In this study, the critical heat flux of bi-porous sintered copper coatings in FC-72 is investigated experimentally. The effects of particle size (45 <= d <= 100 gm), cluster size (250 D <= 675 gm), and coating thickness (0.7 <= t <= 3 mm) on the critical heat flux are considered. The results show that the bi-porous coatings can improve the critical heat flux of mono-porous coatings significantly, by up to 72%. The critical heat flux of bi-porous coatings is shown to be primarily a function of the particle size to cluster size ratio (d/D) and nearly independent of the coating thickness. The critical heat flux attains a maximum value when d/D is approximately 0.15. Based on the experimental results, a correlation for predicting the critical heat flux of bi-porous coatings is proposed as a function of d/D. The proposed correlation is valid over the parameter range typically encountered in heat transfer applications. (C) 2013 Elsevier Ltd. All rights reserved.