Ionic Heat Research Articles

Electrohydrodynamic characteristics in parallel-fin channels and enhanced heat transfer performance of an ionic wind heat sink

High heat flux density may lead to a decline in the performance of highly integrated electronic components, which presents a major challenge to thermal management strategies. This work developed ionic wind heat sinks with parallel-fin channels for cooling high-power chips. The study examined the effects of intake air velocity, number of electrodes, and discharge spacing on the distribution of ionic wind flow and the improved heat transfer performance of the ionic wind heat sink. The findings suggest that the ionic wind heat sink with wire electrodes perpendicular to the fin channels can withstand higher operating voltages and generate more reliable corona discharges. The improved heat transfer capabilities are achieved with reduced inlet air velocity. The heat transfer enhancement factor (HTEF) of the ionic wind heat sink decreases as the discharge spacing increases, leading to a reduction in the peak value of the body force. The heat transfer capacity declines as the number of wire electrodes increases, because marginal effects lessen disruption to the thermal boundary layer. An effective airflow is achieved when wire electrodes are positioned upstream of the heat sink and run parallel to the fins, ensuring a steady and efficient cooling process. The design effectively disrupts the thermal boundary layer, reducing momentum loss in the flow and increasing the HTEF value by 21.2%. This improvement significantly enhances the heat dissipation capacity. The structurally optimized heat sink demonstrates excellent overall performance and is a viable option for improving heat dissipation in electronic devices.

Development and numerical optimization of a cylindrical wire-fin-type integrated ionic wind heat sink for cooling high-power LEDs

Light-emitting diodes (LEDs) are becoming increasingly high-power and compact, which makes rotary fans incompetent in some cooling situations. The ionic wind technique can compensate for the shortcomings of rotating fans, owing to its benefits of no moving parts and compact structure. Integrating the ionic wind generator with heat dissipation fins can effectively reduce the size of LED devices, but research in this area is still insufficient. In this study, an integrated ionic wind heat sink is designed for cooling LEDs. The multi-physical characteristics of discharge, flow, and heat transfer are numerically studied. The geometric parameters’ impact degree and mechanism on the multi-physical characteristics are analyzed. The performance optimization of the integrated heat sink is realized and verified. The fin length, flow channel center angle, and relative position of the fin have a large influence on the average velocity of ionic wind. The relative position of the wire electrode determines the electric field strength distribution, and it has the greatest influence on the ionic wind performance. The emitting electrode being placed at the inlet edge of the collecting electrode produces a high ionic wind flow rate. The integrated ionic wind heat sink designed in this study exhibits an outstanding cooling performance and temperature uniformity. This device can cool down the surface of a heat source with a power of 200 W to below 91 °C and make the average heat transfer coefficient reach 18.6 W/(m2·K). This study proposes a valuable method to optimize the integrated ionic wind heat sink for cooling high-power electronic devices.

ELECTRO-OSMOTIC EFFECT ON PERISTALTIC FLOW OF PHAN–THIEN–TANNER FLUID IN A PLANAR CHANNEL

Abstract There are several factors that can cause the excessive accumulation of biofluid in human tissue, such as pregnancy, local traumas, allergic responses or the use of certain therapeutic medications. This study aims to further investigate the shear-dependent peristaltic flow of Phan–Thien–Tanner (PTT) fluid within a planar channel by incorporating the phenomenon of electro-osmosis. This research is driven by the potential biomedical applications of this knowledge. The non-Newtonian fluid features of the PTT fluid model are considered as physiological fluid in a symmetric planar channel. This study is significant, as it demonstrates that the chyme in the small intestine can be modelled as a PTT fluid. The governing equations for the flow of the ionic liquid, thermal radiation and heat transfer, along with the Poisson–Boltzmann equation within the electrical double layer, are discussed. The long-wavelength ( $\delta \ll 1$ ) and low-Reynolds-number approximations ( $Re \to 0$ ) are used to simplify the simultaneous equations. The solutions analyse the Debye electronic length parameter, Helmholtz–Smoluchowski velocity, Prandtl number and thermal radiation. Additionally, streamlines are used to examine the phenomenon of entrapment. Graphs are used to explain the influence of different parameters on the flow and temperature. The findings of the current model have practical implications in the design of microfluidic devices for different particle transport phenomena at the micro level. Additionally, the noteworthy results highlight the advantages of electro-osmosis in controlling both flow and heat transfer. Ultimately, our objective is to use these findings as a guide for the advancement of lab-on-a-chip systems.

