Continuous Condensation Research Articles

Microscopic and chemical evaluation of the filling quality of five obturation techniques in oval-shaped root canals.

The aim of this study was to assess the filling quality of five obturation techniques in oval-shaped root canals. A total of 212 mandibular first molars with one distal oval canal were selected. Distal canals, shaped with WaveOne Gold Primary, were randomly divided in five groups (n = 40) for obturation: continuous wave condensation, GuttaCore, Thermafil, single cone with AH plus, and single cone with BioRoot RCS. The proportions of gutta-percha-filled areas (GPFA), sealer-filled areas (SFA), void areas (VA), and the sealer/gutta tags into dentinal tubules at 4mm and 2mm from the apex were analyzed by an optical numeric microscope, SEM, and energy-dispersive X-ray (EDX). Data were then compared by Kruskal-Wallis one-way ANOVA on ranks (α = 0.05). At 4mm, a statistically significant higher GPFA and lower SFA were observed in the GuttaCore and Thermafil groups compared with the 3 other groups. A statistically significant lower VA was observed in the continuous wave condensation, GuttaCore, and Thermafil groups than in the two single-cone groups. At 2mm, there were a statistically significant higher GPFA and lower SFA and VA in GuttaCore and Thermafil groups than in the 3 other groups. At the two levels investigated, the presence of gutta-percha tags was clearly demonstrated for GuttaCore and Thermafil groups; no tags were observed in the 3 other groups. Obturation quality was overall improved in GuttaCore and Thermafil groups. Carrier-based techniques may significantly improve the filling quality compared to continuous wave condensation and single-cone technique. The single-cone technique might have inherent limitations especially in oval root canals regardless of the sealer used.

Experimental investigation on performance of desiccant coated microchannel heat exchangers under condensation conditions

Desiccant coated heat exchanger (DCHE), which can be adopted to construct a solar cooling system or desiccant heat pump system, can realize both sensible and latent load removal to provide comfortable supply air. Although it is difficult to avoid condensation in a practical application, the condensation condition of DCHEs is rarely studied. In this paper, a series of condensation experiments are carried out on the desiccant coated microchannel heat exchanger (DCMHE) under conditions with high temperature and high humidity ratio. First, by changing the temperature of cooling water, the unique dynamic characteristics of condensation different from non-condensing conditions are discussed, and the influence of desiccant coating is analyzed. Then, the parametric effects of inlet air velocity and fluid temperature on the mass transfer, heat transfer, and pressure drop performance of DCMHE are analyzed. The results show that the changing trend of the dynamic curve can be used as a sign to judge whether condensation exists or not. And the performance of DCMHE is still stable under continuous condensation conditions, which is not affected by the condensation water. In the dehumidification stage, the condensation dehumidification is dominant. In the aspect of parametric analysis, with the velocity of inlet air increasing from 0.5 m/s to 2.4 m/s, the average moisture removal in a cycle period ΔdDE,ave of DCMHE reduces by 40%, while the dehumidification results per unit time air ΔMDE of DCMHE increases by 192%. The optimal inlet air velocity range is 1.5 m/s–2.4 m/s, considering the dehumidification and heat recovery efficiency synthetically. Due to the thermal resistance of desiccant coating, total cooling load, the effectiveness of heat exchanger, and NTU of DCMHE is about 31%, 27%, and 26% lower than that of MHE. And the effect of desiccant coating on heat transfer performance is comparatively small at high wind speed. The experimental results are expected to provide a reference for the system design of desiccant coated heat exchangers.

Hygrothermal ageing of pultruded GFRP profiles: Comparative study of unsaturated polyester and vinyl ester resin matrices

The durability of pultruded GFRP composites is critical to their performance in civil engineering applications, for which comprehensive and validated data is limited. To address this issue, this study presents an extensive experimental programme on the effects of hygrothermal ageing on the performance of pultruded GFRP profiles made of two alternative resin systems – unsaturated polyester (UP) and vinyl ester (VE) – both comprising identical fibre architecture. The ageing environments included immersion in demineralised and salt water at three different temperatures (20 °C, 40 °C, and 60 °C), and continuous condensation at 40 °C, for durations up to two years. Physical, viscoelastic and mechanical (tensile, flexural, in-plane and interlaminar shear) properties were assessed after a desorption period. As expected, the VE profile had overall better performance than the UP profile. After 24 months, the highest reductions in tensile strength occurred for water immersion at 60 °C, namely 45% and 33% for the UP and VE profiles, respectively. This paper provides a wealth of test data that can be used for degradation models for the prediction of their long-term mechanical property retention.

