Question on Black Globe Temperature?

[jasno999]

I understand what it is and how it is typicalyl measured. However I am not familiar with typical values are in correspondence with say the dry bulb temperature.

I am looking for a table with typical vaues that I could use to do some approximate analysis.

For example is there any data out there that would give me some black globe temperature values on say a day where it is 80F dry bulb and no air movment on a sunny day?

Anything would be helpful. I just want to get a feel for what kind of increase above the dry bulb temperature I am looking at for the black globe temperature.

 

[MintJulep]

With my home made black globe thermometer, on my desk (insulated on a styrofoam cup).

Globe temps are about 1 F higher than air DB temp.

 

[jasno999]

That might be true but is your black globe in direct sunlight? If it is on your desk I assuem it could still be gettign sunlight but not a tremendous amount. If it were outside I would think it owuld get much hotter.

 

[MintJulep]

Full glass wall with southern exposure, but not direct sunlight.

 

[IRstuff]

MJ,

Did you ever find an answer to your black globe question? I've hunted around, but have yet to find anything that describes any equations involving the interior of a black globe.

Do you have any public references you can point to?

Thanks...



TTFN

FAQ731-376

 

[MintJulep]

IR,

No, I never got any replies to my questions here or elsewhere.

ASHRAE Fundamentals contains a few paragraphs about the black globe in chapter 14 in the discussion of Mean Radiant Temperature.

I am led to believe that ASHRAE Standard 55-2004 has some info as well. I've ordered a copy, but it hasn't shown up yet.