Effective Pore Radius Research Articles

Enhancing heat pipe performance through hybrid wick structures: Balancing pore size and permeability

This study investigates the impact of wick structures on heat pipe performance by optimizing the balance between effective pore radius and permeability for efficient heat dissipation. It addresses the challenge of enhancing capillary pumping forces while maintaining optimal liquid replenishment to the evaporator. A novel hybrid wick structure is proposed, strategically integrating sintered and screened elements within the heat pipe to improve thermal performance. Experimental tests include varying inclination angles (antigravity up to 60°) to assess thermal resistance and liquid return capabilities. Results show a 13.31 % reduction in thermal resistance compared to conventional sintered heat pipes, particularly at higher power levels (40 W– 60 W). At a 40° inclination angle, optimal evaporation and liquid flow improve thermal performance, with thermal resistance for sintered and hybrid heat pipes decreasing by 14.05 % and 27.72 %, respectively. However, at 60° inclination, the hybrid’s thermal resistance increases significantly due to local dry-out. The study identifies limitations beyond 45° inclination, which is attributed to increased receding contact angles, and the influence of gravity becomes more pronounced, affecting capillary limits. This research underscores the importance of innovative wick designs in advancing heat pipe technology for diverse applications.

Permeability and Induced Polarization of Mudstones

AbstractElectrical measurements can be used to estimate hydraulic properties such as permeability (k) in sedimentary rocks. Previous work has focused on sandstones, siltstones, and carbonates, while investigations on mudstones have rarely been reported. In this study, we report on electrical geophysical measurements for 23 mudstone samples using an experimental approach designed to reliably saturate these low permeability mudstones. The modified Hagen‐Poiseuille model linking permeability to the formation factor (F) and an effective pore radius (r) provides an excellent fit to the data set with a near‐constant pore radius, indicating that the effective porosity (1/F) is the controlling factor on k. In these samples, the surface area normalized to pore volume (Spor), frequently used in permeability estimation models, varies by 1–2 orders of magnitude and is thus not a reliable proxy of the inverse effective hydraulic radius. The formation factor also exerts the primary control on induced polarization (IP) parameters, whereas Spor shows no relation to the IP parameters. A strong linear relationship is found between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity, although the proportionality factor is significantly lower than those observed in more permeable rocks and sediments. Apparent relationships between the polarization strength‐derived and time constant‐derived geophysical length scales and the effective hydraulic radius appear to be driven by variations in the electrochemical parameters (i.e., specific polarizability and diffusion coefficient). Overall, these findings emphasize that predicting hydraulic properties from electrical measurements in fine‐grained rocks remains challenging and requires further investigation into the electrochemical properties involved.

A Review of Fracturing and Enhanced Recovery Integration Working Fluids in Tight Reservoirs

Tight reservoirs, characterized by low porosity, low permeability, and difficulty in fluid flow, rely on horizontal wells and large-scale hydraulic fracturing for development. During fracturing, a significant volume of fracturing fluid is injected into the reservoir at a rate far exceeding its absorption capacity. This not only serves to create fractures but also impacts the recovery efficiency of tight reservoirs. Therefore, achieving the integration of fracturing and enhanced recovery functions within the working fluid (fracturing-enhanced recovery integration) becomes particularly crucial. This study describes the concept and characteristics of fracturing-enhanced recovery integration and analyzes the types and features of working fluids. We also discuss the challenges and prospects faced by these fluids. Working fluids for fracturing-enhanced recovery integration need to consider the synergistic effects of fracturing and recovery; meet the performance requirements during fracturing stages such as fracture creation, proppant suspension, and flowback; and also address the demand for increased recovery. The main mechanisms include (1) enlarging the effective pore radius, (2) super-hydrophobic effects, and (3) anti-swelling properties. Fracturing fluids are pumped into fractures through pipelines, where they undergo complex flow in multi-scale fractures, ultimately seeping through capillary bundles. Flow resistance is influenced by the external environment, and the sources of flow resistance in fractures of different scales vary. Surfactants with polymerization capabilities, biodegradable and environmentally friendly bio-based surfactants, crosslinking agents, and amino acid-based green surfactants with outstanding properties will unleash their application potential, providing crucial support for the effectiveness of fracturing-enhanced recovery integration working fluids. This article provides important references for the green, efficient, and sustainable development of tight oil reservoirs.

