An experimental investigation of thermally induced flow instabilities in a convective boiling upflow system

Abstract

The two-phase flow instabilities in a single channel, forced convection, open loop, up-flow system have been investigated experimentally using R-11 as the working fluid. The effects of mass flow rate, heat input, inlet liquid temperature and upstream compressible volume on two-phase flow instabilities have been investigated. Two heater surfaces were tested at five different heat inputs with constant inlet temperature, and four different inlet temperatures with constant heat input. For each case, the mass flow rate was varied over a wide range covering the entire scope for boiling two-phase flows. Experiments were also conducted at different compressible volumes, with constant heat input, inlet fluid temperature, and average mass flow rate. The oscillations of inlet mass flow rate, heater inlet pressure, and heater wall temperature were recorded. The effects of mass flow rate, inlet liquid temperature and heat input on the amplitudes and periods of inlet pressure and thermal oscillations are presented in tabular and graphical forms.