A new transport technique of solute molecules in micro channel using the Soret effect and ratchet thermal potential, namely ratchet thermalphoresis, is developed. In the ratchet thermalphoresis, the solute molecules are driven by the Soret effect induced by the gradient of temperature distribution. The ratchet thermalphoresis has the potential of the applications for a separation technique of DNA fragments and a condensation method for protein crystallization. In present study, the validity of the driving theory of Gaussian concentration distribution was confirmed using slope temperature distribution. The Gaussian pattern was transferred by the thermalphoresis using the Soret effect. The displacement of the Gaussian pattern was consistent with the theory.

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A new technique for measuring ion velocity and diffusivity in the vicinity of a microchannel wall was proposed to investigate the ion diffusive phenomena. The technique employs the caged fluorescent dye and the evanescent wave illumination. The velocities and diffusivities in the vicinity of the wall were compared with those in the bulk flow. For the pressure-driven flow, the velocity in the vicinity of the wall was smaller than that in the bulk flow due to the non-slip condition. The diffusivities in the vicinity of the wall were smaller than those in the bulk flow for both the electroosmotic flow and the stationary flow because of the interaction between the ion motion and the microchannel wall.

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High time-resolution flow field measurement in two micro-channels with complex shape is performed by a micro digital holographic particle-tracking velocimetry (micro-DHPTV). The first one has Y-junction, which is cobining from two inlets to one outlet. The two laminar velocity profiles in inlet region merged one laminar velocity profile. The second one has convergence region, which become diverge flow after the flow is once converging. Two re-circulation regions are caused at divergence region. Consequently, approximately 250 velocity vectors in the both case can be obtained instantaneously. For micro-channel with the convergence region, two re-circulation regions at divergence point are captured from the three-dimensional vector field, which the axis of re-circular vortices have some alignment.

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We have synthesized C_<60> crystals using a simple liquid/liquid interfacial precipitation method in a mcrofluidic device. By controlling space, time, temperature, concentration, various C_<60> crystal morphologies were obtained including multiwalled tubes, open-ended hollow columns, dendrites, prisms, and needles. The C_<60> crystal morphologies were categorized mainly by temperature, and similar to the morphologies of snow crystals. This simple method yields complex geometries of C_<60> crystals quickly, and could be applied to all materials synthesis techniques that use liquid/liquid interfacial precipitation such as carbon crystals, protein crystals, clathrate hydrate crystals, and minerals.

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It is predicted that the energy consumption will increase. But, the main energy, oil, will be depleted in the near future. So, the energy recycle system is important. The TPV(Thermo Photo Voltaic) system is one of the energy recycle systems. The TPV system mainly converts the near infrared rays to electrical energy. If the evanescent wave can be applied to TPV system, the energy recycle system which is much effective in the low temperature waste heat recovery will be possible. So, in this paper, We tried to investigate an effect of near-field radiation (evanescent wave) to enhancement of thermophotovoltaic (TPV) generation of electricity.

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In conventional optical measurement technique of thermophysical properties, the spatial resolution is limited by the diffraction limit of light, which is approximately half of the wavelength of the optical beam. Therefore, we have developed near-field optics thermal nanoscopy (NOTN), which is a thermal properties sensing technique (i.e. thermal conductivity and thermal diffusivity) using near-field light. This method has nanoscale spatial resolution (up to 10nm). Also, NOTN enables noncontact and in situ measurement of nanoscale devices and materials. In this paper, the detection of the near-field light with 100nm aperture fiber probe was demonstrated. Also, the evaluation of spatial resolution with 100nm aperture fiber probe was discussed.

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Chemical reaction of platinum cluster ion with methanol and ethylene was investigated by using the FT-ICR (Fourier Transform Ion Cyclotron Resonance) mass spectrometer. Metal clusters with 3-7 were generated by a pulsed vapor laser-vaporization supersonic-expansion cluster beam source directly connected to FT-ICR mass spectrometer. Observed reactions are mainly chemisorptions of methanol and ethylene with dehydrogenation. It also shows that the number of CO molecules which can stably attach to the platinum surface depends on cluster size.

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A nucleation process of a single-walled carbon nanotube (SWNT) is studied using classical molecular dynamics (MD) simulations by considering the dissociation of once-deposited carbon atoms from catalytic metal cluster. In the alcohol catalytic CVD (ACCVD) technique, the dissociation of carbon atoms with dangling bonds through the reaction with oxygen atoms may play a key role. Following an interpretation of the experimental results, the dissociation process is modeled by removing one carbon atom with dangling bonds for every three additional carbon atoms attached to the catalytic metal cluster. The difference between the simulations with and without the dissociation process may be the reason why SWNTs with high purity can be obtained in the ACCVD technique.

