modelInteriorConvection
Information
The interior natural convective heat transfer coefficient hc,i is computed for each interior surface as
hc,i = n1 · Dn2 · (Ta - Ts)n3
where
- D is the characteristic length of the surface,
- Ta is the indoor air temperature, and
- ni 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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Area | A | surface area | |
| Modelica.Units.SI.Angle | inc | inclination | |
| Boolean | linearise | false | = true, if convective heat transfer should be linearised |
| Modelica.Units.SI.TemperatureDifference | dT_nominal | -2 | Nominal temperature difference used for linearisation, negative temperatures indicate the solid is colder |
| Advanced | |||
| Modelica.Units.SI.Length | hZone | 2.7 | Zone height, for calculation of hydraulic diameter |
| Modelica.Units.SI.Length | DhWall | 4*A/(2*A/hZone + 2*hZone) | Hydraulic diameter for walls |
| Modelica.Units.SI.Length | DhFloor | sqrt(A) | Hydraulic diameter for ceiling/floor |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | port_a | ||
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_b | port_b |
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.