Elsevier BV Acta Medica Okayama 0017-9310 264 2026 Improving thermal stability of a microcavity emitter for utilization under atmospheric environment 128798 EN Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Shota Morishige Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Taiyo Sato Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University With the development of micro-fabrication technology, various metamaterials with controlled emission spectra have been proposed as thermal emitters. However, general metamaterials have a risk of deformations and degradation at high temperatures in atmospheric conditions, which is inconvenient for use as a thermal emitter. In this study, we propose a concept to enhance the thermal durability of microcavity-type metamaterials. Although typical microcavities are entirely composed of metal to excite the resonance of electromagnetic waves, we assessed the feasibility of a microcavity consisting of silicon with minimal metal coatings. While usual metals are oxidized at high temperatures, gold is rarely oxidized due to its chemical stability. However, the gold layer deposited on the Si substrate has the potential to melt below 400 °C due to the formation of an Au-Si eutectic alloy, which has a much lower melting point than pure gold. Therefore, we focused on the gold-tungsten bilayer as a suitable metal coating for the silicon microcavity, thereby preventing oxidation and melting that would otherwise influence the emission spectra of the thermal emitter. The numerical analysis ensured that the proposed microcavity exhibited electromagnetic resonance, similar to that of a microcavity entirely composed of metal, unless the metal coating was too thin. The fabricated microcavity with the gold-tungsten coating also exhibited a thermal emission within a limited wavelength range, due to the microcavity resonance. Moreover, the heating experiment revealed that the microcavity with a gold-tungsten coating maintained its emissivity even when heated to 400 °C, which is higher than the oxidation point of tungsten and the melting point of the Au-Si eutectic alloy. Consequently, the gold-tungsten coating would be a reasonable approach to improve the stability of the microcavity-type metamaterial at high temperatures under oxidative conditions. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 1613-6810 2025 Droplet Transportation on Janus Harp Wires for Enhanced Fog Harvesting e06765 EN Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Taku Ishikawa Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Ensuring freshwater resources is a vital issue for human beings worldwide. Fog harvesting is one promising way to provide water from unconventional sources. However, clogging by the captured liquid depresses the fog harvesting performance. Here, a harp-shaped Janus harvesting system, which has thin wires with a superhydrophobic side facing the fog stream and a superhydrophilic back side to transport the droplets, is used to yield simultaneous fog capturing and water transport abilities. Attached droplets on the Janus wire transported along the periphery avoided clogging and enhanced the performance. The Janus system thus suppressed the increase and fluctuations of actual shade coefficients, which indicated blockage of the fog stream. This optimized the design of the harvester. Experiments using a multilayered Janus harvester demonstrated a significant enhancement compared with that constructed with mono-wettability wires. Overall, the results indicated the promise of droplet transportation on single wires for improving fog harvesting, as well as for other applications such as oil mist recovery and demulsification. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 2574-0962 8 13 2025 Microagglomerate of VO2 Particles Packing Paraffin Wax Using Capillary Force as a Latent Thermal Energy Storage Medium 9595 9603 EN Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Kaketo Yamauchi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University This study proposed a material to retain paraffin wax with vanadium dioxide (VO2) particles as a latent thermal energy storage medium, an alternative to core–shell microcapsules containing phase change materials. VO2 microparticles, which were synthesized through a sol–gel method and annealing process, were dispersed in the oil-in-water microemulsion to obtain microagglomerates of VO2 microparticles. The average diameter of microagglomerates was 5 μm, and they retained paraffin wax at the vacancies among VO2 particles. Although the microagglomerates had no complete shells similar to core–shell microcapsules, the microagglomerates successfully trapped paraffin wax droplets without any leakage even in a high-temperature environment. It was because capillary forces acting among VO2 particles strictly prevented any leakage of paraffin waxes. The differential scanning calorimetry revealed that the microagglomerates contained only 16.5 wt % of n-octadecane, used as a paraffin wax. However, since VO2 particles can release or absorb latent heat due to their metal–insulator phase transition, the proposed microagglomerates exhibited higher thermal energy storage densities than phase change microcapsules whose shells do not show phase transitions. Moreover, the microagglomerates exhibited higher thermal conductivity than microcapsules with amorphous inorganic shells because the VO2 particles were crystallized through annealing. The proposed microagglomerate is a promising form for further improving the thermal energy storage density and thermal performance of the latent thermal energy storage medium, especially in the temperature range of 30 to 70 °C. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 0743-7463 41 11 2025 Droplet Impact Behavior on Convex Surfaces with a Circumferential Wettability Difference 7640 7647 EN Taku Ishikawa Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Controlling the bouncing behavior of the impacting droplets is an important issue for splay cooling, icing prevention, and other applications. The bouncing behavior of impacting droplets on superhydrophobic curved surfaces and flat substrates with a wettability difference has been widely investigated, and droplets impacting these surfaces show shorter contact times than those on superhydrophobic flat surfaces and droplet transport. However, there have been few studies on the droplet impact behavior on curved surfaces with a wettability difference, where efficient droplet control could be achieved by combining the features. In the present study, droplet impact experiments were conducted using copper cylinders with different circumferential wettabilities from hydrophilic to superhydrophobic, varying the impact velocity, cylinder diameter, and rotation angle. Droplets that impacted the wettability boundary showed asymmetric deformation and moved to the hydrophilic side, owing to the driving force of the wettability difference. Moreover, the droplet behavior was classified into four types: the droplet bounced off the surface, the droplet bounced off the surface and split, the droplet attached to the surface, and the droplet attached to the surface and split. The droplet behavior was estimated by using the maximum spreading width of the droplet impacted on the flat substrate. We evaluated whether the droplets attached to the surface or bounced off the surface after impact using the Weber number and rotation angle, and the estimations were in agreement with the experimental results for cylinder diameters of 4 and 6 mm. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 0743-7463 40 32 2024 Effect of Droplet-Removal Processes on Fog-Harvesting Performance on Wettability-Controlled Wire Array with Staggered Arrangement 16994 17000 EN Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Junya Oka Graduate School of Natural Science and Technology, Okayama University Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Development of freshwater resources is vital to overcoming severe worldwide water scarcity. Fog harvesting has attracted attention as a candidate technology that can be used to obtain fresh water from a stream of foggy air without energy input. Drainage of captured droplets from fog harvesters is necessary to maintain the permeability of harp-shaped harvesters. In the present study, we investigated the effect of the droplet-removal process on the amount of water harvested using a harvester constructed by wettability-controlled wires with an alternating and staggered arrangement. Droplet transfer from hydrophobic to hydrophilic wires, located upstream and downstream of the fog flow, respectively, was observed with a fog velocity greater than 1.5 m/s. The proportion of harvesting resulting from droplet transfer exceeded 30% of the total, and it reflected more than 20% increase of the harvesting performance compared with that of a harvester with wires of the same wettability: this value varied with the adhesive property of the wires and fog velocity. Scaled-up and multilayered harvesters were developed to enhance harvesting performance. We demonstrated certain enhancements under multilayered conditions and obtained 15.99 g/30 min as the maximum harvested amount, which corresponds to 13.3% of the liquid contained in the fog stream and is enhanced by 10% compared with that without droplet transfer. No potential conflict of interest relevant to this article was reported.

