Foam Heat Sink Research Articles

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

Thermal Modeling and Analysis of Metal Foam Heat Sink with Thermal Equilibrium and Non-Equilibrium Models

Thermal Modeling and Analysis of Metal Foam Heat Sink with Thermal Equilibrium and Non-Equilibrium Models

Hydraulic and thermal performances of metal foam and pin fin hybrid heat sink

In this study, a metal foam and pin fin hybrid heat sink (MFPFH heat sink) is proposed for thermal management of high powered electronic devices. Thermo-hydraulic performance of MFPFH heat sink is numerically investigated under local thermal non-equilibrium condition, and compared with metal foam (MF) heat sink and traditional pin fin (PF) heat sink. Influences of MF morphological parameters on flow and heat transfer of MFPFH heat sink are analyzed, and the thermal performance ratio is evaluated. Thermal contact resistance between PFs and MF is introduced to explain its effects on the thermal performance of MFPFH heat sink for its practical application. Results indicate that significant heat transfer enhancement is achieved by using the MFPFH heat sink, due to the enhanced heat conduction and the improved heat convection by the common contribution of MF and PFs. Heat transfer characteristics of MFPFH heat sink are more sensitive to foam porosity, and pressure drop to pore size. By simultaneously considering the heat transfer enhancement and flow resistance increase, the thermal performance ratio of MFPFH heat sink is 1.6 times higher than the traditional PF heat sink. When thermal contact resistance is 10−3 m2·K/W, the degradation of average Nusselt number is approximately 36%.

Investigation of functionally graded metal foam thermal management system for solar cell

Concentrated photovoltaic cell (CPV) is a solar energy harvesting device that converts solar energy into electrical energy. However, the performance and efficiency of the CPV are heavily dependent on the temperature. Besides, nonuniformity of temperature distribution on the CPV will lead to thermal aging and affects the cycle life. Hence, an effective cooling system is required to remove excess heat generated to ensure that the CPV operates at optimum operating temperature with minimum variation of temperature. Metal foam is a new class of material that possesses huge potential for thermal management. In this study, a functionally graded metal foam is proposed for the CPV thermal management system. Computational thermal fluid dynamic analysis is conducted to investigate the effect of porosity and pore density on the flow field and thermal performance of the aluminum foam heat sink. The investigation results revealed that 10 PPI functionally graded aluminum foam heat sink with two stages of porosity gradient 0.794 and 0.682 produced the lowest pressure drop and highest thermal performance. Temperature difference of 3.9°C was achieved for a solar cell with total heat generation of 900 W under water mass flow rate of 20 gs−1.

Thermal Performance Simulation of the Metal Foam Heat Sink

This study investigated the sintered metal among the regular finned heat sink. And a metal foam heat sink for power module cooling is designed. An improved computational model for effective thermal conductivity was obtained. Contrast to the two types of the heat sink, it is found that under the condition of the constant heat flow density, the heat accumulated is absent in metal foam heat sink. Meanwhile, the heat transfer coefficient of the metal foam heat sink is 3.6 times that of the finned heat sink of equivalent geometric parameter. At the same drop pressure, the air velocity of the metal foam heat sink is lower than that of the finned heat sink. The velocity of air in the foam radiator is lower than that in the finned radiator. Under the same fan power, the gain factor of the four finned metal foam radiators is about 20 times higher than that of the ribbed radiators of the same conditions.

Investigation of water cooled aluminium foam heat sink for concentrated photovoltaic solar cell

Concentrated photovoltaic cell (CPV) is a popular renewable source nowadays. It has high efficient yet cost effective energy harvesting system available in the market. The performance of the CPV depends strongly on the temperature of the solar cell. The efficiency reduces as the surface temperature of the CPV increases. It is crucial to reduce the temperature of the CPV and maintains a small temperature variation along the surface of the CPV. Metal foam is an ideal solution for a CPV thermal management system. It helps to enhance the mixing of coolant due to its porous characteristics and lead to higher heat transfer rate and reduce the overall average temperature of a CPV. The main objective of this study is to enhance the heat removal rate along of the CPV. Aluminium foam is used as a heat sink to removal the heat generated. The effects of porosities and pores density (PPI) of the aluminium foam are measured against the thermal performance. Computational thermal fluid dynamics is conducted to study the thermal performance of aluminium foam heat sink. The parameters required for the simulations are extracted from literature. The results suggested that aluminum foam is able to enhance the heat removal and maintains better temperature uniformity of the CPV. 10PPI aluminum foam with porosity 0.682 provides the most optimum results with average temperature of 55.1 ˚C and temperature different of 7.4 °C at flow rate of 40 g/s. This approach is suitable to promote the efficiency of the CPV and prolong the cycle life.

