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Heat transfer characteristics of a dilute surfactant/water solution in a two dimensional channel has been experimentally investigated. It is known that surfactant solutions do show a large sensitivity of their drag reduction and heat transfer reductlon effectiveness on temperature. In the present experiment, the heat transfer at fixed Reynolds number increased three times when temperature increases only 3 deg. Temperature profile measurements in the thermal boundary layer were also made. It was found that high diffusivity layer exists near the wall in the drag reducing thermal boundary layer. The relation with high difussivity layer and heat transfer coefficient is discussed.

The heat transfer enhancement of drag-reducing flow of high Reynolds number in a two-dimensional channel by utilizing the characteristic of fluid was studied. As the networks of rod-like micelles in surfactant solution are responsible for suppressing the turbulence in drag-reducing flow, destruction of the structure of networks was considered to eliminate the drag reduction and prevent heat transfer deterioration. By inserting wire mesh in the channel against the flow, the drag-reducing function of the micellar structure in surfactant aqueous solution was successfully switched off. With the Reynolds number close to the first critical Reynolds number, the heat transfer coefficient in the region downstream of the mesh can be improved significantly, reaching the same level as that of water. The region with turbulent heat transfer downstream of the mesh becomes smaller as the concentration of surfactant in the solution increases. Three types of mesh of different wire diameter and opening space were evaluated for their effect in promoting heat transfer and the corresponding pressure loss due to blockage of the mesh. The turbulent intensities were measured downstream from the mesh by using a Laser Doppler Velocimetry (LDV) system. The results indicated that the success of heat transfer enhancement is due to the strong turbulence promoted by the mesh which destroys the network of rod-like micelles by applying high shear stress and thus relaxing the shear induced state (SIS).

To obtain acceptable ice-slurry characteristics for low-temperature energy storage and transport systems, methods for preventing ice recrystallization must be developed. Antifreeze proteins (AFPs) are known to be an effective additive in ice-slurry systems, making ice slurries resistant to recrystallization, and thereby improving flowability. However, AFPs are expensive and easily degrade. Therefore, we investigated the use of silane coupling agents (SCAs) as substitutes for AFPs. To determine the SCA's ability to control crystallization, in this study we observed free growth of ice crystals in SCA solutions, and found that SCAs that form long-chain molecules in water are effective for crystallization control. Then we analyzed ice crystal surfaces containing AFPs and SCAs by using scanning tunneling microscopy (STM) to investigate the mechanism of crystallization control with these additives. STM observation of ice crystal surfaces showed that the AFP molecules are adsorbed onto the ice crystal surface on the {2021} planes along the 〈0112〉 directions, preventing further crystal growth from the site where the AFP molecules are adsorbed. Furthermore, we found that long-chain SCA molecules are adsorbed onto ice crystal surfaces, preventing crystal growth from the site where the long-chain SCA molecules are adsorbed.

Micromachining of transparent materials with a well-defined pattern of lines and spaces was carried out by laser-induced backside wet etching (LIBWE). The etch rate of a fused silica plate ranged from 5 to 25 nm/pulse with a KrF laser irradiation from 400 to 1300 mJ/cm2, using an acetone solution containing pyrene at a concentration of 0.4 mol/dm3. Threshold fluences for etching of fused silica and calcium fluoride plates were 240 and 740 mJ/cm2, respectively, which are remarkably lower than those with conventional KrF laser ablation. The mechanism for etching is explained by the attack of super-heated molecules generated by laser ablation of a pyrene–acetone solution during cyclic multiphotonic absorption.

We investigated the laser ablation of an elastomer composite with nanosecond- (ns-), picosecond- (ps-) and femtosecond- (fs-) pulsed UV lasers (ns-laser: λ=248nm, τ=30ns; ps-laser: λ=263nm, τ=8ps; fs-laser: λ=248nm, τ=500fs). Upon laser irradiation, a unique microstructure on the surface of the elastomer composite (acrylate polymer) containing carbon black (particle size: 18-30nm) was observed. The laser-ablated surfaces were analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The formation mechanism is discussed in terms of thermal effects induced by the different pulse durations of the lasers.