The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan Acta Medica Okayama 1880-5566 19 1 2024 Radiative energy transfer via surface plasmon polaritons around metal–insulator grating: For better understanding of magnetic polariton 23-00531 EN Kazuma ISOBE Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University Yutaka YAMADA Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University Akihiko HORIBE Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University Katsunori HANAMURA School of Engineering, Department of Mechanical Engineering, Tokyo Institute of Technology A conventional metal–insulator nanograting has the potential to transmit near-infrared thermal radiation because an electromagnetic wave is resonated in the grating structure. Surface plasmon polaritons (SPPs) take place at the interface between the metal and the insulator with boundaries at both ends. Physicists formulated the resonance frequency of the grating from the Fabry–Pérot interference between the grating thickness and the wavelength of SPPs in a short-range coupled mode. On the other hand, engineering researchers often use a lumped-element model assuming a resonant circuit consisting of an inductance of metal and a capacitance of metal-insulator-metal grating structure. Furthermore, they have considered that the resonant circuit excites a strong magnetic field independent of SPPs. This study compares each physical model and numerical simulation results, then clearly shows that all resonance frequencies and features of the circuit resonance can be described by the Fabry–Pérot interference of the SPPs in short-range coupled mode. Moreover, the estimated resonance frequencies obviously correspond to the local maxima of the transmittance of the nanograting with the various thicknesses and pitches. In this case, a strong magnetic field can be observed in the insulator layer as if it might be an isolated magnetic quantum. However, since materials show no magnetism at near-infrared frequencies, the magnetic response appears due to the contribution of SPPs. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0017-9310 221 2024 Bayesian optimization of periodic multilayered slabs for passive absorptivity control 125047 EN Kazuma Isobe Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Tsuyoshi Yamamoto Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Yutaka Yamada Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University A vanadium dioxide (VO2) film grown on a titanium oxide crystal shows a metal–insulator transition at room temperature with drastically changed optical properties. A multilayered slab with a sub-micron scale VO2 film was proposed to utilize its unique properties for passive intensity control of sunlight absorption and radiative cooling. Its optimal geometries were numerically explored using the Bayesian optimization (BO) method. BO was applied for three types of multilayered slabs, those having one, two, or three isolated slabs of different widths. For each type of multilayered slab, BO could optimize geometric variables with practical calculation times considering the total number of possible combinations of variables, which is subsequently referred to as the total number of candidates. Optimization results revealed that two isolated slabs had the most suitable spectral absorptivity in both hot and cold environments. The infrared absorptivity of the double slab was kept low in cold conditions to suppress radiative cooling. However, the double slab exhibited good radiative cooling performance under hot conditions. Electromagnetic energy density surrounding the slab illustrated that metallic VO2 and gold placed in a parallel manner excited the coupled mode of surface plasmon polaritons to enhance absorptivity. Radiative cooling faded for the triple slab because each slab could couple with radiation propagating only across a portion of the cross-sectional area. Through three BO trials, improvement of the VO2 visible reflectivity was recognized as a future issue for further development of passive sunlight absorption control. No potential conflict of interest relevant to this article was reported.

