# Concentric tube heat exchanger - Overall Heat Transfer coefficient

## Description

Concentric Tube (or Pipe) Heat Exchangers are used in a variety of industries for purposes such as material processing, food preparation, and air-conditioning. They create a temperature driving force by passing fluid streams of different temperatures parallel to each other, separated by a physical boundary in the form of a pipe. This induces forced convection, transferring heat to/from the product.

After the heat transfer coefficients hi and ho are determined, knowing the resistance due to fouling and thermal conductivity of the boundary material kw, the Overall Heat Transfer coefficient Uo can be calculated from the shown formula

If the cross-sectional area of the annulus is not circular, the equivalent (hydraulic) diameter can be used. it can calculated by this formula

Related formulas## Variables

U_{o} | Overall Heat Transfer coefficient (W/(m^{2K})) |

R_{fo} | fouling resistance of the outer tube (m^{2}*K/W) |

R_{fi} | fouling resistance of the inner tube (m^{2}*K/W) |

D_{o} | diameter of the outer tube (m) |

D_{i} | diameter of the inner tube (m) |

k_{w} | thermal conductivity of the tube wall (W/(m*K)) |

h_{o} | convective heat transfer coefficient of the outer tube's fluid (W/(m^{2K})) |

h_{i} | convective heat transfer coefficient of the inner tube's fluid (W/(m^{2K})) |