The liquid ring compressor (LRC) is a compressor suitable for a heat pump which uses water as a working fluid. The LRC has several features: (1) large suction speed; (2) low discharge temperature realized by the ring liquid; and (3) simple structure. However, in order to enlarge the working temperature region of such heat pumps toward lower temperature levels, it is necessary to improve the volumetric efficiency of the LRC, especially in the low suction pressure region. Therefore, a helical liquid ring compressor (HLRC) which has helical blades has been newly designed, as one of the attempts to obtain a higher volumetric efficiency. The HLRC is able to separate a suction space from a compression space along the axis and improve the volumetric efficiency. An experimental test has verified that the suction/compression mechanism of the HLRC functions as expected. © 2000 Scripta Technica, Heat Trans Asian Res, 29(8): 660–673, 2000

The KrF laser ablation of polyarylsulfone (PAS) was investigated for fluences between 90 and 200 mJ/cm2. Neutral fragments were probed using laser post ionization (193 nm) time-of-flight (TOF) mass spectrometry. Decomposition of PAS was found to occur mainly through scission of C-S and C-O bonds as well as via decomposition of the phenylene rings in the chain. The dependencies of both the flight velocities and the Knudsen layer temperature of the fragments on fluence suggest that PAS ablation is a photothermal process. In contrast, the high average translational energies (up to a few tens of eV) indicate the existence of a non-thermal component in the process. In terms of the plume dynamics, the fitting of the arrival profiles of the fragments with a shifted Maxwell–Boltzmann distribution over the full fluence range indicates the existence of a collision during the adiabatic expansion process.

Magnetic attractive forces acting on paramagnetic oxygen have recently been found to induce gas e ow and promote combustion. The study of the interaction between electrically nonconducting gases and magnetic e elds is a new interdisciplinary research area called “ magnetoaerodynamics.” The authors present the magnetic body force acting on the gas and the governing equations for magnetoaerodynamics. The authors used these equations to evaluate the N 2‐air jet numerically to understand the mechanism and physics of this phenomenon. The key results are as follows: 1 ) The magnetic body force becomes nonconservative under gradients of both the O 2 gas concentration and themagneticstrength. 2 )Thenumerical analysesclarifythemechanism of thecoupling between magnetic forces and the convective motion and indicate the existence of air convection and the N 2 jet due to the nonconservative magnetic body force. 3 ) The maximum velocity of the N 2 jet, umax, increases with the magnetic strength at the center of the magnet, B0. For B0 =1:5 T and entrance velocity of the N 2 gas of 7.4 cm/s, umax =44 cm/s. 4) Measured velocities were in good agreement with our simulation. This study suggests the potential use of magnetic e elds to control gas e ows and combustion.

The adsorption of antifreeze protein (AFP) molecules to the ice crystal surface during melt growth from an AFP solution results in disturbance of the growth kinetics at the surface interface. In this paper, the growth pattern related to the potential for crystal growth as well as the crystal surface topography have been studied. The crystal shape and size were found to be strongly dependent on the supercooling in the crystal’s surrounding liquid. In between a transition temperature and the freezing temperature, needle-type crystals were formed, growing rapidly in the c-axis direction. The surface was investigated using a scanning tunneling microscope (STM) and a systematic groove/ridge pattern aligned 653 ($53) to the hexagonal side on one bipyramidal plane observed with length and width similar to the size of the AFP molecule. The depth of the grooves, ranging from 2 to 10 nm indicates the curvature of ice. ( 1999 Elsevier Science B.V. All rights reserved.

We present numerical simulations of the velocity and temperature distributions of a nonconducting fluid (water) heated from below in the presence of an imposed, nonuniform magnetic field, generated with a solenoid-type magnet. The vertically placed magnet induces horizontal and vertical magnetic forces due to the gradient of magnetic strength, and the horizontal force is found to play an important role to damp natural convection. When an imposed magnetic field of strength H 0 in the middle of the magnet, is less than a critical value, H 0c , the damping effect increases with increasing H 0 . For H 0 > H 0c , natural convection is completely replaced by convection induced by the magnetic field. Our results indicate a novel method to control convection of nonconducting fluids, especially in crystal formation processes.

