Local Heat Transfer and flow Patterns During Condensation in a Single Silicon Microchannel

Abstract

Condensation of steam in a single silicon microchannel was investigated using a simultaneous condensate flow visualization and heat transfer measurement along the flow direction. A silicon microchannel of a rectangular cross section covered with a transparent Pyrex glass was used. Different condensate flow patterns were identified, such as mist flow, churn flow, upstream elongated bubble flow followed by a bubble sequence, and slug flow. Both surface temperature measurements and video images obtained for different flows showed that the condensate flows were periodic or stable during time. The local surface temperature, local heat flux, and local heat transfer coefficient related to different condensate flow patterns were of particular interest. The local heat transfer coefficient was deduced from the local heat flux and the local surface temperature was measured through micro-instrumentation in a microchannel. The local thermal performance of condensation flow in a microchannel was better for mist flow and upstream elongated bubble flow relative to slug and bubbly flows.

Keywords:

• microchannel
• condensation
• heat transfer
• flow patterns

Acknowledgments

This work was supported by the Energy program of the National Scientific Research Center (CNRS) of France.