Dynamics of water disposal and water treatment in electric field with cooled air

Abstract

One of the important indicators of technological microclimate, which provides vital functions of plants and animals, is the humidity of air in the working volume of the production facility. The value of the regulating air humidity is stabilized by the supply of water vapor to the air stream, which is achieved in various ways, in particular by spraying water [1-3]. The effectiveness of this method of humidifying the air depends primarily on the variance of cutting and the rate of evaporation of droplets (to avoid their deposition). One of the ways to improve cutting quality is to use an electrostatic field. When the electric field is applied to the spray liquid, the resulting two-phase flow becomes more mono-dispersed and finely divided. The effectiveness of humidifying air depends on a number of parameters, the impact of which on the final humidity must be identified and quantified.

Analysis of recent research and publications. It has now been established that under the action of the electric field, the efficiency increases, as the cutting process [4-10] and subsequent evaporation of droplets of the spray in the air [6, 11]. The paper [12] shows the efficiency of using the electric field to increase the evaporation of water from the open surface. In works [7-9] it was established that the quality of liquid spraying is determined by overlaying the electric field. The paper [13] shows the dynamics of air humidification with spray water. There is no comprehensive study of the evolution of the spray fluid in the presence of an electric field in the literature.

The aim of the study. Installation of influence of an electric field, parameters of a two-phase (air-water mixture) on the process of humidifying of air and ability to control it.

Materials and methods of research. The main method of research is a theoretical analysis of artificial electrification of a liquid and its influence on the process of sawing; On the basis of the analysis of thermal and material balance, processes of evaporation of water and humidity were studied.

When electrifying the liquid in the process of cutting (dispersing) by supplying the potential to the injector nozzle, electrostatic induction, crown discharge and other methods, the fluid flow is in the electric field. Under the influence of this field, a pressure distribution occurs on the surface of the fluid film, which leads to loss of stability, decay and formation of droplets.

It increases the electric potential of droplets, reduces its own internal pressure and, accordingly, surface tension. Charging drops acquire new physical properties, such as increasing the dispersion of spraying and enhancing the transformation of the liquid phase into a pair.

For qualitative analysis and quantification of physical processes, internal pressure and surface tension of an unloaded drop are replaced by these parameters for a drop that has received a certain electric charge or potential.

With known electric charge, the vapor pressure above the drop is determined in accordance with the Laplace Act [4] (hypsometric formula [4,6]) with a modified record (taking into account the loss of mass in the mean) from the equation [4] (1).

In accordance with the existing ideas about the dynamics of two-phase streams of a torch of a liquid air mixture, formed by mechanical nozzles, we present the physical picture of the investigated process in this way. In the stream of spray water, air enters (absorbed into the root of the torch as a result of rarefied pressure) and joins in the process of movement to the surface of the droplets [13]. The drops during the movement evaporate and move in the air saturated with water vapor, increasing the moisture content of the air jet by coordinate. Increasing the moisture content of the air reduces the rate of evaporation.

To compile the mathematical description we assume the following assumptions:

- the droplets "fly off" from the point source on the balloon spray axis, having the same size and do not interact with each other (unipolarly charged particles of droplets evenly dissipate under the action of their volume charge, increasing the volume of the torch of the cut [4]) ;

- the motive force of the evaporation process is the difference of the partial pressure of water vapor on the surface of the drop and in the air, taking into account equations (1) and (5);

- the value of the partial pressure of water vapor on the surface of the drop is equal to the pressure of the saturated vapor at the surface temperature of the drop, and is approximated by the linear dependence, the value of the vapor pressure in the air is the function of the moisture content of the air;

- the mass of droplets, their surface and the mass of air in the volume of the torch are unaltered.

Given the assumptions made and the physical nature of the heat and mass transfer processes in the flare, the two-phase system of the moving flow can be represented as a model of the flow apparatus of the ideal mixing and to determine the change in time of the parameters of air and water at the "outlet" of the torch, that is, when the air saturated with moisture is fed into the user's work volume wet air (camera, room, humidifying object, etc.).

Thus, the obtained equations make it possible to determine the change in the basic parameters of spray water and air over time. Figure 1 shows the graphical dependences of changes in parameters of spray water and air in time, and in Figure 2, the change in the size of the drop in time. Figure 2 determines the time of full evaporation of the droplet with the initial radius.

Conclusions

1. A mathematical model of air humidification process with spray water in an electric field is developed, which allows to determine the change of air parameters during its humidification.

2. We obtained analytical dependences for determining the basic parameters of the dynamics of air humidification and the evaporation of droplets sprayed in an electric field.

3. The performed calculations confirm the possibility of increasing the intensity of the evaporation of droplets in the electric field by 26 ... 30%.