Axial separation is a novel baffle connection configuration of circumferential overlap helical baffle heat exchangers which makes baffle incline angle seriation possible. The adjacent baffle plates are separated by sleeve tubes to form a greater pitched helix for enhancing heat transfer under required pressure drop with the least number of molds for reducing baffle manufacture cost. Numerical simulations of flow and heat transfer performances were conducted and the calculation results were verified by the experimental ones. Performance investigation was conducted on eight normal trisection helical baffle schemes with baffle incline angles from 15 degrees to 23 degrees and five axial separation schemes of equivalent 17-22 degrees angles using 15 degrees baffles. In the calculation scope the average deviations of heat transfer coefficients and pressure drops of the normal helical schemes are respectively about -1.97% and -8.11% per 1 degrees deviation of incline angle. The axial separation schemes using 15 degrees baffles with equivalent 21 degrees and 22 degrees incline angles have deviation values of heat transfer coefficient 1.21% and 1.33% lower and pressure drop 4.96% and 5.55% higher respectively than those of the normal 21 degrees and 22 degrees incline angle schemes. By adopting axial separation approach the seriation step of baffle incline angles can be extended to 8 degrees. (C) 2016 Elsevier Ltd. All rights reserved.