Investigating effective strategies for sustainable operation of a submerged anaerobic membrane bioreactor (SAnMBR) coupled with ceramic ultrafiltration membrane

This study presents a mechanistic approach to explore the key operational parameters governing the flux performance of an SAnMBR system coupled with a ceramic flat-sheet ultrafiltration membrane. Experiments were conducted at mixed liquor suspended solid (MLSS) concentrations of 12, 18, and 24 g/L using biogas sparging, backwashing, and a combination of both to investigate the most effective fouling mitigation strategy by exploring the fouling mechanism at a critical flux regime. To validate the experimental findings, a mathematical model was used to simulate the time-based variation of membrane effective pore radius (m), decrease in membrane porosity (%), thickness of cake layer (m), and membrane resistance (1/m). The study found that at a low biomass concentration, there was a sharp decline in the membrane pore radius leading to an increase in membrane resistance in the absence of any fouling mitigation strategies. However, by implementing these strategies individually and in combination, they maintained a higher pore radius and controlled the increase in membrane resistance even at high biomass concentrations. It was observed that biogas sparging outperformed the conventional backwashing strategy and the SAnMBR system exhibited superior performance attaining higher flux rates for prolonged duration. The advanced spectroscopic analysis confirmed the presence of a higher concentration of polysaccharides responsible for cake layer biofouling, and significant pore blocking due to inorganic foulants at high biomass concentrations. This suggests that the SAnMBR system must be operated at optimised biomass levels below the critical flux for sustained operation. Additionally, the key operational parameters identified using the mathematical model provide a precise assessment of SAnMBR performance, to improve its design efficiency for field applications.

Increase in the effective viscosity of polyethylene under extreme nanoconfinement.

Understanding polymer transport in nanopores is crucial for optimizing heterogeneously catalyzed processes in polymer upcycling and fabricating high-performance nanocomposite films and membranes. Although confined polymer dynamics have been extensively studied, the behavior of polyethylene (PE)-the most widely used commodity polymer-in pores smaller than 20nm remains largely unexplored. We investigate the effects of extreme nanoconfinement on PE transport using capillary rise infiltration in silica nanoparticle packings with average pore radii ranging from ∼1 to ∼9nm. Using in situ ellipsometry and the Lucas-Washburn model, we discover a previously unknown inverse relationship between effective viscosity (ηeff) and average pore radius (Rpore). Additonally, we determine that PE transport under these extreme conditions is primarily governed by physical confinement, rather than pore surface chemistry. We refine an existing theory to provide a generalized formalism to describe the polymer transport dynamics over a wide range of pore radii (from 1nm and larger). Our results offer valuable insights for optimizing catalyst supports in polymer upcycling and improving infiltration processes for nanocomposite fabrication.

Permeability measurement of a 3D-printed AlSi10Mg porous medium: comparisons between first results with different experimental and numerical techniques

In this work, the permeability of a 3D-printed, AlSi10Mg porous medium, with porosity ε = 0.3 and an effective pore radius of 48 μm, developed to operate as wick in a sinter-like heat pipe, has been investigated by means of two different experimental approaches, and of two different numerical methods. The two experimental methods are the capillary rise tests, from which permeability was estimated by fitting the theoretical capillary rise curve to the experimental data, and the direct measurement of the the mass flow rate across the porous sample at an imposed pressure difference. The numerical simulations were performed too using two different approaches and software tools, namely, Lattice-Boltzmann with Palabos, and Finite-Volumes with OpenFOAM. In both cases, the simulation domain was reconstructed from a micro-computer aided tomographic scan of a porous medium sample. Preliminary simulations were run on a simple configuration, both to check simulation setup and validate results, and mesh independence was assessed. Then, pressure-driven and velocity-driven simulations of an incompressible fluid flow across the domain were performed, from which the permeability was estimated using Darcy and Darcy-Forchheimer equations. The results show that the methods, while not in complete agreement, provide a useful estimate. The numerical methods also complement the information given by the experimental techniques by highlighting the flow paths, and allow to analyze scenarios of increased and decreased porosity.

