Formation Of Large Bubbles Research Articles

Microstructure Evolution of the Interface in SiCf/TiC-Ti3SiC2 Composite under Sequential Xe-He-H Ion Irradiation and Annealing Process.

A new type of SiCf/TiC-Ti3SiC2 composite was prepared by the Spark Plasma Sintering (SPS) method in this work. The phase transformation and interface cracking of this composite under ion irradiation (single Xe, Xe + He, and Xe + He + H ions) and subsequent annealing were analyzed using transmission electron microscopy (TEM), mainly focusing on the interface regions. Xe ion irradiation resulted in the formation of high-density stacking faults in the TiC coatings and the complete amorphization of SiC fibers. The implanted H ions exacerbated interface coarsening. After annealing at 900 °C for 2 h, the interface in the Xe + He + H ion-irradiated samples was seriously damaged, resulting in the formation of large bubbles and cracks. This damage occurred because the H atoms reduced the surface free energy, thereby promoting the nucleation and growth of bubbles. Due to the absorption effect of the SiCf/TiC interface on defects, the SiC fiber areas near the interface recovered back to the initial nano-polycrystalline structure after annealing.

Unsteady numerical calculation of flow boiling heat transfer in microchannels with Kagome structures

A three-dimensional microchannel flow boiling model was developed based on the VOF model and the Lee model, and the flow and heat transfer in microchannels with Kagome structures were numerically simulated. The characteristics of bubble flow patterns, gas phase distribution, and heat transfer were analyzed under the heat fluxes of 5–8 MW/m2 and flow velocities of 0.2–0.5 m/s. The results show that at a flow velocity of 0.5 m/s, the disturbances caused by fluid impact on the Kagome structure result in bubble break-up, effectively suppressing the formation of large bubbles. However, at a flow velocity of 0.2 m/s, bubbles tend to be adhered on the surface of the Kagome structure, causing local blockage and deteriorating heat transfer. Compared to the flow velocity of 0.5 m/s, the average heat transfer coefficient in the microchannel decreases by up to 75.4 % and the pressure loss decreases by 45.38 % at the flow velocity of 0.2 m/s.

Coupled Wall Boiling and Population Balance Model for High Void Fraction Flows Under Sub-Cooled Nucleate Boiling Regime: Model Development and Validation

Abstract The subcooled flow boiling of water in a vertical annulus channel is studied numerically at low-pressure conditions. The two-fluid model is developed with flow-regime dependent interfacial transfers for mass, momentum, and energy using the algebraic interfacial area density (AIAD) framework. A discrete population balance model is used to mechanistically determine the vapor bubble diameter in the flow channel by considering the bubble aggregation and breakup effects. Energy balance at the heated wall for the subcooled nucleate boiling is handled using a suitable wall boiling model. A coupling is achieved between the discrete population balance and the wall boiling model for the nucleation and the growth rate of the vapor bubbles along the heated wall. The developed model simulates the reference experimental cases of flow boiling in a vertical channel for various flow and thermal conditions. At low wall heat flux, the wall boiling generates vapor bubbles near the heated wall and within the bubbly flow regime. With an increase in the wall heat flux, the aggregation and evaporation cause the formation of larger bubbles, which progress toward the flow channel core region, a phase that is representative of the transitional flow regime. The model's capability to predict such flow regime transition is validated with the experimental results. The bubble aggregation is found to be dominant compared to the breakup, and thus, proper choice of the aggregation factor is important for the accurate prediction of vapor parameters for the subcooled flow boiling at low-pressure conditions.