AIP Publishing Acta Medica Okayama 0003-6951 123 23 2023 Water/ice mixture- and freezing-front motion in a non-isothermal liquid bridge 231601 EN Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Kodai Okano School of Engineering, Okayama University Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University We experimentally investigate the water/ice mixture- and freezing-front behavior in a water liquid bridge under isothermal and non-isothermal conditions. We find rapid propagation, temporary suspension, and regression of the water/ice mixture front, and finally, it merges with the freezing front when part of the liquid bridge is higher than the freezing temperature. However, freezing-front propagation follows dendritic ice formation, and a protrusion forms at the middle of the liquid bridge as long as the whole liquid bridge is lower than the freezing temperature. We explain those phenomena by quasi-stationary heat-transfer considerations. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 0743-7463 39 44 2023 Analysis of Evaporation of Droplet Pairs by a Quasi-Steady-State Diffusion Model Coupled with the Evaporative Cooling Effect 15587 15596 EN Yutaka Yamada Faculty of Environmental, Life, Natural Science and Technology, Okayama University Kazuma Isobe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akihiko Horibe Faculty of Environmental, Life, Natural Science and Technology, Okayama University Multidroplet evaporation is a common phase-change phenomenon not only in nature but also in many industrial applications, including inkjet printing and spray cooling. The evaporation behavior of these droplets is strongly affected by the distance between neighboring droplets, and in particular, evaporation suppression occurs as the distance decreases. However, further quantitative information, such as the temperature and local evaporation flux, is limited because the analytical models of multidroplet evaporation only treat vapor diffusion, and the effect of the latent heat transfer through the liquid–vapor phase change is ignored. Here, we perform a numerical analysis of evaporating droplet pairs that linked vapor diffusion from the droplet surface and evaporative cooling. Heat transfer through the liquid and gas phases is also considered because the saturation pressure depends on the temperature. The results show an increase in the vapor concentration in the region between the two droplets. Consequently, the local evaporation flux in the proximate region significantly decreases with decreasing separation distance. This means that the latent heat transfer through the phase change is diminished, and an asymmetrical temperature distribution occurs in the liquid and gas phases. These numerical results provide quantitative information about the temperature and local evaporation flux of evaporating droplet pairs, and they will guide further investigation of multiple droplet evaporation. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0195-928X 44 5 2023 Synthesis and Characterization of Silica-Encapsulated n-Tetracosane and the Effect of Surface Modification by Silane Coupling Agents 69 EN Kyosuke Okuno Graduate School of Natural Science and Technology, Okayama University Kazuma Isobe Graduate School of Natural Science and Technology, Okayama University Akihiko Horibe Graduate School of Natural Science and Technology, Okayama University Yutaka Yamada Graduate School of Natural Science and Technology, Okayama University Microencapsulation of n-tetracosane, whose melting point is approximately 50 degrees C, in a silica shell has been performed through the sol-gel method using tetraethyl orthosilicate (TEOS) as the precursor for silica-shell formation. Additionally, two types of silane coupling agents were used to modify the surface of the microcapsules to change the wettability. The morphology of the microcapsules was observed by scanning electron microscopy. The chemical composition was characterized by Fourier transform infrared spectroscopy. The results confirmed the presence of n-tetracosane and silica in the synthesized microcapsules. Wettability analysis showed hydrophobic and hydrophilic features because of the added silane coupling agents. From the results of differential scanning calorimetry measurements, the encapsulation ratio of the microcapsules increased with decreasing TEOS/n-tetracosane ratio, and the highest encapsulation ratio was 87.1 % at a TEOS/n-tetracosane ratio of 0.25. The pH in the microcapsule solution was affected by addition of a silane coupling agent, and shifting the pH to the basic side lowered the encapsulation ratio owing to enhancement of silica condensation. After 100 differential scanning calorimetry cycles, there was no significant degradation in the phase-change temperatures and enthalpies, which confirmed the good phase-change stability and repeatability. Therefore, the microcapsules are a potential material for thermal-energy-storage systems to effectively utilize energy. No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry (RSC) Acta Medica Okayama 2046-2069 12 22 2022 Droplet motion on a wrinkled PDMS surface with a gradient structural length scale shorter than the droplet diameter 13917 EN Yutaka Yamada Graduate School of Natural Science and Technology, Okayama University Kazuma Isobe Graduate School of Natural Science and Technology, Okayama University Akihiko Horibe Graduate School of Natural Science and Technology, Okayama University Droplet transportation using a wettability gradient surface has attracted much attention owing to applications such as in microfluidic devices. A surface with a spatial structural gradient was prepared through a simple and cost-effective process even though understanding of droplet behavior on the structure was still limited. Here, we report impinging droplet motion on a gradient wrinkled surface. Surfaces were prepared through hard film deposition on soft pre-strained polydimethylsiloxane (PDMS) with a mask installed with a slit to control the amount of deposition, which is related to the wavelength of the wrinkles. Droplets were impinged with varying position with respect to the structure, and the droplet motion was observed in the direction away from the region under the slit. We found an asymmetric contact angle and alternate motion on both sides of the three-phase contact line during the motion according to the gradient of the wrinkle wavelength. These results may help not only to understand the behavior of droplet impingement on a gradient structural surface but also to further develop applications using directional droplet transfer. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0195-928X 43 3 2022 Absorptivity Control Over the Visible to Mid-Infrared Range Using a Multilayered Film Consisting of Thermochromic Vanadium Dioxide 44 EN Kazuma Isobe Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University Minoru Tomioka Faculty of Engineering, Department of Mechanical Engineering, Okayama University Yutaka Yamada Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University Akihiko Horibe Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University Vanadium dioxide (VO₂) is a phase transition material that exhibits metallic or insulating characteristics depending upon its temperature. In this study, a multilayered film consisting of ₂, silicon dioxide (SiO₂) and gold was proposed as a metamaterial that switches its absorptivity over a broad wavelength range depending on the ambient temperature as a fundamental element of a building pigment. At high temperatures, the multilayer showed a high absorptivity at mid-infrared wavelengths, promoting radiative cooling. Simultaneously, the multilayer presented a low absorptivity in the visible and near-infrared wavelengths, enhancing sunlight absorption. The daily average heat flux can possibly be suppressed in summer in comparison with a gray body whose emissivity was 0.8. Conversely, at a lower temperatures, the multilayer showed opposite absorptivity in both the mid-infrared and visible ranges, and its daily average heat flux increased in winter. The metal–insulator phase transition of VO₂ caused a drastic shift of the resonant wavelength related to surface phonons and surface plasmons at an infrared wavelength, and optical interference at a visible wavelength, originating at the interface of the SiO₂ layer. Thus, the radiative heat flux for both sunlight absorption and radiative cooling was simultaneously controlled depending on the temperature of VO₂. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 1944-8244 13 29 2021 Wettability Difference Induced Out-of-Plane Unidirectional Droplet Transport for Efficient Fog Harvesting 35079 35085 EN Yutaka Yamada Graduate School of Natural Science and Technology, Okayama University Eiji Sakata Graduate School of Natural Science and Technology, Okayama University Kazuma Isobe Graduate School of Natural Science and Technology, Okayama University Akihiko Horibe Graduate School of Natural Science and Technology, Okayama University Securing freshwater resources is a global issue for ensuring sustainable development. Fog harvesting is attracting great attention as a method to collect water without any energy input. Previous reports that were inspired by insects and plants have given insights such as the effectiveness of in-plane wettability and structural differences for droplet transport, which might enhance artificial water harvesting efficiency. However, further efforts to transfer droplets while maintaining performance are needed because droplet motion owing to these effects is limited to the in-plane direction. In this study, we report droplet transport between three-dimensional copper wire structures with nanostructured hydrophobic and superhydrophilic features. This mechanism enhanced the fog harvesting capability by more than 20% compared with the cumulative value of individual wires. In addition, the relationship between the droplet height and spacing of wires affected the performance. Our results show the importance of out-of-plane directional droplet transport from the wire surface assisted by differences in wire wettability, which minimizes limiting factors of fog harvesting including clogging and droplet shedding. Furthermore, the proposed arrangement reduces the overall system width compared with that of a two-dimensional arrangement while maintaining the amount of harvested water. These results provide a promising approach to designing large-scale and highly efficient fog harvesters. No potential conflict of interest relevant to this article was reported.

