The carbon steel spirally fluted tube is introduced and investigated for replacing the copper smooth tube normally used in high pressure preheaters for power plants, because the copper tubes can be corroded by the boiler feedwater with NH3-H2O, The experimental results show that although the total heat transfer coefficient of the carbon steel spirally fluted tube is 10-17% bigger than that of the carbon steel smooth tube, it is almost equal to that of the copper smooth tube. Therefore, it is feasible to use the carbon steel spirally fluted tubes to replace the copper smooth tubes. Better manufacturing processes for carbon steel spirally fluted tubes are needed to improve the performance of the tubes, (C) 2000 Elsevier Science Ltd. All rights reserved.