Thermal conductivity, conversion table

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). 

Conversion factors for mass, density, pressure, energy, specific energy, specific heat, thermal conductivity, dynamic viscosity, and kinematic viscosity in different systems of units are also given in Chap. 2 (Tables 2.1-2.9). 

TABLE 2.7 Conversion Factors for Units of Thermal Conductivity... 

The most common units for thermal conductivity are cal/cm.s.°C and Btu.in/ft. h.°F. The SI unit for conductivity is W/mK. Since a variety of units has been in practice for thermal properties, the conversion factors are given in Table 12.27. 

A variety of units are used in the literature for thermal properties, and this can be a nuisance when different sets of results have to be compared, or when values from an older publication are being used for ealculations. Prior to the adoption of the SI system, the two most eommon units for thermal conductivity were the cal. cm s C and the BTU in ft h F. There are two units of length in the imperial unit, because area is measured in square feet and thickness in inches, and this inconsistency is a potential pitfall for the unw ary. A self-consistent conductivity unit, the BTU ft h F, is obtained if the temperature gradient is measured in F ft instead of F in. but this is not as common. For diffusivity the e.g.s, unit is the cm s and the imperial unit is the ft h. The SI unit for conductivity is the W niK. and the unit for diffusivity is the m" s. For polymers it is more convenient to use a submultiple of the diffusivity unit, the mm" s. because this eliminates a factor of 10 Conversion factors arc given in Table 1. 

Table 1 Conversion Factors for Some Thermal Conductivity Units...

The proportionality constant, k, is the thermal conductivity or coefficient of thermal conductivity, a value specific for each material and generally reported as W/m K by electrical engineers or as cal/second cm °C by chemists and materials engineers (cf. Appendix Table A-1 for conversion factors). 

The user proceeds with table TABDAT and the second data set with the data set number 3899. The property data, in the current example the thermal conductivity, is listed in the colunm DATA together with the pressure and temperature coordinates PRES and TEMP. Additionally, the corresponding density DENS and, in case of mixtures, the mole fractions MOLl to MOL4 can be stored. In the example only 3 out of 36 points are shown. All points belonging to the same data set are identified by the same data set number DSNO. The data are converted to S.I. units and checked for typing or printing errors. Conversion to S.I. units makes it easier for different data sets to be merged. 

The best current 100% solids epoxy adhesives contain about 70% aluminum oxide by weight and give thermal conductivities in the range of 0.8-1 in the English units shown in Table 2. For convenience, a conversion chart is included in Table 2 to permit conversion to any other set of units. The k values for the best alumina-filled epoxies are 10-12 times greater than for unfilled epoxy resins, but are still much lower than for pure metals or solders. Nevertheless, heat flow is adequate for bonding most components. For example, an adhesive with a thermal conductivity of 0.91 and a bond thickness of 3 mils would be able to transfer about 20 W/cm of surface area, with a AT only about 10 C above the heat sink temperatures ... 

The ef-CNT/BP/DDS system has developed for this application (Chen et al. 2011 Hsu et al. 2012b). The incorporation of ef-CNT in the LCER system induces the formation of crystalline phase in the composite, thus greatly enhances the thermal and mechanical properties of the composite as compared with the pristine LCER system (Table 19.6). Besides, the incorporation of thermal conductive CNT has accelerated the curing reaction of ER. However, the excessive amount of ef-CNT in matrix results in reaching vitrification stage quickly and lowering the degree of conversion. The mechanical properties are decreased when the amount of CNT is >2.00 wt%. 

A series of experiments were conducted at about 460°C. This temperature is closer to the temperature used in commercial units operating at low severity. Testing at moderate conversions minimizes the thermal effects and tends to maximize the differences experienced by a change in variables other than temperature. Results are given in Table V and show that catalytic cracking (Runs Bt(3,4, 5)) produces yields similar to or better than coking (Bt(ll)). A single run at 500°C (Bt(16)) resulted... 

In many instances, however, it is possible to purify imidoyl halides by vacuum distillation. If the compounds are thermally sensitive, purification can be conducted by solution in nonpolar organic solvents, in which the polar by-products, as well as products formed by self-condensation, are less soluble, or completely insoluble. While it is often difficult to establish melting points, because recrystallization and thereby exposure to moisture results in partial conversion to the corresponding carboxylic acid amides, identification by infrared spectroscopy is a good analytical tool. The characteristic spectral feature of the imidoyl halides is the C=N double bond absorption which occurs at 1650-1689 cm in imidoyl chlorides (see Table V). 

This table lists all possibilities of energy conversion from a storing dipole in the energy variety a to any dipole in the variety b. Both varieties can be thermal except in the case of conversion toward a conductive dipole, which is relevant of the dissipation process seen in Chapter 11. 

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