MAXIMUM HEAT FLUX FOR COUNTERCURRENT TWO PHASE FLOW IN A CLOSED END VERTICAL TUBE
An experimental investigation was performed on the maximum axial heat flux of the countercurrent two phase flow in a vertical tube. The experiments were carried out with carbon-tetrachloride, normal-hexane and water. Three different test sections of copper tube with diameters of 8, 10 and 14 mm I.D. were used. A wall surface temperature range of 120 - 350 degrees centigrade was obtained. An expression for the demonstration of the maximum heat flux in dimensionless form was derived employing the flooding correlation based on the countercurrent flow tests of air and water in vertical tubes. The experimental results of the present investigation were presented in the form of dimensionless axial heat flux against dimensionless diameter, D*. The length to diameter ratio of the test section, L/D was shown to influence the correlation and was included. The experimental results of several investigators on wickless heat pipes and vertical thermosyphons were also transformed and compared with results of the present tests. An expression was then proposed for use in the prediction of the maximum axial heat flux. All available data and the experimental results proved to be in very good agreement with the proposed expression.