The photolysis of naphtho[1,8- de ]-1,3-dichalcogeninylidene 1-oxide derivatives ( 4 and 5 ) at >290 nm generates ketenes together with naphtho[1,8- cd ]-1,2-dichalcogenole, which were confirmed by the trapping experiments and the direct observation using IR spectroscopy. The generation of ketenes from the selenium compounds 5 is more effective than that from the sulfur analogs 4 .

Microstructures formed by excimer laser ablation of uniaxially stretched poly(ethylene-2,6-naphthalate) (PEN) films were analyzed as a function of draw ratio, laser fluency, and number of pulses. Before ablation, stretched films with draw ratio higher than 3 exhibit band like structure on the surface running perpendicular to the drawing direction. By TEM observation of the cross section, this structure was found to extend into the bulk region. Upon laser pulse irradiation, microstructures are formed on the surface whose pattern and pitch are similar to those for the original band like structure. With further irradiation of pulses, pleated structures were formed with pitch larger than that for the original band like structure. Spectroscopic analysis of the pleated structure was conducted on the particles scratched off from the ablated surface. It was indicated that the pleated parts were amorphous but partially elongated.

Excimer laser ablation of an elastomer composite containing carbon black produced conical microstructures on the ablated surface upon irradiation with the second harmonic of Nd+:YAG laser. Based on studies by scanning electron microscopy and quadrupole mass spectrometry, the mechanism for the conical structure formation was discussed by comparison of the formation of cone-like microstructures produced by KrF excimer laser ablation.

The effects of target modification on film deposition rates of hexaphenyldisilane (HPDS) due to ablation by a 248-nm KrF excimer laser at different fluences and repetition rates were studied. When the repetition rate was less than 20 Hz and the laser fluence was below 100 mJ/cm2, some interlocked cones were generated on the surface of the HPDS targets, which caused the laser ablative process to grind to a halt after a given number of laser pulses. However, when the repetition rates exceeded 20 Hz, it was possible to prevent the cones from being interlocked, so that the laser ablative process or film deposition process could continue, even though a similar laser fluence was used. The doping of other Si-based organic materials into HPDS affected the critical laser fluences and repetition rates below which the interlocked cones were generated. Finally, a general physical model of the target modification for laser ablation of Si-based organic materials was suggested based on the laser processing parameters.

The rising speed and dissolution rate of a carbon dioxide bubble in slightly contaminated water were investigated experimentally and numerically. We developed an experimental system that uses a charged-coupled device (CCD) camera coupled with a microscope to track the rising bubble. By precisely measuring the bubble size and rising speed, we were able to accurately estimate the drag coefficient and the Sherwood number for the dissolution rate of gas bubbles at Reynolds numbers below 100 in the transient regime, where the bubble changes from behaving as a fluid sphere to behaving as a solid particle. We also numerically estimated the drag coefficient and Sherwood number of the ‘stagnant cap model’ by directly solving the coupled Navier–Stokes and convection–diffusion equations. We compared our experimental results with our numerical results and proposed equations for estimating the drag coefficient and Sherwood number of the bubble affected by contamination and clarified that the gas–liquid interface of the carbon dioxide bubble in water is immobile. We also show that the experimental and numerical results are in good agreement and the stagnant cap model can explain the mechanism of the transient process where the bubble behaviour changes from that of a fluid sphere to that of a solid particle.

We investigated the gas exchange process of a spherical bubble rising in water. We developed an experimental system that use a CCD camera coupled with a microscope to follow the rising bubble. By measuring the bubble size and the rising speed from the bubble motion data recorded with a personal computer, we could precisely estimate the gas exchange rate across the bubble-liquid interface. We also calculated the gas exchange process by estimating the drag coefficients and Sherwood number. The measured and calculated change of bubble radius agree well when the bubble is strongly affected by contaminants. The results also show that when the concentration of carbon dioxide in water is small, the normalized equilibrium radius can be estimated by the initial partial pressures in the bubble and by the pressure of dissolved gas in the water.

