This is a model for a convective heat transfer for exterior, outside-facing surfaces.
conMod determines the model that is used to compute
the heat transfer coefficient:
the convective heat transfer coefficient is set to the value specified by the parameter
then the convective heat transfer coefficient is
computed based on wind speed, wind direction and temperature difference.
The total convection coefficient ht is the sum of the temperature-driven free convection coefficient hn and the wind-driven forced convection coefficient hf,
ht = hn + hfThe free convection coefficient hn is computed in the same way as in Buildings.HeatTransfer.Convection.Interior. The forced convection coefficient hf is computed based on a correlation by Sparrow, Ramsey, and Mass (1979), which is
hf = 2.537 W R √( P v ⁄ A )
where W=1 for windward surfaces and W=0.5 for leeward surfaces, with leeward defined as greater than 100 degrees from normal incidence, R is a surface roughness multiplier, P is the perimeter of the surface and A is the area of the surface. This is the same equation as implemented in EnergyPlus 6.0.
We make the simplified assumption that the surface is square, and hence we set
hf = 2.537 W R √( 4 v ⁄ √(A) )
The surface roughness is specified by the parameter
which has to be set to a type of
Buildings.HeatTransfer.Types.SurfaceRoughness.The coefficients for the surface roughness are
|Roughness index||R||Example material|
Sparrow, E. M., J. W. Ramsey, and E. A. Mass. 1979. Effect of Finite Width on Heat Transfer and Fluid Flow about an Inclined Rectangular Plate. Journal of Heat Transfer, Vol. 101, p. 204.
Walton, G. N. 1981. Passive Solar Extension of the Building Loads Analysis and System Thermodynamics (BLAST) Program, Technical Report, United States Army Construction Engineering Research Laboratory, Champaign, IL.
is_ceiling, for consistency with naming convention.