Flow control in a subcooled tube: an experimental investigation of the effects of crust formation

The flow control of molten liquids in tubes by manipulating the flow cross-sectional area using solidification has been investigated. Eicosane, because of its well characterised thermophysical properties, fixed melting point and known temperature dependent properties, was used as the test fluid. The eicosane data can be used to model the flow control of high temperature slag in the metallurgical industry and to verify the results of mathematical models of slag flow in tubes. Experimental results are presented in the form of pressure drop vs flow rate and dimensionless freezing parameter (Tw^*) vs flow rate. These are compared with a theoretical laminar flow model with solidification. The experimental results cover: 100 < Re < 1000, 0.3 < Tw^* < 5.4 and for cooled length to diameter ratios (L/D) of 41.9, 27.6, 26.3 and 19.8. For Tw^* < 4 the agreement between experiment and theory is within 20%. For Tw^* > 4 it was clearly observed that the experimental pressure drop is significantly lower than the theoretical predictions and can be attributed to either the breakdown of the laminar flow assumption and/or the formation of an air gap between the tube and the solidified crust.