日本鉄鋼協会 Acta Medica Okayama 0021-1575 106 8 2020 糖アルコール系潜熱蓄熱材と熱媒油の直接接触凝固挙動 518 526 EN Akihiko Horibe Graduate School of Natural Science and Technology, Okayama University Yutaka Yamada Graduate School of Natural Science and Technology, Okayama University The purpose of this study is developing a latent heat storage system that uses waste heat from factories in the temperature range 100–200ºC as a heat source. Mannitol and a mixture of mannitol and erythritol, which are sugar alcohols, were used as phase change materials (PCMs). We also studied a direct contact heat exchange method with lower thermal resistance.</br> The solidification behavior was examined in detail using a test section consisting of a Pyrex glass tube with one nozzle hole for injecting heat transfer oil. The tube had an inner diameter of 87 mm and height of 300 mm. There was a nozzle plate with one hole that had a diameter of 2 mm in the lower part of the test section, and heat was transferred to the PCM by injecting heat transfer oil from the hole.</br> The findings were the following. The heat transfer oil droplets from the hole start to solidify on the upper surface of the heat storage material. As time elapses, solidification starts near the nozzle plate. The oil droplet diameter increases with increasing flow rate. The diameter of the liquid column increases owing to solidification near the nozzle plate. The initial solidification shape of the mannitol–erythritol mixture (70% mannitol and 30% erythritol) is different from that of the mannitol. In addition, the observed solidification has a different shape depending on the flow rate. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 44 3 2007 Heat Storage Characteristics of Latent-Heat Microcapsule Slurry Using Hot Air Bubbles by Direct-Contact Heat Exchange 328 336 EN Hideo Inaba Akihiko Horibe Myoung-Jun Kim Tsukamoto Hirofumi <p>This study deals with the heat storage characteristics of latent-heat microcapsule slurry consisting of a mixture of fine microcapsules packed with latent-heat storage material and water. The heat storage operation for the latent-heat microcapsules was carried out by the direct-contact heat exchange method using hot air bubbles. The latent-heat microcapsule consisted of n-paraffin as a core latent-heat storage material and melamine resin as a coating substance. The relationship between the completion time of latent-heat storage and some parameters was examined experimentally. The nondimensional correlation equations for temperature efficiency, the completion time period of the latent-heat storage process and variation in the enthalpy of air through the microcapsule slurry layer were derived in terms of the ratio of microcapsule slurry layer height to microcapsule diameter, Reynolds number for airflow, Stefan number and modified Stefan number for absolute humidity of flowing air.</p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 47 1 2007 The Convective Instability in a Microemulsion Phase-Change-Material Slurry Layer 126 137 EN Hideo Inaba Chuanshan Dai Akihiko Horibe <p>In the present experimental study, the stability of Rayleigh-Benard convection has been investigated in rectangular enclosures filled with microemulsion Phase-Change-Material (PCM) slurry. The PCM slurry exhibited a pseudoplastic non-Newtonian fluid behavior. Hysteresis in convection was clearly observed while the PCM were in a solid phase and in phase changing. The critical Rayleigh number decreases with the PCM mass concentration while the PCM is in phase changing. The fluid temperature at the center of the enclosure showed a time-dependent oscillation during the transition from a heat conduction state to a convection state. The maximum Nusselt number has been observed for all of the slurries while the heating plate was controlled at a temperature that most of PCM was in phase changing.</p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 45 2 2007 Sublimation Behavior of Annular Frost Layer by Impinging Jet Flow 322 330 EN Hideo Inaba Akihiko Horibe Naoki Takamoto Yoshiaki Kawakami Seishi Imai <p>The present paper deals with a new method of defrosting using the frost sublimation phenomenon, which occurs below the triple point of water (273.16K, 610.5Pa). The present experimental study examines the mass transfer of the annular frost layer developed on a cooling pipe exposed to an impinging jet flow. The morphology of the frost layer during sublimation was observed using a digital video recorder. It was understood that the mass flux of the frost layer increased with increasing the jet flow velocity and the difference in the mass concentration of water vapor between the frost surface and the impinging jet flow. The non-dimensional correlation equations of mass transfer of defrosting were derived as functions of various parameters.</p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 45 1 2007 Sorption Characteristics of Honeycomb-Type Sorption Element Composed of Organic Sorbent 183 191 EN Hideo Inaba Takahisa Kida Akihiko Horibe Makoto Kaneda <p>This study deals with the sorption characteristics of a honeycomb-type sorption element composed of a new organic sorbent that was composed of the cross-linked polymer of sodium acrylate. Transient experiments in which moist air was passed into the honeycomb-type sorption element were conducted under various conditions of air velocity, temperature, relative humidity and honeycomb length. As a result, the effective mass transfer coefficient of the organic sorbent adsorbing the water vapor was non-dimensionalized as a function of Reynolds number, modified Stefan number and non-dimensional honeycomb length.</p> No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 33 2 1999 A Numerical Study on the Performance of an Open-type Flat-plate Solar Collector 25 37 EN Hideo Inaba Akihiko Horibe 10.18926/19660 A set mathematical models was developed for predicting the performance of an open-type flat-plate solar collector, and solved numerically through an implicit difference method. The effects of various parameters on the absorption of solar energy for the collector were investigated. The results showed that the solar energy absorptance of the open-type flat-plate collector was relatively high especially for the region where the weather was humid and hot, and there were an optimum length and an optimum tilt angle for the absorbing plate on which the collector could obtain the highest solar energy absorptance. It was found that the latent heat flux of water evaporation could be 5 to 15 times larger than the sensible heat flux. The effects of the magnitude of the solar incident flux, the atmospheric humidity, the atmospheric temperature, the absorbing plate tilt angle, and water film thickness on the temperature rising of the water film were clarified in numerical quantities. The increase of the solar incident flux, the atmospheric humidity or the atmospheric temperature also resulted in a rise in the energy absorptance of the collector. