Study on the control of longitudinal dispersion in oscillatory flows in pipes and on the presentation method of its phenomena

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Longitudinal heat transfer between two fluid reservoirs of different temperature is highly enhanced by fluid pulsation in capillary pipes that connect the reservoirs. The heat transfer is known to be proportional to the product of the longitudinal temperature gradient and the square of the pulsating fluid displacement from analyses for single circular pipes. Pipe bundles are used in practical applications to obtain a sufficient amount of heat transfer. There exist spaces between each three pipes in circular pipe bundles, which deteriorate the heat transfer characteristics. To avoid this disadvantage, pipes of triangular, square and hexagonal section as well as of circular on were considered. Although the triangular pipe showed the best heat transfer characteristics as a single pipe, it was cleared that the wall thickness and its heat conduction coefficient were important parameters to determine the performance as pipe bundles from the analysis under the conditions of the same cross sec … More tional area, wall thickness and fluid pulsation amplitude. The effect of wavy wall was also investigated changing the wave number of the wavy wall, its amplitude and the fluid pulsation frequency and amplitude. The heat transfer was enhanced with the amplitude of the wall waviness. The wavy wall pipes were superior to smooth ones in dynamic response of heat transfer controled by fluid pulsation amplitude and frequency.The mechanism of the heat transfer of this apparatus was investigated closely. We found a region where heat was transferred toward higher temperature end and this occurred in the region where the phase lag between the pulsations of fluid and temperature exceeded π/2. Then visualization methods have been investigated to explain these unseen phenomena to nonexperts including students as well as experts. It was found effective that each image should contain limited informations presented by primitive variables. The phase difference between the pulsations of fluid and temperature was most effectively presented by animations using wire frame model of different colors. The heat flow was obtained quantitatively solving the governing equations and expressed by the motion of virtual particles which represented enthalpy. The lateral motion of the particles was very subtle unlike the impressions given by the conventional qualitative explanation of the mechanism. The visualization method successfully showed that the small lateral motion of heat flow resulted in a significant enhancement of longitudinal heat transfer. Less