Tailoring Substrate Topography to Enhance Wicking Performance of Electrodeposited Cu Porous Films

Porous metallic films have received emerging interests in the fields of catalysts, fuel cells, lithium batteries, and phase-change heat transfer devices. Substrate topography is known to have a strong impact on adhesion and morphology of porous coating layers prepared by electrodeposition. In this study, we have tailored the topography of a Cu substrate by wet etching in a sodium persulfate/sulfuric acid (SPS) solution prior to electrodeposition of porous Cu films. An analytic approach is proposed to quantitatively analyze nucleation and growth of dendritic Cu deposits on the SPS-treated Cu substrates. Such a dendritic porous Cu film can serve as a capillary wick to complete recirculation of condensed liquid in the phase-change heat transfer devices. The maximum heat transfer rate of a heat pipe or vapor chamber indeed is proportional to the capillary performance (K/Reff ) of the wick structure, where K and Reff stand for liquid permeability and effective pore radius of the wick, respectively. A large K/Reff value of 0.975 µm has been attained for the electrodeposited dendritic Cu film on a Cu substrate with an optimal SPS etching treatment. The influence of dendritic deposits on the wicking performance of the electrodeposited Cu film is investigated. Figure 1

The effect of layer thickness on the geometry and capillary performance of strut-based heat pipe wicks manufactured by laser powder bed fusion

Additive manufacturing (AM) can be used to fabricate heat pipes and two-phase heat sinks which have integrated wicking structures. These devices can be customized and have superior performance when compared with devices with conventionally fabricated wicks. The current work investigates the impact of build rate on the capillary performance of AM wicks fabricated by laser powder bed fusion (LPBF). The build rate was examined by varying the layer thickness from 30 µm to 80 µm for four different strut-based wick geometries: (i) body-centered cubic (BCC), (ii) face-centered cubic (FCC), (iii) simple cubic (SC), and (iv) fluorite. The mass rate-of-rise method was used to quantify the wick hydraulic parameters (namely wick permeability, K, and effective pore radius, reff). Layer thickness has a significant influence on wick permeability; layer thickness of 40 µm result in the highest value for all configurations but have a small effect on the effective pore radius. Layer thickness of 40 µm and 60 µm reached the highest K/reff ratio, primarily because of the permeability increase. We attribute this to poor build quality such as missing struts and less defined edges which facilitate low resistance to fluid flow. The SC 60 and BCC 40 configurations achieved the maximum capillary performance with K/reff of 1.34 µm and 1.42 µm, respectively. Overall, it was found that while increasing the build rate by varying layer thickness may affect the part build quality, it promotes hydraulic performance for some configurations by creating random rough surface morphologies and arteries, which help increase permeability.

Adsorption effects on CO2-oil minimum miscibility pressure in tight reservoirs

CO2 miscible injection holds immense potential for enhancing tight oil recovery, where achieving the minimum miscibility pressure (MMP) is pivotal. Adsorption of CO2 and oil in pores affects the CO2-oil MMP in tight reservoirs, necessitating precise nanoscale MMP calculations and understanding influencing factors. Here, we applied a modified Peng-Robinson equation of state (PR-EOS) for nanoscale MMP calculations, incorporating adsorption layers and effective molar volume to describe adsorption effects. Validation against molecular simulations and nanofluidic experiments shows a maximum deviation of 4.6 %. We found that in nanopores, achieving miscibility demands less CO2 than in bulk. The CO2-oil MMP reduces as pore size decreasing, influenced by adsorption, critical point shift and capillarity. At 5 nm, the MMP is 11.12 MPa, 27.8 % lower than the bulk value (15.4 MPa). Adsorption intensifies this reduction by curtailing free molecules and effective pore radius, and becomes more pronounced for lighter hydrocarbon mixtures. However, the nanoscale CO2-oil MMP is equal to the bulk value when rp ≥ 350 nm. Furthermore, a maximum MMP and the corresponding transition temperature exist for each pore size, and increase as pore size increasing. This method provides a valuable tool for optimizing CO2 miscible injection and carbon storage in challenging nanoscale-pore reservoirs.

