DETAILED HEAT-TRANSFER DISTRIBUTIONS IN 2-PASS SQUARE CHANNELS WITH RIB TURBULATORS AND BLEED HOLES

Detailed heat transfer coefficient distributions are presented for a t wo-pass square channel with a 180 degrees turn. One wall of the channe l has periodically placed rib turbulators and bleed holes. Four differ ent configurations of 90 degrees parallel, 60 degrees parallel, 60 deg rees V ribs, and 60 degrees inverted V ribs are studied in conjunction with the effect of bleed holes on the same wall. The surface is coate d with a thin layer of thermochromic liquid crystals and a transient t est is run to obtain the detailed heat transfer distributions. Detaile d distributions show distinctive peaks in heat transfer levels around bleed holes and on rib turbulator tips. The 60 degrees parallel, 60 de grees V, and 60 degrees inverted V ribbed channels produce similar lev els of heat transfer enhancement in the first pass. However, the 60 de grees inverted V ribbed channel produces higher enhancement in the sec ond pass. Regional-averaged heat transfer results indicate that a surf ace with bleed holes provides similar heat transfer enhancement as tha t for a surface without bleed holes although 20-25% of the inlet mass flow exits through the bleed holes. (C) 1998 Elsevier Science Ltd. All rights reserved.