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This paper aims to present a numerical study on heat transfer enhancement of a tubular heat exchanger inserted with novel anti-clockwise clockwise twisted (ACCT) tape. Twelve different combinations of ACCT tapes are investigated; including tapes with four twist ratios (x/b) and three twist angles (θ) in a turbulent flow zone (4000 ≤ Re ≥ 24000). Parametric analysis is carried out to understand the flow characteristics. The results revealed that the proposed insert develops multiple vortices in the flow, increasing the turbulent kinetic energy. The Nusselt number, friction factor and thermal performance factor (TPF) of the tube with ACCT tapes increases with the increasing twist angle and the decreasing twist ratio. The highest enhancement of the Nusselt number and friction factor by 2.98 and 6.86 times is achieved for ACCT tapes with x/b = 3.0, θ = 90° and Reynolds number of 4000. The TPF is above unity for all the considered cases, with the highest being 1.54, verifying that use of the ACCT tapes is an efficient technique. Further by selecting the appropriate twist angle and twist ratio for the ACCT tape, a beneficial balance between increased heat transmission rate and friction factor can be achieved. [ABSTRACT FROM AUTHOR]