The effects of cohesiveness and subsequent agglomeration of particles on the particle behavior and heat transfer characteristics around the horizontal tubes were experimentally studied. The inter-particle cohesive forces due to a liquid bridge were controlled by changing the humidity of the fluidizing air. The behavior of the particles and the bubbles on the tube surface were visualized by throwing a laser light sheet from the inside. This proposed visualization method can clearly distinguish the particles making contact with the tube surface from the bubble.
