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ABSTRACT
A small heat exchanger with segmental baffles and two tube passes was built and experimented to investigate the shellside heat transfer enhancement in our previous research. In the present paper, the full numerical model is constructed for the experimented heat exchanger of two tube passes with the commercial software ANSYS Fluent, where the computation domain consists of not only the fluids on the shell and tube sides but also the solids of baffles and tubes. The conjugated heat transfer between the hot and cold fluids through tubes is modeled. To check the prediction precision of current full model, the computed fluid outlet temperature and heat transfer rate are compared with experimental counterparts. With current full model, the effects of baffle number on the performances of heat transfer and flow resistance are studied, and the discussions are conducted with the scalar contours and velocity vectors. The current research could be used for the industrial application of small segmental baffle heat exchangers with multiple tube passes.
Nomenclature
| bc | = | cut depth of baffle, m |
| cp | = | specific heat of constant pressure, J.kg−1.K−1 |
| CFD | = | computational fluid dynamics |
| d | = | characteristic dimension, m |
| di | = | internal diameter of tube, m |
| do | = | external diameter of tube, m |
| D | = | internal diameter of shell, m |
| E | = | mean rate-of-strain tensor, s−1 |
| f | = | friction factor, dimensionless |
| Gk | = | turbulence kinetic energy generation rate, kg.m−1s−3 |
| h | = | convective heat transfer coefficient, W.m−2·K−1 |
| k | = | turbulence kinetic energy, m2.s−2 |
| K | = | overall heat transfer coefficient, W.m−2·K−1 |
| L | = | length or pitch, m |
| n | = | tube or baffle number, dimensionless |
| Nu | = | Nusselt number, dimensionless |
| p | = | static pressure, Pa |
| Δp | = | static pressure loss, Pa |
| qV | = | volumetric flowrate, m3.s−1 |
| Q | = | heat transfer rate, W |
| Pr | = | laminar Prandtl number, dimensionless |
| Prt | = | turbulence Prandtl number, dimensionless |
| Re | = | Reynolds number, dimensionless |
| T | = | static temperature, K |
| ΔTm | = | mean temperature difference of heat transfer, K |
| u | = | velocity vector, m.s−1 |
| us | = | mean fluid velocity across central row of tubes, m.s−1 |
| ut | = | mean fluid velocity in the tubes, m.s−1 |
| x | = | spatial dimensions, m |
Greek symbols
| ρ | = | density, kg.m3 |
| μ | = | dynamic viscosity, Ns.m−2 |
| ϵ | = | turbulence kinetic energy dissipation rate, m3.s−2 |
| λ | = | thermal conductivity, W.m−1·K−1 |
| δ | = | baffle-shell gap, mm |
| ϕ | = | percentage of heat transfer rate of shellside cross pass |
Subscripts
| b | = | baffle |
| eff | = | effective |
| f | = | fluid |
| i, j | = | tensor |
| l | = | laminar |
| s | = | shell side |
| sol | = | solid |
| t | = | tube side; turbulent |
| tub | = | tube |
| w | = | wall |
Superscripts
| in | = | inlet |
| out | = | outlet |
Additional information
Notes on contributors
Yonghua You
Yonghua You is an associate professor in the State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, China. His research interest includes heat transfer enhancement and optimal design of heat exchangers. Currently, he conducts full model simulation on the small size shell-and-tube heat exchangers with commercial CFD software.
Shuifang Xiao
Shuifang Xiao is studying for the Master degree in the School of Material and Metallurgy, Wuhan University of Science and Technology, China. He is among the team members for the full model simulation of small size shell-and-tube heat exchangers.
Ni Pan
Ni Pan is now a lecturer in the State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, China. She received M. Eng. from Northeastern University of China in 2007, and worked in WISDRI Engineering & Research Incorporation Limited as a designer in the field of industrial furnace from 2007 to 2013. Her research interests are heat and mass transfer in industrial furnace and oil shale retorting.
Zhidan Deng
Zhidan Deng is studying for B.Eng. in the School of Material and Metallurgy, Wuhan university of science and technology, China. He is a team member for the full model simulation of small size shell-and-tube heat exchangers with commercial CFD software.