FC-72 Viscosity

Perfluorohexane (C₆F₁₄), more commonly known as FC-72, is a commonly used highly wetting dielectric fluid for electronics cooling applications. This fluid belongs to the Fluorinert^TM line of electronic liquid coolants sold by 3M^TM. As with any coolant, accurate knowledge of the thermo-physical properties of the fluid and their temperature dependence is very important for the design, development, and implementation of heat transfer applications. Fortunately, 3M has provided us with important thermo-physical properties for this fluid [1]. However, the liquid dynamic viscosity as a function of temperature is not explicitly given here (this property is also not available in EES for this particular fluid). I contacted 3M and obtained a mathematical expression that can be used to compute the liquid dynamic viscosity as a function of temperature [2]. I compared the values predicted by this expression with the tabulated value in [1] at 25 ^oC and also with measurements taken by Morgado et al. [3]. This comparison is shown in the figure below:

 

 

 

As the figure shows, the agreement between the 3M equation and the data by Morgado et al. [3] is good with a maximum difference of about 5.7 % at temperatures above 40 ^oC. Note that the variation in dynamic viscosity with temperature is significant and therefore, it must be taken into consideration. For comparison, the figure above also shows the variation of dynamic viscosity of water with temperature [4]. Note that the temperature dependency of the dynamic viscosity is similar for both fluids. This indicates that the temperature variation seen for FC-72 is not uncommon. For the mathematical expression provided by 3M please see reference [2]. For convenience, the table below tabulates the values of liquid kinematic viscosity, liquid density, and liquid dynamic viscosity for FC-72 in 1 ^oC increment from 0 ^oC to 56 ^oC.

 

T	ν	ρ	μ
[ oC ]	[ mm2/s ]	[ kg/m3 ]	[ mPa-s ]
0	0.543	1740.0	0.946
1	0.535	1737.4	0.930
2	0.527	1734.8	0.914
3	0.519	1732.2	0.899
4	0.511	1729.6	0.884
5	0.504	1727.0	0.870
6	0.496	1724.3	0.856
7	0.489	1721.7	0.842
8	0.482	1719.1	0.829
9	0.475	1716.5	0.815
10	0.468	1713.9	0.803
11	0.462	1711.3	0.790
12	0.455	1708.7	0.778
13	0.449	1706.1	0.766
14	0.443	1703.5	0.754
15	0.437	1700.9	0.743
16	0.431	1698.2	0.732
17	0.425	1695.6	0.721
18	0.420	1693.0	0.711
19	0.414	1690.4	0.700
20	0.409	1687.8	0.690
21	0.404	1685.2	0.680
22	0.398	1682.6	0.670
23	0.393	1680.0	0.661
24	0.388	1677.4	0.652
25	0.384	1674.8	0.643
26	0.379	1672.1	0.634
27	0.374	1669.5	0.625
28	0.370	1666.9	0.616
29	0.365	1664.3	0.608
30	0.361	1661.7	0.600
31	0.357	1659.1	0.592
32	0.353	1656.5	0.584
33	0.349	1653.9	0.577
34	0.345	1651.3	0.569
35	0.341	1648.7	0.562
36	0.337	1646.0	0.555
37	0.333	1643.4	0.548
38	0.329	1640.8	0.541
39	0.326	1638.2	0.534
40	0.322	1635.6	0.527
41	0.319	1633.0	0.521
42	0.316	1630.4	0.514
43	0.312	1627.8	0.508
44	0.309	1625.2	0.502
45	0.306	1622.6	0.496
46	0.303	1619.9	0.490
47	0.300	1617.3	0.485
48	0.297	1614.7	0.479
49	0.294	1612.1	0.473
50	0.291	1609.5	0.468
51	0.288	1606.9	0.463
52	0.285	1604.3	0.458
53	0.282	1601.7	0.452
54	0.280	1599.1	0.447
55	0.277	1596.5	0.442
56	0.275	1593.8	0.438

 

Note: To copy the above table into Excel for example, first copy the table and some text from the previous paragraph into a Word document. From the word document, copy the table and paste it into Excel.

References:

[1] 3M, 2000, "Fluorinert Electronic Liquid FC-72," 3M Specialty Materials.

[2] Cardenas R., 2011, Submerged Jet Impingement Boiling Thermal Management. PhD Dissertation, Oregon State University, Corvallis, OR, pp. 249-250.

[3] Morgado, P., Laginhas, C., M., Lewis, J., B., McCabe, C., Martins, L., F., Filipe, E., J., 2011, “Viscosity of Liquids Perfluoroalkanes and Perfluoroalkylalkane Surfactans,” J. Phys. Chem. B, 2011, 115 (29), pp 9130–9139

[4] Klein, S., A., 2010, "Engineering Equation Solver (EES)," F-Chart Software