Development pattern of tracheal cartilage in human embryos.

IntroductionCongenital tracheal anomalies are associated with high morbidity and mortality. The etiology of congenital tracheal anomalies is not well understood, but often attributed to malformed tracheal cartilage. The development of tracheal cartilage has not been described in detail. In this study, we aimed to investigate the development pattern and timing of normal tracheal cartilage to better understand the etiology of tracheal anomalies.Materials and methodsThe development of tracheal cartilage was examined by studying the trachea in histological sections of 14 healthy human embryos from the Carnegie collection. Two specimens for Carnegie Stages 17–23 (42–60 days of embryological development) were studied.ResultsAt Carnegie Stages 17–19 (42–51 days), a continuous mesenchymal condensation was observed ventral to the tracheal lumen. At Stages 20 and 21 (51–54 days), this pre‐tracheal mesenchyme showed sites of increased condensation indicative of future tracheal rings. Furthermore, growth centers were identified both proximally and distally in the trachea. Characteristic horseshoe shaped tracheal rings were apparent at Carnegie Stages 22 and 23 (54–60 days).ConclusionsIn human embryos, tracheal rings arise from growth centers in the ventral mesenchyme at approximately 51–54 days of embryological development. The observation of proximal and distal growth centers suggests a centripetal growth gradient, potentially contributing to occurrence of complete tracheal ring deformity (CTRD). Although this study shows new insights on tracheal cartilage development, the exact origin of congenital tracheal defects has yet to be elucidated.

Continuous Catalytic Condensation of Ethanol into 1-Butanol: The Role of Metallic Oxides (M = MgO, BaO, ZnO, and MnO) in Cu-M/Graphite Catalysts

Bifunctional catalysts supported over high-surface-area graphite comprising copper and a series of metallic oxides (MgO, BaO, ZnO, or MnO) that exhibit different acid/base properties were studied i...

Solar steam generation in fine dispersions of graphite particles

Abstract The direct photothermal boiling in suspensions of nano- and microscopic particles finds multiple applications in concentrated solar power: turbine-based combined heat and power (CHP) generation, solar distillation, energy storage, and chemical synthesis. However, the most promising application is solar desalination. There have been multiple studies aimed at the evaporation of suspensions using simulated solar light, but there is neither a theory describing the process nor a well-documented prototype study. This article aims at the development of an experiment and a theory, that describe the photothermal boiling in aqueous suspensions of graphite. We develop a laboratory scale steam-fluid loop with continuous condensation that recycles the water back to the process. We clarify how the concentration and incident radiant heat influence the steam generation. The optimum concentration of graphite particles - 1 wt% - was found experimentally at 17.4 suns. We studied the granulometry of the suspension and dynamics of steam bubbles. We document how the particle size distribution and bubbles evolve in boiling suspension. The theoretical description of the process is based on a heat balance analysis for an individual steam bubble. The developed model is validated against three independent experimental datasets, exhibiting accuracy with the lowest average discrepancy of 10%.

Insight into Isoprenoid Biosynthesis by Functional Analysis of Isoprenyl Diphosphate Synthases from Mycobacterium vanbaalenii and Mycobacterium tuberculosis

Comprehensive functional analyses of E-isoprenyl diphosphate synthases (E-IDSs) from nonpathogenic Mycobacterium vanbaalenii have been performed. Mv0992 and Mv1577 represent a nonaprenyl diphosphate (E-C45 ) synthase and a geranylgeranyl diphosphate (E-C20 ) synthase, respectively. Although Mv3536 was identified as an E-C20 synthase using a single enzyme, co-incubation of Mv3536 and Z-IDSs (Mv4662 and Mv3822) strongly suggested it releases an intermediate geranyl diphosphate (E-C10 ) during a continuous condensation reaction. Mv0992 and Mv3536 functions differed from those of the previously reported pathogenic Mycobacterium tuberculosis homologues Rv0562 and Rv2173, respectively. Re-analysis of Rv0562 and Rv2173 demonstrated that their functions were similar to those of Mv0992 and Mv3536 (Rv0562: E-C45 synthase; Rv2173: E-C10-15 synthase). The newly proposed functions of Rv0562 and Rv2173 would be in the biosynthesis of menaquinone and glycosyl carrier lipids essential for growth. Furthermore, a reduced allylic diphosphate could be used as the Z-IDS of the Mv3822 substrate, thereby introducing a potentially novel pathway of cyclic sesquarterpene biosynthesis.

