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The flow and heat transfer characteristics of helical baffle heat exchangers with diverse inclined angles and baffles, but similar baffle pitch and tube layout, were numerically simulated, three using non-continuous trisection baffles, two using non-continuous quadrant baffles, and one using a continuous helical baffle. The results show that, under the same operating conditions, the 20°TCO (trisection circumferential overlap baffles with 20° inclined angle) structure can significantly enhance shell side heat transfer with strong Dean vortex 'secondary flow' and restrained V-notch leakage, because the shapes of trisection baffles are very suitable to equilateral triangle tube layout and there is a row of tubes to dampen the leakage flow in each circumferential overlapped area of adjacent baffles. The shell side Nusselt Number Nuo and comprehensive index ( Nuo/ Euz,o1/3) of 20°TCO structure are 18.31 %, 25.82 %, 5.93 %, 6.36 %, and 15.04 %, and 15.43 %, 18.47 %, 5.30 %, 3.91 %, and 11.10 % higher than those of the 20°TEE (trisection end-to-end baffles with 20° inclined angle), 36.2°TMO (trisection middle overlap baffles with 36.2° inclined angle), 18°QCO (quadrant circumferential overlap baffles with 18° inclined angle), 18°QEE (quadrant end-to-end baffles with 18° inclined angle), and 18.4°CH (continuous helical baffle with 18.4° helical angle) structures, respectively. [ABSTRACT FROM AUTHOR]

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° to 23° and five axial separation schemes of equivalent 17–22° angles using 15° 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° deviation of incline angle. The axial separation schemes using 15° baffles with equivalent 21° and 22° 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° and 22° incline angle schemes. By adopting axial separation approach the seriation step of baffle incline angles can be extended to 8°. [ABSTRACT FROM AUTHOR]