Metal specific heat

Y.S. Touloukian and E H. Buyco, Specific Heat - Metallic Elements and Alloys, Thermophysical Properties of Matter - Volume 4, IFI/Plenum, New York, 1970. 

Touloukian, Y.S., and Buyco, E.H., The TPRC Data Series Vol. 4, Specific Heat-Metallic Elements and Alloys, New York, Washington, 1970. [Be]... 

Dulong and Pedt s law The product of the atomic weight and the specific heat of a metal is constant of value approximately 6-2. Although not true for all metals at ordinary temperatures, these metals and several non-metals approximate to the law at high temperatures. 

The expansion coefficient of a solid can be estimated with the aid of an approximate thermodynamic equation of state for solids which equates the thermal expansion coefficient with the quantity where yis the Griineisen dimensionless ratio, C, is the specific heat of the solid, p is the density of the material, and B is the bulk modulus. For fee metals the average value of the Griineisen constant is near 2.3. However, there is a tendency for this constant to increase with atomic number. 

The specific heats of polymers are large - typically 5 times more than those of metals when measured per kg. When measured per m, however, they are about the same because of the large differences in density. The coefficients of thermal expansion of polymers are enormous, 10 to 100 times larger than those of metals. This can lead to problems of thermal stress when polymers and metals are joined. And the thermal conductivities are small, 100 to 1000 times smaller than those of metals. This makes polymers attractive for thermal insulation, particularly when foamed. 

Metal A lomic number Atomic weight Lattice structure Density at 20°C (g/em ) Melting point (°C) Thermal conductivity at 0-l00°C (W/m°C) Specific heat at 0°C (J/kg C) Coefficient of linear expansion at 20-iOO°C X 70 Thermal neutron cross-section (barns) (10-- m ) Resistivity at 0°C (fiil em) Temperature coefficient of resistance o-ioo°c X 10 ... 

J/g °C. This explains why swimming is not a popular pastime in northern Minnesota in May. Even if the air temperature rises to 90°F, the water temperature will remain below 60°F. Metals have a relatively low specific heat (Table 8.1). When you warm water in a stainless steel saucepan, for example, nearly all of the heat is absorbed by the water, very little by the steel. 

Whereas heat capacity is a measure of energy, thermal diffusivity is a measure of the rate at which energy is transmitted through a given plastic. It relates directly to processability. In contrast, metals have values hundreds of times larger than those of plastics. Thermal diffusivity determines plastics rate of change with time. Although this function depends on thermal conductivity, specific heat at constant pressure, and density, all of which vary with temperature, thermal diffusivity is relatively constant. 

The most marked effect of change of temperature on the specific heat is, however, exhibited by the non-metals, carbon, boron, and silicon. The following values were obtained by H. F. Weber (1875) ... 

The method has been applied by Eucken to determine specific heats of gases (e.g., H2) at constant volume by enclosing them in small metallic vessels. 

Dependence on Density.—If the density of a metal is increased by hammering, its specific heat is slightly decreased. The same change is observed if the change of density is due to a change of crystalline form, or to change from an amorphous state to a crystalline state, and with different allotropic forms (Wigand, loc. cit,). 

Let ado be the heat developed per second in a portion of a homogeneous conductor the ends of which are at temperatures 6 and 6 + d6, when unit current passes from the warmer to the colder end. a is called the specific heat of electricity in the metal. Let the values of [Pg.451]

By means of the experimental methods briefly referred to in 9 a large number of specific-heat measurements have been made at very low temperatures. In Fig. 91 we haye the atomic heats of some metals, and of the diamond, represented as functions of the temperature. The peculiar shape of the curves will. be at once apparent. At a more or less low temperature, the atomic heat decreases with extraordinary rapidity, then apparently approaches tangentially the value zero in the vicinity of T = 0. The thin curves represent the atomic heats calculated from the equation ... 

In these boilers, various interrelated, complex surface chemistry reactions may occur at the metal-water interface, which (apart from the development of a desirable protective magnetite film) can lead to the formation of unwanted deposits. These surface reactions are influenced by the specific heat flux, operating temperatures, and the areas and degree of local metal stress resulting within a particular boiler. 

In an oil cooler 216 kg/h of hot oil enters a thin metal pipe of diameter 25 mm. An equal mass flow of cooling water passes through the annular space between the pipe and a larger concentric pipe with the oil and water moving in opposite directions. The oil enters at 420 K and is to be cooled to 320 K. If the water enters at 290 K, what length of pipe will be required Take coefficients of 1.6 kW/m2 K on the oil side and 3.6 kW/tn2 K on the water side and 2.0 kJ/kg K for the specific heat of the oil. 

It is desired to warm an oil of specific heat 2.0 kJ/kg K from 300 to 325 K by passing it through a tubular heat exchanger with metal tubes of inner diameter 10 mm. Along the outside of the tubes flows water, inlet temperature 372 K and oudet temperature 361 K. 

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