It is shown experimentally that the addition of angled deflectors to the fin region of membrane water-wall heat exchanger surfaces in circulating fluidized beds can lead to a significant increase in local and overall suspension-to-wall heat transfer. The experiments were carried out in the 12 MWth circulating fluidized bed (CFB) boiler at Chalmers University. The results are consistent with calculations based on renewal of packets traveling along the fin.