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!

*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.

Jobs

Sizing Compression Tanks

How do I correctly size a compression tank? by Yorkman
Posted: 2 Aug 06 (Edited 25 Aug 06)

The sizing of compression tanks for closed loop hydronic systems can be calculated by using one of these two formulas.
The high and low pressures are going to be determined by two factors. The pressures at the tank connection are selected as follows;
   The low pressure at the tank connection, is selected to hold a positive pressure at the highest point in the system usually about 10 psig, when the system is cold(ie;50°F)in the case of a heating system.
   The high pressure is usually set by the maximum pressure allowable at the safety relief valve(s) without opening them, at operating temerature.
  In the case of a chilled water system the reverse will be used. The high pressure will be when the system is off(ie;90°F), and the low pressure will be when the system is at operating temperature.
    The formula used will depend on the type of tank you are selecting.
 
 For a closed tank with an air/water interface use;

Vt=Vs{[(v2/v1)-1]-3σΔt}÷[(Pa/P1)-(Pa/P2)]

For a diaphram tank use;

Vt=Vs{[(v2/v1)-1]-3σΔt}÷[1-(P1/P2)]


Where;

Vt=volume of tank,gal.
Vs=volume of water in system,gal.
Δt=(t2- t1),°F
t1=lower temperature°F
t2=higher temperature°F
Pa=atmospheric pressure psia
P1=pressure at lower temperature, psia
P2=pressure at higher temperature, psia
v1=specific volume of water at lower  temperature ft3/lb    
v2=specific volume of water at higher  temperature ft3/lb
σ=linear coefficent of thermal expansion,in/in*  °F
=6.5 x 10-6in/in*°F Copper
=9.5 x 10-6in/in*°F Steel

These are the methods used in the ASHRAE Systems Handbook

Back to HVAC/R engineering FAQ Index
Back to HVAC/R engineering Forum

My Archive


Resources


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:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close