A model of a liquid droplet impinging on a high-temperature solid surfaces

Gulikov, A. V.; Berlin, I. I.; Karpyshev, A. V.

doi:10.1007/s10740-005-0039-y

Cited by 2 publications

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“…Pasandideh-Fard et al 3) evaluated the cooling effectiveness of the impingement of a water drop on a hot solid substrate with a temperature low enough to prevent boiling in the drop. Gulikov et al 4) studied the collision dynamics of a droplet impacting on an extremely hot solid surface (above 400°C), taking account of the presence of a vapor interlayer due to film boiling. Ge and Fan 5) performed three-dimensional simulations of droplet collisions in the Leidenfrost regime.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of the Collision Dynamics and Heat Transfer of Water Droplets Impinging on a Hot Solid

et al. 2007

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nate system. The effects of gravity, viscosity, the surface tension at the free liquid surface between the water droplets and the air, the wettability of the solid, and the heat transfer between water and the solid, are taken into account. The surface temperature is assumed to be held constant slightly below the boiling point of water. The conservation equations are approximated and solved with a finite difference method. The free liquid surface is tracked by the VOF (Volume of Fluid) method. 8) Firstly, the collision of a single droplet with the solid is studied. Secondly, the successive collisions of two droplets are examined. In both cases, the predictions are compared with experimental data. The effects of the impact conditions of the droplets, such as the impact velocity of the droplets, the pre-impact diameters of the droplets, and the distance between the two incoming droplets, on the heat transfer from the solid to the water are investigated in detail. Figure 1 shows a schematic diagram of the collisions of droplets with a hot solid. Two types of droplet collision are considered: the collision of a single droplet with the solid and the successive collisions of two droplets with the solid. Spherical water droplets with no internal velocity fall vertically through the air, and then impinge on a horizontal smooth substrate with temperature maintained at 99.9°C. The time, t, is measured from the instant when the droplet touches the substrate. The initial temperature of the water droplets is 17.0°C. The pre-impact diameter of the droplets and the impact velocity are denoted by D p and v 0 , respectively. The two droplets are assumed to fall coaxially. The distance between the two droplets is DL. The flow characteristics of the leading (first) and trailing (second) droplets are denoted by the subscripts 1 and 2 respectively. Numerical Simulations Conservation EquationsThe flows are assumed to obey the Navier-Stokes equations for incompressible viscous fluids in an axisymmetric coordinate system. In the present model, the effects of gravity, viscosity, the surface tension at the free liquid surface, the wettability of the solid surface, the heat transfer from the solid to the liquid, and the temperature dependence of the physical properties, are taken into account. The heat transfer between air and the solid due to convection and radiation is ignored. The VOF method 8) is applied to track the time evolution of the free surface. A color function, f, is introduced to represent the volume ratio of water in a computational cell. The conservation equations, which consist of the continuity equation, the momentum equations in the radial and axial directions, the energy equation (4) where r and z are the coordinates in the radial and axial directions respectively, and t is the time. u and v are the velocity components in the r and z directions respectively. p, T, c, and l are the pressure, the temperature, the specific heat of water, and the thermal conductivity of water, respectively. F r and F z are the volume force...

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Section: Introductionmentioning

confidence: 99%