There is a lot of confusion and misinformation about what makes one heat transfer fluid better or more efficient than another. And once the salesman begins to brag about how his fluid’s conductivity will reduce degradation or the low density makes for low pressure drop, you may as well get the shovel out and start cleaning up.
Comparing 1 or 2 properties of fluids can be very misleading. For example, low viscosity improves heat transfer but low density reduces it. High thermal conductivity makes water efficient but most non-aqueous fluids have very low conductivity. The only way to compare thermal performance of 2 fluids is to calculate the fluid heat transfer coefficient (also known as the inside film coefficient) using some variation of the Seider-Tate equation. The way the math works in this equation, Viscosity has the most influence on heat transfer, followed by Density, Specific Heat and least of all Thermal Conductivity.
Vapor pressure doesn’t count for heat transfer but more on that later.
If you'd like to receive these TipSheets™ on a monthly basis via email,
please enter your name and email below.
(c)2006
Paratherm Corporation
http://www.paratherm.com
Any voluntary information that you choose to share with
Paratherm will remain in our company database and will be shared only
with our technical representatives in order to assist you. Any analysis
of this information we perform is to learn how to better serve our customers,
whether that be through website design, direct contact with customers,
or advertising choices. Your information will never be passed on to any
advertisers or mailing list companies.
|