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Nano-Forcused Ion Beam (FIB) were studied with molecular dynamics simulation. The target substrate was Silicon crystal (100). Firstly, we choose small computational volume as evaluation of combination of potential function for Si and Ga ion. The combination of Tersoff potential for Si and Ziegler, Biersack and Littmark (ZBL) potential for Ga ion is determined from result of the simulations. Secondly, large-scale molecular dynamics simulations were performed by the combination of the potential. Ga ions from 9 to 100 number impact on Si (100) with an irradiation area. When numbers of Ga ion is small, the sputtering Si atoms cause nearest-neighbors impacting Ga ions. On the other hand, in case of increasing of Ga ion, the sputtering Si atoms are pushed away from between Ga ion and Ga ion.

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We have carried out a molecular dynamics simulation for the mixture of an ice nucleus, supercooled water and a model of amino-acid polypeptide. This nucleus has a hexagonal-shaped crystal. The model has a right-handed helical structure which represents a part of the antifreeze protein type I. It is found from our analysis that the hydroxyl group of one threonine residue is closest to the prism plane of the ice. This is due to the hydrogen bond between the water molecules in ice and the clustering water molecules in liquid phase near the threonine residue.

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To produce a durable display, it is necessary to know the damage of an transparent conductive film from heat. Thermal diffusivity is an important thermophysical property to evaluate the damage. In this study, we used the forced Rayleigh scattering method to measure the in-plane thermal diffusivity of tin doped indium oxide (ITO) thin films with thickness of 125, 174 and 376nm. The ITO films on PET (polyethylene terephthalate) substrate were made by the ion plating technique. From the measurement results, it is confirmed that ITO thin films have a size effect on in-plane thermal diffusivity. Additionally, we found the anisotropic characteristics with the ITO thin films.

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Molecular dynamics simulation of Gay-Berne particles confined between two smooth walls parallel to each other was carried out to study the ordering and transport properties of confined liquid crystals. The equilibration process and ordering were investigated with NhP_<xx>T ensemble (N is the number of particles, h is the distance between two walls, P_<xx> is the element of pressure tensor parallel to walls and T is the temperature) and diffusion coefficients were calculated with NhAE ensemble (A is the area parallel to walls and E is the total energy). There were two kinds of parts: the center part, where the physical properties coincided ones of bulk system and the parts near walls, where liquid crystals possessed higher ordering than center part. The difference of spatial constrain from ordering caused transport properties of two kinds of narts.

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Molecular dynamics simulations were performed to investigate the phase change of a water cluster confined in a single-walled carbon nanotube. The first order phase transition of the water cluster to an ice-nanotube is investigated in terms of the dependence of the freezing temperature on the diameter of the carbon nanotube. The simulation aims to validate the experimental observation of the anomalous tube-diameter dependence with opposite trend from that of bulk water in a capillary tube. As a consequence, the calculated freezing temperature agrees well with those measured in experiments. It is shown that the freezing temperature exhibits a maximum value, about room temperature, for nanotube diameter of d=1.1nm, where the ice-nanotube consists of 5-membered rings. Analyses of the potential energy indicate that the freezing temperature is mainly determined by the structural stability of the ice crystal.

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Recently, natural refrigerants have gotten attention because they have less influence on the global warming and ozone depletion. Especially CO_2 has a lot of advantages. When CO_2 is used as refrigerant, it transit from liquid to supercritical state. A lot of studies on supercritical CO_2 have being done, but large scale simulations are not a lot. It is important to analyze the mechanisms of transit from liquid to supercritical state in more depth. The purpose of this study is to analyze heat transfer process in the micro heat pipe whose working fluid is CO_2 which transits from liquid to supercritical state by Molecular Dynamics simulation. To express CO_2, 2CLJQ (2-center Lennard-Jones plus point quadrupole) and potential parameter suggested by Moller and Fischer is used in this study.

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We apply molecular dynamics simulation of Lennerd-Jones (LJ) system to compare the Isotropic periodic sum (IPS) method [Wu and Brooks, J. Chem. Phys. 122, 044107 (2005)] with the cutoff method for the dynamic properties, which are self diffusion coefficient, bulk viscosity, and thermal conductivity. When the cutoff distance of IPS method was more than 3, self diffusion coefficient was estimated with reasonable accuracy. We also calculated the bulk viscosity and thermal conductivity with reasonable accuracy for IPS method. These results show that IPS method is effective technique in the estimation of dynamic properties of LJ system.

