Foam Fins Research Articles

Experimental study and correlation development for the two-phase frictional pressure drop of flow boiling in copper foam fin microchannels

Experimental study and correlation development for the two-phase frictional pressure drop of flow boiling in copper foam fin microchannels

Numerical simulation of thermal performance of heat sink augmented with phase change material PCM integrated with solid and aluminum metal foam fins

AbstractThis study introduced a novel numerical modeling for the evaluation of a hybrid heat sink design by replacing the solid fins with aluminum foam fins (AFF) for the same thickness of 2 mm within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. Heat fluxes of 2, 3, and 4 kW/m2 were applied to the base. The performance has been verified at set point temperatures (SPT) of 60°C, 70°C, and 80°C, encompassing a range relevant to various applications. Different AFF thicknesses (4 and 6 mm) and foam porosities (0.85, 0.90, and 0.95) were investigated. The study demonstrated that AFFs improve heat transfer by increasing fin surface area and by effectively raising the thermal conductivity of the PCM. Compared to the SF heat sink, the results show that the AFF design extended the operational time by 5%–8% for the range of heat fluxes. Notably, AFFs with a thickness of 6 mm achieved a significant 41% improvement in the operation time at a lower SPT (60°C). The metal foam porosity of ε = 0.85 exhibited superior thermal performance within the investigated temperature range. This research paves the way for optimizing hybrid heat sink designs using metal foam for efficient thermal management and reduction of weight.

An experimental study of the effects of porosity and ratio of fin to channel width on water flow boiling in copper foam fin microchannels

Flow boiling in copper foam fin microchannels (FFMC) has demonstrated better heat transfer performance and flow stability. In this work, systematic experiments are conducted to investigate the effects of structural parameters on flow boiling in five FFMCs with porosities ranging from 0.78 to 0.82 and ratios of fin width to channel width ranging from 0.5 to 2. Five mass fluxes ranging from 68 kg/(m2s) to 408 kg/(m2s) and effective heat fluxes ranging from 2 W/cm2 to 297 W/cm2 are tested. The heat transfer, pressure drop, and flow instability characteristics are analyzed. Generally, the heat transfer in FFMCs follows the “three-zone” model. The heat transfer coefficient first increases with increasing heat flux and then decreases. A “synchronous backflow” phenomenon is observed in FFMCs, which is the direct cause of heat transfer deterioration. Due to the interaction of heat transfer area and the transverse flow resistance through the fins, the heat transfer coefficient increases with decreasing porosity in the low-quality region, while the opposite trend is observed in the high-quality region. The utilization efficiency of the fin area decreases as the fin width increases. An optimal ratio of fin width to channel width exists corresponding to the best heat transfer performance, which equals one in this work. A correlation is developed based on 583 data points considering heat transfer mechanisms in channels and fins. The new correlation predicts the experimental values with a mean absolute percentage error of 9 %, and over 99 % of the data are predicted within a 30 % deviation. A performance evaluation criterion is defined to comprehensively compare the FFMCs, and the FFMC with the porosity of 0.78 demonstrates the best flow boiling performance due to higher heat transfer coefficients and lower pumping powers when the ratio of fin to channel width is equal to one.

Numerical thermal performance assessment of phase change process in a PCM/foam-fins enclosure under various thermal conditions

ABSTRACT The low ability of phase change material (PCM) to transfer thermal energy has created a serious challenge for the development of latent heat storage (LHTES) units. Embedding foam with high thermal conductivity material like copper has attracted significant attention. Besides, high porosity, lightweight, and easy usage are other important benefits of copper. However, its higher cost and decreasing effective volume of PCM led to the creation of amendments in the foam design. Employment of the foam in the form of fin or foam fin has emerged as an alternative method to benefit from the advantages of porous material and overcome its defects. In this study, various LHTES units with different numbers of foam fins have been simulated numerically and compared with pure PCM and fully foam PCM enclosures. Two practical boundary conditions including constant temperature and constant heat flux were examined for the designed systems. The obtained results demonstrated that foam fins have a remarkable effect on the thermal performance enhancement of LHTES under constant temperature boundary condition. For LHTES with six foam fins, 42% and 30% reductions in melting time were achieved for both types of boundary conditions including constant temperature and heat flux, respectively. At the beginning of charging process, a significant enhancement of input heat rate was proved for LHTES with 6 foam fins and fully foam up to 112% and 155%, respectively. In addition, the foam fins method provided some free volume of PCM to permit the falling out of natural convection of molten PCM.

