Yasuo Kurosaki

Bio: Yasuo Kurosaki is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Heat transfer & Heat exchanger. The author has an hindex of 9, co-authored 69 publications receiving 283 citations. Previous affiliations of Yasuo Kurosaki include University of Electro-Communications.

Downward flame spread along two vertical, parallel sheets of thin combustible solid

Abstract: This paper is concenred with the steady, two-dimensional vertical downward spread of flame along two parallel sheets of paper placed in air. The purpose of the present study is to correlate experimentally the flame spread rate, the distance separating, the two sheets and the width of the paper, and to model theoretically the flame spread in the presence of interaction of multiple flames. The flame spread rate depends more on the separation distance between the two sheets of paper than on the width of the paper. Within the narrow space region, C≤0.3 cm, the flame spread rate is reduced to about a half of that for burning of a single sheet of paper. On the other hand, in the wider space region, C≥0.5 cm, the flame spread rate increases and becomes greater than that of a single sheet. It reaches the maximum value at a finite separation distance, C=1.5∼2.0 cm. A simple theoretical model was used to explain the experimental results. The theoretical flame spread rates predicted from the model were found to be in good agreement with the experimental data. It is concluded from the experimental and theoretical results that in the narrow space region between the burning sheets of paper the convective heat transfer predominates and controls the flame spread rate, whereas in the wider space region the radiative heat transfer from the opposite flame and ember plays an important role in controlling the flame spread rate.

Downward flame spread along several vertical, parallel sheets of paper

Abstract: This paper is concerned with the steady, two-dimensional vertical downward spread of flame along several, parallel sheets of paper in air. The flame spread regime is divided into the following classes according to the separation distance. In the wider space region, C ≥ 5 mm, the flame spread rate is greater than a single sheet of paper and passes through a maximum value at a finite separation distance. It also increases with the number of sheets and approaches asymptotically a constant value. A simple model for the analysis of heat transfer to the unburned paper is employed to predict the flame spread rate in the presence of multiple flames. On the other hand, within the narrow space region, C ≤ 3 mm, the flame is unable to spread vertically downward over three parallel sheets of paper because no flame can exist in the narrow space between sheets of paper.

Experimental study on heat transfer from parallel louvered fins by laser holographic interferometry

Abstract: The objectives of this paper are to study experimentally the details of the heat transfer process in louver arrays and to propose the geometrical arrangement of louvers that would be most effective in improving the performance of heat exchangers. That goal is approached via the following steps. In the first step, the temperature field around louvers is visualized, employing the simple flat-louver model made of a thin bakelite plate and thin nichrome foil heaters, and at the same time the heat transfer coefficient on the louvers is measured. The isotherms are visualized by means of laser holographic interferometry. The isotherms for various louver arrangements were obtained; the thermal boundary layer and the wake generated by an upstream louver extending toward the downstream louvers were observed. It is found that the heat transfer coefficient on the downstream louver is sensitive to the behavior of those boundary layers and wakes. In the second step, the arrangement of louvers is examined with the purpose of enhancing heat transfer. A displacement of a downstream louver out of the influence of the heated air wake from the preceding upstream louver is proposed on the basis of both the observation of isotherms and the measurement of heat transfer coefficients in staggered louver arrays. The experimental results indicate that the performance of heat exchangers may be improved by rearranging the louvers with a small-magnitude displacement.

Method for connecting transparent thermoplastic resin member by laser

Abstract: PROBLEM TO BE SOLVED: To provide a method which can deal with a precise application and connect a transparent resin member in an extremely short time without impairing an appearance of a product by maintaining the member excellent transparency original in the member even after the connection SOLUTION: The method for connecting the transparent thermoplastic resin member by laser comprises the steps of superposing a plurality of transparent resin members at contact surfaces in a state in which a very thin infrared absorption transparent film having an absorbability of a laser beam is interposed between adjacent transparent thermoplastic resin members each having non- absorbability of the laser beam, and fusion-bonding the resin members by irradiating the outside surfaces of the transparent resin members with the laser beam When the superposed resin members are irradiated with the laser beam, the infrared absorbing transparent film interposed between the transparent resin members absorbs the radiation energy of the laser beam to generate a heat, thereby fusion-bonding the transparent resin members COPYRIGHT: (C)2003,JPO

