Sadik Kakac
Department of Mechanical Engineering,TOBB University of Economics and Technology, Ankara-Turkey; and LIPING CAO, Westinghouse Electric Company, LLC, PA; and Department of Mechanical Engineering, University of Miami, Florida - USA
T. Nejat Veziroglu
University of Miami, Miami, FL
H. S. Ergur
Middle East Technical University, Ankara, Turkey
I. Ucar
Middle East Technical University, Ankara, Turkey
In this study, the effect of inlet subcooling on sustained and transient boiling flow instabilities induced by forced convection in a heated single channel upflow system has been experimentally investigated by using Freon-113 and Freon-11 as the test fluids. Two major modes of oscillations, i.e., density-wave and pressure-drop types have been identified. Stable and unstable regions have been determined in system pressure-drop versus mass flow rate planes for various values of inlet fluid temperature. Stability and instability boundaries at each constant heat flux are obtained on a mass flow rate versus inlet subcooling plane. Transient instabilities resulting from a step increase in power input and a step decrease in flow rate at various values of inlet subcooling have also been investigated.