Jrr wrote;
Bare zinc galvanized steel is a selective absorber !!! a = 0.7 , e = 0.15
see the CRC Handbook of Chemistry and Physics.
seanr53 wrote:
I have been attempting to simulate (using designbuilder) the performance of a lightweight, uninsulated, galvanised steel roof with a painting system with the following performance parameters:
Solar absoptance = 0.15
Thermal absoptance = 0.1
The roof is over an an unconditioned, naturally ventilated space. I have made a parametric run, using the same roof construction, but with the following surface characteristics:
Solar absoptance = 0.9
Thermal absoptance = 0.5
I have run the simulations using the detailed convection algorithm option, however, my issue is that, despite the different surface characterisitcs of the two models, the simulation results, with respect to roof fabric gains, and internal radiant temperatures are the same.
How do the EnergyPlus convection algorithms take into account radiant heat transfer, as the algorithms don't seem to account for any variations in solar or thermal absoptance?
Or have I missed something ?
Regards,
Sean
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