Study on heat dissipation performance of a lattice porous structures under jet impingement cooling

For improving the heat dissipation of heat sink, a porous lattice structure under jet impingement was developed and its flow and heat transfer properties were investigated via simulation and experiments. The effects of its height (4–12 mm), porosity (0.52–0.92) and jet velocity (1–4 m s-1) on the flow and heat transfer characteristics were investigated. Results show that for a given inlet velocity, as the decrease of porosity, the heat transfer is increased, as well as the pressure drop or pump power. For a low pump power case, higher porosity such as 0.82 will be helpful for heat transfer, but lower porosity will be helpful for a high pump power instance. As the increase of height of lattice structure, the Nusselt number increased and subsequently decreased, with an optimal height of 6 mm. The lattice porous structure offers better heat transfer performance with comparison to conventional fin and foam fin heat sinks. At CfRe3 equal to 8.45 × 1012, the Nusselt number of the lattice porous structure is approximately 35% more than the other two structure. Also, Experiments were carried out in this study and experimental results agreed well with the simulated ones.

Multi-objective hydrothermal optimization of nanoparticles shape in nanofluid flow through an annular pipe having metal foam fins

The objective of this contribution is twofold. First, a multi-objective hydrothermal optimization is performed to determine the optimum nanoparticles (NPs) shape in nanofluid flow through an annular pipe having metal foam fins, in the forced convection regime. Second, the suitability of the performance evaluation criterion (PEC), as a common method to analyze the hydrothermal performance of thermal systems, is examined by comparing the outcomes of the multi-objective optimization method with those obtained by maximizing PEC. It is found that, depending on the value of the Reynolds number, the cylindrical-shaped NPs or the blade-shaped NPs exhibit the highest heat transfer performance. The lowest value of the required pumping power belongs to the spherical-shaped NPs. The results indicate that PEC attains its maximum value in the spherical-shaped NPs, the NPs fraction of 0.01, the nondimensional fin length of 0.4, the Darcy number of 0.01, and the medium porosity of 0.75. However, the multi-objective algorithm provides several optimum circumstances, each for a certain criterion indicating the suitability of this strategy for hydrothermal performance optimization of the system.

Investigating the effect of distribution form of copper foam fins on the thermal performance improvement of latent thermal energy storage units

Investigating the effect of distribution form of copper foam fins on the thermal performance improvement of latent thermal energy storage units

Computational Study of Phase Change Heat Transfer and Latent Heat Energy Storage for Thermal Management of Electronic Components Using Neural Networks

The phase change heat transfer of nano-enhanced phase change materials (NePCMs) was addressed in a heatsink filled with copper metal foam fins. The NePCM was made of 1-Tetradecanol graphite nanoplatelets. The heatsink was an annulus contained where its outer surface was subject to a convective cooling of an external flow while its inner surface was exposed to a constant heat flux. The governing equations, including the momentum and heat transfer with phase change, were explained in a partial differential equation form and integrated using the finite element method. An artificial neural network was employed to map the relationship between the anisotropic angle and nanoparticles fractions with the melting volume fraction. The computational model data were used to successfully train the ANN. The trained ANN showed an R-value close to unity, indicating the high prediction accuracy of the neural network. Then, ANN was used to produce maps of melting fractions as a function of design parameters. The impact of the geometrical placement of metal foam fins and concentrations of the nanoparticles on the surface heat transfer was addressed. It was found that spreading the fins (large angles between the fins) could improve the cooling performance of the heatsink without increasing its weight. Moreover, the nanoparticles could reduce the thermal energy storage capacity of the heatsink since they do not contribute to heat transfer. In addition, since the nanoparticles generally increase the surface heat transfer, they could be beneficial only with 1.0% wt in the middle stages of the melting heat transfer.

Flow boiling heat transfer and pressure drop characteristics of water in a copper foam fin microchannel heat sink

Flow boiling of water in a copper foam fin microchannel (FFMC) heat sink is investigated experimentally. The heat sink has nine channels, which are 487 μm in width and 1061 μm in height. Experiments are conducted under a wide range of operating conditions: inlet temperature of 80 ℃, outlet pressures of 100 ∼ 134 kPa, mass fluxes of 76 ∼ 408 kg/m2s, effective heat fluxes of 0 ∼ 296.5 W/cm2, and outlet qualities of −0.020 ∼ 0.874. Heat transfer and pressure drop characteristics of the FFMC are compared with those of a solid fin microchannel (SFMC) heat sink with the same geometry. The heat transfer coefficient of the FFMC is improved by up to 80 %, and the pressure drop is increased to 1.2 to 2 times. The critical heat flux of the FFMC is improved by 25% at the mass flux of 102 kg/m2s. Flow instability of the FFMC is mitigated significantly, including the reverse flow, the wall temperature fluctuation and the pressure drop fluctuation. Heat transfer mechanisms in the FFMC are analyzed with the help of the flow visualization. Nucleate boiling and thin film evaporation dominate in different Bo number ranges. The heat transfer coefficient of the FFMC first increases and then decreases with increasing the heat flux (also the quality) at low mass fluxes, and increases monotonically at high mass fluxes. The reduction of the wall temperature fluctuation and the pressure drop fluctuation are due to the transverse flow between the channels in the FFMC heat sink.

