Yoshiyuki Yamaguchi

A uniform inlet velocity profile is widely used in the numerical simulations of fluid flow and heat transfer in ducts for both incompressible and compressible flows. In incompressible flows, the calculated fluid pressure at the inlet edge is extremely high and affects the calculation of the average pressure. In compressible flows, the fluctuation of pressure in the flow direction results in the fluctuation in the velocity. This has motivated this study to numerically investigate a physically realistic velocity profile at the inlet of a pipe rather than using a uniform velocity profile. The numerical simulations were based on the control volume-based power law scheme and the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The continuity and momentum equations for a flow in a pipe with the rounded inlet corner were solved to obtain a physically realistic inlet velocity profile. The obtained inlet velocity profile was expressed by a simple expression in the range of Reynolds number from 100 to 2000. Using this velocity profile, both the incompressible and compressible flows in a pipe were numerically investigated. The results resolved the previously observed inconsistencies in the pressure that were previously observed in the numerical simulations with uniform inlet velocity profiles.

Two different analytical models were developed on water type Stirling engine. One is the resonance model which qualitatively clarifies the relationship between performance and resonance tube length, and the other is the heat transfer model considering heat transfer between working gas and the tube walls of heating and cooling units. These analyses and experiments were carried out changing the resonance tube length variously, then it was confirmed that the resonance tube length which maximizes the water column amplitude of the power piston agrees well and the oscillations of water columns at that resonance tube length also agrees. In addition, a series of analysis using the heat transfer model was carried out with changing cross sectional area of the resonance tube, loss factors of the elbows, heat transfer area of heating and cooling unit, and pressure of working gas. By this numerical investigation, the effect on the resonance tube length and the work at the length in which these parameters maximize the amplitude of power piston water column was clarified.

It is well known that moist fire protection materials show good fire resistance characteristics. For this reason, these materials are usually made of mixtures of perlite-mortar and high-water-content materials such as silica gels or moist perlites. The latent heat of water plays an important role in the resistance of heat propagation in these materials. A superabsorbent polymer gel that absorbs calcium chloride solution contains much water, and it is one of these high-water-content materials. In this study, numerical simulations of fire resistance tests were conducted for materials of different mixing ratio of perlite-mortar and the super absorbent polymer gel to investigate the effect of the mixing ratio on the fire resistance characteristics. The effective thermal conductivity and the water content of the materials were measured and those values were used for computations. One of the test materials shows excellent fire resistance characteristics, and its fire resistance time at 60 mm thick is about 300 min. The relations of thermal properties and composition of the test material and the effects of mixing ratio of the gels and the perlite-mortar on the fire resistance characteristics are discussed.

Driving device for heat transfer enhancement in a fluid layer heated from above was developed. The device was composed of a coil spring made of shape memory alloy and a closed vessel that is flexible in axial direction telescopically. It shrinks and sinks under water when it is hot, and it expands and floats on water when it is cold. Therefore, the device was named "Negative Thermal Expansion Capsular Object" shortly NTE capsule. Two types of the NTE capsule were proposed. One is the inner spring type and the other is outer spring type. Their performance was proved experimentally. Their operating characteristics were compared to each other and their potentialities in heat transfer enhancement were discussed. As a result, it was proven that the heat transfer enhancement effect could desire NTE capsule of the outside spring type.

Three-dimensional natural convection heat transfer characteristics in a vertical air layer partitioned into cubical enclosures by partition walls of finite thermal conductivity and finite thickness were obtained numerically. The air layer is differentially heated from each surface. In this work, the analyses were performed using finite thickness and finite conductivity of the partition wall for Ra=10(4) and 10(5), and for wide range of thickness and the conductivity of the partition wall. The results were presented in the form of overall convection and total heat transfer coefficient. From the comparison of the results with the traditional ideal boundary conditions such as "conduction, " "adiabatic," and "no-thickness," the correlation of the heat transfer with the actual partition wall and the ideal boundary conditions were developed. After examinations of the results, it was shown that the proportion of the heat transfer quantity in the partition wall to the total heat transfer quantity from the hot wall is a function of a product of the thermal conductivity and the thickness of the partition wall.