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Unformatted text preview: tivity. In fact, many ceramics that are used for thermal insulation are porous. Heat transfer across pores is ordinarily slow and inefﬁcient. Internal pores normally contain still air, which has an extremely low thermal conductivity—approximately 0.02 W/m-K. Furthermore, gaseous convection within the pores is also comparatively ineffective. Thermal conductivity (Btu/ft-h-°F) FIGURE 17.4 Thermal conductivity versus composition for copper–zinc alloys. (Adapted from Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th edition, H. Baker, Managing Editor, American Society for Metals, 1979, p. 315.)...
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- Spring '08