Increase In Melting Rate Research Articles

Effect of mechanical activation on the thermal stability of polytetrafluoroethylene powder

It was found that processing in a planetary activator leading to amorphization of the structure of polytetrafluoroethylene powder was not accompanied by a noticeable decrease in its thermal stability. It was established that the temperature at the onset of melting drops slightly, the melting rate increases, and the enthalpy of the endoeffect declines noticeably heating.

Melting of a vertical ice cylinder inside a rotating cylindrical cavity filled with binary aqueous solution

AbstractThe melting of a vertical ice cylinder into a homogeneous calcium chloride aqueous solution inside a rotating cylindrical cavity with several rotating speeds is considered experimentally. The melting mass and temperature are measured on four initial conditions of the solution and four rotating speeds of the cavity. The temperature of the liquid layer becomes uniform by the mixing effect resulting from cavity rotation and it enhances the melting rate of the ice cylinder. As the cavity‐rotating speed increases, the melting rate increases. The dimensionless melting mass is related to the Fourier number and the rotating Reynolds number in each initial condition, therefore an experimental equation that is able to quantitatively calculate the dimensionless melting mass is presented. It is seen that the melting Nusselt numbers increase again in the middle of the melting process. The ice cylinder continues to melt in spite of the small temperature difference between the ice cylinder and the solution. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(6): 359–373, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20211

Melting of a Vertical Ice Cylinder Inside a Rotating Cylindrical Cavity Filled with Binary Aqueous Solution

Melting of a vertical ice cylinder into a homogeneous calcium chloride aqueous solution inside a rotating cylindrical cavity with several revolution speeds is considered experimentally. Melting mass and temperature are measured on four initial conditions of the solution and four rotating speeds of the cavity. Temperature of liquid layer becomes uniform by the mixing effect resulting from cavity rotation and it enhances the melting rate of ice cylinder. As cavity-rotating speed becomes fast, melting rate increases. Dimensionless melting mass is related to Fourier number and rotating Reynolds number in each initial condition, therefore the experimental equation that is able to quantitatively calculate a dimensionless melting mass is presented. It is seen that melting Nusselt number re-increases in the middle of melting process. Ice cylinder continues to melt in spite of small temperature difference between ice cylinder and solution.

Impacts of clearcut harvesting on snow accumulation and melt in a northern hardwood forest

Snow accumulation and melt on north- and south-facing slopes in the Turkey lakes watershed (TLW) in central Ontario were compared for a mature hardwood maple stand and an adjacent clearcut in late winter and spring of 2000 and 2001. Snow accumulation in the clearcut exceeded that in the forest, although the degree of difference varied with slope aspect and year. Melt was significantly larger in the south-facing clearcut and forest relative to corresponding north-facing sites. The south-facing forest sites lost all snowcover 27 days before the north-facing clearcut in 2000, and 4 days before the north-facing clearcut in 2001. Daily melt in the clearcut was slightly greater and more spatially variable than in the adjacent forest, with the exception of the south-facing slope in 2000. Nevertheless, the effect of aspect on spatial variations in melt was larger than that due to clearcutting. There was a slight increase in melt rate with decreased canopy density in the south-facing clearcut and forest; however, variations in canopy density did not explain inter-point differences in daily melt within either the north-facing clearcut or the forest. The hydrological consequences of greater pre-melt snow water equivalent and larger daily melt in clearcuts include quicker delivery of meltwater to the soil surface and promotion of rapid near-surface runoff to receiving waters relative to undisturbed forest stands at TLW.

Impacts of clearcut harvesting on snow accumulation and melt in a northern hardwood forest

Snow accumulation and melt on north- and south-facing slopes in the Turkey lakes watershed (TLW) in central Ontario were compared for a mature hardwood maple stand and an adjacent clearcut in late winter and spring of 2000 and 2001. Snow accumulation in the clearcut exceeded that in the forest, although the degree of difference varied with slope aspect and year. Melt was significantly larger in the south-facing clearcut and forest relative to corresponding north-facing sites. The south-facing forest sites lost all snowcover 27 days before the north-facing clearcut in 2000, and 4 days before the north-facing clearcut in 2001. Daily melt in the clearcut was slightly greater and more spatially variable than in the adjacent forest, with the exception of the south-facing slope in 2000. Nevertheless, the effect of aspect on spatial variations in melt was larger than that due to clearcutting. There was a slight increase in melt rate with decreased canopy density in the south-facing clearcut and forest; however, variations in canopy density did not explain inter-point differences in daily melt within either the north-facing clearcut or the forest. The hydrological consequences of greater pre-melt snow water equivalent and larger daily melt in clearcuts include quicker delivery of meltwater to the soil surface and promotion of rapid near-surface runoff to receiving waters relative to undisturbed forest stands at TLW.

シグマ熔接における自己制御特性の原因の一考察

A simple calculation shows that the radiant heat from the molten pool of base metal is too small to explain the self adjusting phenomena of sigma welding, i. e. increase of melting rate of welding rod in shorter arc length.As is well known, the arc voltage increases as the arc current is increased under constant arc length in sigma welding.This positive characteristcs of high current density arc is believed to be mainly due to the increase in anode current density, which in turn results in increase in anode drop.When the welding current is increased, current distribution adjusts iteslf from Fig. 1(a) to Fig. 1(c), resulting in a increase of anode drop. It must be noticed however, that the increase of anode drop would be more pronounced if the current is confined only to the lower plane of the electrode.Fig. 2 shows the current distribution when the arc length is varied with constant current, and we see that the current concentrates to the lower end of electrode when the arc length becomes shorter (Fig. 2a), resulting in a larger anode drop.This increase of anode energy can explain the so-called self regulating action of sigma welding. For the case of D. C. S. P., the phenomena may be explained by assuming the increase of ion current component.