Heat transfer performance and electrohydrodynamic characteristics optimization of a dividing-wall-type ionic wind heat exchanger

Heat exchangers play a major role in reducing emissions and conserving energy. There is a plethora of theoretical research on the enhancement of heat transfer caused by ionic wind, but there is still a lack of studies on the practical application of ionic wind in heat exchangers to increase heat exchange capacity. This work developed an original ionic wind heat exchanger with a dividing wall. It may be applied to difficult circumstances when conventional heat exchangers fail for air-to-air heat exchange. The study conducted experiments to investigate the impact of many factors, including intake air velocity, discharge spacing, and electrode distribution scheme, on the ionic wind intensity and the heat exchanger's increased heat transfer coefficient. A two-dimensional model was used to analyze the internal flow and thermal properties of the heat exchangers with wire emitters. By combining active and passive heat exchange technologies, an ionic wind heat exchanger with serrated grounded electrodes was presented. The outcomes demonstrated that a suitable intake air velocity enhances the heat exchanger's capacity for heat exchange. The improved heat exchange effect of ionic wind is more important when the inlet wind speed is less than 1 m/s. When the intake air velocity approaches 1.3 m/s, the ionic wind has less of an impact on the heat exchanger's capacity for heat exchange. The benefits of improved heat transfer are promoted by placing the emitter closer to the channel entry. Increasing the operating voltage further enhances the heat transfer enhancement ratio (HTER). The number and arrangement of wire electrodes should be chosen with consideration for the 'barrier effect' between neighboring emitters and the distance from the entrance when utilizing multiple wire electrodes. In comparison to the three-wire and five-wire electrodes, the four-wire electrode heat exchanger's HTER values were increased by 5.9 % and 14.3 %, respectively. The ionic wind heat exchanger's capacity for heat transfer is further increased using a zigzag grounding electrode. The zigzag uses a decreased aspect ratio, and the emitter is positioned slightly above the tip, improving the system's heat transfer capabilities. When compared to a heat exchanger with a flat plate grounded electrode, the four-wire electrode heat exchanger produced a 158 % increase in HTER value.

Efficient removal of heavy metals from sewage sludge using a low-cost protic ionic liquid: Investigation of mechanism and ecological risk

Land utilization for the disposal of sewage sludge (SS) is an effective strategy, yet the existence of heavy metals (HMs) in the SS represents critical constraints to its implementation on a larger scale. By the principles of simple synthesis steps and low synthesis cost, a low-cost double cationic protic ionic liquid was produced in this study for HMs removal from SS. The influence of reaction time, protic ionic liquid to SS mass ratio, and reaction temperature on HM removal were thoroughly investigated. This result indicated that the integration of protic ionic liquid and heat treatment was efficacious in the efficient elimination of HMs. Under 60°C, 15 min, and protic ionic liquid: SS of 0.5, the removal efficiency of Zn, Fe, Ni, and Cd exceeded 80%, and Cr achieved a removal efficiency of up to 93%. The BCR sequential extraction procedure and calculation of the potential ecological risk index revealed a significant reduction in the ecological risk associated with the treated SS, transitioning from a high to a low-risk level. The alterations in elemental and chemical bonding within the solid phase of SS and changes in polysaccharide and fluorescence properties within the liquid phase of SS were investigated using redundancy analysis, two-dimensional correlation analysis, and parallel factor analysis. These findings suggest that dehydration, deamination, and decarboxylation reactions may be responsible for removing HMs within SS. These findings have a positive impact on further elucidating the effects of protic ionic liquid in SS pretreatment, thereby facilitating the efficient utilization of municipal SS resources.