Applying the improved stratigraphic modified Lorenz technique for dividing the highly heterogeneous clastic reservoirs into hydraulic flow units

The present study applies the improved stratigraphic modified Lorenz (ISML) technique to divide the Matulla Formation in Muzhil Oil Field in the Gulf of Suez into some hydraulic flow units (HFUs) and to check the flow efficiency contribution of each hydraulic flow unit (HFU) to the total bulk flow capacity of the reservoir in 3 wells (Muzhil-4, 7, and 8). The output of the ISML plot is applied in integration with the vertical plot of the porosity (∅), permeability (k), and effective pore radius (R35) against depth to measure the efficiency of each HFU contribution to the total flow capacity of the Matulla reservoir, and to delineate the main attributor to the flow capacity. It is indicated that the Matulla sandstone reservoirs can be subdivided into 7 HFUs to the NW of the field, while it is subdivided into four and five HFUs in the center and to the SE of the field; i.e., its heterogeneity increases to the NW at Muzhil-7 well. On the other side, the best reservoir quality is assigned to the southeast at Muzhil-4 well (av. ∅ = 20.8%, av. k = 596.6 md, and R35 = 12.1 μm). The efficiency of the obtained HFUs was estimated and described both mathematically and graphically. Also, the measured porosity and permeability values indicate relatively low reservoir properties to the NW of the field. The reservoir heterogeneity is also measured using the Dykstra-Parsons technique which indicates extremely high heterogeneity (0.89 ≤ V ≤ 0.98).

Analysis of Drying Front Propagation and Coupled Heat and Mass Transfer During Evaporation From Additively Manufactured Porous Structures Under a Solar Flux.

Drying front propagation and coupled heat and mass transfer analysis from porous media is critical for soil-water dynamics, electronics cooling, and evaporative drying. In this study, de-ionized water was evaporated from three 3D printed porous structures (with 0.41 mm, 0.41 mm, and 0.16 mm effective radii, respectively) created out of acrylonitrile butadiene styrene (ABS) plastic using stereolithography technology. The structures were immersed in water until all the pores were invaded and then placed on the top of a sensitive scale to record evaporative mass loss. A 1000 W/m2 heat flux was applied with a solar simulator to the top of each structure to accelerate evaporation. The evaporative mass losses were recorded at 15 min time intervals and plotted against time to compare evaporation rates from the three structures. The evaporation phenomena were captured with a high-speed camera from the side of the structures to observe the drying front propagation during evaporation, and a high-resolution thermal camera was used to capture images to visualize the thermal gradients during evaporation. The 3D-structure with the smallest effective pore radius (i.e., 0.16 mm) experienced the sharpest decrease in the mass loss as the water evaporated from 0.8 g to 0.1 g within 180 min. The designed pore structures influenced hydraulic linkages, and therefore, evaporation processes. A coupled heat-and-mass-transfer model modeled constant rate evaporation, and the falling rate period was modeled through the normalized evaporation rate.

The Influence of Inert Fluoropolymer on Equilibrium and Dynamic Hydration Characteristics of MF-4SC Membrane

The influence of the type and amount of an inert component in perfluorinated MF-4SC sulfonic cation-exchange membrane on its equilibrium physicochemical and transport properties has been studied. The exchange capacity, water content, specific conductivity, and diffusion and electroosmotic permeability of two series of MF-4SC membranes obtained by casting from polymer solutions in dimethylformamide with variable contents of inert fluoropolymers have been investigated. A relationship between the equilibrium and dynamic hydration characteristics of the samples has been found as a result of studying water distribution over water binding energies and effective pore radii and the numbers of water transport in an external electric field. The type and content of an inert component in the perfluorinated membrane have been found to affect more significantly the state of water under equilibrium conditions than the electroosmotic water transport.

Adsorption Kinetics of Poly(benzyl acrylate) Chains onto Alumina Interface during the Flow-Driven Translocation through Cylindrical Nanochannels.