Effect of electric field on bubble dynamics in channel flow boiling using lattice Boltzmann method

The application of an electric field in flow boiling has been proven to effectively enhance heat transfer and reduce pressure drop instability. This study aims to elucidate the mechanism of the impact of electric fields on flow boiling bubble dynamics through the pseudo-potential lattice Boltzmann method (LBM). The interplay between the externally imposed electric field incoming velocity in different gravity conditions examined. These factors can regulate flow boiling heat transfer in horizontal channel. The results demonstrate a competitive relationship between electric field and gravity and between incoming velocity and gravity. Therefore, under higher gravity condition, an electric field is less effective to enhance flow boiling heat transfer than in low gravity condition and vice versa. Additionally, there exists a synergistic relationship between incoming velocity and the electric field that mitigates their competition. Moreover, when considering multipoint nucleation processes, applying an electric field can attenuates bubble–bubble interactions and inhibit large bubble formation so as to accelerates bubble condensation in supercooled flows and enhance boiling heat transfer. This work provides comprehensive physical insights into the mechanism of electric field to enhance the heat transfer in flow boiling, which is instructive for the development of electrohydrodynamic technique in flow boiling enhancement.

Prior implantation of hydrogen as a mechanism to delay helium bubbles, blistering, and exfoliation in titanium

This study explores the delaying of the formation of helium bubbles and blisters in pure titanium by hydrogen pre-implantation. Titanium, implanted with helium (40 KeV, 5 × 1017 ions/cm²), exhibited large bubbles that cause exfoliation after heat treatment, whereas hydrogen pre-implantation inhibited bubble growth at room temperature and reduced the exfoliation after heat treatment.In the samples pre-implanted with hydrogen, we found evidence of helium diffusion delay by: (a) a fourfold reduction in bubble pressure (b) faceted cavities in the samples (c) a smaller increase in titanium lattice parameters (d) a 16-fold reduction in average bubble size and a sixfold reduction in bubble area fraction (e) a more than twofold decrease in exfoliation (f) a tendency toward the formation of larger bubbles as a result of heat treatment. We believe that it is reasonable to assume that the inhibition of helium diffusion between tetrahedral interstitial lattice sites takes place because of the occupation of the intermediate octahedral sites by hydrogen atoms.Evidence for the opposite effect, that is inhibition of the diffusion of hydrogen in the presence of helium, is found in the retention of hydrogen in the specimens at elevated temperatures. This retention allowed the existence of titanium hydride after heat treatment at 680 °C. The present study sheds light on the intricate interplay between hydrogen and helium in titanium, providing insights into mechanisms that can potentially mitigate helium-induced damage in materials.

SIRT1 Inhibition-Induced Mitochondrial Damage Promotes GSDME-Dependent Pyroptosis in Hepatocellular Carcinoma Cells.

Hepatocellular carcinoma (HCC) is a malignant tumor that affects the liver and poses a significant threat to human health. Further investigation is necessary to fully understand the role of SIRT1, a protein linked to tumorigenesis, in HCC development. To investigate the effect of SIRT1 on HCC and elucidate the underlying mechanism. Eight pairs of HCC and paracancerous normal tissue specimens were collected. The levels of SIRT1 and GSDME in tissue samples were assessed using immunohistochemistry and western blotting. SIRT1 levels were determined in HCC (Huh7, HepG2, SNU-423, SNU-398, and HCCLM3) and L-02 cells using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. SNU-423 and HCCLM3 cells were transfected with si-SIRT1 and/or si-GSDME to knock down SIRT1 or GSDME expression. RT-qPCR and western blotting were performed to measure the expression of SIRT1, pro-casp-3, cl-casp-3, GSDME, GSDME-N, PGC-1α, Bax, and cytochrome c (Cyto C). Cell proliferation, migration, invasion, and apoptosis were assessed using the cell counting kit-8 (CCK-8), wound healing assay, Transwell invasion assay, and flow cytometry, respectively. The release of lactate dehydrogenase (LDH) was evaluated using an LDH kit. SIRT1 was upregulated in HCC tissues and cells, and a negative correlation was observed between SIRT1 and GSDME-N. SIRT1 silencing suppressed the proliferation, migration, and invasion of HCC cells while also promoting apoptosis and inducing mitochondrial damage. Additionally, the silencing of SIRT1 resulted in the formation of large bubbles on the plasma membrane of HCC cells, leading to cellular swelling and aggravated GSDME-dependent pyroptosis, resulting in an increase in LDH release. Inhibition of GSDME reduced SIRT1 silencing-induced cell swelling, decreased LDH release rate, and promoted apoptosis. SIRT1 silencing promotes GSDME-dependent pyroptosis in HCC cells by damaging mitochondria.

