.IDEAS.Buildings.Components.BaseClasses.ConvectiveHeatTransfer.InteriorConvection

Information

The interior natural convective heat transfer coefficient h_c,i is computed for each interior surface as

h_c,i = n₁ · Dⁿ² · (T_a - T_s)ⁿ³

where

• D is the characteristic length of the surface,
• T_a is the indoor air temperature, and
• n_i are correlation coefficients.

The parameters {n₁, n₂, n₃} are equal to

• {1.823, -0.121, 0.293} for vertical surfaces [Awbi 1999],
• {2.175, -0.076, 0.308} for horizontal surfaces, wherefore the heat flux is in the same direction as the buoyancy force [Khalifa 2001], and
• {0.704, -0.601, 0.133} for horizontal surfaces, wherefore the heat flux is in the opposite direction as the buoyancy force [Awbi 1999].

The interior natural convective heat transfer coefficient is only described as a function of the temperature difference. Similar to the thermal model for heat transfer through a wall, a thermal circuit formulation for the direct radiant exchange between surfaces can be derived [Buchberg 1955, Oppenheim 1956].

References

[Awbi 1999]: H.B. Awbi, and A. Hatton, "Natural convection from heated room surfaces", Energy and Buildings, vol. 30, no. 3, pp. 233–244, 1999.
[Buchberg 1955]: H. Buchberg, "Electric analogue prediction of thermal behavior of an inhabitable enclosure", ASHRAE Transactions, vol. 61, pp. 339–386, 1955.
[Khalifa 2001]: A.J.N. Khalifa, "Natural convective heat transfer coefficient – a review: II. Surfaces in two- and three-dimensional enclosures", Energy Conversion and Management, vol. 42, no. 4, pp. 505–517, 2001.
[Oppenheim 1956]: A.K. Oppenheim, "Radiation analysis by the network method", Transaction of American Society of Mechanical Engineers, vol. 78, pp. 725–735, 1956.

Revisions

• June 17, 2025, by Lucas Verleyen:
  Replaced images with inline equations. See #1440.
• July 11, 2016 by Filip Jorissen:
  Adjusted formulation of correlation such that the Jacobian computation of non-linear algebraic loops do not lead to negative exponents.