1. Key Laboratory for Green Chemical Technology of Ministry of Education, R & D Center for Petrochemical Technology, Tianjin University, Tianjin 300072, China 2. Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China
Shell-and-tube heat exchanger with helical baffles is superior to that with segmental baffles in reducing pressure drop, eliminating dead zone and lowering the risks of vibration of tube bundle. This paper focused on the small-angle helical baffles that have been merely reported in open literature. These baffles are noncontinuous helical baffles with a helix angle of 10° to 30°, and their shapes are 1/4 ellipse, 1/4 sector and 1/3 sector. To assess the integrative performance, α/?p is employed, and the calculated results show that among the three baffle shapes the heat exchangers with a 1/4 sector helical baffle have the lowest pressure drop. At β = 10° and 20°, 1/4 sector helical baffle heat exchangers show the best integrative performance; at β = 30°, 1/4 ellipse and 1/4 sector helical baffle heat exchangers perform almost the same. For the study of helix angles, we found that 30° has the best integrative performance at low mass flow rate, almost the same as 20° at high mass flow rate.
Baf?e spacing for segmental baf?es or helical pitch for helical baf?es (mm)
Cp
Speci?c heat (J?kg?1?K?1)
Di
Inside diameter of shell (mm)
D1
Tube bundle-circumscribed circle diameter (mm)
do
Outer diameter of tube (mm)
l
Effective length of tube (mm)
M
Mass ?ux (kg?s?1)
n
Tube number
?P
Pressure drop (Pa)
Pr
Prandtl number
Re
Reynolds number
Eij
Mean rate-of-strain tensor
?tm
Logarithmic mean temperature difference (K)
t
Temperature (K)
p
Tube pitch (mm)
Q
Heat exchange quantity (W)
Tab.1
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α
Heat transfer coefficient (W·m?2?K?1)
β
Helix angle
λ
Conductivity factor (W·m?1?K?1)
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ρ
Density (kg?m?3)
<?PubTbl row rht="0.37in"?>
υ
Kinematics viscosity (m2?s?1)
μ
Dynamic viscosity of fluid (Pa?s)
Tab.2
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in
Inlet
<?PubTbl row rht="0.35in"?>
out
Outlet
s
Shell side
t
Tube side
w
Tube wall
Tab.3
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