heat transfer coefficient

The heat transfer coefficient is used as a fudge factor in calculating heat transfer in thermodynamics. The heat transfer coefficent is often calculated from the Nusselt number (a dimensionless number). Below is an example where it is used to find the heat lost from a hot tubing to the surrounding area. There are different heat transfer relations for different flow regimes, such as the Dittus-Boelter heat transfer corelation, valid for Reynolds numbers between 100000 and 120000 and Prandtl numbers between 0.7 and 120. An exapmle is shown below where it is used to calculate the heat trasfer from a a tubing wall to water. The heat transfer coefficient has SI units in watts per meter squared per degree Kelvin. Often times it can be estimated by dividing the thermal conductivity by a length scale. Heat transfer coefficients add inversly, like resistences. It can be thought of as a thermal resistance. Shown below is an addition of heat transfer coefficients where one is estimated as a thermal conductivity divided by a length scale.

Heat Transfer Coefficient

See also