Review of phase change heat transfer enhancement by metal foam

• Enhancement characteristics of metal foam on solid-liquid phase change heat transfer and liquid-gas phase change heat transfer are reviewed. • The mechanism of metal foam enhancing phase change heat transfer and the factors affecting the phase change heat transfer process are comprehensively discussed. • Existing methods for optimizing phase change heat transfer performance within metal foam are classified and evaluated. • The practical applications of metal foam enhanced phase change heat transfer in recent years are summarized and compared. • This review will lead to a better understanding on the designing and applying of efficient metal foam-phase change heat transfer systems. Metal foam is a novel multifunctional material with high porosity, high surface density, and excellent heat transfer performance. Embedding metal foams into phase change heat transfer systems can be used to improve the comprehensive heat transfer performance, which is receiving increasing attention in the field of thermal management. This paper focuses on the lasted advances in solid-liquid phase change heat transfer and liquid-gas phase change heat transfer within metal foams, and specifically analyzes the influencing factors on phase change heat transfer performance as well as the mechanism of metal foam effects on phase change heat transfer. Different optimized techniques for improving phase change heat transfer within metal foams and the current state of metal foam engineering applications for improving phase change heat transfer are reviewed and discussed. It is concluded that the addition of metal foam can significantly enhance the heat transfer performance of solid-liquid phase change systems and liquid-gas phase change systems, but it is accompanied by an inhibitory effect on natural convection, an obstructive effect on bubble overflow and an elevated effect on pressure drop. The application of gradient porous structure, metal foam fins, V-groove structure or changing the surface wettability of metal foam is a feasible way to alleviate the above problems. Meanwhile, it is pointed out that the heat transfer performance of phase change within metal foam is influenced by the interaction of various factors, and some key issues regarding the influence mechanism of PCM-device orientation, pore distribution, surface wettability, and structural properties on heat transfer performance still need to be studied to develop more efficient and compact heat sinks.

Thermal performance improvement of thermal energy storage systems by employing a contrastive experiment

The thermal storage system is widely used to reduce the mismatch between thermal energy supply and demand in time and space, and its thermal performance is a critical factor in the system's thermal efficiency. The thermal performance of the Sensible Thermal Energy Storage Unit (STESU), the Latent Thermal Energy Storage Unit (LTESU), and the LTESU integrated with Copper Foam Fin (CFF) were compared through comparative experiments. The experimental results showed that the thermal changing rate of STESU was higher than that of other units, and there was no apparent thermal stratification. However, LTESU had the lowest thermal changing rate with apparent thermal stratification. During the thermal charging process, the solid-liquid interface on the LTESU cross-section formed an inverted-triangle shape. The lower part of the PCM could not change its phase as a dead zone and failed to participate in the thermal charging and discharging. Even so, the thermal efficiency of LTESU was 18.7% higher than that of STESU. Integrating with CFF could increase the thermal charging capacity, the thermal discharging capacity and the thermal efficiency by 51.1%, 55.9% and 10.8%, respectively.

Numerical study of natural convection in an annulus between two concentric cylinders provided with metal foam fins

Natural convection in an annular space provided with metal foam fins attached to the inner cylinder is studied numerically. The metal foam fins made of copper were inserted in different axial sections with three fins in each section. The temperature of the inner cylinder is kept constant while the annular outer surface is adiabatic. The thickness effect of the inner pipe wall was considered. Naiver Stokes equation with Boussinesq approximation is used for the fluid regime while Brinkman-Forchheimer Darcy model is used for metal foam. In addition, the local thermal non-equilibrium condition in the energy equation of the porous media is presumed. The effect of Rayleigh number and number of foam fins in the axial direction, on fluid flow and heat transfer characteristics, were examined. The current model was valid with the available published results and good agreement is noticed. Results showed that as the Rayleigh number increases the dominated of convection mode increases and average Nusselt increases. It was found that at Rayleigh of 106 Nusselt reached its higher value which is 4.6 for the case of adding seven axial metal foams. A comparison between adding foam fins and copper fins was established for a range of Rayleigh numbers between 104 and 106. It showed a good enhancement in Nusselt number and the greatest enhancement percentage was 45.9% at Rayleigh equal 106 for the case of using seven sections of foam fins.

