Fired Heater Learning Center

The equivalent length of a return bend may be obtained from the following curves based on Maxwell table and corrected using the Reynolds number correction factor.

Fact_{Nre} = Reynolds number correction |

L_{rb} = Equivalent length of return bend, ft |

Where,

G = Mass velocity, lb/sec-ft^{2} |

D_{i} = Inside tube diameter, in |

Visc = Viscosity, cp |

Description | Velocity Heads | Equivalent Length, Tube Dia |

Long Radius 90° Elbow | 0.30 | 16.5 |

Short Radius 90° Elbow | 0.50 | 27.5 |

Long Radius 180° Return | 0.50 | 27.5 |

Short Radius 180° Return | 0.75 | 41.25 |

Velocity Head | 1.00 | 55 |

D_{p} = Pressure drop, psi |

d_{i} = Inside diameter of tube, in |

G = Mass velocity of fluid, lb/sec-ft^{2} |

V_{lm} = Log mean specific volume correction |

F = Fanning friction factor |

L_{equiv} = Equivalent length of pipe run, ft |

V_{1} = Specific volume at start of run, ft^{3}/lb |

V_{2} = Specific volume at end of run, ft^{3}/lb |

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The formulas and correlations presented herein are all in the public domain and are to be used only as a learning tool. Note that any product, process, or technology in this document may be the subject of other intellectual property rights reserved by sponsors or contributors to this site. This publication is provided as is, without any warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of fitness for a particular purpose, or non-infringement.

The formulas, correlations, and methods presented herein should not be considered as being recommended by or used by the sponsors of this site. The purpose of this site is educational and the methods may or may not be suitable for actual design of equipment. Only a fired heater design engineer is qualified to decide if a calculation or procedure is correct for an application.