Photolyses of 1,2;4,5- and 1,2;3,4-benzenetetracarboxylic dianhydrides (3a and 3b), which would be precursors of 1,4- and 1,3-benzdiyne (2a and 2b), were studied by a matrix isolation technique and a selective irradiation technique using three kinds of excimer lasers in order to directly observe intermediates produced stepwise. The photolyzed products in the matrix were characterized by FT-IR and UV–vis spectroscopies. As a result, sequential decarboxylation and decarbonylation from one anhydride moiety of 3a and 3b produced corresponding benzocyclopropenone and benzyne intermediates in the initial stage. In both the photolyses, further decomposition proceeded to form 1,3,5-hexatriyne (4) as a final product. Although neither 2a nor 2b was observed directly, it seems that the benzdiynes including another isomer, 1,2,3,5-tetradehydrobenzene (2c), participated as precursors to acyclic C4H–Câ–·C–H biradical 13 and/or carbene 14, which were formed in the reaction from benzdiyne to 4. Additionally, as a result of CCSD(T)/6-31G**//CASSCF(4,4)/6-31G** level calculations for 2a, 2b and 2c, it is clear that the energy of 2c was comparable to those of 2a and 2b, which supports the formation of 13 from 2a/2b and of 14 from 2c after isomerization of 2a→2c and 2b→2c.

In order to clarify the growth of ice crystals containing adsorbed silane coupling agents (SCAs), a fundamental and microscale analysis has been conducted. By using an optical microscope, the growth patterns of the ice crystals were experimentally investigated while neglecting the influence of heat flux. It was found that some SCAs that particularly have three hydrophilic groups in a molecule can be adsorbed by the ice crystal surface preventing further growth of the crystals towards a-axis direction. We also investigated the surface of the ice crystals by using a scanning tunneling microscope (STM) in order to determine the influence of SCA on the microscale surface structure. Systematic grooves aligned about 75° to the hexagonal side on one bipyramidal plane were observed. Those grooves were at least 500 nm long, 30∼70nm deep, and existed at about 200 nm intervals.

It is known that frictional drag in turbulent flow can be reduced considerably by adding a small amount of surfactant to the fluid. In order to investigate the mechanism of this phenomenon, the turbulent characteristics in surfactant aqueous solution flow in a planer two-dimensional channel has been investigated through visualization by dye injection, velocity measurements by LDV and time scale measurements through temperature fluctuation. Analysis of velocity fluctuation showed that Reynolds shear stress and turbulence production is diminished in drag reducing flow. Coherent structure was not obvious in this flow. It was observed that integral time scale become large near the wall. This finding suggests smaller dissipation and weakening of cascade process of turbulence energy. Lower turbulent diffusion can be explained by these characteristics found in drag reducing flow.

The high heat flux region near the burnout heat flux has recently been utilized not only in the nuclear power plant and the boiler system but also in the electrical and laser equipments. Since the mechanisms of the burnout heat flux modeled so far has some unclear aspects in predicting the dynamics behavior of thin liquid films under the boiling bubbles, the thickness of the boiling bubbles has been challenged to measure in this paper. To measure the thickness of the liquid film on the heat transfer surface under the boiling bubble, a capacitance probe has been newly devised. The thickness of the thin liquid film under the boiling bubble was obtained, and the relationship between the bubble shape around the bottom rim and the thickness of the thin liquid film under the bubbles (micro layer) was clarified for predicting the critical heat flux mechanism.

Major peaks were assigned to direct fragments and recombination products ejected from the PS surface. The arrival profiles of these ablation products varied from product to product and were fitted by using a shifted Maxwell–Boltzmann distribution with a center-of-mass flight velocity [(1.4-5.6) ×105 cm/s] and a Knudsen layer temperature (350–3810 K). Two types of ablation products, whose velocities and temperatures showed different dependences on laser fluence, were found to exist. Dynamical aspects in the decomposition of the polymer chain, the ejection of various fragments, and their expansion are discussed on the basis of a photothermal ablation model, where a heated surface layer with a temperature gradient along its depth plays an important role.

