Conversion factors thermal conductivity

In order to assign and compare catalyst reactivity rates, measured conversions were "normalized" to 3000 GHSV by multiplying observed conversions by the factor actual GHSV/3000. The normalized conversions were used to specify rates to individual products and rates for overall CO conversion. The reaction has b n shown not to be mass or heat transfer limited (12). CO and irreversible H2 chemisorption were measured at room temperature, the former using a pulse injection system and a thermal conductivity detector, and the latter using a static system. Prior to measurements, catalysts were reduced under the same schedule as for reactor runs. 

Product analysis was carried out using a Hewlett-Packard 5890II gas chromatograph, fitted with both a thermal conductivity detector, and a methanator/flame ionisation detector. Separation of the products was achieved using a 3m Porapak Q packed column, with argon carrier gas. Reference data and pure component injections were used to identify the major peaks, and response factors for the products and reactants were determined and taken into account in the calculation of the conversion and product distribution. In all cases stoichiometric gas mixtures were used and carbon balances were better than 97%. Conversions and yields were calculated as follows ... 

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). 

This most useful technique has been applied to the liquid PEG 200, 300, and 400. Fletcher and Persinger [131] studied this application using PEG 200, 300, and 400 and reported the determination of response factors relative to ethylene glycol for conversion of peak areas to weight percent when a thermal conductivity detector was used. 

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