Thermodynamic Estimating the Mass Transfer of Compounds of Rare Metals under Conditions of a Filtration Combustion Wave

A thermodynamic calculation of the possibility of mass transfer of metal compounds in conditions of filtration combustion of metal-containing mixtures was carried out. According to the results the metals were divided into two groups: the first group includes metals that form both condensed and gaseous phases, and the second group includes metals that are only in the condensed phase. Under conditions of filtration combustion wave due to continuous evaporation and condensation, it is possible to organize mass transfer of compounds of the first group metals in order to concentrate them in a specific zone of the reactor. Metals of the second group do not participate in mass transfer under the conditions of a filtration combustion wave and will remain in solid combustion products (in ash). Their concentration is possible only if there is a large amount of a combustible component in the initial mixture. In this case, due to the burnout of the combustible part and the preservation of metal compounds in the ash residue, their concentration will occur. Concentration of metals will allow performing their further economically justified recovery by traditional methods.

Influence of root canal filling techniques on sealer penetration and gutta percha/sealer ratio: a confocal laser scanning microscopy analysis

Objective: The influence of four root canal filling techniques on the penetration of an endodontic sealer into dentinal tubules and the gutta percha/ sealer ratio (GP/SR) in root canals was evaluated using confocal laser scanning microscopy (CLSM). Material and Methods: Roots of the maxillary central incisors (n=40) were prepared with ProTaper Universal files up to file F5 and assigned to five groups: continuous wave condensation, lateral condensation, single cone, Thermafill®, and negative control group. After root canal filling with gutta-percha and AH26, along with the addition of 0.01% fluorescein, the roots were cut into 2-mm slices. Using CLSM, the specimens were transversely sectioned at 3, 6, and 10 mm from the apex. Results: Sealer penetration was deeper and more frequent at 10 mm than at the 6mm and 3mm for all obturation technique. Penetration was not significantly affected by obturation techniques except single master cone tecnique. Single cone technique demonstrated the lowest sealer penetration at all levels. However, sealer thickness was strongly dependent on obturation technique. Termafill® demostrated superior GP ratio followed by continuous wave condensation, lateral condensation and single cone. Conclusion: In conclusion, the single cone technique resulted in lower sealer penetration than the other techniques, which did not differ significantly from each other. However, sealer thickness was strongly dependent on obturation technique. Termafill® demostrated superior GP ratio followed by continuous wave condensation, lateral condensation and single cone.KeywordsObturation techniques; Dentinal tubule penetration; Gutta percha, sealer ratio; Confocal laser scanning microscopy.

Anticorrosion performance of hafnium oxide ultrathin films on AZ31 magnesium alloy

Amorphous hafnium oxide films from 15 to 60 nm in thickness were deposited by atomic layer deposition (ALD) on AZ31 magnesium alloy. The films exhibited high anticorrosion performance in the Hank's balanced salt solution, whose pH and ion concentrations were close to those of the human blood plasma. Voltammetry identified reduction of the corrosion rates to be above three orders of magnitude. The electrochemical impedance spectroscopy (EIS) implied a localized corrosion with diffusion limitations within the corrosion products. Scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS) identified a phosphating process with development of a distinctive surface network structure composed of oxygen, phosphorous and calcium. Protection of Mg alloys by the ultrathin hafnium oxide films provides an opportunity to tailor the corrosion rate and, at the same time, to release only trace amounts of hafnium in vivo. The anticorrosion performance was also evaluated by testing the samples under continuous condensation conditions according to standards ISO 6270-1:2018 and ISO 12944-6:2018. The specimens have met the protection requirements for the corrosivity, which is typical of industrial and coastal areas as well as indoor areas, such as those in chemical plants, swimming pools, coastal ship and boat yards.

Depletion of Lubricant from Nanostructured Oil-Infused Surfaces by Pendant Condensate Droplets.

