Suppression of Boiling Flow Oscillations in Parallel Microchannels by Inlet Restrictors

Abstract

Geometrical effects of MEMS-based microfabricated inlet orifices on the suppression of parallel channel and upstream compressible volume instabilities commonly exhibited during flow boiling in parallel microchannels have been investigated. The heat fluxes at the onset of unstable boiling have been obtained over effective heat fluxes ranging from 9 to 614W∕cm2 and mass fluxes from 115to389kg∕m2s. A dimensionless parameter M, which accounts for the pressure drop increase imposed by the inlet restrictors, has been used to correlate the extent of flow instability suppression. It has been shown that the onset of unstable boiling asymptotically increases with M. At sufficiently high M values, parallel channels and upstream compressible volume instabilities are completely eradicated although it gives way to another instability to develop, namely, the critical heat flux conditions. A correlation has been developed in terms of M to predict the conditions leading to unstable boiling.