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According to Laplace's equation, a bubble becomes stable when the pressure difference between inside and outside of the bubble is equilibrated with the surface tension of the surrounding liquid. However, this equation has not been tested for its validity from microscopic viewpoint. In this study, we focused on the pressure part of Laplace's equation using molecular dynamics simulation. A bubble was formed by removing a part of liquid droplet and inserting a part of low density fluid in the vacancy. The following behavior of the bubble, expansion or shrinkage, was observed by changing the pressure inside the bubble.

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We observe the gradual, one-directional freezing procedure of the aqueous solution of HPLC6, which is the major fraction of the antifreeze protein type I. The location of the protein is obtained from the fluorescence tagged to the protein. It is observed that the proteins slide on the interface. Also, long, narrow liquid regions are formed inside the ice from the depression parts due to the highly associated proteins. It is found from our supplementary computation that these liquid regions can be predicted.

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Methanol crossover to the cathode not only lowers fuel utilization efficiency but also adversely affects the oxygen cathode in direct methanol fuel cell (DMFC). Because methanol is transported by diffusion and convection, diffusion coefficient of methanol aqueous solution in membranes is important parameter for the performance of DMFC. In the present study, we have developed Soret Forced Rayleigh Scattering Method (S-FRSM) using CO_2 laser to measure diffusion coefficient of methanol solution in polymer membrane. To control the pulse time and timing of the laser irradiation, two acoust-optic modulators (AOMs) were adopted in the apparatus newly developed.

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An experimental study using a sub-scale single cell was carried out to investigate the issues of concentration overvoltage due to oxygen transport under high current density operation of proton exchange membrane fuel cell. The result shows that the oxygen mole fraction drop in the cathode occurred mainly in the substrate of GDLs and the contribution of it to the overall diffusion is obtained as 60%. In addition, observation of porous structure of GDL by scanning electron microscope shows that the oxygen diffusion in GDLs is strongly affected by porous structure.

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In the present study, cathode side GDL of PEFC is modeled as a flat plate with many straight holes with different diameters. Using the model, the mechanism of flooding of PEFC is considered. In the study, water transmission and the oxygen diffusion through the holes are considered. As the generation volume of water in PEFC is very small compared with the volume necessary to overcome the pressure required for the water inflow through small conduits, small conduits are free from water inflow. Therefore, no flooding phenomenon occurs in GDL. It is thought that the relation between the thickness of the water layer between GDL and the catalyst layer and the limit of the amount of the oxygen diffusion is important for the flooding problem in the future.

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The power generation experiments were carried out using the anodes of Ni/GDC(Gd_2O_3-doped CeO_2) with BCY(BaCe_<0.8>Y_<0.2>O_<3-δ>), Ni/GDC with SCYb(SrCe_<0.95>Yb_<0.05>O_<3-δ>), Ni/YSZ(Y_2O_3-stabilized ZrO_2) with SCYb and Ni/YSZ with SZY(SrZr_<0.95>Y_<0.05>O_<3-δ>) to investigate the effects of proton-conducting ceramics on the characteristic of anodes. The Ni/GDC-BCY (GDC:BCY=90:10vol%) anode had higher performance than Ni/GDC-SCYb (GDC:SCYb=90:10vol%) and Ni/YSZ-SZY(YSZ:SZY=70:30wt%). It seemed to be dependent on that BCY shows the highest conductivity of the three. However, Ni/YSZ-SZY had higher performance relatively. Although the SZY had lower proton conductivity, it seemed to have the contribution to the anodic reaction.

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In this paper, we investigate the power generation performance of a small-scale tubular solid oxide fuel cell (SOFC), in particular the effects of steam content in fuel flow on the terminal voltage are discussed. In the present experiments, hydrogen and nitrogen mixture, of which volume ratio H_2/N_2 was adjusted at 5%/95%, was supplied into the anode side of the single cell. The performance curves, i.e., the relationships between current and voltage, were measured on the different fuel flow rate conditions and the constant furnace temperature of 800℃. At the same current output operation, the voltage of the wet fuel supply was lower than that of the dry fuel case. In order to investigate the influence of steam addition on the voltage drop, we tried to measure the voltage loss, which was caused by the electrical and ionic resistance, through the current-interruption method. As a result, it is found that the ohmic voltage drops in the wet and the dry cases account for 9% and 27% to the total voltage drops, respectively. The absolute value of the ohmic loss is independent on the steam content. Hence, we guess that the larger voltage loss in the case of the wet fuel results from activation and concentration overpotentials.

