FloEFD用于车灯耐热和起雾分析

TaylorZhang

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The task was considered as internal and adjusted for using radiation transparent materials with absorption. The bulb and headlight front glasses materials were defined as transparent and absorptive for radiation. For bulbs the standard material ‘Quartz Glass’ was used. For two glasses the user defined material as ‘Transparent polycarbonate’. The three band DO radiation model was used to simulate the spectral radiation heat transfer.
To simulate the radiation from lamps the radiation sources with black body spectrum were used. These sources were defined on special bodies, which are modeling hot filaments. The sources were placed inside lamp bulbs with some portion of xenon. To model the convective heat transfer from the hot filament to the bulb through xenon we applied temperature sources with the temperature 2927 K to the radiation source bodies. In addition, white body radiation surface was set at the source body surfaces. This radiation condition helps us to avoid additional radiation transmission from the filament, because for this purpose radiation sources were used.
To achieve the energy balance for the filament, a special approach with Goal depended radiation sources was used. This means that the radiation source power was calculated using the following formula:
Radiation source power = Lamp electric power – filament convective heat transfer rate (it was set as a goal)
The environment conditions for our internal task were:
Heat transfer coefficient = 5 W/m^2/K
Temperature of external fluid = 273.15 K
Using this approach we obtained a stationary basic solution inside the lamp. After that, this solution was used for the Tracer Study to investigate the condensation.  Pictures 1 and 2 show the temperature distribution for the basic flow field inside the lamp:

Pic. 1

Pic. 2

Condensation modeling:
The basic solution could be used for Tracer Study calculation to model passive scalar transfer through the basic flow field. To model the condensation we created Tracer Study case using Water as passive scalar.
This Tracer Study was created in assumption that the front internal wall of the glass body has condensed water on its entire surface. That means that this surface could be used as a passive scalar source.  Using this approach we obtained the water mass flux distribution for condensate. See the picture 3 below.

Pic. 3
On this picture the domains with negative mass flux (blue) are the places with potential risk of condensation in real conditions. The domains where there is evaporation (red domains) show the places where glass will be clarified.

Flo-fluid

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