Numerical simulation and optimization of ionic wind heat sink with needle-fin electrode

Numerical simulation and optimization of ionic wind heat sink with needle-fin electrode

Numerical Investigation on the Impact of Linear Variation of Positive Electrode Porosity upon the Performance of Lithium-Ion Batteries

The diffusion process of lithium-ions in the positive electrode solid phase as within the liquid phase is one of the pivotal factors in determining the battery performance. The effective conductivity and diffusion coefficient of the solid and liquid phases can be regulated by changing the distribution of the volume fraction of active material and porosity on the positive electrode. These crucial parameters can affect the transfer of lithium-ions in the solid and liquid phases and ultimately affect the battery’s performance. In this paper, a pseudo-three-dimensional (P3D) electrochemical-thermal-mechanical (ETM) coupling model is employed to study the non-uniform porosity of the positive electrode, especially the effect of porosity variation on the battery temperature and stress during the discharge process. Through numerical results, we find that reasonable porosity distribution can make the electrode lithiation more uniform and reduce the battery surface temperature by decreasing ionic ohmic heat. In addition, we display the stress distribution on the electrode and inside the active particles after adopting the linear porosity. The results are helpful for an in-depth understanding of the effect of the non-uniform porosity of the positive electrode on the lithium transport mechanism, the stress mechanism, and the thermal mechanism during the operation of lithium-ion batteries (LIBs).

Fabrication and characterization of O/W emulsion stabilized by Octenyl Succinic Anhydride (OSA) modified resistant starch

Reducing fat content without compromising its sensory qualities is a major technological challenge to the food industry in manufacturing healthy tasty food. Based on the fact that Octenyl Succinic Anhydride (OSA) starch emulsifiers have been successfully applied in food applications for stabilizing oil-in-water (O/W) emulsions, further converting native starch to resistant starch is an attractive alternative which does not require fat reduction but can protect fat droplets against enzymatic digestion. The main purpose of this study was to determine the feasibility of a combined process of debranching and OSA esterification to prepare resistant starch emulsifier for food applications. Following debranching, the resistant starch content of the modified starches markedly increased in comparison with the native starch and reached 43.09% when the enzyme concentration was set at 80 NPUN/g. In contrast, the degree of substitution (DS) of resistant starch was significantly decreased compared with native starch. The resulting resistant starch emulsifier exhibited weaker emulsifying capacity compared to native counterparts, this is caused probably by their lower DS. The environmental stability of resistant starch emulsions has also been investigated and it was observed that these emulsions remained stable after a storage period of 21 days at 4 and 25 °C, respectively however, they showed reduced stability at low pH, increased ionic strength and heat treatment. The overall research study provides useful insights into the utilization of resistant starch emulsifiers in novel food formulations for reduced fat digestion.

Toward a Sustainable Azeotrope Separation of Acetonitrile/Water by the Synergy of Ionic Liquid-Based Extractive Distillation, Heat Integration, and Multiobjective Optimization

Toward a Sustainable Azeotrope Separation of Acetonitrile/Water by the Synergy of Ionic Liquid-Based Extractive Distillation, Heat Integration, and Multiobjective Optimization

The effects of cations and concentration on reaction mechanism of alkali-activated blast furnace ferronickel slag

