Hi All

I'm running a transient CFD simulation using Flow Simulation and am encountering an issue I can't make sense of. I'm modelling an enclosed box with the following setup:

• Gravity, Fluid Flow, Conduction + Radiation using Discrete Ordinates and Absorption in solids enabled.
• Default outer wall thermal condition: Heat transfer coef. (3.17 W/m^2/K). Temp external fluid: 25C
• Default wall radiative surface & Default outer wall radiate surfaces: MDF (Emissivity: 0.93, Solar absorptance: 0.7)
• Default material set to Chipboard (Therm. Conductivity: 0.15W/(m*k), absorption coeff.: 0.5 1/mm, refractive index: 1.5)
• A heat lamp represented by a Directional radiative source (1000W) placed above the chamber.
• A black-body radiation receiving surface is applied to a recessed vertical and horizontal aluminium sheet (Diffusive reflection, emissivity coef. = 0.94 & Solar absorptance = 0.96)
• A polycarbonate sheet covers the top and front side of the box to trap air (Absorption properties defined via table. Roughly 1% at 250nm, 50% at 360nm, 93% at 440nm to 750nm).
• Ambient air is pulled into the box through an environmental pressure opening, by an outlet volume flow (0.004484 m^3/s).

The simulation spans 42 minutes total:

• 0 - 2 minutes - settling period: heat lamp toggled off, outlet volume flow = 0 m^3/s
• 2 - 22 minutes - light on, outlet vol flow = 0 m^3/s
• 22 - 32 minutes - light on, outlet vol flow = 0.00484 m^3/s. (ramped over 2 seconds)
• 32 - 41m, 58s - light off, outlet vol flow = 0.00484 m^3/s
• Fan ramped down over 2 seconds.

Changes to the temperature trajectories of the internal air and surface temperatures of the solar receiving surface do not correlate with the light being toggled either on or off. I have tried varying the power of the lamp via Dependency table, with with no perceived difference in the results.

My questions are: 

• Why might the radiation source be having no apparent (or miss timed) thermal effect?
• Is there a known limitation or setting in SolidWorks Flow Simulation that might cause this kind of behaviour?
• or more likely - Is there something I may be missing in the set-up?

I'd greatly appreciate any insights, suggestions, or similar experiences. Thanks in advance!

Best regards,

Magnus