The effect of different heater surface configurations on two-phase flow instabilities has been investigated in single channel, forced convection, up-flow and horizontal systems. Freon-11 is used as the test fluid, and different heater tubes with various surface configurations have been tested at different heat inputs. The effect of augmentation on flow isntabilities is studied with three different tubes made of different inner surfaces, at various inlet temperatures. All experimetns are carried out at constant system pressure and exit restriction. Steady-state characteristics of the system composed of different tubes are found and presented in pressure-drop versus mass flow rate diagrams. Dynamic instabilities, such as pressure-drop-type, density-wave-type instabilities and thermal oscillations are found to occur in every system, and boundaries for the appearnance of these oscillations are found. The dependence of the characteristics of these oscillations on the augmented surfaces is emphasixed, and comparisons between the bare tube and the augmented tubes are made.
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