×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

# Contact US

Log In

#### Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
To Your Posts
• Keyword Search
• One-Click Access To Your
Favorite Forums
• Automated Signatures
On Your Posts
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

# Temperature rise due to thermal load?

 Forum Search FAQs Links MVPs

## Temperature rise due to thermal load?

(OP)
I have aluminum and fiberglass enclosures approx this size 12.2"x10.2"x6.25" (WxHxD) respectively. These enclosures will be installed outside and the solar load on them will be 1120W/m2. Consider the ambient temperature to be +55 deg C. So can someone tell me how to calculate the additional rise in temperature just due to the solar load?
Thanks!

### RE: Temperature rise due to thermal load?

emissivity? absorptivity? windspeed? internal heat load?

Given the additional information, you simply equate the incoming solar and internal heat load with the exiting radiated and convected heat.  There will be a single surface temperature that satisfies the equality.

IF you do not have an HT text, you should get one; this one is free for downloading: http://web.mit.edu/lienhard/www/ahtt.html

### RE: Temperature rise due to thermal load?

(OP)
Thanks 'IRstuff' and 'ione' for your inputs. Right now I am considering no internal heat load. What I want to know is if this equation still holds good - Q=A*K*(delta T)/L
where Q = Solar Load, A = area exposed to solar load, K = thermal conductivity of aluminum, delta T = temperature difference between ambient and inside of enclosure, L = thickness of aluminum enclosure
Basically I am saying that the solar load is a heat source inside the enclosure and now want to know the rise in ambient temperature due to it?

### RE: Temperature rise due to thermal load?

You have to equal the heat transferred by radiaton (Stefan-Boltzman law) to the heat transferred by internal convection (from the inside of the box to the wall) + conduction through the box's walls + external convection.
This method doesn't offer a direct solution, you have to start with a guess temperature and iterate the procedure until it converges.

### RE: Temperature rise due to thermal load?

No, your equation is not appropriate here.  Read the book.

### RE: Temperature rise due to thermal load?

(OP)
Where I am coming from is Telcordia standard GR-487 specifies '+46 deg C as ambient temperature + solar load' for design of electronic enclosures. I am assuming solar load of 1120 W/m2 on the enclosure and want to know how much it translates to temperature as I want to specify the ambient temperature range of +46 deg C + temp (not solar load). Hope I am explaining what I am looking for?

### RE: Temperature rise due to thermal load?

I understood that from the first post.  However, you've been given the procedure a couple of different ways already, and you seem to be not forthcoming on data.  The basic equation looks like:

solar_load*absorptiivity*area1 = area2*htc*(Tbox-Tair)+ area3*emissivility*Planck*(Tbox^4 - Tamb^4)

Tamb is the emissive temperature of the environment
Tair is the air temperature
Solve for Tbox, which can be done manually, or through a solver routine such as the one inside of Excel.

### RE: Temperature rise due to thermal load?

(OP)
I don't know any other data besides what I already mentioned. My questions are:
absorptivity of what? aluminum?
area 1 = ?
area 2 = ?
area 3 = ?
htc = ?
planck = ?
what's the difference between Tamb and Tair?
What's Tbox4?
Can you plug the numbers that I have already provided in your equation so I know what is what?
Thanks!

### RE: Temperature rise due to thermal load?

Is this for school?

### RE: Temperature rise due to thermal load?

(OP)
No it's not for school!
Thanks!

### RE: Temperature rise due to thermal load?

If this is actually for work, then as an engineer, you should be able to analyze the problem and come up with the missing parameters, as is the case for the areas.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

### Reply To This Thread

#### Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!

Already a member? Close this window and log in.