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ABSTRACT
Numerical simulation was conducted on oil–water heat transfer in five circumferential overlap trisection helical baffle shell–and–tube heat exchangers (cothSTHXs) with 16 tubes and incline angles of 12°, 16°, 20°, 24°, and 28° and a segmental baffle heat exchanger of the identical tube layout for comparison under laminar flow calculation conditions. The local images represent shell-side flow patterns, and heat transfer properties are presented showing the detailed “secondary vortex flow” and “shortcut leakage flow” patterns to explain the different characteristics of the six schemes. The simulation curves of the heat transfer coefficient and pressure drop are compared with those of the experimental ones, with satisfactory agreement. The average values of the shell-side heat transfer coefficient and the comprehensive index ho/Δpo of the 12° helical scheme are respectively 47% and 51% higher than those of the segmental baffle scheme with about the same pressure drop.
Nomenclature
| A | = | heat transfer area based on outer diameter of tube (m2) |
| cp | = | specific heat at constant fluid pressure (J · kg−1 · K−1) |
| d | = | diameter (m) |
| G | = | flow rate (kg · s−1) |
| H | = | heat transfer coefficient (W · m−2 · K−1) |
| K | = | overall heat transfer coefficient (W · m−2 · K−1) |
| k | = | turbulence kinetic energy (m2 · s−2) |
| l | = | length of heat transfer tube (m) |
| p | = | pressure (Pa, kPa) |
| Pr | = | Prandtl number |
| Q | = | heat transfer rate (W, kW) |
| Re | = | Reynolds number |
| T, t | = | temperature (K, °C) |
| u | = | velocity (m · s−1) |
| v | = | velocity (m · s−1) |
| Δpo | = | shell-side pressure drop (kPa) |
| Δtm | = | logarithmic mean temperature difference (K) |
| ϵ | = | turbulence kinetic energy dissipation rate (m2 · s−3) |
| λ | = | thermal conductivity (W · m−1 · K−1) |
| μ | = | dynamic viscosity (Pa · s) |
| ρ | = | density of fluid (kg · m−3) |
| Subscripts | = | |
| eff | = | effect |
| exp | = | experiment |
| i | = | tube side |
| i | = | direction variable |
| in | = | inlet |
| o | = | shell side |
| sim | = | simulation |
| w | = | tube wall |
Nomenclature
| A | = | heat transfer area based on outer diameter of tube (m2) |
| cp | = | specific heat at constant fluid pressure (J · kg−1 · K−1) |
| d | = | diameter (m) |
| G | = | flow rate (kg · s−1) |
| H | = | heat transfer coefficient (W · m−2 · K−1) |
| K | = | overall heat transfer coefficient (W · m−2 · K−1) |
| k | = | turbulence kinetic energy (m2 · s−2) |
| l | = | length of heat transfer tube (m) |
| p | = | pressure (Pa, kPa) |
| Pr | = | Prandtl number |
| Q | = | heat transfer rate (W, kW) |
| Re | = | Reynolds number |
| T, t | = | temperature (K, °C) |
| u | = | velocity (m · s−1) |
| v | = | velocity (m · s−1) |
| Δpo | = | shell-side pressure drop (kPa) |
| Δtm | = | logarithmic mean temperature difference (K) |
| ϵ | = | turbulence kinetic energy dissipation rate (m2 · s−3) |
| λ | = | thermal conductivity (W · m−1 · K−1) |
| μ | = | dynamic viscosity (Pa · s) |
| ρ | = | density of fluid (kg · m−3) |
| Subscripts | = | |
| eff | = | effect |
| exp | = | experiment |
| i | = | tube side |
| i | = | direction variable |
| in | = | inlet |
| o | = | shell side |
| sim | = | simulation |
| w | = | tube wall |