Numerical simulation of the heat transfer performance of trisection helical baffled electric heaters

ABSTRACT

Trisection helical baffled electric heaters are proposed to overcome the defects of low heat transfer coefficient and nonuniform tube spacing in conventional segmental baffled electric heaters with multicircular U-tube layouts. Novel trisection helical baffled electric heaters are of equilateral triangle tube layout distributed annularly in groups of one-plus-two U-tube units. Numerical simulation and comparison were conducted on the flow and heat transfer performance and the tube wall temperature uniformity of five helical baffled electric heaters and two segmental baffled ones. Each helical baffle scheme consists of nine one-plus-two U-tube units with a total of twenty-seven Φ16 mm U-tubes supported by the trisection helical baffles of 15 or 20° inclined angle, while each segmental baffle scheme consists of thirty Φ16 mm U-tubes of two-ring annular layout supported by segmental baffled plates spanned either 200 or 300 mm. The calculation results with compressed nitrogen show that the average heat transfer coefficient and comprehensive index (h/Δp^1/3) of the helical baffled H15°-1862 scheme with only 68.5% effective heating area are, respectively, 68.2 and 34.3% higher than those of the segmental baffled S200-2462 scheme, while the average tube wall temperature of the H15°-1862 scheme is 31.7 K lower than that of S200-2462 scheme.