During the operation of evaporative micro-channels, flow instability could be encountered. This phenomenon usually occurs when the Bond number of the fluid in the micro-channels is less than unity, so that a growing bubble is severely squeezed in the narrow channel and expands towards both upstream and downstream simultaneously. To reduce the flow instability, installation of an inlet orifice at the upstream, or making the micro-channel expanding at the downstream are found to be effective. An instability model for micro-channels was established, which takes into account the effects of both the inlet orifice and the channel expansion. Experiments of evaporating water micro system of 48 parallel micro-channels with 353 μm hydraulic diameter were conducted. The instability criterion of evaporative micro-channels with the effects of inlet orifice and expanding channel area are validated. Furthermore, to assist the general design of complex micro-channel network systems, a computational scheme is developed.

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