The surface dehydrochlorination of poly(vinyldenchloride) film was performed to produce a conjugated polyyne and polyene structures by photo-irradiation with a KrF excimer laser at 248 nm in a vacuum chamber. The reaction was confirmed by detection of HCl with a mass spectrometer and by measurement of chlorine content on the film with X-ray photoelectron spectroscopy. UV-visible absorption spectroscopy for the laser-treated film showed the formation of new broad absorption bands in the visible and near IR region, indicating that sequential dehydrochlorination induced the formation of conjugated carbon multiple bonds in the polymer chain. Its conjugation number is estimated to be 30 for a triple bond and 10–25 for a double bond from the peak positions on the Raman spectrum of the film. ESR spectra of laser-irradiated PVDC powder also showed long-lived radicals having a narrow band width (ΔHpp = 0.15 mT), suggesting that the radicals were delocalized on the conjugated bonds. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2483–2487, 1998

Laser ionization time-of-flight (TOF) mass spectrometry has been employed to probe the dynamics of ablation of polyethersulfone (PES) at 266 nm. Neutral products arriving at an ion extraction position, which was 65 mm from a PES film surface, were detected by delaying a post-ionization laser pulse with respect to an ablation laser pulse. At a low fluence of 30 mJ/cm2, the strongest peak indicating early arrival of C3H3 (m/e = 39) was observed at post-ionization delay times of 12−22 μs. As the delay time increased (16−46 μs), some prominent peaks (m/e = 140, 164, 188, 216, 234, 262, 264, 280, 288, 312, 333, and 336) and many weak peaks with m/e up to about 690, which were assigned to direct fragments from PES or secondary products, were observed. Analysis of the products indicates that the decomposition of PES occurs due to both the scission of the polymer chain itself and the cleavage of some phenylene rings in the chain. The average flight velocities of major products ranged from 1.8 × 105 cm/s for C15H1...

In order to control both molecular structures and molecular orientation simultaneously, we investigated organic molecular beam deposition combined with a laser-induced photochemical reaction. Bis(ethynylstyryl) benzene (BESB) films of trans,trans-isomer were deposited by this new method. The cis,cis-molecules were sublimed and cis-to-trans photoisomerization was conducted upon KrF excimer laser irradiation (λ = 248 nm) in this process. The laser irradiation after and during the deposition at the substrate temperature of 25 °C yielded amorphous films. In contrast, the growth of well-oriented crystalline films was achieved upon the laser irradiation during the deposition at the substrate temperature of 60°C. At this substrate temperature only the trans,trans-molecules were deposited on the substrate surface, which indicated that unreacted cis,cis-isomer was re-evaporated from the substrates. It can be explained that the crystal growth proceeds favorably due to the surface migration of the trans,trans-isomer and the absence of the cis,cis-isomer. It was thus found that simultaneous progress of the laser-induced isomerization and the deposition caused the growth of the well-oriented crystalline films of trans,trans-BESB.

The gas dissolution process of a spherical rising gas bubble was investigated experimentally and numerically. We developed an experimental system that uses a chargedcoupled device (CCD) camera coupled with a microscope to follow the rising bubble. By measuring the bubble size and the rising speed from the bubble motion data captured by a personal computer, we could precisely estimate the drag coefficients and the Sherwood number for the dissolution of gas bubbles at Reynolds numbers below 100. We also numerically estimated the drag coefficients and Sherwood number for dissolution of gas bubbles in an infinite liquid by directly solving the Navier–Stokes equation and the convection-diffusion equation. The experimental and numerical results are in good agreement. Moreover, we compared the experimental results with several proposed equations for estimating the drag coefficients and Sherwood number and clarified the applicable region of each equation. Finally, based on correlation with the numerical results, we present an equation for estimating the Sherwood number in the range where the Reynolds number is less than 100 and the Peclet number is greater than 1.