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In-line direct gas mass spectroscopy (DGMS) was applied for real-time monitoring of exhausted gas of a polymer electrolyte fuel cell (PEFC) in order to investigate degradation behaviors of the fuel cell. It was shown that hydrogen emission in cathode exhausted gas was larger under OCV operation than load operation, and that intermittent peaks of carbon dioxide emission in cathode exhausted gas were detected with positive sweep of cell potential, suggesting that carbon corrosion of the cathode catalyst proceed under load cycle operation.

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A continuous Ogako-drying apparatus using solar energy has been developed. Thermal performance of the apparatus was analyzed in a view point of energy balance. Drying experiment using the developed Ogako-drying apparatus was carried out simultaneously. Consequently, concerning temperature change on the Ogako-drying process, an agreement between the simulation calculations and the measurements was fairly good. Also in the experiment, moisture content of Ogako was decreased by 13% from 21.6% to 8.6% and contribution of solar energy into the Ogako-drying was 52.4Gcal/d that rates as 57% of incident solar radiation.

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Dimethyl ether (DME) is used as a gaseous fuel which has many merits, and easy to transport and store. Catalytic combustion is a promising method to attain stable low temperature combustion. However, DME has less activity of catalytic combustion in comparison with hydrogen and methanol. Nonetheless, there is still few in a report of a study about the catalytic combustion of DME. The main objective in the present study is to investigate fundamental characteristics of DME catalytic combustion. The results showed that O_2 concentration of premixed gas affects the steady and transient behavior of DME catalytic combustion.

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Solid oxide fuel cells (SOFC) are expected to become highly efficient power generation devices in distributed energy systems. The fuel flexibility of SOFC is appropriate for the small-scale power generation driven with the fuel derived from biomass resources. In this paper, the effects of fuel composition on a micro gas turbine (μGT)-solid oxide fuel cell (SOFC) hybrid power generation system is investigated by using the part-load performance prediction analysis based on thermodynamic cycle simulation. The four different fuel compositions, i.e., CH_4/H_2O, CH_4/H_2, CH_4/CO and CH_4/CO_2, are taken up, and the volume fractions of methane are fixed at 50% in the all cycle analyses. As a result, it is found that the power generation efficiencies of the mixed fuel cases are lower than the efficiency of methane case, because the μGT fractional power increases in the case of the mixed fuel. Carbon monoxide has a most significant effect on the performance degradation among the four mixed fuel cases. The major factor of the μGT power increase depends on the change of air flow rate, which is caused by the variation in the balance of the heat released from the SOFC and the heat absorbed into the reforming process. This characteristics means that the operating conditions of the μGT with the mixed fuels become overload to obtain the same power output as the standard value of the methane case.

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Effective utilization of waste heat from biomass power plants has become very important to reduce CO_2 emissions. However, it is difficult to use waste heat on site or very near by. This is so that there is too much waste heat to use as heating and cooling applications on the site. We need a method to transport waste heat to heating and cooling applications of other sites. Kobe Steel Ltd. and Kobelco Eco-Solutions Co., Ltd are developing latent thermal energy storage equipment for this transport system. The erythritol of phase change material (PCM) and direct contact heat transfer technology are being used for this equipment. Direct contact heat transfer technology is a thermal energy storage method of contacting heat medium to PCM directly. The advantages are high performances of heat input and heat output and light weight equipment without heat exchanger. Therefore, in this paper, we report on a study of a new model of thermal storage cassette, for the target performance of maintaining fixed heat output at a temperature of 90℃ for 8 hours, and performing 90% or more of heat recovery.

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We are developing a new co-generation system for apartment houses (Neighboring Co-Generation: NCG). The key concept of this system is to install a heat accumulator with a hot water supply and a room heating function at each household and to connect different households with single loop of heat transfer line. As a result, time leveling of the heat supply and heat transferring among households become possible. Thus, the costs of the piping and the heat source equipment decreases. We newly developed heat accumulator with normal pressure tank of hot water for space heating. In this paper, we report the outline of the heat accumulator and the result of accumulation and heat supply test.