Due to recent advances in nanofabrication, phase-change condensation heat transfer has seen a renaissance. Compared to conventional heat transfer surfaces, nanostructured surfaces impregnated with chemically matched lubrication films (hereinafter referred to as "nanostructured lubricated surfaces") have been demonstrated to improve vapor-side phase-change condensation heat transfer by facilitating droplet nucleation, growth, and departure. While the presence of nanoscale roughness improves performance longevity by stabilizing the lubrication film via capillary forces, such enhancement is short-lived due to the eventual loss of lubrication oil by the departing droplets. The objective of this study is to characterize oil depletion caused by pendant droplets during condensation. For our study, we nanostructured, chemically functionalized, and lubricated horizontal copper tubes that are widely used in shell-and-tube heat exchangers in power plants and process industries. Using high-speed fluorescence imaging and thermogravimetric analysis, we show that shedding droplets exert a shear force on the oil in the wetting ridge at the water-oil interface. The viscous shear draws the lubrication film from the nanostructured surface onto the upper portion of the droplet and forms a ring-like oil skirt. Through detailed theoretical analysis, we show that the thickness of this oil skirt scales with the classical Landau-Levich-Derjaguin (LLD) theory for dip-coating. Our results reveal that droplets falling from horizontal tubes break unequally and leave behind small satellite droplets that retain the bulk of the oil in the wetting ridge. This observation is in stark contrast with the earlier description of droplets shedding from tilted flat plates where the entire oil-filled wetting ridge is demonstrated to leave the surface upon droplet departure. By selecting lubrication oils of varying viscosity and spreading coefficient, we provide evidence that the contribution of the wrapping layer to the rate of oil depletion is insignificant. Furthermore, we show that due to the nanoscale features on the tubes, nearly half of the lubrication film remains on the surface after 10 h of continuous steam condensation at ambient pressure, 23 °C, and 60% relative humidity, a 2-3-fold improvement over previous results.The insights gained from this work will provide guidelines for the rational design of long-lasting nanostructured lubricated surfaces for phase-change condensation.

Numerical simulation of the long-term radiolytic gas accumulation in diversified measurement pipeline for BWR using GASFLOW-MPI

Unforeseen radiolytic gas combustions have occurred in many Boiling Water Reactors (BWRs) and caused severe damages in the past. This combustion is caused by the long-term accumulation of radiolytic combustible gas in a pipeline with a top dead-end due to the main steam continuous condensation. The main objective of this study is to conduct a numerical simulation for a diversified measurement pipeline for BWR with GASFLOW-MPI, in order to evaluate its the long-term radiolytic gas accumulation. Firstly, the model for the radiolytic gas absorption in the condensing film is developed in GASFLOW-MPI and is validated with the experiment of “Hamaoka pipe”. The calculated temperature profiles along the pipe centerline agree well with the experimental data. Then a 3D model for part of the diversified measurement pipeline of BWR is built and analyzed with GASFLOW-MPI to evaluate the long-term radiolytic gas accumulation. Moreover, two factors are discussed in this paper, one is the local condensation enhancement at the floating chambers which is, different from the rest part of the pipeline, not covered by insulator, and the other is the radiolytic gases absorption model. The result shows that there will not be strongly local accumulation of radiolytic gases at the “dead-end” of the pipeline, because the momentum of the reservoir can be balanced with the buoyancy caused by the density difference. Moreover, a mass balance can be established when the mass of radiolytic gases sucked from the reservoir is balanced with that absorbed in the film when considering the absorption model. As a result, the concentration of the radiolytic gases accumulated is far below the combustible limit for the pipeline.

Hybrid Phase-Change Lattice Boltzmann Simulation of Vapor Condensation on Vertical Subcooled Walls

Abstract Saturated vapor condensation on homogenous and heterogeneous subcooled walls is presented in this study by adopting a hybrid phase-change multiple-relaxation-time Lattice Boltzmann model. The effects of wall wettability on the condensation process, including droplets' growth, coalescence and falling, and the influence of vapor flow to condensation are investigated. The results demonstrate that the heat fluxes around the triple-phase contact lines are higher than that in other cold areas in homogeneous subcooled walls, which actually indicates the fact that filmwise condensation is preventing the continuous condensation process. Furthermore, the dropwise condensation can be formed more easily on the heterogeneous surface with a mixed surface wettability. At last, the dynamic process of condensation of continuous vapor flow is also investigated by considering the homogenous and heterogeneous subcooled surfaces. The results show that the heterogeneous surface with mixed wettability does not significantly contribute to the formation, growth of droplets, when compared to the homogeneous surface. It is expected that this study can bring more attention to simulate condensation using multiphase LBM for complex geometries in heat transfer community.