In this work, the adsorption kinetics of the PBAN/AAO system under flushing condition has been investigated, where PBAN and AAO represent poly(benzyl acrylate) and anodic alumina oxide (AAO, average pore radius R0 ≈ 10 nm) nanochannel, respectively. Our specially designed double-pump flushing system is proved to eliminate the overshoot phenomenon and in situ monitor transmembrane pressure (ΔP) as a function of flushing time (t) and flow rate (Q), which gives the effective pore radius (R), cross-sectional coverage factor (χ = [1 - (R/R0)2]), and characteristic ratio (rc) of the increments of χ during each adsorption/desorption cycle at a given bulk solution concentration (Cbulk). Our findings include: (1) by gradient increasing Cbulk from 10 to 200 mg/L at Q = 10 mL/h, the shortest PBA40 displays a saturation adsorption behavior when Cbulk ≥ 80 mg/L and t ≥ 2000 s, which agrees well with the prediction of blob model, whereas for the longer PBAN chains, the chain length (N) and concentration-dependent adsorption tendency get stronger as N increases from 40 to 620 at t ≥ 2000 s, in particular, R/R0 ∼ N-0.20 is observed at Cbulk = 140 mg/L; (2) by focusing on the platform χ in the saturation adsorption regime (χsat), the longer PBAN displays a stronger adsorption trend with partially reversible feature at Q = 5.0 mL/h, namely, as N increases from 40 to 620, χsat increases from 0.15 to 0.83 at Cbulk = 100 mg/L, where rc changes from 0.25 ± 0.10 to 0.80 ± 0.10 as the adsorption/desorption flushing cycle increases from 1 to 8 at Cbulk = 100 mg/L; (3) by further assuming a solvent nonpenetrating and nondraining adsorption layer, χsat determined in the case of curved surface can be comparable to the physical meaning of adsorption thickness (Δad) in the case of flat-surface adsorption, and the fitting result indicates χsat ∼ Δad ∼ N0.58, falling between Δad ∼ N1/2 and Δad ∼ N1.0 predicted by the mean-field and scaling theories for real multichain adsorption, respectively. Overall, the present work not only clarifies some controversies but also provides unambiguous evidence supporting the existence of tightly adsorbed internal and loosely adsorbed external layers.

Effect of evaporation and condensation section length ratio on thermal performance of aluminum flat plate heat pipe with different micro grooved wicks

The length of the evaporation or condensation section has a significant impact on conventional heat pipe or copper flat heat pipe heat transfer performance. Based on this demand, a novel concept of the length ratio of evaporation and condensation section (LREC) of the flat plate micro grooved heat pipe (FPMHP) was proposed and the effect of the LRECs on the thermal performance of aluminum-based FPMHP with different micro grooved wicks was experimentally investigated for the first time. The experiment explored the effects of nine different LRECs on the thermal performance of FPMHP with the same section size, filling mass, rectangular and triangular micro grooved wicks installed at 90°, a constantly increasing input heat flux, and forced air cooling. The findings demonstrate that rectangular micro grooved wick flat heat pipe (FPMHP-r) and triangular grooved wick flat heat pipe (FPMHP-t) have the shortest startup times when LREC is 1.0, with FPMHP-r starting 70 s sooner than FPMHP-t. When 0.8 ≤ LREC ≤ 1.25, the heat transfer performance of FPMHP-t and FPMHP-r is excellent, better than performance when LREC < 0.8 or LREC > 1.25, and the LREC is recommended to be 0.8 ∼ 1.25 in practical applications. The optimal LREC value of aluminum-based FPMHP is 1.0, which can maximizes the heat transfer performance. Under the same conditions, the heat transfer performance of FPMHP-r is better than FPMHP-t, flat heat pipe wicks with high permeability, low porosity and effective pore radius should be designed in practice. The results can provide a theoretical basis for the design and optimization of aluminum-based FPMHP application.

Enhancing capillary performance of copper wicks by electrodeposition of superhydrophilic dendritic structures

Capillary wick is a critical component that sustains working fluid circulation in heat-spreading vapor chambers. A preferred wick layer requires a porous structure of multiscale porosity to meet the requirements of high liquid permeability (K) and large capillary pressure (ΔP). In this study, we controlled the etched substrate topography to modulate the morphology and capillary dynamics of the electrodeposited porous films on a specifically treated Cu substrate. The effective pore radius (Reff) of porous Cu films depends on the size and density of the dendritic bushes grown on Cu substrates treated with sodium persulfate/sulfuric acid (SPS) solution. An analytical approach was used to quantitatively analyze the dendritic deposits grown on the SPS-treated Cu substrates. The surface profile and roughness of Cu substrates were investigated by alpha-step profilometer. Scanning electron microscopy, contact angle analyzer and x-ray diffractometer were used to characterize the surface morphology, wetting behavior and oxide formation of the electrodeposited Cu films, respectively. The capillary performance (K/Reff) of the electrodeposited Cu film was measured using the capillary rate-of-rise test. The effect of dendritic bush distribution on fluid transport properties was investigated. A high K/Reff value of 0.975 μm was obtained for the electrodeposited Cu film on a Cu substrate with an optimal SPS etching treatment.

