FLOW AND MEASUREMENTS OF MICRO-SCALE IMPINGEMENT COOLING HEAT TRANSFER FROM A MICRO SLOT AIR JET

摘要

Micro-scale impinging wall jet flow and the impingement heat transfer along the wall are studied experimentally. The jet is issued from a micro slot nozzle, which has the width of 200 urn, and impinges on a small thermal chip (1.2 cm * 1.2 cm) that can be heated uniformly. Both the nozzle and the thermal chip are made by the MEMS techniques. Flow visualization for the impinging wall jet by smoke wire techniques and the local heat transfer measurements along the thermal chip were made. The wall jet flow structure and the heat transfer along the small thermal chip are found surprisingly different from the case of large-scale macro jet impingement process. The heat transfer Nusselt number can be well correlated if the nozzle-to-plate spacing ratio is normalized with a proper length scale, i.e. the breakdown length of the impinging jet. Further discussion on Reynolds number effect on the wall jet flow and the micro-scale heat transfer will be presented.