Experimental validation of the mechanism and condition for the onset of significant void in subcooled flow boiling

In evaluating the axial void fraction profile in the subcooled boiling region in heated channels, accurate determination of the point of onset of significant void (POSV) is of critical importance. Recently, it has been reported that the POSV can be predicted with high accuracy if the onset of significant void (OSV) is assumed to be caused by a sudden decrease in the interfacial area due to global bubble coalescence (GBC) leading to the formation of large bubbles. Therefore, in this work, experimental investigations were carried out to measure the void fraction, bubble size and bubble number density. The experimental results were utilized to validate the mechanism causing the OSV in subcooled flow boiling. The experimental results were in qualitative and quantitative agreement with the model based on the GBC concept. Thus, it was validated that the sudden decrease in condensation rate due to large bubble formation is the main cause of OSV. It was also confirmed that the GBC occurs when the local void fraction near the heated wall reaches about 0.3, analogous to the flow regime transition from bubbly flow to slug flow in adiabatic gas-liquid two-phase flows.

Genomic characterization and phylogenetic analysis of Aleutian mink disease virus identified in a sudden death mink case

Aleutian mink disease (AMD) is one of the most serious diseases in minks worldwide, it brings tremendous financial losses in mink farming. AMD virus (AMDV) has unusually high genetic diversity, its genomic structure remains unclear. In 2014, sudden death of breeding minks was occurred in northeast China. After clinical signs evaluation and virus isolation, AMDV was identified in all sudden death minks, we investigated the complete genomic sequence of AMDV-LM isolated from the sudden death case. The full-genome sequence of AMDV-LM was 7 nucleotides (nts) or 8 nts longer than isolates AMDV-BJ and AMDV-G. AMDV-LM contained two unique nucleotide changes in VP2 (G79T, T710C), which led to two amino acid changes G27W and L237S. For NS1, some unique point mutations, such as A374C, A428C, A463C, and T476A were found and resulted in four unique amino acid mutations at N24V, H125P, V143P, K155Q, and V159N, respectively. The predicted secondary structure of the 5′ terminal of AMDV-LM formed a large bubble formation near the 5′ end, which affected the stability of the U-shaped hairpin. Phylogenetic analysis demonstrated that AMDV-LM was closely related to Chinese isolates and confirmed that AMDV strains circulating in China had different origins of ancestors. This study was first to investigate the association of sudden death of adult breeding minks with AMDV infection. Our findings provide useful suggestions for evaluation of the pathogenic potential of AMDV, additional details on AMDV genome characterization were also presented. Future work should focus on the importance of AMDV-LM strain in mink infection.

Tritium Desorption Behavior and Microstructure Evolution of Beryllium Irradiated at Low Temperature Up to High Neutron Dose in BR2 Reactor

The present study investigated the release of tritium from beryllium irradiated at 323 K to a neutron fluence of 4.67 × 1026 m−2 (E > 1 MeV), corresponding up to 22,000 appm helium and 2000 appm tritium productions. The TPD tests revealed a single tritium release peak during thermal desorption tests, irrespective of the heating mode employed. The tritium release peaks occurred at temperatures ranging from 1031–1136 K, depending on the heating mode, with a desorption energy of 1.6 eV. Additionally, the effective tritium diffusion coefficient was found to vary from 1.2 × 10−12 m2/s at 873 K to 1.8 × 10−10 m2/s at 1073 K. The evolution of beryllium microstructure was found to be dependent on the annealing temperature. No discernible differences were observed between the as-received state and after annealing at 473–773 K for 5 h, with a corresponding porosity range of 1–2%. The annealing at temperatures of 873–1373 K for 5 h resulted in the formation of large bubbles, with porosity increasing sharply above 873 K and reaching 30–60%.

CC-115 Mediates GSDME-Dependent Pyroptosis in Lung Adenocarcinoma Through the Akt/Bax Pathway.