An integrated workflow for seismic interpretation, petrophysical and petrographical characterization for the clastic Mangahewa reservoir in Pohokura gas field, Taranaki Basin, New Zealand

This research aims at delineating the main structural elements controlling the geologic setting of Taranaki Basin in New Zealand which in turn control the hydrocarbon potential of this basin and in particular of Pohokura Field which is considered one of the main gas-producing fields in the basin. This can be achieved utilizing the seismic data including three different marine seismic data sets covering 514.6 km2 with 12.5 m horizontal resolution. A synthetic seismogram and a set of seismic attributes were created to achieve this target. In addition, an integrated reservoir characterization study is applied to the Mangahewa reservoir in the Pohokura Field. This integrated characterization includes a detailed petrographical lithofacies analysis, well logging, and core analysis studies. Based on the petrographical study, eight lithofacies are described in Pohokura Field: 1) Laminated sandstone; 2) Massive sandstones; 3) Granular laminated sandstones; 4) Bioturbated sandstones; 5) Sand dominated and mud rich bioturbated sandstones; 6) Muddy bioturbated sandstone; 7) Laminated and rippled laminated mud rocks, and 8) Coal lithofacies which have been deposited in high energy shoreface setting. On the other side, the available well logging data includes caliper, GR (gamma-ray), sonic, neutron, density, and resistivity (shallow and deep resistivities). Logging interpretation enabled the estimation of the effective porosity (av. ∅ = 11.4%), hydrocarbon saturation (av. Shc = 62.87%), and the shale volume (av. VSh = 18.02%) with a total net pay thickness of all wells = 196 m. The available core data includes porosity, density, and permeability which are used to estimate the reservoir quality ranks; the effective pore radius (R35); the flow zone indicator, the discrete rock type (DRT), and the reservoir quality index (RQI). Considering the porosity, permeability, and the DRT values, the available core data are grouped into five reservoir rock types (RRTs) with the best reservoir quality assigned for the RRT1 (bioturbated, laminated and massive sandstones), while RRT5 has the lowest reservoir quality (muddy bioturbated sandstone, Granulated laminated sandstone, and laminated and rippled mudstone). This integrated study is applicable and extendable to the other basins in New Zealand and the southwestern Pacific. The proposed workflow is also applicable to the other analogs in the various basins elsewhere.

A tight polyethersulfone ultrafiltration membrane fabricated via polyion complex assisted phase inversion for dye desalination

In this work, a tight polyethersulfone (PES) -based ultrafiltration (UF) membrane was fabricated to separate dye and salt of textile wastewater via a novel polyion complex assisted phase inversion method in one step. Thereinto, sulfonated polysulfone (SPSF) and poly-(diallyl dimethylammonium chloride) (PDADMAC) were added into the PES dope and coagulation bath, respectively. During the phase inversion process of the precast PES/SPSF film, polycation PDADMAC could assemble with anionic SPSF and facilitate SPSF enrichment on membrane surface, forming a dense barrier layer via the electrostatic interaction between quaternary ammonium and sulfonate groups. Morphology, chemical composition, surface charges and pore size analysis characterized via SEM, FTIR, XPS, Zeta potential and Dextran filtration experiment, respectively, testified that a nonporous skin layer comprising of polyion complex and enriched SPSF was successfully constructed on the top of the PES matrix with an effective pore radius of 1.44 nm, which is smaller than that of the reference membrane prepared without using polyion complex assisted phase inversion (2.74 nm). This resultant membrane exhibited a high pure water permeance of 94 LMH/bar. When it was utilized to separate a dye/salt mixture of 100 ppm Congo red (CR) and 2 g/L Na2SO4 at 1 bar, the rejection of CR could reach 99.7%, alongside a very low Na2SO4 rejection of 8.4%, while the water permeance of dye solution maintained 61 LMH/bar. In addition, the membrane also possessed excellent stability in the pH range of 1–13 due to the strong electrostatic interaction between SPSF and PDADMAC and long-term operation stability, demonstrating its application potential in textile wastewater treatment.

