Effect of tilt angle on the stability of free convection heat transfer in an upward-facing cylindrical cavity: Numerical analysis

Abstract

The critical cavity tilt angle is defined to mark the stability of free convection heat transfer shifting from steadiness to unsteadiness with the cavity rotating from sideward to vertical upward. In this article, taking a cylindrical cavity subjected to constant heat flux as object, experiments were firstly performed to show the possible reason why the unsteady free convection heat transfer was not discovered in previous experimental studies. Afterwards, on the basis of three-dimensional steady and unsteady simulation models, the concept of critical cavity tilt angle was proved and its magnitude was determined. For the compromising of computation cost and accuracy, the verified steady state model was employed to analyze the effects of aperture ratio and heat flux on critical cavity tilt angle. Also the importance of selecting appropriate monitoring parameters was detailed. Results show that in general, the critical cavity tilt angle increases with decreasing aperture ratio or increasing heat flux for partially open cavities. Remarkable differences may occur among scenarios having different monitoring parameters. Hence, to identify the critical cavity tilt angle accurately, more parameters, especially those inside the cavity should be taken into account.