×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Minimum Water Volume

Minimum Water Volume

Minimum Water Volume

(OP)
Hi

I just wanted to ask a quick question to other people designing chilled water reticulation systems for process cooling and operating during low ambient temps (no less than 5degC).

What minimum water volume are people using for these systems, as we are considering the need for a loop or buffer tank to be installed in the system.

I would appreciate information in SI units, but i'll try and convert imperial if you have them.

Thanks in advance.

Nathan

RE: Minimum Water Volume

Hi Nathan,

The following is a formula I've used to size a buffer vessel. This gives the total system requirement and sometimes can be used to demonstrate that a buffer vessel is not required (ie if the chiller, pipework and associated equipment already contain more than the calculated volume):

V = (N x 60 x Z) / (4.18 x dt)

V = total water volume (Litres)
N = Capacity of the chiller's first step (kW)
Z = Minimum allowable running time (min 5 minutes)
dt = Temp difference at minimum partload condition (approx 2 deg C)

This will provide sufficient thermal storage within the system to give 5 minutes operation when the machine is not running, therefore ensuring that the equipment will not continuously stop and start at low loads.Of course, you can increase the 5 minutes if you want, this will proportionally increase the volume of water required.

N is in kW
Z is in minutes (but multiplied by 60 to give seconds)
dt is in deg C.
4.18 is approx specific heat capacity in kJ/kg degC

Hope this helps,

Graham

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!


Resources