The effects of ion species and alkalinity on the alkali activated furnace ferronickel slag (FNS) were studied in this paper. NaOH and KOH with different concentration (2 M & 6 M) were used as activator. XRD , FT-IR and BET results show that more C-A-S-H gels were produced than the crystalline phases at lower activator concentration, while more crystalline phases formed at high concentration. Isothermal calorimetry and ICP results show that the effects of cations are different at different concentration. At lower concentration, higher reaction rate and higher concentrations of Si and Al were found in NaOH activated FNS although the alkalinity of NaOH is lower. This is due to the stronger polarization ability of Na + than K + can stabilize Si and Al anions in the solution and improve the reaction rate. At higher concentration, isothermal calorimetry shows large differences between NaOH and KOH while only small differences was found in ICP data. This indicates that cations have greater impact on the reaction process at higher concentration. A hypothesis was proposed to explain the anomalous phenomenon at higher concentration. At high concentration, there are not enough water molecules in the solution for ion hydration. Na + with higher ionic polarization and hydration heat will strongly bind to dissolved anions and accelerate the reaction near the FNS particle. While K + bind to less water molecules which enable faster diffusion of anionic species and promote the later reaction. • The effect of cations on the reaction kinetics of alkali-activated furnace slag is different at different concentrations. • At 2 M concentration, Na + with a high charge density could stabilize the Si and Al anions and the reaction rate is higher. • At 6 M concentration, the strong polarization ability of Na + decrease the molar conductivity of NaOH solution.

Ionic heat dissipation in solid-state pores.

Energy dissipation in solid-state nanopores is an important issue for their use as a sensor for detecting and analyzing individual objects in electrolyte solution by ionic current measurements. Here, we report on evaluations of heating via diffusive ion transport in the nanoscale conduits using thermocouple-embedded SiNx pores. We found a linear rise in the nanopore temperature with the input electrical power suggestive of steady-state ionic heat dissipation in the confined nanospace. Meanwhile, the heating efficiency was elucidated to become higher in a smaller pore due to a rapid decrease in the through-water thermal conduction for cooling the fluidic channel. The scaling law suggested nonnegligible influence of the heating to raise the temperature of single-nanometer two-dimensional nanopores by a few kelvins under the standard cross-membrane voltage and ionic strength conditions. The present findings may be useful in advancing our understanding of ion and mass transport phenomena in nanopores.

INVESTIGATION OF HEAT TRANSFER ENHANCEMENT BY MULTISTAGE IONIC WIND HEAT SINK USING NEEDLE-MESH ELECTRODE

Ionic wind technology as a potential substitute for traditional heat dissipation technology has attracted great attention. In this study, two types of multistage ionic wind heat sink using needle-mesh electrodes were studied. The relationship between the number of needles, the number of stages and the coefficient k is determined through numerical calculation, and the cooling performance of the two different structures are tested and quantitatively analyzed. The results show that compared with the single-stage ionic wind heat sink, the cooling performance of multistage ionic wind heat sink has been greatly improved. The maximum enhancement factor is 3.705. The integrated multistage ionic wind heat sink can achieve better cooling performance under lower working voltage. The volume of integrated structure has been reduced by more than 60%.

The Optimization of Needle-Net Ionic Wind Generator Electrode Structure and Heat Dissipation Performance

The Optimization of Needle-Net Ionic Wind Generator Electrode Structure and Heat Dissipation Performance

OPTIMIZATION OF CONTINUOUS MICROWAVE INACTIVATOR FOR POLYPHENOL OXIDASE INACTIVATION ON GREEN TEA PROCESSING USING RESPONSE SURFACE METHODOLOGY

Microwave treatment is a promising technology for food processing such as drying, extraction, and enzyme inactivation because of its ionic heat transfer. This study develops and optimizes the fixation process in green tea using a microwave-based enzyme inactivator. A continuous microwave enzyme inactivator with a dimension of 3300 (L) × 550 (W) × 600 mm3 (H) was built to study the effect of temperature, microwave radiation time, and the number of microwaves on the catechin content of green tea. The optimum condition for the inactivation process was determined using response surface methodology and central composite design. The result shows that the model can predict the effect of temperature, microwave radiation time, and the number of microwaves on catechin content. Temperature, fixation time (conveyor velocity), and the number of microwaves, have a significant impact on enzyme inactivation when using a continuous microwave. The optimum microwave inactivation condition for polyphenol oxidase enzyme was four at 70C temperature and 30 rpm conveyor speed.