Thermal Conductivity of Nanoparticle -Fluid Mixture

Abstract: Effective thermal conductivity of mixtures of e uids and nanometer-size particles is measured by a steady-state parallel-plate method. The tested e uids contain two types of nanoparticles, Al 2O3 and CuO, dispersed in water, vacuum pump e uid, engine oil, and ethylene glycol. Experimental results show that the thermal conductivities of nanoparticle ‐e uid mixtures are higher than those of the base e uids. Using theoretical models of effective thermal conductivity of a mixture, we have demonstrated that the predicted thermal conductivities of nanoparticle ‐e uid mixtures are much lower than our measured data, indicating the dee ciency in the existing models when used for nanoparticle ‐e uid mixtures. Possible mechanisms contributing to enhancement of the thermal conductivity of the mixtures are discussed. A more comprehensive theory is needed to fully explain the behavior of nanoparticle ‐e uid mixtures. Nomenclature cp = specie c heat k = thermal conductivity L = thickness Pe = Peclet number P q = input power to heater 1 r = radius of particle S = cross-sectional area T = temperature U = velocity of particles relative to that of base e uids ® = ratio of thermal conductivity of particle to that of base liquid ¯ = .® i 1/=.® i 2/ ° = shear rate of e ow Ω = density A = volume fraction of particles in e uids Subscripts

Heat transfer enhancement by using nanofluids in forced convection flows

Abstract: In the present paper, the problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water–γAl2O3 and Ethylene Glycol–γAl2O3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol–γAl2O3 nanofluid appears to offer a better heat transfer enhancement than water–γAl2O3; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered. For the case of radial flow, results have also shown that both the Reynolds number and the distance separating the disks do not seem to considerably affect in one way or another the heat transfer enhancement of the nanofluids (i.e. when compared to the base fluid at the same Reynolds number and distance).

Heat transfer and pressure drop correlations for the rectangular offset strip fin compact heat exchanger

Abstract: The development of thermal-hydraulic design tools for rectangular offset strip fin compact heat exchangers and the associated convection process are delineated. On the basis of current understanding of the physical phenomena and enhancement mechanisms, existing empirical f and j data for actual cores are reanalyzed. The asymptotic behavior of the data in the deep laminar and fully turbulent flow regimes is identified. The respective asymptotes for f and j are shown to be correlated by power law expressions in terms of Re and the dimensionless geometric parameters α, δ, and γ. Finally, rational design equations for f and j are presented in the form of single continuous expressions covering the laminar, transition, and turbulent flow regimes.

Numerical investigation of laminar flow and heat transfer in a radial flow cooling system with the use of nanofluids

Abstract: Nanofluids, because of their enhanced heat transfer capability as compared to normal water/glycol/oil based fluids, offer the engineer opportunities for development in areas where high heat transfer, low temperature tolerance and small component size are required. In this present paper, the hydrodynamic and thermal fields of a water–γAl2O3 nanofluid in a radial laminar flow cooling system are considered. Results indicate that considerable heat transfer enhancement is possible, even achieving a twofold increase in the case of a 10% nanoparticle volume fraction nanofluid. On the other hand, an increase in wall shear stress is also noticed with an increase in particle volume concentration.

Thermal radiation properties of dispersed media: theoretical prediction and experimental characterization

Abstract: The aim of this paper is to carry out a review of radiative heat transfer in dispersed media. Firstly, the solution of the governing equations for radiative transfer in such media as well as the theoretical basis for the modelling of their radiative properties are briefly recalled and discussed. Thereafter, emphasis is placed on practical applications dealing with several types of particulate media which play an important role in a number of industrial processes. Radiative property predictive models as well as studies dealing with property experimental determination are examined and discussed.