Excimer laser ablation of an elastomer composite containing carbon black produced dome-like and cone-like microstructures on the surface at 90 mJ cm −2 and 500 mJ cm −2 , respectively. The mechanism for microstructure formation was investigated by scanning electron microscopy (SEM) and quadrupole mass spectrometry (QMS).

Formation of microstructures on surfaces of polymer materials by excimer laser irradiation is reviewed from the viewpoint of morphological surface modification. Although the microstructures is not explained by a simple model, the factors controlling the shape and size of microstructures are discussedon the basis of SEM micrographs of polymer surfaces. In addition it is shown that the microstructure formedby excimer laser ablation of acrylate rubber containing carbon black has a visco-elastic property which is interesting in tribological control. Finally the applications of microsctures on polymer materials are described.

The gas dis solution process of a spherical rising carbon dioxide bubble in water was investigated experimentally and numerically. We developed an experimental system that use a CCD camera coupled with a microscope to follow the rising bubble. By measuring the bubble size and the rising speed from the bubble motion data captured by a personal computer, we could precis ely estimate the drag coefficients and the Sherwood number for the dis solution of gas bubbles at Reynolds numbers below 100. The experimental results show that the drag coefficients of the carbon dioxide bubble in water show the same value of solid particle even when we use relatively clean water. We also numerically estimated Sherwood number for dis solution of gas bubbles in an infinite liquid by directly solving the Navier-Stokes equation and diffusion equation. The experimental and numerical results are in good agreement. Moreover, we compared the experimental results with a proposed equation for estimating the drag coefficients and Sherwood number and clarified the applicable region of the equation.

ぎ酸メチルを介在した二段階液相メタノールの分解・合成反応による長距離熱エネルギー輸送システムの研究・開発を紹介した.ぎ酸メチルの水素化によるメタノールの合成反応における触媒内の輸送過程も含めた総括反応速度に対し, プレート式ラネー銅触媒の展開条件の影響を検討するため, オートクレーブ反応装置を用い, 反応によるガスの圧力の減少量を測定し, 総括反応速度を求めた.触媒の展開時間を変えて, 触媒の活性層の厚さの総括反応速度に対する影響を調べた.また, 触媒の内部の表面積, 細孔径, 電子顕微鏡写真などミクロ的な視点からの観察結果も得た.触媒粒子のミクロな観察結果と総括反応速度の実験結果より, 各触媒厚さにおける触媒の粒子径や形状等のミクロな構造に伴う触媒の活性化の変化によって, そして, 触媒内部の輸送過程の影響も加わって, 総括反応速度の最適値が存在することが解った.

For the development of flowable ice for storage and long distance transportation purposes, that is resistant to recrystallization and contains defined crystal structures, the characteristics of an ice slurry generated from an antifreeze protein solution have been examined. Three methods for obtaining the antifreeze protein are described. In crystal growth studies it has been shown that controlling the supercooling is important to generate the desired needle-type crystals, coming from an effective adsorption of antifreeze proteins to the ice surface. The ice slurry's thermal storage ability is found using a differential scanning calorimeter. Furthermore, the slurry's flowability is examined using both a capillary tube viscometer and a test loop, the latter is used for comparison of the pressure drop with liquid pure water as well as for the visualization of the slurry flow. For an ice content of 30%, the pressure drop in a 6-mm-i.d. tube at 1 m/s flow is found to be twice the value for liquid pure water.

The ablation of pentafluorophenylazide (FPA), which was isolated in a chemically inert C6F14 solid matrix at 85 K, was carried out by irradiation with a KrF excimer laser in vacuum. A large amount of pentafluorophenylnitrene (FPN) was ejected explosively as fragments from the matrix during irradiation. The photolysis of FPA was followed by mass spectrometry, UV–visible absorption spectroscopy and optical emission spectroscopy. It was found that the fragment beam of photolysed FPA was useful for the surface chemical modification of organic materials, such as a poly(ethylene terephthalate) film and alkylthiol monolayer. Surface analyses of these materials by X-ray photoelectron spectroscopy and Fourier transform IR reflection absorption spectroscopy indicated that FPN was immobilized on the surface through chemical bonding. The modified surface showed hydrophobic properties due to a decrease in surface polarity by the deposition of the fluorinated group of FPN. © 1997 Elsevier Science S.A.

