The trisection helical baffled shell-and-tube heat exchangers have structural features of more suitable to the equilateral triangular tube layouts and less baffle parts. In particular the circumferential overlap trisection helical baffled shell-and-tube heat exchangers are of anti-shortcut structure that accommodates one row tubes in each circumferential overlapped zone between adjacent baffles for dampening shortcut leakage. The performance tests were conducted on both oil-water and water-water heat transfer in heat exchangers with equilateral triangle tube layout of 16 tubes including five helical baffle schemes with incline angles of 12, 16, 20, 24, 28 and a segmental baffled one for comparison. The test results show that both the shell side heat transfer coefficient h(o) and pressure drop Delta p(o) increase but the comprehensive index h(o)/Delta p(o) decreases with the increase of the mass flow rate of all schemes; and that the shell side heat transfer coefficient, pressure drop and the comprehensive index h(o)/Delta p(o) decrease with the increase of the baffle incline angle at certain mass flow rate, except that the curves of comprehensive index h(o)/Delta p(o) of 12 and 16 helical baffle schemes are almost coincide. The average values of shell side heat transfer coefficient, the comprehensive index h(o)/Delta p(o) of the 12 helical baffled scheme are about 50% higher than those of the segmental one with almost same pressure drop. The correlation equations for shell side Nusselt number and axial Euler number are presented varying with axial Reynolds number, Prandtl number and helical baffle incline angle. (C) 2015 Published by Elsevier Ltd.