Recently there have been a number of enquiries, and requests from the textile industry for the development of high‐strength fibers. Increasing the degree of crystallinity by chain entanglement control is a method to manufacture high strength fibers. The objective of the research project was characterization and evaluation of chain entanglement behavior of polymeric materials through theoretical, and computational approaches to achieve the final target of an optimum design for the melt‐spinning system.The first part of the paper analyses the results of experiments on chain entanglement behavior using OCTA simulation system (Dual Slip‐Link Model Simulator). The second part of the paper deals with the theoretical analysis of the chain entanglement behavior using Mead‐Larson‐Doi theory. The possibility of polymer chain entanglement control is also discussed.
Heat and fluid flow in a horizontal layer is experimentally studied high Rayleigh number conditions by electrochemical mass transfer technique. The experiment simulates a LNG tank heated from the bottom and the sidewalls and cooled from the top surface. From the experiment, following results are obtained. When sidewalls are heated, the heat transfer along the bottom surface is reduced. Heat transfer along sidewalls is independent of bottom heating, and is modeled by an equation for laminar natural convection flow even for Ra>(10)^9.
A model is developed to explain the water movement in a hydrophilic gas diffusion layer (GDL) of PEFC. In the model, a fine hydrophilic columnar fiber is set perpendicular to the surface of the catalyst layer covered by water film. The fiber stands in the channel air flow of the PEFC. The water climbs along the fiber surface up to several tens micron meters for fibers with a diameter range between 3 to 30 micron meters. The calculated results of the evaporation rate from a set of parallel fibers simulating GDL with a void fraction of 0.5 are shown to be much higher than the water generation rate at the catalyst layer with a power density of 1A/cm^2.
An accelerated method is developed for radiative heat-transfer analysis in nongray media by the Monte Carlo method. Instead of deciding all the parameters of each energy particle used in the Monte Carlo procedure by a stochastic method, the wave number assigned to each energy particle is determined by a deterministic method in the present study. This change in the Monte Carlo algorithm reduces the computation time to one-ninth of the original time. To reduce the amount of iteration required to converge the temperature profile in a nongray media layer, an acceleration factor is incorporated to determine the new values of temperature in each iterational loop. The value of the acceleration factor is found to be related to the optical thickness of each media element. By using an appropriate acceleration factor, the amount of iteration is reduced to one-fourth of the original. Moreover, the total computation time becomes 1/36 of the original by the two improvements.
Combined forced and natural convection heat transfer from upward-faceing horizontal heated flat plate is nodeled by phenomenological method modifying natural convection heat transfer model at high layer. In this model, mixed or pure natural convection heat transfer coefficient is estimated as averaged one. In the model new boundary layer is assumed to start its growth from a position that previous layer finishes by releasing hot fluid plume "Thermal", and vanishes again at a point where a certain critical condition is satisfied. This theory can explain the transitional phenomena from pure forced convection to pure natural convection through mixed convection. The varidity of the theory is confirmed by experiment using upward-faceing horizontal heated flat plate.
