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7108
Users Guide
7.2.10.2
The temperature range of water may be extended by using a solution of 1 part
water and 1 part ethylene glycol (antifreeze). The characteristics of the ethylene
glycol-water solution are similar to water. Use caution with ethylene glycol since
the fluid is very toxic. Ethylene glycol must be disposed of properly.
7.2.10.3
Methanol or methyl alcohol is often used at low temperatures below 0 °C.
Methanol is relatively inexpensive, has good control characteristics, and has a
low freeze point. Methanol is very toxic so care must be taken when using and
disposing of this fluid.
7.2.10.4
Mineral oil or paraffin oil is often used at moderate temperatures above the range
of water. Mineral oil is relatively inexpensive. At lower temperatures mineral oil is
quite viscous and control may be poor. At higher temperatures vapor emission
becomes significant. The vapors may be dangerous and a fume hood should be
used. As with most oils mineral oil will expand as temperature increases so be
careful not to fill the bath too full that it overflows when heated. The viscosity and
thermal characteristics of mineral oil is poorer than water so temperature stability
will not be as good. Mineral oil has very low electrical conductivity. Use caution
with mineral oil since it is flammable and may also cause serious injury if inhaled
or ingested.
7.2.10.5
Silicone oils are available which offer a much wider operating temperature range
than mineral oil. Like most oils, silicone oils have temperature control
characteristics which are somewhat poorer than water. The viscosity changes
significantly with temperature and thermal expansion also occurs. These oils
have very high electrical resistivity. Silicon oils are fairly safe. These oils are
relatively expensive.
7.2.11 Fluid Characteristics Charts
Table 3 and Figure 3 have been created to provide help in selecting a heat ex-
change fluid media for your constant temperature bath. The charts provide both a
visual and numerical representation of most of the physical qualities important in
making a selection. The list is not all inclusive; many usable fluids may not have
been shown in this listing.
7.2.11.1
Every effort has gone into making these charts accurate; however, the data here
does not imply any guarantee of fitness of use for a particular application.
Working near the limits of a property such as the flash point or viscosity limit can
compromise safety or serviceability. Sources of information sometimes vary for
particular properties. Your company's safety policies as well as personal
judgment regarding flash points, toxicity, etc. must also be considered. You are
responsible for reading the Material Safety Data Sheets and making a judgment
here. Cost may require some compromises as well. Hart Scientific cannot be
liable for the suitability of application or for any personal injury, damage to
equipment, product or facilities in using these fluids.
7-4
Ethylene Glycol
Methanol
Mineral Oil
Silicone Oils
Limitations and Disclaimer
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