| At present,most of the research on the collision of droplets is the study of the collision law between water droplets or between water droplets and the wall surface.There are few studies on the collision law between metal droplets and the wall surface.This paper is the first time to study the collision of sodium metal droplets on the wall surface.behavior was studied.As a metal droplet,the density,viscosity coefficient,thermal conductivity and specific heat capacity of sodium droplet are very different from those of ordinary water droplets.Under the same Weber number and Reynolds number,the velocity of sodium droplet is larger than that of water droplet,and the diameter of sodium droplet is smaller than that of water droplet.In addition,the density and surface tension coefficient of sodium droplet are also quite different from that of water droplet.Therefore,it is necessary to study the collision fusion process of two sodium droplets on the wall.The research background of this paper is that the cooling pipe of the nuclear power plant leaks,and the sodium droplet with inert gas helium ejected from the breach hits the wall with the same temperature as the sodium droplet and lower temperature than the sodium droplet,so as to study its spreading behavior on the wall.In order to study the effects of various parameters on the process of sodium droplet impacting the wall,the effects of Weber number,Reynolds number,contact angle between sodium droplet and the wall,velocity,diameter and temperature of sodium droplet on the spreading behavior of sodium droplet impacting the isothermal surface were analyzed.In addition,the effects of the Weber number,Reynolds number and the contact angle between the sodium drop and the wall on the spreading behavior of the sodium drop when the sodium drop hits the low-temperature surface are studied.Finally,the effects of various parameters of the sodium drop on the maximum spreading diameter of the sodium drop are analyzed,the effects of various factors are obtained,and the variation curve of the maximum spreading diameter with the parameters is fitted.The research conclusions of this paper mainly include the following aspects:1)The research shows that the contact angle between sodium drop and wall,sodium drop velocity,Weber number and Reynolds number will have a decisive influence on the spreading behavior of sodium drop on wall.The smaller the contact angle between the sodium drop and the wall,the faster the spreading speed of the sodium drop on the wall and the larger the spreading diameter of the sodium drop.For the spreading behavior of sodium droplets on the low-temperature surface,the smaller the contact angle between sodium droplets and the wall,the faster the heat transfer rate of sodium droplets on the wall and the faster the temperature of sodium droplets decreases.Whether the sodium drops fall on the low-temperature surface or isothermal surface,the relationship between the maximum spreading diameter of the fused sodium drops and the contact angle is an exponential function.2)The velocity of the tail sodium drop will also change the impact fusion mode of the head and tail sodium drop on the wall.With the same Reynolds number,when the velocity of the sodium drop is u<6m/s,the maximum spreading diameter of the fused sodium drop will increase with the increase of the Weber number of the sodium drop.When the speed of sodium drop is 6m/s?u<12m/s,the maximum spreading diameter of fused sodium drop will decrease with the increase of Weber number of sodium drop due to the increase of capillary force.When the velocity of the sodium drop is 12m/s?u?74m/s,the maximum spreading diameter of the fused sodium drop will still increase with the increase of the Weber number of the sodium drop due to the further increase of the velocity of the sodium drop.3)When the Weber number of sodium drops is the same,the relationship between the maximum spreading diameter of sodium drops and the Reynolds number of sodium drops is similar to the relationship between Weber number and the maximum spreading diameter of sodium drops.With the same Weber number,when the sodium drop velocity u(27)6m/s,the maximum spreading diameter of the sodium drop will still increase with the increase of the Reynolds number of the sodium drop.When the velocity of sodium drops is 6m/s(27)u?74m/s,for sodium drops with Weber numbers of 10,40 and 70,the maximum spreading diameter of sodium drops will decrease with the increase of Reynolds number of sodium drops.When the Weber number is 10,with the increase of the Reynolds number of the sodium drop,when the velocity of the tail sodium drop is less than or equal to 6m/s,the maximum spreading diameter of the fused sodium drop will still increase with the increase of the Reynolds number of the sodium drop.When the Weber number is 7,although the sodium drop velocity is10.31m/s and greater than 6m/s at Reynolds number 200,the capillary force will reduce the maximum spreading diameter.However,the maximum spreading diameter at Reynolds number 200 will be larger than that at Reynolds number 100 due to the small inertial force and gravity on the sodium drop.When the Weber number is 100,the maximum spreading diameter of the sodium drop will increase with the increase of the Reynolds number of the sodium drop because the inertia force on the sodium drop is too large.4)The velocity,diameter and temperature of sodium droplets also have a great influence on the collision and fusion behavior of the first and last sodium droplets on the wall.Under the same diameter,when the velocity of sodium drop is 29.457m/s?u?58.91m/s,the relationship between the velocity of sodium drop and the maximum spreading diameter of sodium drop is a power function.At the same speed,when the diameter of sodium drop is2.4979?m?D?9.9916?m,the relationship between the diameter of sodium drop and the maximum spreading diameter of sodium drop is also a power function.Similar to the effect of Reynolds number of sodium drop on the maximum spreading diameter of sodium drop,for the fused sodium drop impacting the wall in the form of liquid bridge,when the temperature of sodium drop is less than or equal to 500 ℃,the maximum spreading diameter of sodium drop will decrease with the increase of sodium drop temperature due to the decrease of capillary force on sodium drop.5)When the sodium droplet falls on the low-temperature wall,the variation law of the maximum spreading diameter of the fused sodium droplet with the Reynolds number of the sodium droplet is similar to the previous conclusion.When the Weber number is 40,the maximum spreading diameter of the fused sodium drop will gradually decrease with the increase of the Reynolds number of the sodium drop.When Reynolds number is 200,the maximum spreading diameter of fused sodium drops will increase with the increase of Weber number. |
PDF Full Text Request