Thermal hydraulic performance of micro-channel heat sink with composite metal foam-solid fin design

<p indent="0mm">Three-dimensional (3D) interconnect technology promises significant performance advantages for the next generation of high speed and multi-functional electronic devices, however, the large-scale integration of electronic circuit and vertical stacking of multi-functional dice have been demonstrated to result in substantially increased waste-heat generation rates and localized hotspots. Efficient thermal management solutions are imperative to ensure the operating temperature of components below a reasonable level. Among various cooling techniques, metal foam heat sink has been identified as a promising alternative for electronic cooling, because of the large specific surface area, high effective thermal conductivity and intensive fluid mixing capability that foam material provided. In this study, a novel micro-channel heat sink with combined metal foam-solid fin, namely combined fin heat sink (CFHS), was established for electronics cooling. Numerical simulations based on Brinkman-Darcy extended momentum equation and local thermal non-equilibrium energy equations were carried out to investigate the fluid flow and heat transfer characteristics. To simplify the computations, a single channel was used as the computational domain with a dimension of 20 mm×2.4 mm× <sc>6 mm.</sc> The constant heat flux of <sc>100 W/cm²</sc> was supplied at the bottom wall to simulate the high-powered electronic device. Metal foam and fin were made of high thermal conductivity copper, and pure water was used as the working coolant. It was assumed that the metal foam was fully saturated with fluid in laminar flow state and the thermal resistance between the metal foam and fin was neglected. Effects of combined fin configuration on the flow and heat transfer performances were studied to determine the optimal porosity and dimensionless metal foam layer thickness for designing the CFHS. The thermal performance of the novel heat sink was compared to that of the conventional heat sink, and the total thermal resistance was analyzed based on the simplified thermal resistance network. The results indicate that the CFHS is more favorable in promoting thermal performance that the average Nusselt number of CFHS is 2.53 times higher than that of the conventional heat sink, while accompanied by the high pressure drop as a penalty. The flow resistance and specific area are two conflicting parameters that affect the thermal and hydraulic performances of the CFHS, our results show that there exists a critical dimensionless metal foam thickness and optimal porosity, which are 0.9 and 0.3, respectively. Compared with the conventional heat sink, the total thermal resistance of CFHS is significantly reduced by 56%, and the thermal performance factor of CFHS performs 1.32 times higher. The presented CFHS thus provides a feasible solution for thermal management of electronic devices with high-powered density.

Experimental and artificial neural network investigation on the effect of inclination angle on the interface temperature of CPU/metal foam heat sink

Purpose This study aims to clarify the relationship between inclination angle of hot surface of CPU and its temperature in absence and presence of aluminum foam as a cooling system. It proposes application of the artificial neural [multi-layer perceptron (MLP) and radial basis function] networks and adaptive neuron-fuzzy inference system (ANFIS) to predict interface temperature of central processing unit (CPU)/metal foam heat sink. Design/methodology/approach To provide a consistent set of data, the surface of an aluminum cone with and without installing Duocel aluminum foam was heated in a natural convection using an electrical resistor. The hot surface temperature was measured using five K-type thermocouples (±0.1°C). To develop the predictive models, ambient temperature, input power and inclination angle are taken as input which varied from 23°C to 32°C, 4 to 20 W and 0° to 90°, respectively. The hot surface temperature is taken as the output. Findings The results show that in the presence of foam, the hot surface temperature was less sensitive to the variations of angle, and the maximum enhancement of the heat transfer coefficient was 23 per cent at the vertical position. Both MLP network and ANFIS are comparable, but the values predicted by MLP network are in more conformity with the measured values. Originality/value The effect of metal foam on the inclination angle/hot surface temperature dependence is identified. The optimum angle is clarified. The applicability of the MLP networks to predict interface temperature of CPU/heat sink is approved.

Eğimli Dikdörtgen Bir Kanalda Köpük Isı Alıcılardan Doğal Taşınımın Deneysel Olarak İncelenmesi

In this present study, free convection from an in-line 5x1 array of aluminum foam heat sinks which were placed on the bottom wall of the inclined rectangular channel was investigated. Aluminum foam heat sinks were made of Al-6101 alloy. All heat sinks mounted on a bottom wall of the channel was discrete form and exposed to uniform heat flux. Aluminum foam materials with three different pore densities (10, 20 and 40 PPI) were used in experiments. Air was used as coolant fluid (Pr =0.7). The experiments were made for Rayleigh Number range from 2.03 x107 to 1.33 x108 and the channel inclination angles were varied from 0° to 90°. Moreover, the heat transfer results from the aluminum foam heat sinks were also compared to the results obtained for foam-free (without foam) surfaces. The results showed that both the channel inclination angle and the usage of foam heat sinks are significant influences on heat transfer results.