Formation mechanism of nanocomplex of resveratrol and glycated bovine serum albumin and their glycation-enhanced stability showing glycation extent

The application of protein-based bioactive molecule complexes is limited by their instability under environmental conditions, such as pH, ionic strength, and ultraviolet irradiation. In this study, Bovine serum albumin (BSA) and BSA-glucose conjugates (GBSA) with different glycated extent were complexed with resveratrol (RES). Formation of the BSA/GBSA-RES nanocomplexes was confirmed by UV–visible spectroscopy. Fluorescence quenching spectra indicated that the BSA-RES and GBSA-RES nanocomplexes were formed via noncovalent interactions by a self-assembly method. Interestingly, BSA with a greater glycation extent showed a higher binding affinity for RES. Compared with BSA/GBSA I (BSA glycated in water system)-RES, the GBSA II (BSA glycated in natural deep eutectic solvent system)-RES nanocomplex obtained highest Z-average diameter, encapsulation efficiency and loading capacity. Fourier transform infrared and X-ray diffraction spectra indicated that RES was complexed with BSA/GBSA in an amorphous form. Compared with BSA-RES nanocomplexes, GBSA-RES (particularly GBSA II) nanocomplexes showed better environmental stress (ionic strength, heat, and pH) and storage stability. The advantages of the glycated proteins may provide an effective alternative to protect and deliver bioactive compounds in the food and pharmaceutical industries.

Structure and Dynamics in Self-Healing Polymer Electrolytes Based on PVDF-HFP for Battery Applications

Lithium dendrite formation is a key limitation in rechargeable Li metal batteries. Here we report on a novel polymer electrolyte with self-healing capabilities, consisting of PVdF-HFP membranes imbibed with an ionic liquid electrolyte EMIM-TFSI + LiTFSI and mechanically reinforced by alumina nanowires. Similar membranes were reported to have self-healing capability via resistance to dendrite formation at the electrode-electrolyte interface.1 We have investigated the structure and dynamics in these membranes by nuclear magnetic resonance (NMR). Double resonance and 2D NMR methods show that the EMIM cation interacts with CF3 group present in HFP, forming an ion-dipole association which may be related to the desired self-healing properties. Moreover, addition of alumina nanowires has been reported2 to increase the ionic conductivity in the membrane in addition to imparting mechanical strength. We have used pulsed field gradient (PFG) NMR to investigate how alumina nanowire doping into the PVDF-HFP-IL matrix improves the Li+ diffusivity. Additional characterizations such as electron dispersion X-ray (EDX) spectroscopy to study nanowire distribution in the polymer and ionic conductivity measurements, will also be discussed. Keywords: Ionic Liquids, Self-healing, Dendrite formation, PVDF-HFP membranes, NMR spectroscopy, EDX References Chen, T. et al. Ionic liquid-immobilized polymer gel electrolyte with self-healing capability, high ionic conductivity and heat resistance for dendrite-free lithium metal batteries. Nano Energy 54, 17–25 (2018).Kwon, S. J. et al. Influence of Al2O3 Nanowires on Ion Transport in Nanocomposite Solid Polymer Electrolytes. Macromolecules 51, 10194–10201 (2018).

A preliminary assessment of the sensitivity of uniaxially driven fusion targets to flux-limited thermal conduction modeling

The role of flux-limited thermal conduction on the fusion performance of the uniaxially driven targets studied by Derentowicz et al. [J. Tech. Phys. 18, 465 (1977) and J. Tech. Phys. 25, 135 (1977)] is explored as part of a wider effort to understand and quantify uncertainties in inertial confinement fusion (ICF) systems sharing similarities with First Light Fusion's projectile-driven concept. We examine the role of uncertainties in plasma microphysics and different choices for the numerical implementation of the conduction operator on simple metrics encapsulating the target performance. The results indicate that choices that affect the description of ionic heat flow between the heated fusion fuel and the gold anvil used to contain it are the most important. The electronic contribution is found to be robustly described by local diffusion. The sensitivities found suggest a prevalent role for quasi-nonlocal ionic transport, especially in the treatment of conduction across material interfaces with strong gradients in temperature and conductivity. We note that none of the simulations produce neutron yields that substantiate those reported by Derentowicz et al. [J. Tech. Phys. 25, 135 (1977)], leaving open future studies aimed at more fully understanding this class of ICF systems.