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This paper describes influence of operating modes on the primary energy saving of a residential cogeneration system. Recently, some 1[kW]-class cogeneration systems (CGS) have been developed. However, daily electricity and thermal demands in one home, especially thermal demand, change very sharply minute to minute, and the thermal/electric load ratio also fluctuates very widely. There are quantitative changes of demands, in addition, with season even in an identical home. Therefore, the introduction effect of such a CGS will change largely with the demand pattern and the CGS operational pattern, and it is thought that selecting the effective operational pattern responding to the demands of each home is quite necessary for energy saving. This paper proposes a daily start and stop algorithm for a residential CGS using the estimated thermal demand curve of the day which derived from integrating the averaged thermal demands of three days before the day. Simulation results shows that about 20[%] primary energy reduction in winter season can be obtained if choosing the optimal combination of engine output and the start-up time precisely with the estimated thermal demand curve, and that when rather small engine output is selected, early start-up time is preferable for improvement of the energy saving.

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This paper analyzes CGS effectiveness for the CO_2 reduction, and the effects of use of heat pump for heating were investigated at various power plant efficiencies and the COP of heat pump. In the next-generation, it is essential to apply the system with heat pump for heating instead of boiler. The calculation results show that CGS benefit for CO_2 emission is strongly affected by the COP of heat pump and the electric efficiency of CGS is needed to be close to that of power plant efficiency to have a beneficial effect in the prospective system with heat pump. The electrical efficiency of CGS must be higher than the present system with boiler to get the benefits.

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The cogeneration system (CGS) has been expected to play an effective role in terms of energy conservation. To enhance the efficiency of the CGS in the actual situation, constructing clusters of the various energy demand would be effective. In order to examine the energy conservation effect of the CGS on the actual situation, the primary energy consumption of Keio University Shonan Fujisawa Campus (SFC) was calculated based on the actual energy demand assuming replacement of the existing CGS with four different sizes of the CGS. The energy conservation effect of the CGS was also examined for the case of greater reutilization of the exhaust heat among the buildings at SFC and providing generated power of the CGS to other campuses. As a result, the energy conservation effect could be enhanced if the load factor of the exhaust heat reutilization and the power generation are increased by constructing appropriate demand clusters among the plural buildings or campuses, as well as it would be important that the CGS operation could lead to the curtailment of the peak power load on the grid.

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This study shows an exergetic analysis based on both enthalpy and exergy flow, aiming at the efficient use of biomass energy. Several technologies for heat and power derived from woody biomass can be assessed by means of exergy efficiency, which indicates work potential of energy amount. It also makes clear the lost opportunities to do work in the energy conversion process and offers plenty of room for improvement. The results show significant difference between thermal and exergy efficiencies. The largest exergy loss in biomass power plant is found at the boiler, however the largest enthalpy loss takes place in the steam turbine.

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Introduction of hydrogen energy system using fuel cell is expected because of reduction of the environmental impact, diversification of energy source of supply and decentralization of electronic power supply. However it is necessary for realization of such hydrogen energy system to build the infrastructures of storage and transport of hydrogen demanding huge capital investment and long term. Consequently, the hydrogen energy system which by-product hydrogen from steel mill and oil factory is supply source is focused on. The objective of this study is designing of distributed hydrogen energy system enabling supply fuel cell and fuel cell vehicle with by-product hydrogen. Operation characteristic and economic efficiency of the energy system are estimated by using energy and economic model.

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The pyrolysis of woody biomass has been studied experimentally in attending to the mass transfer. The transfer has been controlled by three phenomena. Firstly, the volume of gaseous products doesn't change and main gases are not detected by Gas Chromatography. Therefore the evaporation of water can be occurred. Secondary, the volume increases dramatically because the cellulose in the biomass can be decomposed. Finally the volume increases slightly and approaches to the light gas. The pyrolysis of the biomass has been modeled by using the heat history, which is regarded as the heating rate of the biomass layer.

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The optical fiber cable has a firm structure consisted of silica, steel, strings and plastics so that, is rarely recycled. Recently, plastics and steel of the cable have been reusing by means of the exclusive stripping machine, but it is not easy to recover the high purity silica. The hydrothermal pyrolysis characteristics of the optical fiber coating to reuse the silica are determined in this paper. The major controlling factors such as, temperature and pressure in the reactor, through the pyrolysis are experimentally clarified. The overall decomposition rate is also described in a modified Arrhenius equation.

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We analyzed heat recovery performances of a counter-flow type catalytic converter that has a heat exchanging function, by developing a simulation model. Numerical solutions were obtained by coupled analysis of fluid mechanics (Full Navier-Stokes equation for two dimensional compressible viscous flow), thermal process and chemical reaction. The model estimated the effects of chemical reaction constant, length of catalytic layer and flow rate on temperature distribution in the catalytic converter.

