Experimental investigation into the impact of density wave oscillations on flow boiling system dynamic behavior and stability

Abstract

In order to better understand and quantify the effect of instabilities in systems utilizing flow boiling heat transfer, the present study explores dynamic results for pressure drop, mass velocity, thermodynamic equilibrium quality, and heated wall temperature to ascertain and analyze the dominant modes in which they oscillate. Flow boiling experiments are conducted for a range of mass velocities with both subcooled and saturated inlet conditions in vertical upflow, vertical downflow, and horizontal flow orientations. High frequency pressure measurements are used to investigate the influence of individual flow loop components (flow boiling module, pump, pre-heater, condenser, etc.) on dynamic behavior of the fluid, with fast Fourier transforms of the same used to provide critical frequency domain information. Conclusions from this analysis are used to isolate instabilities present within the system due to physical interplay between thermodynamic and hydrodynamic effects. Parametric analysis is undertaken to better understand the conditions under which these instabilities form and their impact on system performance. Several prior stability maps are presented, with new stability maps provided to better address contextual trends discovered in the present study.