Radiation - Solar Loads - Material properties

chris_ztop · November 9, 2015, 11:59

Hi everybody,

i try to simulate the irradiation on a solar thermal collector.
After activating radiation>s2s radiation>solar loads i am now struggeling with the "Physics Values" for the surface where the energy should be absorbed. Basically it is a alloy plate and i can change the "Emissivitiy" and "Transmissivity" of the selected "Boundary".
I am wondering why it is not possible to specify the "absortion coefficient".
Can anyone please help because at the moment i have no idea how to prescribe the absorption on that surface.

Thanks a lot!

me3840 · November 9, 2015, 15:29

Transmissivity, reflectivity, and absorption are all coefficients that must add to 1. You can specify transmissivity and reflectivity to give you a certain absorption.

chris_ztop · November 10, 2015, 03:43

Thanks! I was trying it that way but the plate is not heating up at all. Maybe i should use the the multiband thermal radiation instead of the gray thermal radiation so i can define the tranmissivity etc. for different wave lengths. I was just wondering because there was no increase in temperature..

me3840 · November 10, 2015, 12:05

Perhaps your boundary is just in shadow? If you plot the boundary irradiation is it nonzero?

chris_ztop · November 11, 2015, 10:04

Ok, now it is working. Thanks

November 9, 2015, 11:59	Radiation - Solar Loads - Material properties	#1
chris_ztop New Member Join Date: Nov 2015 Posts: 3 Rep Power: 11	Hi everybody, i try to simulate the irradiation on a solar thermal collector. After activating radiation>s2s radiation>solar loads i am now struggeling with the "Physics Values" for the surface where the energy should be absorbed. Basically it is a alloy plate and i can change the "Emissivitiy" and "Transmissivity" of the selected "Boundary". I am wondering why it is not possible to specify the "absortion coefficient". Can anyone please help because at the moment i have no idea how to prescribe the absorption on that surface. Thanks a lot!

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November 9, 2015, 15:29		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Transmissivity, reflectivity, and absorption are all coefficients that must add to 1. You can specify transmissivity and reflectivity to give you a certain absorption.

November 10, 2015, 03:43		#3
chris_ztop New Member Join Date: Nov 2015 Posts: 3 Rep Power: 11	Thanks! I was trying it that way but the plate is not heating up at all. Maybe i should use the the multiband thermal radiation instead of the gray thermal radiation so i can define the tranmissivity etc. for different wave lengths. I was just wondering because there was no increase in temperature..

November 10, 2015, 12:05		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Perhaps your boundary is just in shadow? If you plot the boundary irradiation is it nonzero?

November 11, 2015, 10:04		#5
chris_ztop New Member Join Date: Nov 2015 Posts: 3 Rep Power: 11	Ok, now it is working. Thanks