Nomenclature
| Symbol | Name | SI Units | English Units |
| C | fluid specific heat | kJ/kg.K | BtU/lb.F |
| Di | inside diameter of tube | m | ft |
| g | acceleration of gravity | 9.81m/s2 | 32.2ft/s2 |
| Gi | fluid mass velocity through tubes | kg/m2.s | lb/ft2.h |
| hi | heat transfer co-efficient through tubes referred to inside bare surface | W/m2.K | BtU/ft2.F.h |
| JH | heat transfer factor | dimensionless | |
| f | friction factor | dimensionless | |
| k | fluid conductivity | W/m.K | BtU/ft.F.h |
| L | tube length | m | ft |
| Np | number of tube passes | dimensionless | |
| Nt | total number of tubes | dimensionless | |
| Rei | Reynolds number | dimensionless | |
| W | mass flow through tubes | kg/s | lb/h |
| ρ | density of fluid at mean temperature | kg/m3 | lb/ft3 |
| μ | dynamic viscosity at mean temperature | mPa.s | lb/ft.h |
| μW | dynamic viscosity at mean wall temperature | mPa.s | lb/ft.h |
| Z | pressure drop factor | 9.807x10-5 | 5.36x10-10 |
| ΔP | pressure drop through tubes | Bar | lb/in2 |
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