Tube-side heat transfer coefficient
Film coefficient inside tubes by Gnielinski, Dittus–Boelter and Sieder–Tate — velocity, Reynolds and Prandtl numbers, with water properties built in.
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How this calculator works
The film coefficient h on the inside of a tube is the first resistance in any heat exchanger's overall U. This calculator works out the velocity in each tube, the Reynolds and Prandtl numbers and h by the correlation that fits the flow: Gnielinski (with the Petukhov friction factor) for turbulent and transitional flow — the most accurate of the common correlations, typically within about 10 % — and Sieder–Tate for developing laminar flow. Dittus–Boelter and turbulent Sieder–Tate are shown alongside, because many data sheets and older calculations use them. Water properties — density, heat capacity, viscosity and conductivity — come from the IAPWS formulations; for other fluids enter them.
Example: 100,000 kg/h of cooling water at 30 °C through 120 tubes per pass of 15.75 mm inside diameter (¾-inch, 16 BWG), 6.1 m long: 1.19 m/s, Re = 23,470, Pr = 5.42, and a film coefficient of 6,006 W/m²·K by Gnielinski (Dittus–Boelter 5,534, Sieder–Tate 5,804); the tube friction is 0.07 bar per pass. The correlations were checked against the open-source ht library at a range of Reynolds and Prandtl numbers (agreement to 0.0001 %), and the water properties against the iapws library (within 0.3 %).
Limits: single-phase flow in round, smooth tubes; between Re = 2,300 and 10,000 any correlation is uncertain. For liquids give a wall temperature (or wall viscosity) to apply the viscosity correction — it matters for oils. Add the shell-side coefficient, the wall and the fouling resistances for U; the LMTD calculator works out the area. References: V. Gnielinski, Int. Chem. Eng. 16 (1976) 359; Sieder and Tate, Ind. Eng. Chem. 28 (1936) 1429; Dittus and Boelter (1930); Incropera and DeWitt, Fundamentals of Heat and Mass Transfer, ch. 8; IAPWS-IF97, IAPWS 2008 and 2011.