.Buildings.Fluid.HeatExchangers.BaseClasses.RayleighNumber

Information

This model calculates the rayleigh number for a given fluid and characteristic length. It is calculated using Eq 9.25 in Incropera and DeWitt (1996). The equation is:

Ra_L = Gr_L Pr (g B (T_S - T_F) L³) /(ν*α)

where:
Ra_L is the Rayleigh number, Gr_L is the Grashof number, Pr is the Prandtl number, g is gravity, B is the isobaric expansion coefficient, T_S is the temperature of the surface, T_F is the temperature of the fluid, L is the characteristic length, ν is the kinematic viscosity and α is the thermal diffusivity.

This model is currently only used in natural convection calculations for water. As a result, the calculations reference functions to identify properties of water instead of a medium model.

References

Fundamentals of Heat and Mass Transfer (Fourth Edition), Frank Incropera and David DeWitt, John Wiley and Sons, 1996

Contents

Name	Description
Medium	Fluid medium model

Revisions

• February 26, 2013 by Peter Grant
  First implementation