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The development of Methane Hydrate (MH) recovery system has recently been brought to public attention. Although many systems have been proposed, the production technology has not yet been established. In the present study, we focused on a gas lift system as one possible recovery system and the following experiments and numerical analysis were conducted. (1) Laboratory scale experiments. (2) Measurement and prediction of MH decomposition rate. (3) Three-phase flow analysis in the recovery pipe in full-scale system. (4) Optimization of inlet shape at the bottom of the recovery pipe. From these experiments and numerical analysis, the possibility and applicability of the gas lift system for the MH recovery system were examined.

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Methane hydrate dissociation was numerically simulated in a water-rich sand layer by a 3D CFD method with unstructured grid systems. We modeled the sand layer as spherical sand particle locating in a face-centered cubic lattice. In this model sand layer, three cases of methane hydrate morphology are assumed: pore-coating, pore-bridging, and pore-filling models. The resultant penetration and dissociation rates were compared well with existing experimental results.

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Nucleation, growth, and ageing of methane hydrate crystals were visually observed in a porous medium filled with liquid water presaturated with methane. The pressure-temperature conditions, at which hydrate formation was initiated, correspond to the following system subcoolings ; 3.4K and 14.1K. Faceted hydrate crystals grew and bridged the pore spaces without intervention of a liquid water layer when the subcooling was equal 3.4K. At the subcooling of 14.1K, the dispersive formation of dendritic crystals and subsequent morphological change into particulate crystals were observed. Dissociation behaviors due to heat input or depressurization were observed in the porous medium. Formation and permeation of methane gas bubbles or slugs observed during dissociation varied depending on the dissociation method.

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The electron charging control (ECC) method for high speed synthesis of gas hydrates was proposed. In this method, water droplets are sprayed into high pressurized gas molecules from nozzles by applying a low voltage at its outlet. The purpose of the electron charging is to promote nucleation of gas hydrates. This phenomenon should be induced by decreasing diameter of water droplets, avoiding their coalescence, rectifying their flow and increasing heat transfer coefficient. In this paper, experiments on methane hydrate formation were performed and mechanisms on the nucleation and the induction period were clarified.

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This paper reports how effected the electrical field to hydrate production system. In the past experiment, the electrical field accelerated the hydrate production speed, and that reduced its induction time. But that reason was not sufficiently analysised. This reason was guessed that this effect owe to the change of the structure of water molecule clusters by the electrical field. So that, we calculated the effect of the electrical field to water molecule clusters, and the pattern analysis of the methane hydrate growth.

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A new gas hydrate formation method using micro-bubbles with a tubular reactor has been developed. The bench-scale experiments for gas hydrate formation using methane have been performed. A new tubular reactor with hydrate recirculation has been implicated to ensure continuous operation without increase in pressure loss. Experimental results of these improvements are described.

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Hydrate formation behavior of mixed gases of methane, ethane and propane has been studied as a model examination of NGH (Natural Gas Hydrate) production, because it is expected to be a novel transportation medium of natural gas. A batch-wise experiments were carried out with the initial gas phase composition corresponding to the equilibrium state which is calculated by using CSMHYD program. It has been found that the effect of the pressure on the amount of hydrate gas was small and the production rate of the mixed gases was nearly equal to that of methane.

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The dissociation rate of the methane hydrate was measured over the range of pressure from 0.1 to 6MPa in gaseous methane and mixture water. The results indicate that driving force of the decomposition is ΔT, difference in temperature between water and hydrate surface. The interfacial temperature of dissociating hydrate is three-phase equilibrium temperature at system pressure. When system pressure is lower than 2.55MPa, by assuming the interfacial temperature becomes the freezing point, the dissociation model is able to express the rate of mass transfer

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CO_2 ocean storage is one of greenhouse gas control technologies. This paper describes the formation and dissolution of CO_2 hydrate films on the surface of liquid CO_2 for CO_2 ocean storage. The induction time for the formation of the hydrate films was decreased with an increase in subcooling. A thick layer including CO_2 hydrate films was formed by removal and re-formation process of the hydrate films due to disturbing of the interface between water and liquid CO_2. The dissolution rate of CO_2 hydrate films was obtained from dissolution experiments of CO_2 drops covered with the hydrate films under water-flow conditions. The experimental dissolution rate was smaller than that predicted form a theoretical model with mass transfer coefficient from Ranz-Marshall's equation.

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