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high pressure sodium lights fraction radiant, visible, return air values?

asked 2016-07-31 16:32:00 -0500

siddharthpatil5's avatar

updated 2016-07-31 16:46:17 -0500

I am using a high pressure sodium lights for modeling a grow room. I know the energy per space floor area value but couldn't really find values for fraction radiant, visible and return air. Do I need these values to represent the kind of lighting that I am using or just the energy density is enough? And where will I find these values?

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Our first grow-room question? It's about time.

__AmirRoth__'s avatar __AmirRoth__  ( 2016-07-31 16:47:09 -0500 )edit

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answered 2016-07-31 16:54:38 -0500

Return air fraction is non-zero only if the lamps are recessed into a return air plenum, which they probably are not. Visible fraction (i.e., luminous efficiency) for high pressure sodium lamps is 12-22% according to Wikipedia. Radiant fraction is the remainder.

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Just adding for posterity since the Wikipedia article's source is no longer online: Engineering Toolbox has efficacy values (not efficiency). The conversion from efficacy to efficiency is to divide by 683 lm/W

matt's avatar matt  ( 2021-07-21 12:37:41 -0500 )edit

answered 2016-08-02 11:24:09 -0500

updated 2016-08-02 15:56:10 -0500

You need to look at Photosynthetically Active Radiation (PAR). See

rpg: oh, I see. Never mind.

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PAR is only relevant to the plant growth bit. I believe the OP is merely interested in defining the luminaires correctly with respect to the building energy model, Randolph. Believe it or not, Amir's answer -- complete with Wikipedia reference -- is a better one, given the context.

rpg777's avatar rpg777  ( 2016-08-02 11:46:43 -0500 )edit

Even I can't believe it!

__AmirRoth__'s avatar __AmirRoth__  ( 2016-08-02 16:44:01 -0500 )edit

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Asked: 2016-07-31 16:32:00 -0500

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Last updated: Aug 02 '16