×
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

30% Propelyene Glycol/Water Mixture

30% Propelyene Glycol/Water Mixture

30% Propelyene Glycol/Water Mixture

(OP)
I am trying to find the specific heat of a 30% Propylene Glycol/Water mixture.  Is the heat transfer capability lower or higher than just pure water?  If the heat transfer is lower, why are solutions like this used instead of just water in heat exchange systems (corrosion?)?  

Thanks.

RE: 30% Propelyene Glycol/Water Mixture

30% Glycol is used as an antifreeze to stop it freezing water on its own is a better choice if your ambient temperature stays above freezing for cost and heat transfer

RE: 30% Propelyene Glycol/Water Mixture

My table shows the specific as 0.955.

Lots of systems can be out of service - either intentionally or by accident - in sub freezing weather. Water filled systems will freeze and split.

RE: 30% Propelyene Glycol/Water Mixture

30% Ethylene Glycol and water mixture is preferably used if the working temperature is below zero
 
Beside this, ethylene glycol mixture has higher boiling point than the water which allow for the working of the radiator at higher temperature.

RE: 30% Propelyene Glycol/Water Mixture

The specific heat of prop glycol/water mix is less than pure water (around 0.9 at 100F) , ie, it carries less heat per gallon.

The kinematic viscocity is also higher than water and has a pump energy penalty.

RE: 30% Propelyene Glycol/Water Mixture

RJB32482,

The specific heat varies with both concentration and temperature.  According to the old program I have from Dow, the specific heat of 30% propylene glycol is:

.901 @ 10 F

.933 @ 100 F

.969 @ 200 F

The heat transfer properties of propylene glycol are slightly less than those of water, (or ethylene glycol for that matter).  The reasons are (1) lower specific heat (2) lower thermal conductivity, and (3) higher viscosity.

Glycols are usually used to prevent freezing.  However, it appears that the freezing point of 30% propylene glycol is around 8 deg F.

Regards,

Speco

RE: 30% Propelyene Glycol/Water Mixture

Specific heat of water is 1 btu/lbm-F I dont know of routinely used water based mixtures that can beat that.

RE: 30% Propelyene Glycol/Water Mixture


I'm not 100% sure but aqueous ammonia might, although by a small margin.

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