Convective Mass/Heat Analysis of an Electroosmotic Peristaltic Flow of Ionic Liquid in a Symmetric Porous Microchannel with Soret and Dufour

This research deals with the mathematical model for the development of the peristaltic principle of the combination of the pressure and electroosmotic flow (EOF) of ionic liquid across microchannels with electrokinetic effects. For thermomechanical dynamics, the convective conditions on the boundary for mass and heat transfer at the walls of the channel are quantified. For the microchannel, a porous structure is presumed. Soret, Dufour, and Joule heating are also listed in the scope of the problem addressed. The corresponding equations for the ionic fluid flow, mass, and heat transfer along with the Poisson–Boltzmann equation within the electrical double layer (EDL) are studied. The exact solution has been obtained based on lubrication theory (i.e., low Reynolds number and long wavelength approximations). The channel height is therefore believed to be much higher than the electrical double layer (EDL) thickness. Various dimensionless pertinent parameters illustrate the important aspects of electroosmotically controlled flow and subsequent convective mass/heat transfer attributes in a microchannel. A linear dependency on the fluid flow rate is exhibited by the pressure drop. The analysis shows that the electroosmotic parameter gives a reducing effect on the channel permeability. The distribution of temperature and concentration is greatly affected by convective heat and mass parameters, respectively. In biomedical engineering, the application areas of the study proposed are for the design of the devices such as a microfluidic pump to pump a small amount of ionic liquids by regulating the variation in temperature and concentration.

Construction and characterization of Mesona chinensis polysaccharide-chitosan hydrogels, role of chitosan deacetylation degree

A novel kind of polyelectrolyte complex hydrogels was generated through polymerization of Mesona chinensis polysaccharide (MCP) and chitosan (CH) on the basis of physical crosslinking without the addition of ionic crosslinking agents or heat. Rheological measurement, Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric analysis, and scanning electron microscopy were used to explore the properties of MCP−CH hydrogels. The effects of CH deacetylation degree (DD) on the gel properties and structural characteristics of MCP−CH hydrogels were also studied. Results showed that 0.5 % MCP and 1% CH could form stable and homogeneous hydrogels with favorable properties via electrostatic interaction. The viscoelasticity, water holding capacity, and thermostability of hydrogels were promoted with the increase in DD. The new crystallization peaks appeared with the formation of MCP−CH hydrogels. Moreover, the honeycomb-liked microstructure of MCP−CH hydrogels improved with the increase in DD. These findings may lay the foundation for the further application of MCP−CH hydrogels.

Polyimide composite separator containing surface-modified hollow mesoporous silica nanospheres for lithium-ion battery application

Polyimide (PI) hybrids of biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA), containing surface-treated hollow mesoporous silica (AHMS) nanospheres, are synthesized by chemical imidization and freeze-drying. The resulting xerogels exhibit high ionic conductivity and heat resistance. The volume shrinkage of the wet gels, which occurs during the drying process, is avoided by adding AHMS nanoparticles, resulting in the formation of a robust network structure of PI hybrid xerogels as a crosslinker. The cross-sectional structure of the xerogels containing AHMS nanospheres exhibits a network of interconnected polyimide microfibers. Lithium ion batteries are fabricated by inserting the PI hybrid xerogel separator between electrodes. In the repeated charge/discharge experiment, the electrolyte uptake and interfacial compatibility of the PI hybrid xerogel separator are improved significantly compared to those measured from the PI separator.