Towards Thermal-Acoustic Co-Design of Noise-Reducing Heat Sinks

Several thermal management applications involve fan-mounted heat sinks that result in fan-generated noise as an undesired by-product. These applications require noise reduction and attempt to reduce noise using separate muffler devices. However, space for separate heat-sinking and noise-reducing functionalities may be challenging in high-performance applications such as electronics cooling, data centers, automotive, aviation, and various others. A first-principles-based approach for combined heat sinking and noise reduction in the same functional volume is discussed in this paper. This paper reports on thermal-acoustic co-design of 3-D periodic porous foam structures. In order to enable a design strategy, an analytical framework that characterizes the governing performance indicators of both acoustic and thermo-fluid design on a unifying platform is laid out. A combination of analytical and phenomenological models is used to predict the absorption coefficient, transmission loss (TL), and other acoustic performance indicators. For thermal predictions, an experimentally validated semiempirical model is presented to estimate thermal resistance and static pressure drop of foam heat sink as a function of geometrical parameters as well as flow rates. Octave-band weighted values of acoustic indicators are then compared against thermal indicators to investigate thermal-acoustic co-design aspects. As hydraulic pore radius of porous foam decreases, the acoustic absorption coefficient increases reaching local maxima. Concomitantly, the pore radius decrease not only increases the absorption coefficient while dissipating heat, but also increases the heat sink pressure drop. For a chosen sound absorption region of interest, there exists a particular static pressure drop that maximizes heat sink dissipation for a given radius. The paper concludes by reporting TL and heat sink thermal performance for a generic electronics cooling configuration while elucidating the nuances of the proposed heat sink design using a thermal-acoustic index.

Experimental investigation of heat transfer and pressure drop of alumina–water nano-fluid in a porous miniature heat sink

ABSTRACTThe thermal management of electronic devices has become of great concern in the last decade. Recent research has focused on heat transfer enhancement methods for heat removal from such devices. In this study, we investigated the convective heat transfer and pressure drop of alumina–water nano-fluids in a miniature heat sink occupied with a copper porous medium under a 62.5 heat flux. Nano-fluid volume fractions of 0.1, 0.3, and 0.5% were synthesized by a two-step method, and the thermal conductivity and kinematic viscosity of the nano-fluids were measured experimentally. Two copper metal foam heat sinks, with different pore densities of 15 pores per inch (PPI) and 30 PPI, were manufactured and inserted into a channel. The results indicated an enhancement in the convective heat transfer coefficients and Nusselt numbers with increase in the Reynolds number. The enhancement in the heat transfer coefficients using different nano-fluid volume fractions in higher- and lower-porosity media varied from 1 to 22% and 2.3 to 26.4%, respectively. An increment in the nano-fluid volume fraction, and pore density, led to a higher heat transfer rate. However, the higher pore density medium caused larger pressure drops. The thermal resistance of the samples was also studied. The results indicated an increase in Reynolds number, and volume fraction decreased the thermal resistance. According to the efficiency index, a lower pore density medium as well as higher nano-fluid volume fractions provided better performance in this porous heat sink.

Wearable Thermoelectric Generator With Copper Foam as the Heat Sink for Body Heat Harvesting

Wearable thermoelectric generator (TEG) is an attractive technology to enable self-powered electronics and sensors for healthcare and the Internet of Things through its ability to convert body heat into electricity. However, the actual inner temperature gradient in the thermoelectric legs is relatively small when a TEG is worn on the body, which leads to a low voltage and power generation. To enhance the output performance, the structural design of a wearable TEG with copper foam as the heat sink is proposed. A thermal resistance model was developed to investigate the effects of using copper foam heat sink on the heat transfer and performance of the TEG. In addition, for comparison, the inner temperature gradients and open-circuit voltages of the TEGs with and without plate-fin heat sink were analyzed. Then, these different TEGs were fabricated and tested using an experimental setup. The results showed that TEGs with heat sinks could generate greater open-circuit voltage and output power values, while the TEG with copper-foam heat sink achieved the highest power-to-weight ratio. Finally, a wearable TEG with copper-foam heat sink was connected to a step-up circuit and worn on the wrist to power a miniaturized accelerometer for body motion detection. The results demonstrated that the wearable TEG with the copper-foam heat sink design provided a potential pathway for the realization of electronics powered by harvesting the human body heat.