Chemotherapeutic agents remain the first-line treatment for solid tumors, including lung cancer, but chemotherapy resistance is hampering global efforts to treat this disease. CC-115 is a novel antitumoral compound used in phase I clinical trials. However, it is unclear whether CC-115 is effective against lung adenocarcinoma (LUAD). In the present study, we found that CC-115 induced lytic cell death in A549 and H1650 tumor cells via swelling of cells and formation of large bubbles on the plasma membrane that closely resembled those typical of pyroptosis, a type of programmed cell death linked to chemotherapy. We demonstrated that CC-115 exerts antitumor effects in LUAD through gasdermin E (GSDME)-mediated pyroptosis by acting as a dual inhibitor of DNA-PK and mTOR. CC-115 can inhibit Akt phosphorylation, impairing its inhibitory effect on Bax, thereby inducing pyroptosis via the Bax-mitochondrial intrinsic pathway. CC-115-induced pyroptosis was abrogated by treatment with the Akt activator SC79 or by depletion of Bax. Importantly, CC-115 significantly upregulated the expression of Bax and GSDME-N in a xenograft mouse model, with a reduction in tumor size. Our results revealed that CC-115 suppresses tumor growth by inducing GSDME-mediated pyroptosis through the Akt/Bax-mitochondrial intrinsic pathway, indicating CC-115 as a promising therapeutic agent for LUAD.

Overall particles flow pattern in a two-zone gas-solid fluidized bed with a secondary-gas stream

Fluidized bed reactors with multiple input streams have been developed over the last decades to satisfy industries in the scope of multiphase catalytic reactions, and two-zone fluidized beds have been developed to perform reaction and catalyst regeneration simultaneously. However, the presence of the secondary gas nozzle in the bed significantly impacts the hydrodynamics and efficiency. Particle image velocimetry (PIV) and digital image analysis (DIA) techniques have been used to study different particle flow patterns in a two-zone pseudo-2D fluidized bed with lateral gas injection. The secondary flow nozzles' location has been changed, and different particle flow patterns have been observed in the fluidized bed. It was found that at low excess gas flow rates, when the lateral nozzle is located at the middle part of the bed, particles move downwardly at the bed center and upwardly near the walls; while when the lateral nozzle is located at the top part of the bed, particles have a reverse movement trend. At higher gas velocities for both mentioned nozzle locations, particles move upwardly at the bed center and downwardly near the walls. The formation of large bubbles was less probable when the nozzle was located at the middle of the bed.

Understanding Bubble-Induced Overpotential Losses in Multiphase Flow Electrochemical Reactors

Green hydrogen production via water electrolysis can play a significant role in decarbonizing energy and multiple industrial processes. In this electrolysis process, water molecules are oxidized to produce oxygen in the anode, while protons are reduced to hydrogen in the cathode. Both of these electrochemical products are gaseous species that lead to bubble nucleation at the surface of electrodes. This bubble evolution phenomena results in substantial energy losses due to the blockage of ion conduction pathways, reduction of the available electrocatalytic area, and disruption of concentration gradients at the electrode–electrolyte interface. In this study, we implement a microfluidic water electrolyzer to elucidate the impacts of electrochemical reaction conditions and convective flows on bubble-induced overpotential losses. We show that high Reynolds (Re) number flows (i.e., Re > 20) mitigate the formation of large bubbles, resulting in minimal bubble-induced overpotential losses. For flows with smaller Re, periodic evolution of large bubbles leads to overpotential fluctuations on the order of ∼100 mV. Furthermore, to understand the impact of bubbles on concentration overpotentials, we use fluorescence microscopy and pH sensitive dyes to capture the spatiotemporal dynamics of pH gradients and correlate the strength and shape of these gradients to the applied potential and convective forces. We find that the presence of large bubbles at low Re can result in more severe concentration gradients that are affected by the hydrodynamic flows around the bubbles. The findings presented in this work provide insights into the effects of convective flows in mitigating bubble-induced overpotential losses.

