| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Lateral growth of a clathrate-hydrate film along a planar interface between liquid water and an immiscible hydrate-forming fluid (or guest fluid), such as HFC-32 or HFC-134a, was studied experimentally and numerically. It was found that the instantaneous rate of lateral film growth along the water/guest-fluid interface (i.e., the linear speed of the film-front) decreased asymptotically for several seconds after its nucleation. The asymptotic growth rate of HFC-32 hydrate film was about 5 mm/s at pressure, P = 617 kPa and a system subcooling, ΔT = 10.9 K, while that of HFC-134a hydrate film was about 0.4 mm/s at P = 246 kPa and ΔT = 6.0 K. In addition, two analytic models for the heat-transfer-controlled lateral growth of a clathrate-hydrate film along a planar interface between liquid water and a guest fluid were presented. The two models are different from each other only regarding the assumption of the film-front geometry. Either model assumes the film to be uniform and constant in thickness, ignoring possible changes in the thickness on a time scale relevant to its lateral growth. Another fundamental assumption employed in the model is that the film's hydrate-forming front is maintained at the hydrate/guest/water three-phase equilibrium temperature, thereby forming a two-dimensional temperature distribution in the surrounding three-phase space. Based on these assumptions, the transient, two-dimensional conductive heat transfer from the film front into the three phases is formulated and numerically solved to give the instantaneous lateral growth rate of clathrate-hydrate, while the film thickness is arbitrarily assumed as a fitting parameter. By comparing the predicted rate of film growth with the corresponding experimental data obtained with HFC-32 as the guest fluid, we estimated the film thickness to be about 1 μm at P = 617 kPa and ΔT = 10.9 K.
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