The 21st Heat Transfer Photogallery was sponsored by the K-22 Heat Transfer Visualization Committee for the 2015 International Mechanical Engineering Congress and Exhibition (IMECE) held in Houston, TX on Nov. 13–19, 2015. The Photogallery sessions at the 2015 IMECE presented a total of 19 entries, and the peer-reviewed evaluation conducted by the participants has identified the 11 final entries for publication in this ASME Journal of Heat Transfer August issue of 2016.

The purpose of publishing these entries is to draw attention to the innovative features of visualization techniques and esthetic qualities of thermal processes. To focus on visualization images and schematics for each entry, the text is kept to a minimum and further details should be found directly from the authors. Our wish is that the journal readers enjoy viewing these collections, acquire knowledge of the state-of-the-art features, and also promote their participation in the 2016 IMECE Photogallery to be held in Phoenix, AZ on Nov. 11–17, 2016.1

The Call for Photographs for the 2016 IMECE is also announced in this issue of Journal of Heat Transfer.