Numerical and experimental study of circulation flow rate in a closed circuit due to gas jet impingement

Abstract

Purpose

The purpose of the present investigation is to compute the circulation flow of a liquid in a closed chamber when the liquid is fired by a gas jet through number of nozzles.

Design/methodology/approach

The conservation equations for mass and momentum have been solved in a closed container along with the conservation of volume fraction of the secondary phase in order to take into account the gas phase present in the liquid. The drag force created by the gas on the liquid has been incorporated in the momentum equation as a source term and the resulting equations have been solved numerically using a finite volume technique in an unstructured grid employing a phase coupled pressure linked velocity solver for the pressure correction equation, which is usually known as the Eulerian Scheme for two phase flow solution. An eddy viscosity based k‐ε turbulence model for the mixture was considered to update the fluid viscosity with iterations and capture the turbulence in the overall mixture rather than computing the individual turbulence in both the phases, which was found to be extremely time‐consuming and computationally unstable to some extent.

Findings

The model thus developed was tried to predict the circulation flow rate in an experimental setup where air was injected to drive the water in a long U tube setup. The computed circulation flow rate was found to be within 15 percent deviation from the experimentally observed values. The circulation flow rate of water was found to be increasing with the injected airflow rate. After this model validation, circulation flow rate of steel in an industrial size Ruhrstal‐Haraeus (RH)‐degasser was computed by injecting argon into the liquid steel through the up‐leg of the RH vessel. It was found that the circulation flow rate of steel in the RH degasser was increasing when the argon flow was being varied from 800 to 1,600 NL/min, which confirms the industrial findings.

Research limitations/implications

The present computation could not use the energy equation to compute the swelling of the gas bubbles inside the chamber due to huge computing time requirement.

Practical implications

The present computation could compute realistically the circulation flow rate of water in a U tube when fired by a gas jet by using a two‐phase Eulerian model and hence this model can be effectively used for industrial applications where two‐phase flow comes into picture.

Originality/value

The original contribution of the paper is in the use of the state‐of the‐art Eulerian two‐phase flow model to predict circulation flow in an industrial size RH degasser.

Citation

Anil Kishan, P. and Dash, S.K. (2006), "Numerical and experimental study of circulation flow rate in a closed circuit due to gas jet impingement", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 16 No. 8, pp. 890-909. https://doi.org/10.1108/09615530610702050