.AixLib.Utilities.HeatTransfer.HeatToRad

Information

Overview

The model cobines the HeatPort and the RadPort connector. To model longwave radiation exchange of surfaces, just connect the HeatPort connector to the heat port of a surface and connect the RadPort connector to the RadPort connectors of an unlimited number of corresponding surfaces.

Concept

Since exact calculation of longwave radiation exchange inside a room demands for the computation of view factors, it may be very complex to achieve for non-rectangular room layouts. Therefore, an approximated calculation of radiation exchange basing on the proportions of the affected surfaces is an alternative. The underlying concept of this approach is known as the "two star" room model.

Limitations / Assumptions

According to [1]:

• Index 1 is the component at port conv
• Heat flow exchange between two grey bodies
• Body 2 encloses body 1 (A₂ > A₁)
• Body 1 is convex (view factor Φ₁₁ = 0)

Q̇_1⇌2 = A₁ ⋅ σ ⋅ ( T₁⁴ - T₂⁴) / ( 1/ε₁ + A₁ / A₂ ⋅ ( 1/ε₂ - 1 ) )

• The closer ε is to 1, the smaller is the loss of information due to the simplification that only one surface area and no view factors are known.
• The greater A₂ compared to A₁ the smaller the simplification.

References

[1] Reinhold Kneer. Formelsammlung Wärme- Und Stoffübertragung WSÜ. RWTH Aachen University, Institut für Wärme- und Stoffübertragung (WSA) September 15, 2014.

• March 30, 2020 by Philipp Mehrfeld:
  #886: Add equation, limitations and assumptions to documentation
• November 5, 2019  by David Jansen:
  Make area a conditional paramter #issue689
• February 16, 2018  by Philipp Mehrfeld:
  #535: Add max functions to prevent negative solutions.
• Mai 19, 2014  by Ana Constantin:
  Uses components from MSL and respects the naming conventions
• April 01, 2014 by Moritz Lauster:
  Moved and Renamed
• April 10, 2013  by Ole Odendahl:
  Formatted documentation appropriately
• June 21, 2007  by Peter Mattes:
  Extended model based on TwoStar_RadEx.