Experimental Investigation of the Effect of the Metal Foam Material on CPU Cooling

One of the most important component of computers is processors (CPU). Because of the reasons like running too many programs simultaneously and playing games may cause the processor to overheat. This situation may cause unwanted computer malfunction. The CPU capacity and heat quantities increase with increasing the CPU speed and its performance. In order to run the system effectively, this heat must be removed and the critical surface temperature of the CPU must be kept below approximately 85 °C. In this present study, aluminum open cell metal foam (Al-6101) heat sink having pore density of 10 and 40 PPI (pore per inch) was used instead of the conventional plate type aluminum heat sink. 10 and 40 PPI aluminum metal foam materials are compared with each other and the results are presented in graphics at different fan speeds (1140, 1742, 2439, 2944, 3308 and 4187 rpm). According to the results, in %0-10 CPU usage (standby), lower surface temperatures were reached while using 10 PPI aluminum metal foam material. However, in %100 CPU usage, lower surface temperatures were reached while using 40 PPI aluminum metal foam material.

Forced convection heat transfer from porous heat sinks placed in partially open cavity: Some case studies

ABSTRACTIn this present study, the forced convection heat transfer from aluminum foam heat sinks with 10, 20, 40 PPI pore density placed in a discrete form in a partially open cavity were experimentally investigated. Air was used as working fluid. The uniform heat flux was applied to 3 × 3 array of foam heat sinks horizontally mounted in the cavity. The experimental studies were performed for the 3363–9743 range of Reynolds number and the 2.7 x 106 and 7.5 x 106 range of modified Grashof number. The effects of the Reynolds number, the modified Grashof number and the pore density of foam heat sink on the heat transfer were investigated. The results obtained were compared with the results obtained without foam heat sink cases. In addition, the most heated elements within the cavity were identified and solution proposals were presented. In addition, the most heated elements within the cavity were identified and solution proposals were presented.

Effect of aluminum-foam heat sink on inclined hot surface temperature in the case of free convection heat transfer

The need to more powerful electronic chips cause more heat generation as a consequence. So it leads to apply metal foam heat sink as a powerful cooling methods. The objective of this paper is to experimentally investigate the effect of inclination angle on the temperature of a heated surface with and without metal foam in the case of free convection heat transfer conditions. Experimental modeling has been conducted using an electrical resistor on an aluminum plate with and without aluminum metal foam in different angles with respect to the horizontal direction. The results show that the temperature variations have a linear dependency to the sine of inclination angle up to 45° and 60° for plate with and without metal foam, respectively. The slope of the lines are positive in low power input and negative in high power input. The effect of applying metal foam depends on the input power and inclination angle. In the presence of foam, the surface temperature has a decrease of 16°C with respect to a flat plate. The maximum cooling efficiency using foam is about %17 at 90° inclination angle.

Numerical Analyses on Aluminum Foams Cooling Plate for Lithium-ion Batteries

Successful implementation of electric vehicle relies strongly on its energy storage systems. Li-ion battery is the best candidate for the energy storage systems due to its energy density, power density and low maintenance. Temperature will affect the power availability, driveability and cycle life of the battery. Hence, effective thermal management system is needed to prolong cycle life and ensure balance charging/discharging among the cell in the battery pack. In this study, a battery module comprised three pieces of Li-ion pouch cell is arranged side by side and attached to aluminum foam heat sink to extract heat generated. The performance of two different type of pores density aluminum foams with different porosity were investigated numerically. Experimental correlation of Nusselt Number, permeability and resistance loss coefficient from the literature was extracted and used in the steady state CFD simulation. Among the metal foams, 10 PPI aluminum foam with 0.918 porosity offered the highest thermal performance and lowest flow resistance. Hence, it was shown that aluminum foam can be used to replace heat sink in the battery pack.

