SYLTHERM XLT heat transfer fluid

Hi, cannot get a definite answer anywhere on how heat transfer occurs with this fluid. All that the manufacturer gives is "excellent heat transfer". Water has excellent heat transfer due to convection currents. Need to know if this fluid also heats by convection rather than conduction. Conduction can be a very slow process. Viscosity of this fluid close to water which may be a good indication that it heats by convection.
Cannot test because I cannot get a small sample of 4 LITRES. Manufacturer will only supply a barrel for $1900.
Does anyone know on this forum? Have tried the manufacturer but they don't seem to know the difference between convection and conduction. Thanks.

petercl14 said:

Summary: syltherm xlt heat transfer by convection or conduction.

Hi, cannot get a definite answer anywhere on how heat transfer occurs with this fluid. All that the manufacturer gives is "excellent heat transfer". Water has excellent heat transfer due to convection currents. Need to know if this fluid also heats by convection rather than conduction. Conduction can be a very slow process. Viscosity of this fluid close to water which may be a good indication that it heats by convection.
Cannot test because I cannot get a small sample of 4 LITRES. Manufacturer will only supply a barrel for $1900.
Does anyone know on this forum? Have tried the manufacturer but they don't seem to know the difference between convection and conduction. Thanks.

It's all in the datasheet. Amazing what you can find with google.
https://www.dow.com/documents/en-us...01468-01-syltherm-xlt-heat-transfer-fluid.pdf

BTW, discounting metals, I think all liquids move heat better by physical transport (convection, or turbulent flow) than conduction. The big thermal gradient at the surface when a new, cold, molecule pushes out the older hotter one is a big advantage. Plus, in my limited experience, they are all crappy conductors.

I must disagree Dave. Have previously used another heat transfer oil. Had a heater element in the base, tank was 1 foot deep. Very little increase in temperature of oil at surface while at the base getting very hot. Would have burnt out element if I hadn't turned off the power. Typical example of heat by conduction.
Another example Dave. Oil filled column heaters. They take over an hour to heat up. If heating by convection this would be minutes to heat up. For instance if they were filled with water they would only take minutes to heat up. These heaters were tested by Choice magazine.
The reference you have given just says excellent heat transfer. It doesn't say what kind of heat transfer it is, convection or conduction. The difference determines if the liquid takes minutes or hours to heat up.

There's no magic here; all fluids transfer heat by convection and conduction. The more viscous, the less convection. What dominates/matters depends on the application.

petercl14 said:

I must disagree Dave. Have previously used another heat transfer oil. Had a heater element in the base, tank was 1 foot deep. Very little increase in temperature of oil at surface while at the base getting very hot. Would have burnt out element if I hadn't turned off the power. Typical example of heat by conduction.
Another example Dave. Oil filled column heaters. They take over an hour to heat up. If heating by convection this would be minutes to heat up. For instance if they were filled with water they would only take minutes to heat up. These heaters were tested by Choice magazine.

I think you misunderstood, that was exactly my point. For liquids to move heat effectively the molecules have to move, they typically have high thermal resistivity. If you stirred that tank the temperature gradient would have been much smaller.

petercl14 said:

The reference you have given just says excellent heat transfer. It doesn't say what kind of heat transfer it is, convection or conduction. The difference determines if the liquid takes minutes or hours to heat up.

Did you look at page two? They give you about as much data about their material as they can.


What they can't do is tell you how your system will work. Convection depends on the details of your application. That part is your problem, not theirs.

Can't stir the tank in a closed system as in oil filled column heaters. I guess you could shake the oil filed column heater if you were a weight lifter for faster heating. Viscosity means the ease of pouring as with water. The lower the viscosity the easier it is to pour. Convection has nothing to do with the details of the application. It depends on the liquid. Water probably the best of all liquids for convection.

OK, I'm done here. I hope you find the answers you seek.