×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

# Heat Loss from a Closed Tank

## Heat Loss from a Closed Tank

(OP)
I have a large fire protection tank, 34ft tall x 29ft dia, holds 175000 gallons of water. I have a Lowest One Day Mean Temp of 25F and the min target temp is 42F. Tank is made of carbon steel.

Using the NFPA 22 figure 16.1.4, heat loss = square area x (heat difference) / R, I get a heat loss of 8,164kW, or 24 million BTU/hr.
Assumed: R=0.0031 ft2 F hr/BTU, A=4400 ft2, deltaT = 17

However using Q=hA(deltaT), I get a heat transfer rate of 12.4kW or 42308 BTU/hr
Assumed: h = 3.231 W/m2 K, deltaT = 9.44 K, A = 408m2

These are wildly different results and I can not seem to find the reason.

### RE: Heat Loss from a Closed Tank

If I use h = 1/R, and convert your h = 3.231 W/m2 K. I get R = 1.757 ft2 F hr/BTU.

4400 x 17 / 1.757 = 42,562 BTU/hr.

Conversion error?

Good Luck,
Latexman

### RE: Heat Loss from a Closed Tank

(OP)
Ever just stared at something for the longest time and couldn't see it... Thanks Latexman!

### RE: Heat Loss from a Closed Tank

Your h is a bit low, since it only accounts for ideal natural convection. somewhere between 5 and 7 W/m^2-K accounts for some wind and some radiation.

Your R, inverted, comes out to 1831.6979 W/m^2-K, so a factor of ~600 larger than your h; this magnitude is more for convection in a water-cooled application.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

#### 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.

#### 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
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!