Glass film heater - QuickField simulation example
Electric film heater is used to heat up the window glass.
How to find temperature rise in glass film heaters?
Answer Typical applications Geometry
Given
Task
Solution
In QuickField we specify the convection coefficient value that is reciprocal to the surface resistance value:
A set of problems with different power sources is simulated. Creation of the new problems, data modification and results measurements are automated with LabelMover.
Result
References:
Engineering question
Set up a plane-parallel QuickField Steady-state Heat Transfer problem for a glass film heater and evaluate temperature rise from computed field results.
glass film heaters, window defogging heaters, transparent resistive heaters
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Simulation problem
Problem Type
Plane-parallel problem of Heat Transfer.
Film thickness t = 0.01 mm, heat power q = 0..1000 W/m².
Thermal conductivity of glass 1 W/m*K, thermal conductivity of film 4 W/m*K.
Inside air temperature +20°C, surface resistance* 0.13 K·m²/W.
Outside air temperature -15°C, surface resistance* 0.04 K·m²/W.
Calculate the glass temperature as a function of the heater power q.
In QuickField we specify volume power density:
Volume power [W/m³] = Heat power q [W/m²] / Film thickness t [m].
αinside = 1/0.13 W/(K·m²),
αoutside = 1/0.04 W/(K·m²).
After the film heater power reaches 250 W/m² the outer side of the glass temperature becomes positive.
After the film heater power reaches 500 W/m² the inner side of the glass temperature becomes higher than a dew point** temperature of 11°C.
When film heater power reaches 750 W/m² the inner side of the glass temperature becomes warmer than that of the inner air the glass starts to heat up the air inside.
Temperature distribution in the glass with the film heater power of 500 W/m² is shown on the picture below. The temperatures in LabelMover are displayed in Kelvins.
* ISO 10077-2:2012 Thermal performance of windows, doors and shutters.
** Wikipedia, Dew point.
Video
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