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 34 1-2 2000 Falling Snow Melting Characteristics of Warm Water Flowing along Sheet Channels Spread on a Roof 1 12 EN Hideo Inaba Akihiko Horibe 10.18926/15354 The experiment for investigating the falling snow melting characteristics of warm water flowing along sheet channels spread on a roof was performed in Tookamachi city, Nigata prefecture from February 6 to February 7, 1995. The sheet surface temperatures at 11 positions in 3 channels were measured. A physical model for a gas-water-snow system was constructed to compare the predicted results with the measured ones. A fully spread uniform water film in the sheet channel was observed in the experiments. The experimental results elucidated that it was feasible to use warm water flowing along sheet channels for melting falling snow on roofs. The temperature drop in the sheet channel mainly depended on the snowfall intensity, atmospheric temperature and wind speed. Under the influence of the roof edge, the temperature drop in the channel next to the side edge was much larger than that in middle channels. A water-snow two phase flow or a snow covered frozen water was experienced temporarily in the lower reaches of the water flowing channel. These suggest that a larger water flow rate is needed for the channel next to the roof edge, and a higher inlet temperature or a greater water flow rate is required for a severe weather condition. There was reasonably good agreement between the measured and predicted water temperatures. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 41 1 2007 Heat and Mass Transfer Analysis of Fluidized Bed Grain Drying 52 62 EN Hideo Inaba Akihiko Horibe Naoto Haruki 10.18926/14084 The effects of heat and mass transfer parameters on the efficiency of fluidized bed drying have been studied to optimize the input and output conditions. The analysis was carried out using two different materials, wheat and corn. Energy and exergy models based on the first and second law of thermodynamic are developed. Furthermore, some unified non-dimensional experimental correlations for predicting the efficiency of fluidized bed drying process have been proposed. The effects of hydrodynamics and thermodynamics conditions such as the inlet air temperature, the initial moisture content and well known Fourier and Reynolds numbers on energy efficiency and exergy efficiency were analyzed using the developed model. A good agreement was achieved between the model predictions, non-dimensional correlations and the available experimental results. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 66 650 2000 衡突噴流による円環状霜層の昇華特性 149 156 EN Hideo Inaba Akihiko Horibe Naoki Takamoto Yoshiaki Kawakami Seishi Imai The present paper has dealt with a new method of defrosting by using the frost sublimation phenomenon which occurs below the triple point of water (273.16K, 610.5Pa). The present experimental study has focussed to examine the mass transfer of the annular frost layer developed on a cooling pipe exposed to an impinging jet flow. Morphology of the frost layer during sublimating was observed by using a CCD camera. It was understood that the mass flux of the frost layer increased with increasing the jet flow velocity and the difference of the mass concentration of water vapor between the frost surface and the inpinging jet flow. The nondimensional correlation equations of mass transfer of defrosting were derived as functions of various parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 63 610 1997 形状安定化球状潜熱蓄熱体を用いた流動層型潜熱蓄熱槽の流動および蓄熱特性 291 298 EN Hideo Inaba Akihiko Horibe Kouichi Ozaki Takayuki Yamazawa This paper deals with fluidization and heat storage characteristics of shape-stabilized latent heat storage particles packed into a fluidized bed-type heat storage vessel. The shape-stabilized latent heat storage material consists of normal paraffin (pentacosane C_<25>H_<52>, latent heat 164 kJ/kg, melting point of 327.2 K) as a latent heat material, and polyethylene as a shape-stabilizing material. The pressure losses both on fluidized and on fixed particle layers were measured in order to investigate flow behavior in the heat storage vessel. It was found that the pressure loss of the fluidized particle layer was lower than that of the fixed particle layer. Furthermore, the effects of hot air flow rate, inlet air temperature and the amount of heat storage particles packed into the heat storage vessel on the completion time of the heat storage process were investigated. As a result, the nondimensional correlations for the completion time of the heat storage process were expressed in terms of nondimensional pumping power, the Stefan number and the ratio of the packed particle layer height to the diameter of the cylindrical heat storage vessel. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 63 616 1997 形状安定化球状潜熱蓄熱粒子を用いた流動層型潜熱蓄熱槽の放熱特性 207 214 EN Hideo Inaba Akihiko Horibe Koichi Ozaki Takayuki Yamazawa This paper deals with heat energy release characteristics of shape-stabilized latent heat energy storage particles packed into a fluidized bed-type cylindrical heat energy storage vessel. This type of latent heat energy storage material consists of normal paraffin (pentacosane C_<25>H_<52>, latent heat : 164 kJ/kg, melting point of 327.2K) as a latent heat material, and polyethylene as a shape-stabilizing material. The effects of cold inlet air temperature and flow rate, and the amount of heat energy storage particles on the outlet air temperature from the heat storage vessel and the completion time of the heat energy release process were investigated. As a result, the non-dimensional correlations for the outlet air temperature from the heat storage vessel and the completion time of the heat energy release process were expressed in terms of non-dimensional pumping power, Stefan number and ratio of the packed particle layer height to the diameter of the cylindrical heat storage vessel. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 64 618 1998 傾斜配置した平板状形状安定化潜熱蓄熱材充填矩形蓄熱槽の蓄熱特性 200 207 EN Hideo Inaba Tu Ping Akihiko Horibe Koichi Ozaki The present study deals with the heat storage characteristics of the inclined rectangular vessel packed with spape-stabilized paraffin plates as a latent heat storage material by numerical analysis. It was found that the heat storage characteristics were remarkedly affected by the inclination angle of the rectangular vessel and the heat transfer medium flow direction, due to the presence of natural convection in the fluid flow channel between the paraffin plates. Numerical results revealed flow patterns, temperature profiles and heat storage characteristics for various inclination angles, inlet velocities and temperatures of the heat transfer medium fluid, and widths of the fluid flow channel. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 64 621 1998 繊維質系流動抵抗軽減剤添加水の直管内流動抵抗および熱伝達特性 178 185 EN Hideo Inaba Naoto Haruki Akihiko Horibe Koichi Ozaki Some kinds of surfactants are useful to reduce flow drag in a turbulent pipe flow by Toms effect. However, it needs a lot of cost to make these surfactant harmless material to the environment. On the other hand, the fibrous substance such as pulp fibers and cellulose are harmless additives to the environment. This paper has dealt with the flow drag reduction and heat transfer characteristics of the water suspension flow mixed with fine fibers in a straight pipe. Measurements of velocity and temperature profile in a circular pipe flow were made in order to examine the flow drag and heat transfer characteristics of the turbulent and laminar flow. The nondimensional equations of pipe flow resistance and heat transfer were derived in terms of various nondimensional parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 64 627 1998 フッ素系不活性液体を熱回収用媒体として用いた液-液直接接触熱交換に関する研究 : 温水中を降下するフッ素系不活性液滴群についての伝熱特性 312 319 EN Hideo Inaba Akihiko Horibe Koichi Ozaki Naoki Yokoyama This paper deals with the heat transfer characteristics of a liquid-liquid direct contact operation in which a Perfluorocarbon (PFC) liquid is released in a hot water stream, a low-grade heat source such as urban sewage, for the purpose of heat recovery from it. The paper reports on a set of experiments in which a PFC liquid (1800 kg/m^3 at 20℃) was continuously injected from a single, downward-facing nozzle into a slow, upward flow of hot water to be disintegrated into droplets descending in, and thereby heated from the water flow. The results of the experiments show how the size distribution and the translational motions of the droplets affect the overall coefficient for the water-flow-to-droplets heat transfer and also the temperature effectiveness for the droplets. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 65 631 1999 架橋ポリエチレン粒子充填潜熱蓄熱槽の非定常放熱特性 161 168 EN Hideo Inaba Zhongmin Li Akihiko Horibe Koichi Ozaki Transient heat release characteristics of a latent heat storage vessel packed with surface cross-linked form stabilized high-density polyethylene pellets as a phase change material (PCM) have been investigated numerically and experimentally. The obtained results revealed the effects of the inlet velocity, the inlet temperature of ethylene glycol/water solution as a heat transfer medium, and the amount of the PCM on the heat release characteristics. As a result, the nondimensional correlation equation of the completion time of the heat release process was derived as a function of some nondimensional parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 65 635 1999 直接接触熱交換法を用いた中温度潜熱蓄熱槽の放熱特性 268 275 EN Hideo Inaba Akihiko Horibe Koichi Ozaki Kazuo Emoto Hiroyuki Kakiuchi Experiment has been performed of heat transfer characteristics of the middle temperature latent heat storage system of the direct-contact heat transfer by using m-E (meso-Erythritol, melting point of 119℃, latent heat of 375 kJ/kg) droplets as a latent heat storage material and silicone oil as a heat transfer medium. In the present study the liquid m-E was injected into the heat tranfer medium through a circular nozzle. The m-E droplets changed from liquid to solid phase during falling in the heat transfer medium at low temperature. From the measuring results of m-E droplet diameter, falling velocity, and solidification rate, the nondimensional empirical equations of the arithmetic mean diameter of the droplets and falling velocity, the solidification rate and the overall heat transfer coefficient were derived as a function of the characteristic arithmetic mean diameter, the terminal velocity, temperature and physical properties. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 65 639 1999 繊維系有機吸着剤の過渡的脱着特性 239 246 EN Hideo Inaba Koichi Ozaki Akihiko Horibe Rikio Shimoyama Takahisa Kida An experimental investigation was performed to determine the transient desorption characteristics of a fibrous type organic adsorbent, which was composed of the bridged complex of sodium polyacrylate as a new kind of adsorbent. The test fibrous adsorbent was packed in a cylindrical vessel, and dry air was passed through it. The experiments were conducted under various conditions of air velocity, temperature, relative humidity and vessel length. As a result, the pressure loss for the packed bed of the test fibrous adsorbent showed a similar tendency to that for the packed bed of spherical particles. The mass transfer data was correlated by the modified Sherwood number, the Reynolds number, the Schmidt number, the ratio of desorbed water vapor mass to fibrous adsorbent mass, the nondimensional temperature and the ratio of vessel length to fiber diameter. Fourier number for the completion times of adsorption processes were also correlated by Reynolds number, and the ratio of desorbed water vapor mass to fibrous adsorbent mass, the nondimensional temperature and the ratio of vessel length to fiber diameter. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 66 645 2000 温空気泡群と潜熱マイクロカプセルとの直接接触熱交換による蓄熱特性 231 238 EN Hideo Inaba Akihiko Horibe Hirofumi Tsukamoto Myoung-Jum Kim This paper has dealt with the heat storage characteristics of fine microcapsules packed with latent heat storage material in the water layer. The heat storage operation to the latent microcapsules was carried out using hot air bubbles by direct contact heat exchange. The microcapsule consists of n-paraffin as a core latent-heat storage material and melamine resin as a coating substance. The relation of the completion time of latent-heat storage to some parameters was examined experimentally. The non-dimensional correlation equations for the completion time of latent-heat storage process had were derived in terms of the ratio of water layer height to diameter of microcapsule, Reynolds number for air flow, Stefan number and modified Stefan number for absolute humidity of flowing air. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 66 647 2000 管内流動抵抗低減用界面活性剤を添加した低温水の曲がり管部における流動抵抗低減効果と熱伝達特性 204 211 EN Hideo Inaba Naoto Haruki Akihiko Horibe This paper has dealt with the flow resistance and heat transfer characteristics of flowing cold water with flow drag reduction additive in curved pipes. A cationic surfactant was used as the flow drag reduction additive. The flow drag resistance and the local heat transfer coefficient of cold water flow in some curved pipes were measured under the constant heat flux heating wall condition. It was found that the flow drag and heat transfer reduction effect by the surfactant was depended on the angle and curved ratio of the curved pipes. The nondimensional correlative equations of flow resistance and heat transfer coefficient of cold-water flow with the surfactant in the curved pipe were derived in terms of various nondimensional parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 66 651 2000 着霜2円管の昇華による除霜挙動 212 219 EN Hideo Inaba Akihiko Horibe Yoshiaki Kawakami The present paper has dealt with a new defrost measure by using sublimation phenomenon which occurs below the triple point of water (273.16 K, 610.5 Pa) The present experimental study has focused to examine the mass transfer of annular frost layers developed on two cooling horizonal pipes set in a vertical direction which was exposed to an impinging jet air flow. The morphology of the frost layer during sublimating was observed by using a CCD camera. The nondimensional correlation equations of mass transfer were derived as a function of various parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 66 652 2000 有機系収着剤を塗布したハニカム状収着エレメントの収着特性 164 171 EN Hideo Inaba Takahisa Kida Akihiko Horibe Makoto Kaneda This paper has dealt with the sorption characteristics of honeycomb shape type sorbent element composed of new organic sorbent which was composed of the bridged complex of sodium polya-crylate. The transient experiments in which the moist air was passed into the honeycomb type sorbent element were conducted under various conditions of air velocity, temperature, relative-humidity and honeycomb length. As a result, the effective mass transfer coefficjent of the organic sorbent sorbing the water-vapor was non-dimensionalized as a function of Reynolds number, modified Stefan number and non-dimensional honeycomb length. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 67 660 2001 湿り空気による粉末状有機系収着剤流動層の水蒸気収着特性 237 244 EN Hideo Inaba Takahisa Kida Akihiko Horibe Kiyohiro Kameda Tamio Okamoto Joung-kuen Seo This paper has dealt with water vapor sorption characteristics of powder type organic sorbent bed by flowing a moist air. The powder type sorbent was fluidized in a rectangular vessel by the moist air flow. The sorption rate of vapor and the variation in temperature in the sorbent bed were measured under various air temperature and humidity conditions. It was found that the volume of the sorbent particles increased with in an increase in the amount of water vapor sorption. Finally, Sherwood number for water vapor mass transfer was expressed in terms of Reynolds number, the modified Stefan number, the ratio of sorbent particle diameter to fluidized bed height and Schmidt number. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 67 660 2001 平板状フィン付き加熱面を有する傾斜矩形潜熱蓄熱槽内の自然対流挙動 245 252 EN Hideo Inaba Kouichi Matsuo Akihiko Horibe The present paper has dealt with the natural convection heat transfer in a melted liquid layer appeared in the inclined rectanglar latent heat storage vessel having one heating wall with plate fins. The effects of plate fin length, inclination angle of the rectangular vessel and heat wall temperature on the melting behavior of paraffin wax as a latent heat storage material. and natural convection heat transfer were investigated experimentally under a heat storage process. As a result, non-dimentional correlation equations of natural convection heat transfer were derived in terms of some non-dimentional parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 68 665 2002 等熱流束加熱を受ける円管内を流動する潜熱マイクロカプセル混合水スラリーの熱伝達特性(数値計算による検討) 161 168 EN Hideo Inaba Myoung-Jun Kim Akihiko Horibe The present numerical analysis has been performed for obtaining the heat transfer characteristics of microencapsulated solid-liquid phase change material and water mixed slurry flow in a circular tube heated with constant wall heat flux. The energy equation was formulated by taking into consideration of the heat sink due to melting process and the heat transfer enhancement induced by the motion of microcapsules. The heat source function in the energy equation was derived from solutions for melting in a spherical latent heat material. The governing parameters were found to be latent heat material concentration, pipe diameter. microcapsule diameter, heat flux, and the slurry velocity. The numerical results revealed that mean heat transfer coefficient for latent microcapsule slurry was about 1.3～1.8 times greater than that for the single phase of water. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 68 666 2002 ワイヤーコイルを用いた流動抵抗低減用界面活性剤添加水の直円管内熱伝達促進 191 198 EN Hideo Inaba Naoto Haruki Toru Nakata Akihiko Horibe Naoyuki Furumoto Kenji Sato This paper has dealt with the heat transfer enhancement of flowing water with flow drag reduction additive into a heat transfer tube by inserting wire coils. The non-ion type surfactant was used as the additive to decrease the pipe flow resistance for the heat energy transport system. However, the decrease in the flow resistance was allowed to reduce the heat transfer coefficient in the heat transfer tube. Some kinds of wire coils having different diameters were tried to enhance the heat transfer in the heat transfer tube. The effects of wire coils on the pipe friction and the heat transfer coefficients were elucidated under various experimental parameters of flow velocity, wire coil diameter, pitch and length. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 68 669 2002 ゲル状潜熱蓄冷熱体混合水からの空気泡群による直接接触採冷熱 221 228 EN Hideo Inaba Akihiko Horibe Naoto Haruki Masahiro Murakami This paper has dealt with cold heat extraction characteristics from the gel latent-cold-heat storage-material suspension with surfactant to air bubbles. The gel latent-cold-heat storage-material consisted of n-paraffin as the core latent-cold-heat storage-material and water as a heat transfer medium. The relationship between outflow air temperature in latent-cold-heat release process and various parameters was examined experimentally. As a result, especially concentration of the gel latent material added to water exerted an influence on gas holdup and cold heat extraction characteristics to air bubbles. The non-dimensional correlation equations for the temperature effectiveness of latent-heat storage process were derived in terms of the ratio of water layer height to diameter of latent heat material, Reynolds number of air flow, Stefan number and modified Stefan number including air humidity. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 68 673 2002 等温冷却壁を有する円管内を流動する潜熱マイクロカプセル混合水の蓄冷熱特性 156 163 EN Hideo Inaba Myoung-Jun Kim Akihiko Horibe The present experiment and numerical analyses have been performed for obtaining the cold heat storage characteristics of a water mixture of microcapsules packed with liquid-solid phase change material (PCM) flowing in a pipe cooled under the constant temperature wall condition. The energy equation was formulated by taking into consideration of the heat release due to the PCM solidification process and the heat transfer enhancement induced by the microconvection of microcapsules. The heat source function in the energy equation was derived from solutions for the solidification in a spherical latent heat material. The governing parameters were found to be latent heat material concentration, cooling wall temperature, microcapsule diameter and velocity of water mixture of the microcapsules. The experimental and numerical results revealed that mean heat transfer coefficient for the water mixture of the latent microcapsules was about 1.6～2.5 times greater than that for the single phase of water. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 69 685 2003 対向垂直加熱・冷却壁を有する矩形密閉容器内の潜熱マイクロカプセルスラリーの熱伝達 138 145 EN Hideo Inaba Kouichi Matsuo Akihiko Horibe This paper has dealt with the natural convection heat transfer of the microcapsule slurry composed of phase change material (PCM) as a latent heat storage substance. A rectangular cavity with two opposing heating and cooling vertical walls was selected as the present research model. The temperature difference between heating and cooling walls, the width of the cavity and the PCM concentration were set as parameters of natural convection heat transfer. The heat transfer coefficient of heating and cooling wall, the flow velocity profile and the temperature distribution of the microcapsule slurry were calculated by numerical computation. It was clarified that the transportation of latent heat evolved by melting and solidifying of the PCM in the slurry exerted on a strong influence on the natural convection heat transfer. Moreover, it was found that the heat transfer coefficient reached at the local maximal value with an increase in temperature difference between heating and cooling walls. In addition, Nusselt number was influenced by the transportation effect of latent heat that was caused by melting and solidifying of the PCM. The numerical results revealed quantitatively that the natural convection heat transfer depended on the PCM concentration, temperature difference between heating and cooling walls, and width of the rectangular cavity. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 69 687 2003 強制対流下における球状吸着剤矩形充填層の側面冷却による吸着促進 90 97 EN Hideo Inaba Jeong-Kyun Seo Akihiko Horibe The present paper has dealt with the one-sidewall cooling effect of spherical adsorbent paticles packed in a rectangular bed on water vapor adsorption characteristics by a 2-dimensional numerical analysis. The analysis model was considered that one-sidewall of a rectangular packed bed with the homogeneous spherical silica-gel particles was cooled and another walls were adiabatic. The moist air flowed into the rectangular packed bed with spherical adsorbent particles. The silica-gel B with high adsorption ability over high relative humidity was selected as a suitable adsorbent. Numerical results revealed the effects of moist air inlet humidity and airflow velocity, size of spherical silica-gel particles and width of the rectangular packed bed and the sidewall cooling terperature on the amount of water vapor adsorption. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 70 689 2004 垂直加熱面を有する潜熱マイクロカプセルスラリー充填矩形蓄熱槽の蓄熱特性に関する数値計算 209 216 EN Hideo Inaba Koichi Matsuo Akihiko Horibe This paper has dealt with the Heat storage characteristics of the microcapsule slurry composed of phase change material (PCM) as a latent heat storage material and water. A rectangular cavity with a heating vertical wall, which was filled with the microcapsule slurry, was selected as the present research model. The heating wall temperature, the width of the cavity and the PCM concentration were set as parameters. It was clarified that the transportation of latent heat evolved by melting of the PCM in the slurry exerted on a remarkable influence on the natural convection heat transfer. In addition, it was found that the heat transfer coefficient reached a local maximum value with an increase in initial temperature difference between heating wall and PCM. The heat storage completion time also have a local maximum value with an increase in heating wall temperature due to the latent heat by melting the PCM in the slurry. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 70 690 2004 減圧下における水蒸気凝結現象を利用した固-液相マイクロカプセルスラリー潜熱蓄熱材の採熱特性 444 451 EN Masatoshi Katayama Hideo Inaba Akihiko Horibe Naoto Haruki Tsuyoshi Manabe Recently, studies have begun on a functional heat transfer medium using fine spherical microcapsules encapsulated with phase-change material and dispersed in water. This enables the medium to maintain fluidity whether the phase-change material is solid or liquid. The present study has clarified the laten-heat storage characteristics of microcapsule slurry by increasing its heat transfer coefficient with the help of evolved heat condensing of vapor from the slurry in heat storage. Paraffin wax with the melting point of 62℃ was encapsulated into the fine microcapsules and used as a phase-change material. The cooling coil surface temperature and concentration of paraffin in the microcapsule slurry were selected as the experimental parameters. As a result, the non-dimensional correlation equations of the heat release completion time and heat transfer coefficient were derived in terms of non-dimensional parameters. No potential conflict of interest relevant to this article was reported.

社団法人日本機械学会 Acta Medica Okayama 0387-5016 71 702 2005 直円管内を流動する界面活性剤添加有機プラインの流動抵抗と熱伝達挙動 573 580 EN Naoto Haruki Hideo Inaba Akihiko Horibe Shinji Tanaka Toru Nakata Kenji Sato The flow drag and heat transfer reduction effects of brine flow with drag reduction surfactants have been investigated from the viewpoint of the effective energy consumption in an industrial cooling system. In this study, Oleyldihy-droxyetyl Amine Oxide (ODEAO) of non-ion surfactant was used as a drag reduction surfactant additive, and Ethylene Glycol (EG) was used as a organic brine. It was found that the viscosity of EG brine with ODEAO had the non-Newtonian behavior. The flow friction coefficient and mean forced convection heat transfer coefficient of the EG brine with ODEAO in a straight pipe were measured for each parameter of concentration of EG, concentration of ODEAO and temperature of the brine with ODEAO. The obtained experimental results indicated that the EG brine with ODEAO exerted an influence on the flow drag and heat transfer reduction. No potential conflict of interest relevant to this article was reported.