Eulerian simulations of bubbling and jetting regimes in a fluidized bed

The mode of gas-injection is known to influence the local bubbling and jetting behavior in gas–solid fluidized beds. The resultant bubbling behavior influences the mixing and distribution of the gas and solid phases, which in turn can influence heat and mass transfer, and reaction performance in large-scale gas–solid fluidized beds. In the present work, we simulated unary gas–solid flow of particles differing in density, fluidized using uniform and two-jet distributors at different UG. The predictions are validated using the measured local gas-phase area fraction fluctuations, bubble size distribution, and bubble rise velocity. The effect of the models used for calculation of gas–solid drag (βgs), solids frictional pressure (Ps,f), and specularity coefficient (φ) on the bubbling characteristics under dense and dilute flow conditions are analysed. Under dense bed condition (UG = 1.1 Umf), an increase in the Ps,f and φ led to an increase in solids viscosity, which in turn led to a decrease in the bubble rise velocity and size. In the case of the two-jet distributor, an increase in βgs predicted merging of the larger jets and formation of larger bubbles. Further, to predict the different jetting regimes (isolated jets, breakage/merging of jets, and generation of larger bubbles) at different UG correctly, we show that different βgs models are required. Whereas, in the case of gas–solid flows comprised of particles of different density fluidized with the uniform distributor, a single βgs model predicted the bubbling characteristics reasonably well with measurements.

Studying the effect of direction and strength of magnetic field on fluidization of nanoparticles by recurrence analysis

Effect of the intensity and direction of the magnetic field was studied on fluidization of titanium oxide nanoparticles (anatase phase) mixed with ferromagnetic Iron (III) oxide nanoparticles using the recurrence analysis. The bed expansion and visual observation revealed that these particles operate in the ABF regime in all cases. Minimum fluidization velocities were obtained through the standard deviation of pressure fluctuations. Agglomerates samples were taken to study the effect of the magnetic field on the size of agglomerates. It was observed that at low field strength, the vibration has a major effect on fluidization than the magnetic force. At field strengths less than 400 Gauss, the vibration of solenoid improved the quality of fluidization by decreasing the size of agglomerate and minimum fluidization velocity, regardless of the field direction. At field strengths greater than 400 Gauss, the upward direction increases the interaction of agglomerate which results in a stochastic pattern of fluidization and lower ABF characteristics. At high magnetic field strengths, the effect of field direction becomes more noticeable. At high field strengths, the downward field results in less movement of the bed material and resistance against fluidization as well as the formation of larger bubbles and their deterministic effect on the bed.

Microscopic mechanism analysis of calcareous sand in electrolysis desaturation using 1H L-F NMR

Electrolysis desaturation is a novel method to improve the liquefaction resistance of liquefiable foundations. The microscopic mechanism of the horizontal-layered electrolysis desaturation of calcareous sand specimens was revealed using a low-field nuclear magnetic resonance (1H L-F NMR) apparatus. The expansion and recovery of sand pores was detected, and variation pattern of saturation distribution was explored, as well as the generation and migration of gas bubbles. The test results show that the electrolysis mainly discharged free water from the specimen, and the content of bound water or mechanical bound water kept basically unchanged. The rapid generation of the bubbles could lead to the expansion of the sand pores. Within 3 h after stopping electrolysis, the macropores in the calcareous sand essentially returned to the initial state, and the expansion of micropores and mesopores also remained basically stable. The construction method of prolonged low-current electrolysis or short-time multiple electrolysis could be applied for on-site desaturated foundation treatment. The shape and size of the bubbles produced by electrolysis were related to the calcareous sand pores. The migration of gas after stopping electrolysis was mainly in the vertically upward direction, resulting in the fusion of bubbles and the formation of larger bubbles.

Irradiation-induced large bubble formation and grain growth in super nano-grained ceramic

In this work, 0.5TRPO•0.5Gd2Zr2O7 ceramic with an average grain size of only ∼15 nm was prepared by a high pressure (5 GPa/520 °C) sintering method. Phase evolutions and microstructure changes of the as-fabricated super nano and micron-grained ceramics under a high-dose displacement damage induced by 300 keV Kr2+ ions were investigated. The results show that the super nano-grained ceramic has low degree of amorphization, obvious grain growth (2–3 times in grain size) and big Kr bubbles (10–68 nm) formation after irradiation. The micron-grained ceramic was severely amorphized after irradiation and many microcracks were formed parallel to its surface. The formation mechanism of Kr bubbles in the super nano-grained ceramic is on account of grain boundary diffusion and migration induced by the accumulation of the injecting Kr ions and irradiation defects. Nevertheless, microcracks formed in the micron-grained sample are caused by the accumulation of Kr atoms.