A mass rate-of-rise model for additively manufactured wick structures

The hydraulic performance of heat pipes is typically characterized by the ratio of the wick's permeability to effective pore radius, K/reff. To experimentally quantify these values, mass rate-of-rise (mROR) testing is performed by dipping the tip of the wick into a liquid reservoir to track liquid uptake; the experimental data is then fitted to an ROR model. For conventional wicks, the gravity-based m-t model is free of user decisions and the most reliable. However, here we show that this model poorly fits ROR data for additively manufactured (AM) wicks, resulting in underprediction of K/reff. Experimental tests were conducted using 2 AM wicks—grooved and simple cubic—fabricated by laser powder bed fusion. Visual observations revealed that AM wicks exhibited a superposition of two wicking behaviors: a primary flow and microgroove/corner flow. The primary flow quickly fills the innermost area of the wicking structure. In contrast, the secondary flow gradually creeps up the 3D-printed strut surface through the printed fine scale features. A third term was introduced to improve the data fitting, based on previous research on capillary rise in corners. The revised model measured the AM grooved and simple cubic wicks' K/reff values as 1.23 μm and 1.02 μm, respectively.

Iontophoresis on Porcine and Human Gingiva.

Iontophoresis is a noninvasive method that enhances drug delivery using an electric field. This method can improve drug delivery to the tissues in the oral cavity. The effects of iontophoresis on gingival drug delivery have not been investigated. The objectives of this study were to (a) determine the flux enhancement of model permeants across porcine and human gingiva during iontophoresis, (b) examine the transport mechanisms of gingival iontophoresis, and (c) evaluate the potential of iontophoretically enhanced delivery for three model drugs lidocaine, ketorolac, and chlorhexidine. Passive and iontophoretic fluxes were determined with porcine and human gingiva using a modified Franz diffusion cell and model drugs and permeants. To investigate the transport mechanisms of iontophoresis, the enhancement from the direct-field effect was determined by positively and negatively charged model permeants. The electroosmosis enhancement effect was determined with neutral permeants of different molecular weight. The alteration of the gingival barrier due to electropermeabilization was evaluated using electrical resistance measurements. Significant flux enhancement was observed during gingival iontophoresis. The direct-field effect was the major mechanism governing the iontophoretic transport of the charged permeants. Electroosmosis was from anode to cathode. The effective pore radius of the iontophoretic transport pathways in the porcine gingiva was ~0.68 nm. Irreversible electropermeabilization was observed after 2 and 4 h of iontophoresis under the conditions studied. Iontophoresis could enhance drug delivery and reduce transport lag time, showing promise for gingival drug delivery.

Thermal performance of a thin flat vapor chamber with a multiscale wick fabricated by SAC305/Sn58Bi micro-sized particles

In this study, we theoretically and experimentally investigated the thermal performance of a thin flat vapor chamber (TFVC) with a multiscale wick to understand the effect of the additional capillary microstructures on the cooling performance. To fabricate the multiscale wick with the additional capillary microstructures, micro-sized particles of SAC305 (Sn3.0%Ag0.5%Cu) and Sn58Bi were mixed in ethanol, including indium flux. The suspensions were sequentially sprayed onto a conventional screen mesh wick and spontaneously sintered at 150 ℃. The rate-of-rise method was used to measure the capillary performance of the multiscale wick experimentally. When the results were compared with that of the conventional screen mesh wick, the effective pore radius and permeability of the multiscale wick were 45.4 and 29.5% lower than those of the conventional screen mesh wick, respectively. The capillary performance of the multiscale wick enhanced up to 30% higher than that of the conventional screen mesh wick. With the measurement data of the multiscale wick, the thermal performance of TFVCs with multiscale wicks was theoretically obtained. Based on the theoretical results, it is shown that the maximum heat transfer rate of the TFVC using the multiscale wick increased by up to 82.8% compared with the conventional screen mesh wick.