THE SIMULATION AND FEATURES OF COUNTERCURRENT FLOW IN VERTICAL CHANNELS OF CONTACT DEVICES

Abstract

The aim of the work is to study the modes of motion of the phases at the interface of the film of water-air flow in the vertical channel during the countercurrent motion of the phases of the coolant. To achieve this goal, the following problems are solved: for each of the phases, the stationary Navier-Stokes equations and continuity are recorded, taking into account the direction of gravity. The obtained system of equations in the two-dimensional formulation in cylindrical coordinates with corresponding boundary conditions is solved in the package COMSOL MULTIPHYSICS 5.6. In the specified package the modeling of the influence of factors on the behavior of the interface of the film water-air flow in the vertical channel during the countercurrent movement of the phases is carried out. It is concluded that the existence of concomitant flows at the interface of the phases, depending on the height of the channel and the flow of phases in the vertical channel. As a result of the simulation, it was found that the countercurrent phases in the laminar mode in the vertical channel, the hydrodynamics at the interface of the phases differs in the height of the channel. At the inlet, at the bottom of the channel, the airflow creates a concomitant flow in the flowing film of water at the interface. Accordingly, at the top of the channel, at the inlet, the film of water creates a concomitant flow in the flow of wind, moving countercurrent. And in the canal itself, there is an area where the movement of water and air flows has no concomitant flows. That is, as a result of simulation it was found that the countercurrent phases in the laminar mode in the vertical channel, the hydrodynamics at the phase boundary differs, depending on the zone at the height of the channel and three such zones. Factors that affect the size of the above three zones are the height of the channel, flow rate, or speed of each of the phases. In particular, at the inlet of the water film into the channel with a speed  = 0,3…1,1 m/s and a thickness of 0.25 mm (= 60… 210), the calculated value of the thickness of the concomitant airflow is (0.4 .. 1.6) 103 m and is directly proportional to the speed of the water film. Also, with a decrease in the height of the canal three times, from 0.150 to 0.050 m, the existence of three zones in the canal is maintained, but the height of the zone without concomitant flow decreases in direct proportion by one order - from 0.137 m to 0.0113 m. The establishment of co-directed flows at the phase separation boundary in the channels of film contact devices for selection of the hydrodynamic regime to increase the efficiency of heat exchange.