Perturbation effects of additional linkers on the spin−spin coupling in biphenyl-4,4‘-dinitrene (1) were examined by introducing a linking group between 2- and 2‘-positions of 1. Five different doubly linked systems showed triplet ESR spectra corresponding to quinonoid dinitrenes. Curie law analyses suggested that all those triplet states were thermally excited triplet states. In addition, the singlet−triplet energy gaps, which were determined by the Curie law analyses, were well correlated with their corresponding zero-field-splitting (zfs) D values. The result could be explained by the stability of dinitrene character which is estimated from the resonance energy of the intervening π-system. Our semiempirical molecular orbital calculations supported the experimental correlation between the singlet−triplet energy gap and the zfs D value.

The adhesion of the PTFE substrate whose surface was modified upon ArF excimer laser irradiation under a hydrazine atmosphere was examined by a tensile test for the sample prepared by jointing the laser-treated PTFE substrate and a carbon steel rod through chemical adhesives. The tensile strength at breaking point was over 12 MPa almost comparable to that of PTFE itself. The modified layer formed as a result of laser processing had a strong intimacy with PTFE itself and possessed mechanical properties comparable to that of PTFE. The degree of modification was gradual from the upper layer to the inner layer of PTFE.

Drag coefficients of a spherical rising gas bubble were estimated experimentally and numerically. We developed an experimental apparatus in which a CCD camera with a microscope follows the rising bubble and used it to precisely estimate the drag coefficients of the bubble below Reynolds number of 100 by measurement of the bubble size and the terminal velocity. We also estimated numerically drag coefficients of a gas bubble in an infinite liquid by directly solving a Navier-Stokes equation. The experimental results agree well with the numerical results. Moreover, we compared the experimental results with several proposed equations for estimating drag coefficients and determined the region of applicability of each equation. Finally, we proposed an equation for estimation of drag coefficient by correlating with experimental results.

Ice slurry systems have recently attracted much attention in Japan for their ability to reduce electricity peaks caused by high energy-consumption by air-conditioners in the daytime. While conventional storage systems involve compact ice generation, these days ice slurry systems are introduced for transporting flowable ice in pipelines. Even though seveal methods for dynamic ice formation have been researched and developed, there are still problems related to the recrystallization of ice crystals for realizing long-term storage and long-distance transportation. Antifreeze proteins (AFPs) strongly influence ice crystal growth by adsorption to the ice crystal surface. In this paper. we present results from investigations of ice slurry made from an AFP solution, and of its thermophysical properties such as thermal storage and flowability characteristics, as well as the results from observation of crystal growth and ice slurry flow. For ice storage applications, the benefits of this additive are the ability to create well-defined crystal structures and the inhibition of recrystallization.

Recently, magnetic field gradients have been found to induce gas flow and promote combustion in diffusion flames. For example, when N2 gas stream was injected into air toward a weaker magnetic field, it was accelerated and behaved like a jet stream. This phenomenon was explained qualitatively by a magnetic attractive force acting on paramagnetic oxygen gas. In this study, such a magnetically induced jet stream of N2 gas was quantitatively analyzed. First, the magnetic body force acting on the gas flow and the governing equation of magnetic gas dynamics are presented. Using them, a numerical simulation was carried out for N2-Air convective flow under a magnetic field gradient. Calculated results show that the jet flow is accelerated to 80 cm/sec when the initial N2 gas velocity is 3.9 cm/sec and maximum magnetic induction is 1.5 T. Furthermore, calculation shows the existence of a convective air flow around the N2 jet flow. The results of the present study show good agreement with the experimental results.