Effect of copper foam fin (CFF) shapes on thermal performance improvement of the latent heat storage units

To overcome the poor thermal change of Phase Change Material (PCM), Copper Foam Fin (CFF) was innovatively utilized to enhance the PCM heat transfer capability and improve the thermal performance of vertical shell-and-tube latent heat storage units (LHSUs). Three CFF shapes, including annular CFF (ACFF), longitudinal CFF (LCFF) and compound CFF (CCFF), were designed with the same filling ratio of 30%. A contrastive experiment with three flow rates was conducted to evaluate the heat transfer capacity of LHSUs integrated with three CFF shapes. Experimental results showed the CFF shape had the large effects on the thermal performance of LHSU and that ACFF showed the most excellent thermal performance. Compared with LCFF and CCFF, adding ACFF could increase the melting rates by 14.1% and 3.9%, the solidification rates by 10.1% and 2.7%, and the thermal efficiency by 21.9% and 42.0%, respectively. And ACFF and CCFF units showed better performance in the liquid interface distribution and the temperature uniformity. Moreover, the volume flow rate had the small influence on the temperature response rate, but could improve the thermal efficiency significantly.

Experimental investigation on flow boiling heat transfer of R134a in a minichannel heatsink with copper foam fins

Metal foam is widely used for heat-transfer enhancement. Flow boiling of R134a in a minichannel heatsink with copper foam fins was studied. The heat sink contained four channels that were 503 μm in width and 990 μm in depth, and the copper foam fins had a porosity of 0.8. The mass flux in the experiment ranged from 595 to 1213 kg/m2 s, and the heat flux was in the range of 22–172 W/cm2. Heat transfer coefficients under different mass flow rates, heat fluxes, and qualities were obtained. The heat transfer deterioration phenomenon at different heat fluxes was analyzed. Compared with a solid-fin minichannel heat sink, the heat transfer was enhanced at low heat fluxes, whereas it was weakened at high heat fluxes. The turning point heat flux was between 87 and 100 W/cm2 and increased as the flow rate increased. Mechanisms of the heat transfer deterioration in the copper foam minichannel heatsink were explained by comparing flow patterns in the two heatsinks at the high heat flux.

Thermal-Hydraulic Optimization of Open-Cell Metallic Foams Used as Extended Surfaces

Abstract A one-dimensional analytical validated model for predicting temperature distribution, heat transfer, pressure drop, and fluid pumping power in an open-cell metal foam (OCMF) fin is developed. A foam length optimization technique based on its performance factor (PF) is proposed. Every optimized foam's efficiency is shown to be 33.2%, regardless of its pores per inch (PPI) or porosity. Although it can be applied to other porous materials, the model has been illustrated for aluminum foams with 5–40 PPI and 0.88–0.96 porosity (ε). The highest PPI, lowest porosity foam gives the best unit area goodness factor φu=jH/f, heat transfer, and heat transfer per unit volume Q˙V, while the greatest goodness factor φ (heat transfer rate to fluid pumping power) is achieved by the lowest PPI, lowest porosity foam. The highest PPI, highest porosity foam yields the best heat transfer per unit mass Q˙M. Thus, optimum foam selections strongly depend on the application. An often-used fin optimization criterion recommends that the fin effectiveness should equal or exceed 2. This study shows that the effectiveness of any optimized foam always exceeds 2. However, the converse, i.e., requiring the foam effectiveness to at least equal 2, does not guarantee an optimal foam, which implies that the PF-based optimization criterion is an inclusive one. It is also proved that a previously suggested optimization criterion of maximizing a foam's geometric mean efficiency will result in a suboptimal foam design.

Inclination angles on the thermal behavior of Phase-Change Material (PCM) in a cavity filled with copper foam partly

In this study, the influence of the inclination angle was analyzed on the thermal behavior of PCM in the cavity filled with copper foam fins. Twelve inclination angles from 0° to 360° were studied for the thermal storage unit, while the two-temperature equation thermal transfer model was built. The liquid fraction, the temperature response rate, and the average heat flow were employed as evaluation parameters. Numerical results displayed the inclination angle had the great influence on the PCM thermal performance and by optimizing the inclination angle, the whole phase-change time was shortened by 43.16% with the inclination angle from 0° to 180°. In melting and freezing processes, the inclination angle had the opposite rules and affected the thermal performance difference obviously. With the inclination angle from 0° to 180°, the difference values were reduced from 17904s, 712 w/m2 and 0.00867 °C/s to 1709s, 31 w/m2 and 0.00051 °C/s for full phase-change time, the average heat flow and temperature response rate, respectively. And the optimum inclination angle was 180° in the view of a melting and freezing period and the reasonable inclination angle could be selected according to thermal storage and release rules in the engineering application.

