation analysis in a three-dimensional impinging jet porous heat sink under local thermal non-equilibrium condition

A precise heat transfer simulation of a three-dimensional impinging jet porous heat sink is presented and is analyzed from thermodynamics vantage point under local thermal non-equilibrium condition. To increase the computational efficiency of the analysis, pore-scale modeling based on lattice Boltzmann method (LBM) is used inside the porous media (at a meso-scale), whilst finite volume method (FVM) is employed around it (at a macro-scale). The effects of the Reynolds number, porous layer thickness, solid/fluid thermal conductivity ratio, and porosity on the critical heat transfer and entropy generation parameters are investigated. Additionally, the relations between viscous entropy generation and pressure drop and thermal entropy generation with thermodynamic non-equilibrium are presented. The results indicated that among all parameters, the effects of the porous layer thickness on the fluid permeability are more substantial than other investigated parameters. Also, it is found that increasing the Reynolds number or porous layer thickness increases the total pressure drop, average viscous entropy generation number, and Nusselt number. For each porous layer thickness and Reynolds number, the minimum thermal conductivity ratio (that porous layer had no significant effect on heat transfer) is obtained 200. Moreover, it is determined that increasing the porous layer thickness or reducing the solid/fluid thermal conductivity ratio reduces the thermal entropy generation number, leading to a move toward the local thermal equilibrium condition. Additionally, in contrast to the fluid-phase thermal entropy generation number, the total entropy generation number in most porous layer cases was greater than the entropy generated by the surface without porous media.

全固态碟片激光器的多孔泡沫热沉传热特性研究

全固态碟片激光器的多孔泡沫热沉传热特性研究

Nonlinear thermal analysis of a convective-radiative longitudinal porous fin of functionally graded material for efficient cooling of consumer electronics

In this paper, nonlinear thermal analysis and optimisation of a convective-radiative longitudinal porous fin of functionally graded material is presented. The present work aims at characterisation of optimum parameters for heat transfer enhancement. The developed thermal models are solved using differential transform method. The effects of non-homogeneous index of functionally graded material, convective and radiative parameters on the thermal performance of the porous heatsink are investigated. Parametric study shows that increase in the non-homogeneous index of functionally graded material, convective and radiative parameter improve the thermal efficiency of the porous fin heat sink. The result of the present solution is validated using established approximate analytical and numerical solutions. It is hoped that the results of the present study would assist in the design of thermally-efficient cooling approaches for various consumer electronics.

Numerical Study of Performance of Porous Fin Heat Sink of Functionally Graded Material for Improved Thermal Management of Consumer Electronics

The ever-increasing demand for high-performance electronic and computer systems has unequivocally called for increased microprocessor performance. However, increasing microprocessor performance requires increasing the power and on-chip power density of the microprocessor, both of which are associated with increased heat dissipation. In recent times, thermal management of electronic systems has gained intense research attention due to increased miniaturization trend in the electronics industry. In this paper, we present a numerical study on the performance of a convective–radiative porous heat sink with functionally graded material (FGM) for improved cooling of various consumer electronics. For the theoretical investigation, the thermal property of the FGM is assumed as a linear and power-law function. We solved the developed thermal models using the Chebyshev spectral collocation method (CSCM). The effects of inhomogeneity index of FGM and convective and radiative parameters on the thermal behavior of the porous heat sink are investigated. This paper shows that increase in the inhomogeneity index of FGM and convective and radiative parameters improves the thermal efficiency of the porous fin heat sink. Moreover, for all values of Nc and Rd, the temperature gradient along the fin of FGM is negligible compared to HM fin in both linear and power-law functions. For comparison, the thermal predictions made in this paper using CSCM agree excellently with the established results of Runge–Kutta with shooting and homotopy analytical method.

