The range of thermal conductivities is enormous. As we see from
Fig.
1.6
,
k
varies by a factor of about 10
5
between gases and
diamond
at
room temperature. This variation can be increased to about 10
7
if we in-
clude the effective conductivity of various cryogenic “superinsulations.”
(These involve powders, fibers, or multilayered materials that have been
evacuated of all air.) The reader should study and remember the order
of magnitude of the thermal conductivities of different types of materi-
als. This will be a help in avoiding mistakes in future computations, and
it will be a help in making assumptions during problem solving. Actual
numerical values of the thermal conductivity are given in Appendix
A
(which is a broad listing of many of the physical properties you might
need in this course) and in Figs.
2.2
and
2.3