Boiling evaporation characteristics of sessile droplets and its transition evaporation mode

Providing an enormous heat transfer, droplet boiling evaporation is widely used in the liquid cooling for nucleate reactors and high-power electronic devices and other fields. This paper reported a combined theoretical and experimental study on the evaporation characteristics of the droplets attached to a high temperature wall (>100°C). Different from the non-boiling evaporation, the effect of droplet temperature on evaporation time, contact angle and evaporation process are investigated. Nucleate boiling regime in the evaporation of a single droplet, especially the transition from static evaporation to nucleate boiling is investigated. Our results report that the evaporation of sessile droplets in boiling regime is very intense, and can be classified into five stages according to the change in internal bubble morphology, namely the wall bubble germination, wall bubble growth, global bubble germination, global bubble growth, and central large bubble formation. Droplet evaporation does not follow the constant contact diameter pattern in the non-boiling regime, but consists of growth period, steady period, and decline period. Basically consistent with the experimental results, the feasibility of numerical simulation to study the droplet evaporation in the boiling regime is verified.

In situ transmission electron microscopy studies of 30 keV H2+ and He+ dual-beam irradiated Pd: defect generation and microstructural evolution under varied temperatures and foil thicknesses

To fully understand the tritium aging behavior of palladium (Pd), an important material applied in hydrogen isotope storage and tritium engineering, an in situ irradiation of 30 keV H2+ and He+ dual beam was performed for the investigation of the microstructural evolution in Pd. The irradiation dose, temperature, and sample thickness obviously affected the morphology, distribution characteristics, density, and size of dislocation loops, bubbles, and bubble-loop complexes. Highly dense loops were aggregating at lowered temperatures, whereas the loop density dropped dramatically, producing bubble-loop complexes at elevated temperatures. Most of loops were 1/3<111> Frank loops with quasi-circular under a low dose at 573 K and then transformed to 1/2<110> perfect loops with wavy and polygonal shape at a high dose. The difference in growth behavior between faulted and perfect loops suggested that there was a critical transform loop size ~32 nm in diameter. The heterogeneity in size and shape of bubbles could be attributed to the interaction between bubbles and the periphery loop. Moreover, the hydrogen resulted in the formation of larger bubbles when compared with the single-beam helium irradiation. The unfaulting transition of loops led to bubble redistribution. The corresponding mechanisms of in situ irradiation experimental results were discussed.

Flow-field analysis of a continuous gas–solid separation fluidized bed equipped with a moving scraper

Continuous gas–solid separation fluidized beds are one of the most widely used practical operation units for the dry separation of coal in China, particularly in Northwest China, and they can effectively promote the efficient and clean utilization of raw coal. In a continuous gas–solid separation fluidized bed, the bed flow field is the concrete manifestation of the fluidization characteristics. However, the complexity of the flow field increases under the action of a moving scraper. In this study, a combination of computational fluid dynamics (CFD) simulations and experimental measurements was used to study the changes in the flow field of a fluidized bed. The results showed that when the scraper moved, the local flow field (mainly characterized by the movement of medium particles) near the scraper was affected not only by the common airflow or bubbles, but also by the lateral driving force of the scraper. When the scraper speed was vl<6.0cm/s, it reduced the frequency of the formation of large bubbles and alleviated the random fluctuation of the nearby particle collision stress signals, which improved the fluidization stability of the bed. Additionally, the movement of the scraper affected the global flow field. The flow field shifted to the right near the scraper, with the direction of the scraper movement, while the flow field exhibited a leftward trend on the surface of the bed, accompanied by some vortices, in the middle and lower parts of the bed. Additionally, the critical height of the area, directly affected by the scraper, increased from 52 to 54mm with an increase in its operating speed from vl=2.96cm/s to vl=4.44cm/s, respectively. This provides a theoretical basis for further understanding the hydrodynamic characteristics of fluidized beds.

