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Radiators - Heat Emission

Calculate heat emission from column and panel radiators.

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Heat output from a radiator is determined by the

  • ambient surrounding temperature
  • temperature of the radiator surface
  • surface area of the radiator

The formulas below can be used to estimate the heat emission from radiators where the temperature difference between the radiator surface and the ambient air is 50oC (inlet water temperature 80oC, outlet water temperature 60oC and ambient air 20oC).   

Heat Emission from Column Radiators

column radiator heat emission

The heat emission from a column radiator can roughly be estimated as

P = kc Ve                                            (1)


P = heat emission (W)

kc = 15000 - 17000 - constant for column radiator

Ve = external radiator volume (m3)

Heat Emission from Panel Radiators

panel radiator heat emission

The heat emission from a panel radiator can roughly be estimated as

P = 41 kp l (1 + 8 h)                                    (2)


P = heat emission (W)

kp = constant for panel radiator

l = radiator length (m)

h = radiator height (m)

Typical panel radiator configuration constants - kp:

  • 3.1 : for a  single panel
  • 4.1 : for a panel - convector
  • 4.9 : for two panels
  • 5.8 : for a panel - convector - panel
  • 7 : for a panel - convector - convector - panel
  • 7.6 : for three panels
  • 8.8 : for a panel - convector - panel - convector - panel  
  • 9 : for four panels

Panel Radiator Calculator

- kp - panel radiator constant

- l - radiator length (m)

- h - radiator height (m)

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  • Engineering ToolBox, (2008). Radiators - Heat Emission. [online] Available at: [Accessed Day Mo. Year].

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