Proposal of Jet Control Method by Elucidating Inclined Impact Jet Characteristics on Local Air Conditioning System

Abstract

We have been developing a local air conditioning system which supplies airflow locally to users. This system directs a composite jet to users, created by colliding jets from nozzles on either side of a wall. However, Coanda effect near the nozzle caused instability at the collision point of the two jets, resulting in the composite jet not being delivered to the user. This research aims to control passively the suppression of Coanda effect by changing the wall shapes near the nozzle to convex type or concave type. The effects of convex thickness and concave groove width on the suppression of Coanda effect were examined by numerical simulation and flow visualization. As a result, Coanda effect becomes larger as the jet velocity slows down, and as a result, the two jet collision points oscillate greatly to the left and right. Moreover, Coanda effect can be suppressed if the thickness and groove width were larger, and consequently the composite jet was centered. On the other hand, the jet was influenced by the wall in the smaller sizes, and the composite jet was shifted to the left and right.