The plastic smooth twisted tape can not be used for heat exchangers with low fluid velocity of less than 1.0 m8226;s-1 to prevent and remove fouling and it can not enhance heat transfer.A new twisted strip was proposed to enhance heat transfer.It was capable of being used in the circumstances with lower flow velocity of 0.5 m8226;s-1.Oblique teeth were attached asymmetrically on both surfaces of the twisted strip at regular intervals.The fluid for heat transfer was directed by the teeth with asymmetrical reaction forces on the twisted strip to form an additional rotating moment.With this arrangement

total moment was increased by 75%～101% and heat transfer coefficient was raised by 171% as against that of the smooth twisted strip.Though the resistance coefficient of fluid flow became greater

the total flow resistance of the equipment was still within the permissible range of engineering application

e.g. for a heat exchanger of 4 tube circuits and 6 meter long tubes

the resistance was about 36000 Pa.The new twisted strip could be used to automatically remove fouling and enhance heat transfer with low flow velocity of 0.5—1.0 m8226;s-1.