Microscopic observations of formation processes of clathrate-hydrate films at an interface between water and carbon dioxide

Heat Transfer Related to Gas Hydrate Formation/Dissociation

“…The further growth of hydrate is controlled by mass transfer of water or hydrate former through the film. Many experimental and/or theoretical studies on the growth of hydrate film have been carried out by several groups (Freer et al, 2001;Ma et al, 2002;Mochizuki and Mori, 2006;Mori, 2001;Ohmura et al, 2000Ohmura et al, , 2005Peng et al, 2007Peng et al, , 2008Peng et al, , 2009Saito et al, 2010Saito et al, , 2011Sun et al, 2007;Taylor et al, 2007;Uchida et al, 1999Uchida et al, , 2002, including the morphology of hydrate film, the growth rate of hydrate film, the thickness of hydrate film, the mechanism of hydrate film growth, and so on. However, so far it is still a controversial topic on the growth mechanism of hydrate film.…”

“…For example, Uchida et al (1999) presented a model analysis of the twodimensional growth of a carbon dioxide hydrate film (Figure 1). Uchida et al (1999) In this model, they assumed that one half of the film is in water phase, and the other half is in guest phase. The hydrate film has a semicircular front and is uniform in thickness.…”

“…The heat released by the hydrate crystal formation is diffused away from the film front and into the water and guest-fluid phase. Based on these assumptions, they formulated the heat balance at the edge of the film as (Uchida et al, 1999), the conductive heat transfer from the film front was deduced from the temperature gradient, which was deemed as with little physical reasoning (Mochizuki and Mori, 2006;Mori, 2001). Mori (2001) presented an alternative model of hydrate film growth based on the idea that the front of hydrate film, which grew on the interface between stagnant water and guest fluid, could be viewed to be held in stratified flow of the two fluids with the velocity which was opposite in sign but equal in magnitude to the velocity of the hydrate film front.…”

“…Mori (2001) presented an alternative model of hydrate film growth based on the idea that the front of hydrate film, which grew on the interface between stagnant water and guest fluid, could be viewed to be held in stratified flow of the two fluids with the velocity which was opposite in sign but equal in magnitude to the velocity of the hydrate film front. In his work, the heat removed from the film front to the liquid phases was treated as a steady convective heat transfer and other assumptions were same as those of Uchida et al (1999). The heat balance over the hemicircular front of the film was formulated as follows:…”

Improving Water Spray Efficacy for Fire Suppression via CO2 Addition at High Pressures and Low Temperatures: Evidence for CO2 Clathrate Hydrate Formation

“…13,14 The random nature of hydrate nucleation has presented significant difficulty in understanding the complex nucleation mechanism, 12 This paper describes a technique for achieving a compact aqueous spray that incorporates CO2 into the spray at low temperatures (T < 10°C) and high pressures (P > 10 MPa). A high-pressure spray apparatus was used to explore the effects of temperature (4-25°C), nominal CO2 mole fraction (0-0.12), in-line filter pore size (0.5-7 ím), and additives on the high-pressure (12)(13)(14)(15)(16)(17)(18)(19) water spray patterns. Divergence of the high-pressure H2O-CO2 spray was significantly reduced at low temperatures, with addition of sodium lauryl sulfate or aqueous film-forming foam (AFFF), and with a small-pore-size (0.5 ím) filter.…”