Water (Distilled); Mineral Oil; Silicone Oil (Dow Corning 200.05, 200.10, 200.20); Fluid Characteristics Charts - Fluke 7103 User Manual

7103 Micro-Bath User's Guide
Bath Fluid
8.3.10.1

Water (Distilled)

Water is often used because of its very low cost, availability, and excellent tem perature
control characteristics. Water has very low viscosity and good thermal conductivity
and heat capacity which makes it among the best fluids for control stability at low
temperatures. Temperature stability is much poorer at higher temperatures because
water condenses on the lid, cools and drips into the bath. Water is safe and relatively
inert. The electrical conductivity of water may pre vent its use in some applications.
Water has a limited temperature range, from a few degrees above 0°C to a few degrees
below 100°C. At higher temperatures evaporation becomes significant. Water used in
the bath should be distilled or softened to prevent mineral deposits. Consider using an
algaecide chemical in the water to prevent contamination.
8.3.10.2

Mineral Oil

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 use of a fume hood is highly
recommended. As with most oils mineral oil will expand as temperature increases
so be careful not to fill the bath too full that it over flows 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 flam mable and may also cause serious injury if inhaled or
ingested.
8.3.10.3

Silicone Oil (Dow Corning 200.05, 200.10, 200.20)

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.
Silicone oils are fairly safe and non-toxic. Silicone oils are fairly expensive.
8.3.11

Fluid Characteristics Charts

Table 3 on page 25 and Figure 6 on page 26 have been created to provide help in
selecting a heat exchange fluid media for your constant temperature bath. These 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. There may be other useful
fluids not shown in this listing.
The charts include information on a variety of fluids which are often used as heat
transfer fluid in baths. Because of the temperature range some fluids may not be useful
with your bath.
24
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