Heat Development and Comparison Between the Steady and Pulsating Flows Through Aluminum Foam Heat Sink

Continuous improvements in electronic devices for high-performance computers have led to a need for new and more effective methods of chip cooling. The first purpose of this study was to investigate the heat transfer development and characteristics of aluminum foam heat sink subjected to steady water flow for electronics cooling (Intel core i7 processor). The second purpose was to implement a new type of water flow through the aluminum foam, which is pulsating or oscillating flow in order to achieve more uniform temperature distribution over the electronic surfaces. The aluminum foam heat sink was subjected to a water flow covering the non-Darcy laminar flow regime (297–1353 Reynolds numbers). The bottom side of the heat sink was heated with a heat flux between 8.5 and 13.8 W/cm2. The pulsating flow frequency was ranged from 0.04 to 0.1 Hz. In addition, in order to complement the experimental studies, a numerical model was developed using finite element method and compared with the experimental data. The results revealed that the thermal entry length of the fluid flow through metal foam (porous media) is much smaller than that for laminar internal flow through empty channel. The result also showed that the local surface temperature increases along with increasing the axial flow direction for steady water flow case. On the other hand, for pulsating flow, the local temperature distributions act as a convex profile with the maximum surface temperature at the center of the test section. In addition, it was observed that the pulsating water flow through the aluminum foam heat sink achieves enhancement by 14% in the average Nusselt number and by 73% in temperature uniformity over the surface compared with steady water flow case.

Geometric Mean of Fin Efficiency and Effectiveness: A Parameter to Determine Optimum Length of Open-Cell Metal Foam Used as Extended Heat Transfer Surface

High porosity open-cell metal foams have captured the interest of thermal industry due to their high surface area density, low weight, and ability to create tortuous mixing of fluid. In this work, application of metal foams as heat sinks has been explored. The foam has been represented as a simple cubic structure and heat transfer from a heated base has been treated analogous to that of solid fins. Based on this model, three performance parameters namely, foam efficiency, overall foam efficiency, and foam effectiveness have been evaluated for metal foam heat sinks. Parametric studies with varying foam length, porosity, pore density, material, and fluid velocity have been conducted. It has been observed that geometric mean of foam efficiency and foam effectiveness can be a useful parameter to exactly determine the optimum foam length. Additionally, the variation in temperature profile of different foams heated from one end has been determined experimentally by cooling these with atmospheric air. The experimental results have been presented for open-cell metal foams (10 and 30 PPI) made of copper/aluminium/Fe–Ni–Cr alloy with porosity in the range of 0.908–0.964.

Thermal Performance Analysis of Biporous Metal Foam Heat Sink

The present study presents a concept of biporous metal foam heat sink applicable to electronic cooling. This heat sink has two metal foam layers arranged in parallel along the primary flow direction, with different metal foam thickness, porosity, and pore density for each layer. The forced convective heat transfer in biporous metal foam heat sink is numerically investigated by employing the Forchheimer–Brinkman extended Darcy momentum equation and local thermal nonequilibrium energy equation. The effects of geometrical and morphological parameters on thermal and hydraulic performance are discussed in detail, and the heat transfer enhancement mechanism of biporous metal foam is analyzed. The thermal performance of biporous metal foam heat sink is compared with that of uniform metal foam heat sink. The results show that the thermal resistance of the biporous metal foam heat sink decreases with decrease of top layer metal foam porosity at a fixed bottom metal foam porosity of 0.9. It is seen that the biporous metal foam heat sink can outperform the uniform metal foam heat sink with a proper selection of foam geometrical and morphological parameters, which is attributed to the presence of high velocity gradient at the boundary layer that can enhance the convective heat transfer. The best observed thermal performance of biporous metal foam heat sink is achieved by employing 30 pores per inch (PPI) metal foam at the bottom layer, with a fixed 50 PPI metal foam at the top layer for the porosities of both layers equal to 0.9, and the optimal thickness of the bottom foam layer is about 1 mm.

3D modeling and analysis of the thermo-mechanical behavior of metal foam heat sinks

Metal foams are metallic materials that contain a high percentage of porosity. They can be manufactured as open-cell or closed-cell foams. Open-cell metal foams are ideal for thermal applications due to the high ratio of surface area to volume, which provide more surface contact between the material and the fluid. In this work, a detailed approach to utilize micro-computed tomography scan to create a detailed and accurate 3D metal foam model is discussed. The model is implemented into a finite element analysis software and used in an application of heat sinks. Experiments are performed to record the temperature profile of the heat sink, and then the heat transfer coefficient h for the numerical model is calibrated using the temperature data. The 3D metal foam heat sink model is validated against experiments as well. Finally, the complete validated model is used to study the thermo-mechanical behavior of 1, 2, and 3 fins metal foam heat sinks. The developed model and approach provides more insight into the coupled behavior of metal foam heat sinks by being able to calculate the developed stresses due to the thermal loading of the heat sinks.