Thermal conductivity alloys Table

The designation of these Cu—Ni—Zn alloys is based on the silver-like color. Their composition ranges from 45 to 49wt%Cu, 10 to 12 wt%Ni, with the balance composing Zn. Up to 2 wt% Pb is added for better drilling and turning behavior. Ni increases the yield stress and decreases the electrical and thermal conductivity (see Table 3.1-107). 

Electrical—Thermal Conductivities. Electrical conductivities of alloys (Table 5) are often expressed as a percentage relative to an International Annealed Copper Standard (lACS), ie, units of % lACS, where the value of 100 % lACS is assigned to pure copper having a measured resistivity value of 0.017241 Q mm /m. The measurement of resistivity and its conversion to % lACS is covered under ASTM B193 (8). 

Electrical conductivity is comparatively easy to measure, whereas thermal conductivity is not. Electrical conductivity values for the important cast alloys are Hsted in Table 2. Eigure 1 schematically shows the electrical conductivity of cast copper-base alloys compared with various other cast metals and alloys. The equation Y = 4.184 + 3.93a gives an approximation of thermal conductivity in relation to electrical conductivity, where Tis in W/(m-K) at 20°C and X is the % lACS at 20°C. 

TABLE 2-376 Thermal Conductivity of Some Alloys at High Temperature ... 

The thermal conductivity of cupro-nickel alloys = 50 W/m K and, from Table 9.16, scale resistances will be taken as 0.00020 m2K/W for the water and 0.00018 m2K/W for the organic. 

Pure metals have high thermal conductivities, and one would think that metal alloys should also have high conductivities. One would expect an alloy made of two metals of thennal conductivities and 2 to have a conductivity k between A , and ki. But this turns out not to be the case. TTie thermal conductivity of an alloy of two metals is usually much lower than that of either metal, a.s shown in Table 1-2. Even small amounts in a pure metal of foreign molecules that are good conductors themselves seriously disrupt the transfer of heat in that metal. For example, the thermal conductivity of steel containing just 1 percent of chrome is 62 W/m °C, while the thermal conductivities of irort and chromium are 83 and 95 W/m C, respectively. 

Monolith substrate materials suitable for use in high-temperature combustion are either various ceramics or certain alloys. In Section II.C, the demands on a combustion catalyst were already summanzed. The substrate should have a high thermal shock resistance, but at the same time the melting temperature should be higher than the maximum anticipated operating temperature A number of interesting materials are summarized in Table 2, accompanied by thermal expansion coefficients and thermal conductivities. 

The temperature dependence of thermal conductivity for liquids, metal alloys, and nonconducting solids is more complicated than those mentioned above. Because of these complexities, the temperature dependence of thermal conductivity for a number of materials, as illustrated in Fig. 1,11, does not show a uniform trend. Typical ranges for the thermal conductivity of these materials are given in Table 1.1, We now proceed to a discussion of the foundations of convective and radiative heat transfer. 

TABLE 2.34 Density and Thermal Conductivity of Alloys (Continued)... 

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