New hybrid finite volume-thermal lattice Boltzmann method, based on multi relaxation time collision operator

Hybrid FVM-LBM schemes are developed in the past few years to use capabilities of both Navier-Stokes based finite volume method (FVM) and lattice Boltzmann method (LBM) to solve macro-meso multiscale problems. In this scheme, the major task is to develop some lifting relations that reconstruct distribution functions in LBM sub-domain from macroscopic variables and their derivatives. The macroscopic variables are computed using Navier-Stokes based FVM in macroscale sub-domain, while distribution functions are computed using LBM in mesoscale sub-domain. The pioneer works in this area used the single relaxation time (SRT) version of LBM. However, it is known that the numerical stability and accuracy of the multiple relaxation time (MRT) version of LBM is superior to the SRT one. Based on this fact, a new hybrid FVM-LBM scheme based on the MRT version of LBM for fluid flow simulation is proposed in our previous work. But, our previous hybrid scheme is limited to fluid flow problems. In the present research, some additional lifting relations are developed to extend the working area of our previous hybrid FVM-LBM (MRT) scheme to heat and mass transfer problems. The computational efficiency of the resulting hybrid method is proved by comparing its CPU time with those of LBM and Navier-Stokes based FVM for a sample meso-macro scale problem. Afterward, the new hybrid scheme is validated in two and three dimensions by solving three benchmark heat transfer problems. Additionally, to indicate the applicability of the present hybrid scheme in a meso-macro scale problem, three-dimensional heat transfer from a porous heat sink is simulated in pore scale. The fluid-solid conjugate heat transfer inside porous media is simulated using LBM, while the surrounding free fluid region is simulated using Navier-Stokes based FVM. The results indicate the superiority of the proposed new hybrid scheme over the previous ones.

Thermal characteristics of CPU cooling by using a novel porous heat sink and nanofluids

In this paper, different heat sinks are investigated to improve CPU cooling experimentally. Different types of copper heat sinks including a novel “porous heat sink” are proposed and compared to obtain the optimum heat transfer rate. Water and Al2O3/water nanofluids (40 nm) in two different volume fractions (0.1 and 0.2 vol.% from 40-nm nanoparticles) are used as heat transfer fluid to cool the CPU. Different flow rates are also examined in the experimental study. The Nusselt number, wall temperature, thermal resistance and LMTD temperature have been analyzed for a wide range of parameters of the heat sinks. Also, the effect of geometry, heat transfer fluid, input power and flow rate on the heat transfer rate is reported. The result shows that the geometry of the heat sink has an important effect on the thermal performance of the system. The rate of heat transfer in the proposed novel porous heat sink is larger than the other cases. The Nusselt number in the porous heat sink by using nanofluids is 2.2 times larger than the heat sink with an inline pattern.

Performance of novel liquid-cooled porous heat sink via 3-D laser additive manufacturing

The performance of five water-cooled heat sinks is experimentally investigated. The test samples include the reference chevron-type corrugation, and four novel Body-Centered Cubic (BCC) porous structure. The proposed BCC structures include a homogeneous porous structure, non-uniform porous structure, non-uniform porous structure with augmented fin efficiency, and the non-uniform porous structure with augmented fin efficiency and inlet compactness design. The test samples are made from laser-powered metal additive manufacturing process having Titanium alloy as the construction materials. Test results indicated that the proposed BCC porous structure shows a much lower pressure drop than the traditional metal foam, and the proposed homogeneous porous BCC structure is superior to the reference chevron-type corrugation except at the low flowrate. The thermal resistance can be reduced about 55% at a pumping power of 1 W. The non-uniform porous structure can effectively force the working fluid toward the heating surface and results in an appreciable increase in heat transfer performance. With a further increase of the strut diameter at the lower part of the cold plate from 0.3 mm to 0.6 mm, the design with augmented fin efficiency shows the best performance among all test samples, the lowest thermal resistance reaches about 0.0118 K/W at a flowrate of 6 LPM. Yet this non-uniform porous structure with augmented fin efficiency outperforms all other structures in the entirely operational range. The proposed non-uniform porous structure with augmented fin efficiency outperforms most existing studies.