Influence of the Copper Foam Fin (CFF) shapes on thermal performance of Phase-Change Material (PCM) in an enclosed cavity

Phase-Change Material (PCM) attracted much attention due to its high thermal storage density under the small temperature variation, its poor thermal conductivity limited the thermal charging/discharging efficiency significantly. To overcome this deficit, fins were produced by copper foam to improve the thermal performance of PCM and seven Copper Foam Fin (CFF) shapes were considered with the same filling ratio of 50%. The numerical simulation was employed with the two-temperature non-equilibrium model. Results showed the solidifying process with the liquid fraction variation from 100% to 30% had the similar rules with the melting process with the liquid fraction variation from 0% to 70%, but the solidifying time with the liquid fraction variation from 30% to 0% was much higher than the melting time with the liquid fraction variation from 70% to 100%. The preferable CFF shape was gained with the longer left-side length, close to the hot and cold source. And there was the natural-convection heat transfer in solidifying and melting processes, but the natural convection intensity was too small to be considered in the solidifying process.

Performance augmentation of a solar air heater using herringbone metal foam fins: An experimental work

The transformation of massive solar irradiation into applicable energy forms like thermal energy plays an essential role in sustainable energy. Solar air heaters (SAH) are a way to transform solar irradiance into heat energy appropriate for human utilization. In the present study, experimental work was implemented to assess the thermo-hydraulic efficiency of a single duct single glazed SAH with herringbone metal foam fins attached beneath the absorber plate. Three corrugation angle values (30, 60, 90°) for the herringbone fins were examined. Metal foam fins porosity assists the air flows across the fin structure to exploit more heat from the absorber plate. Air flows were circulated by a centrifugal fan, their speeds varying between 0.01 to 0.05 m3/s. The experiments were implemented under realistic outdoor weather conditions in Baghdad, Iraq, from January to March 2020. The results showed that when the corrugation angle increases, the useful energy decreases. At an air flowrate of 0.05 m3/s, maximum useful energy at noon is 709, 588, and 442 W/m2 for corrugation angles of 30, 60, and 90°, respectively. The maximum outlet air temperature for a finned SAH with a corrugation angle of 30° is 60.4°C against 42.1°C for an unfinned SAH, at 0.01 m3/s air flowrate. Maximum thermal efficiency obtained by a finned SAH with a corrugation angle of 30° was 87.7% at an air flowrate of 0.04 m3/s, against 29.4% for an unfinned SAH at an air flowrate of 0.05 m3/s.

The Effect of Staggered porous fins on the performance of Photovoltaic panel in Baghdad

The performance of photovoltaic (PV) panel having staggered metal foam fins was examined experimentally in Baghdad, Iraq. Three staggered metal foam fin configurations attached to the backside of the PV panel were studied. The measured parameters were front and back surfaces temperature, open voltage and current circuits, maximum power, and PV efficiency. It was noted that the maximum electrical efficiency enhancement was 4.7% for staggered metal foam fins (case III) than the reference PV panel. The operating temperature of the cell was increased when the value of solar intensity was high. Thereby, the electrical efficiency was decreased. It was found that the metal foam fins decreased the PV temperature by 2-3 oC.

Numerical Comparison of Dehydriding Behaviors of Full-Scale Depleted Uranium Beds Equipped with Copper Foam or Copper Fins

In this study, a three-dimensional transient metal hydride model is applied to two different depleted uranium (DU) bed designs. One bed is designed to contain 1.86 kg DU for a hydrogen isotope storage capacity of 70 g, and it is loaded with copper foam to enhance internal heat transfer. The other bed is designed to contain 5.26 kg DU for a hydrogen isotope storage capacity of 200 g, and it uses copper fins to enhance internal heat transfer. A numerical study is conducted to analyze the dehydriding characteristics of two different DU bed designs. A parallel computing methodology is used to effectively reduce the computational turnaround time involved for full-scale DU bed geometries. The detailed simulation results show the evolution of temperature and hydrogen-to-metal atomic ratio contours at different hydrogen desorption stages and reveal the different DU dehydriding behaviors of the two DU beds. In sum, the present work elucidates the effects of key bed design parameters and helps identify optimal DU bed design strategies to effectively charge and discharge hydrogen isotopes.