The effect of moisture on hydrocarbon-based solvent liquefaction of pine, cellulose and lignin

In this paper we examined the effect of moisture on the solvent liquefaction of loblolly pine, cellulose, and lignin in tetralin at 280 °C and pressures ranging from 15 to 70 bar. Solvent liquefaction experiments were conducted in a quasi-batch reactor capable of continuous pressure control and external vapor condensation. Moisture was varied by the controlled addition of de-ionized water. Control over the system pressure subsequently impacted the removal of water vapor from the reactor. Liquid yield decreased by 25, 21, and 35 wt%, for pine, cellulose, and lignin, respectively, when moisture content was increased from 1 to 50 wt% at 42 bar. Humins were observed in the solid residue from liquefaction of wet cellulose. Wet lignin yielded a substantial amount of solid residue compared to dry lignin with a corresponding decrease in total phenolic monomer production. It was concluded that the ionic dissociation of water was an important factor in loss of liquid yield in the presence of water. Although water was less than 20 wt% of the solvent loading in these experiments, it strongly influenced the liquefaction of biomass and biomass components.

Improved cooling capacity of a solar heat driven adsorption chiller

This paper discusses two investigations which indicate the benefit of exploiting multiple adsorption containers to increase the cooling energy output of a limited supply of solar heat. First, the optimum working conditions on the output of a solar-powered 3-bed adsorption cooling scheme working in a series and secondly, the performance of a new parallel system of 4-beds has been investigated. It is seen that especially when the source of heat is limited, the output of solar assisted adsorption cooler can be enhanced if the total amount of adsorbent can be distributed in three identical small adsorption beds. As a continuation of the study with multiple beds, the performance of a newly proposed cooling unit with 4-beds has also been studied. This parallel system of 4-beds is considered in such a way that, when one conventional 2-bed chiller is in adsorption/desorption mode then the other chiller is in the preheat/pre-cool mode and the system goes on alternately. Both of these chillers are linked with a single evaporator and condenser, resulting in a continuous evaporation and condensation process. Both of these new systems with multiple beds can utilize maximum entropy as exploits a longer precool time and improves specific cooling capacity (SCC).

Experimental and numerical investigation of noise generation due to acoustic resonance in a cavitating valve

In order to study cavitation induced noise generation in a hydraulic system, cavitation is generated at a planar orifice. The sudden condensation (implosion) of vapor results in shock waves which excite the connected hydraulic pipes with pressure fluctuations. The synchronization between the continuous condensation and evaporation process and shock wave reflection can result in a stationary wave with superelevated pressure amplitudes. The fluid-borne sound is transferred through the mechanical structure into the air, where it can be perceived as a distracting whistling noise. A high-speed camera is used to visualize the void volume. Dynamic pressure signals are recorded in the vicinity of the orifice to analyze the pressure pulsation. The operating point is varied, the orifice geometry is changed and the reflection properties of the pipe on the up- and downstream sides are changed too. In addition, CFD (Computational Fluid Dynamics) simulations of the test bench are used to investigate the root cause of the whistling noise. With regards to representative operating points, the numerical results confirm the measured shedding vapor frequency, particularly the pressure pulsation frequency in the pipe and its amplitude. The conjunction of the experimental and numerical investigations provides the following findings: By reducing the discharge pressure, the void volume increases, which leads to a reduction of the resonance frequency of the pipe downstream of the orifice. For large void volumes, the pressure wave reflection at the void volume can be identified in the amplitude spectrum. The whistling noise depends on the history of the flow field. So, the increase and the reduction of the discharge pressure level leads to different whistling ranges. The whistling range decreases with the increasing length of the pipe resonator. Besides that, the order of the dominant resonance frequency increases. The experimental and numerical results indicate that the whistling noise only occurs, when the jet downstream of the orifice and hence the vapor is perpendicular to the sound propagation in the pipe resonator.

Humidity effects on the detection of soluble and insoluble nanoparticles in butanol operated condensation particle counters

Abstract. In this study the impact of humidity on heterogeneous nucleation of n-butanol onto hygroscopic and nonabsorbent charged and neutral particles was investigated using a fast expansion chamber and commercial continuous flow type condensation particle counters (CPCs). More specifically, we measured the activation probability of sodium chloride (NaCl) and silver (Ag) nanoparticles by using n-butanol as condensing liquid with the size analyzing nuclei counter (SANC). In addition, the cutoff diameters of regular butanol-based CPCs for both seed materials under different charging states were measured and compared to SANC results. Our findings reveal a strong humidity dependence of NaCl particles in the sub-10 nm size range since the activation of sodium chloride seeds is enhanced with increasing relative humidity. In addition, negatively charged NaCl particles with a diameter below 3.5 nm reveal a charge-enhanced activation. For Ag seeds this humidity and charge dependence was not observed, underlining the importance of molecular interactions between seed and vapor molecules. Consequently, the cutoff diameter of a butanol-based CPC can be reduced significantly by increasing the relative humidity. This finding suggests that cutoff diameters of butanol CPCs under ambient conditions are likely smaller than corresponding cutoff diameters measured under clean (dry) laboratory conditions. At the same time, we caution that the humidity dependence may lead to wrong interpretations if the aerosol composition is not known.

