Effects of width and location of a flow disturbing circular plate on nucleate pool boiling heat transfer of water at atmospheric pressure have been investigated experimentally. Through the tests, changes in the degree of intensity of liquid agitation and its effect on heat transfer on a heated tube have been analyzed. According to the results, the plate changes fluid flow around the tube as well as heat transfer coefficients on the tube. It is identified that plate width changes the rate of circulating flow whereas its location changes the growth of active agitating flow. Moreover, flow chugging was observed at the downside of the plate. (C) 2003 Elsevier Ltd. All rights reserved.