Analysis of Influence of Cathode Current Collector Wettability on Current Loss By Crossover Evaluation Both at Cathode and Anode Side

Hydrogen gas crossover, which increase current loss, is critical issue in high pressure PEMWE (Polymer Electrolyte Membrane Water Electrolysis). To reduce the crossover, controlling wettability of current collector (CC) at cathode side has been proposed [1]. Different wettability of CC causes different bubble behavior of hydrogen bubble produced at cathode, and possibly changes the hydrogen gas crossover to anode side. To elucidate and maximize this idea, this study tests two carbon CCs. one has high hydrophobicity (SGL 39BA) and the other one has less hydrophobicity (SGL 39AA). Here, they are named as HCC and LHCC, respectively. PEMWE embedded by the CC was operated under 2 MPaG at cathode side and under atmospheric pressure at anode side. This study carefully evaluates the hydrogen gas crossover. Evaluation of the gas crossover was carried out both at cathode and anode side. In the cathode evaluation, hydrogen gas flow rate is measured at the outlet of cathode, and it is compared with theoretical production of hydrogen gas, providing hydrogen crossover. In the anode evaluation, hydrogen concentration in oxygen gas is measured at the outlet of anode, and it is converted to hydrogen gas flow rate in anode side, providing hydrogen crossover. The CC with different hydrophobicity impacts on bubble behavior of hydrogen gas at cathode side and is thought to influence the hydrogen crossover. To understand the influence of the CC wettability, gas/liquid two phase flow model in the through plane direction in cathode CC was developed. The theoretical model can estimate gas saturation and gas phase pressure at cathode catalyst layer, which determine hydrogen gas crossover. In the two phase flow model, boundary condition of gas saturation at the interface between CC and channel is critical, which governs the calculation result based on the model (distribution of gas saturation and pressure in CC). To provide accurate boundary condition, hydrogen bubble behavior, which is possibly converted to the gas saturation at the interface between CC and channel, was visualized. A high speed camera captured the bubble behavior in several micrometer and millisecond time resolution through the window embedded in cathode separator.Obtained Hydrogen gas crossover, evaluated at both cathode and anode side, suggested that HCC case had better performance and showed smaller crossover. Among the two kind of crossover evaluation, the evaluation at cathode side showed higher crossover rate than that at anode side. As shown in the figure, evaluation at cathode side tends to overestimate the hydrogen crossover, because the evaluation also detects hydrogen gas leakage to outside in addition to the influence of hydrogen crossover to anode side. On the other hand, evaluation at anode side tends to underestimate the crossover, because it detects the combustion possibly happened at anode catalyst layer with oxygen gas produced there. These characteristic of the evaluation is thought to cause that the evaluation at cathode side showed higher crossover rate than that at anode side. In the visualization, various size of bubble was appeared on the CC. Statistical processing for the visualization revealed that HCC case shows the large size of bubble compering with LHCC case. The bubble size difference between the HCC and LHCC case is thought to cause a different capillary pressure and saturation of hydrogen gas bubble in current corrector. Theoretical analysis based on the two phase flow model shows also that HCC case provides less crossover. It is noted that the theoretical value positioned between cathode and anode evaluation result. This indicates that the theoretical analysis has some reliability. Detail information obtained by the theoretical analysis shows that HCC case provides smaller hydrogen gas saturation and gas phase pressure at the cathode catalyst layer. However, the gas pressure difference between the two CC case was not significant. Thus, the reason why HCC show less crossover is thought to be that HCC causes large bubble formation at the interface between CC and channel and suppresses gas saturation at the cathode catalyst layer and reduces the hydrogen crossover to anode side. In conclusion, hydrogen crossover significantly occurred in high pressure PEMWE can be suppressed by controlling wettability of CC.[1] Kohei Ito, et.al., ECS Transactions, 75 (14) 1107-1112 (2016), 75, 14, 1107-1112, 2016.10 Figure 1