Conversion Factors for Thermal Conductivity Units

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...

Convert thermal conductivity of 10 kcal/h m-°C to SI units. Select the appropriate conversion factor for these imits ... 

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