Dropwise Condensation on Multiscale Bioinspired Metallic Surfaces with Nanofeatures.

Nonwetting surfaces engineered from intrinsically hydrophilic metallic materials are promising for self-cleaning, anti-icing, or condensation heat transfer applications where the durability of commonly applied hydrophobic coatings is an issue. In this work, we fabricate and study the wetting behavior and the condensation performance on two metallic nonwetting surfaces with varying number and size of roughness tiers without the need for further hydrophobic coating procedure. On one hand, the surface resembling a rose petal exhibits a sticky nonwetting behavior as drops wet the microscopic roughness features with consequent enhanced drop adhesion, which leads to filmwise condensation. On the other hand, the surface resembling a lotus leaf provides super-repellent nonwetting behavior prompting the continuous nucleation, growth, and departure of spherical drops in a dropwise condensation fashion. On a lotus leaf surface, the third nanoscale roughness tier (created by chemical oxidation) combined with ambience exposure prompts the growth of drops in the Cassie state with the benefit of minimal condensate adhesion. The two different condensation behaviors reported are well supported by a drop surface energy analysis, which accounts for the different wetting performance and the surface structure underneath the condensing drops. Further, we coated the above-mentioned surfaces with polydimethylsiloxane, which resulted in filmwise condensation due to the smoothening of the different roughness tiers. Continuous dropwise condensation on a hierarchical bioinspired lotus leaf metallic surface without the need for a conformal hydrophobic coating is hence demonstrated, which offers a novel path for the design and manufacture of noncoated metallic super-repellent surfaces for condensation phase change applications, among others.

Effect of different aging conditions on the shear performance of joints made between GFRP and glass with a UV absorbance coating

In this experimental study, a series of tensile tests were conducted on double-lap specimens, where UV absorbance laminated glass was adhesively bonded on GFRP polyester pultruded support. Three different types of adhesives were compared, two epoxy and one polyurethane, and both un-aged and aged conditions were investigated. Three ageing conditions, simulating the external environment exposure, were investigated, i.e. temperature/moisture changes (continuous condensation), UV exposure, temperature/moisture changes and UV exposure, in order to test the effectiveness of the UV absorbance film and the durability of the bonding system. This experimental campaign aims to verify if the UV film affects the compatibility of the bonding system between GFRP and glass to be used for structural applications.The experiments showed that the PU adhesive is not the most suitable for structural applications, since it shows a great deformability of the joint with a very small stiffness, if compared with the epoxy ones. With regard to artificial aging, the experiments showed that aging has a different impact on different types of adhesives; in particular a slight effect on the mechanical performances or sensitive reduction of the load carrying capacity and of the joint elongation were observed. In general the continuous condensation produced the worst effects on the specimens, while better results were observed after the UV radiations, even though the beneficial effect of the UV rays, which improve the mechanical behavior of the joint for a further polymerization of the adhesive, are impeded by the UV absorbance film.

The effect of disjoining pressure on the shape of condensing films in a fin-groove corner

Thin film condensation is commonly present in numerous natural and artificial processes. Phase-change driven passive heat spreaders such as heat pipes, which are widely used in electronics cooling, employ a continuous condensation process at the condenser region. When the wick structure of a heat pipe is composed of grooves, the top surfaces of the walls (fins) located between consecutive grooves function as the major source of condensation and the condensate flows along the fin top into the grooves. Modeling of this condensation problem is vital for the proper estimation of condensation heat transfer, which constitutes the basis for the overall performance of a heat pipe together with the evaporation process. In the current study, a solution methodology is developed to model the condensation and associated liquid flow in a fin-groove system. Conservation of mass and momentum equations, augmented Young-Laplace equation and Kucherov-Rikenglaz equation are solved simultaneously to calculate the film thickness profile. The model proposed enables the investigation of the effect of disjoining pressure on the film profile by keeping the fin-groove corner, where the film becomes thinnest, inside the solution domain. The results show that dispersion forces become effective for near isothermal systems with sharp fin-groove corners and the film profile experiences an abrupt change, a slope break, in the close proximity of the corner. The current study is the first computational confirmation of this behavior in the literature.