Ackermann correction

This equation, which is analogous in form 10 Eq. (2.4-8) fur the effect of mass flux on mass transfer coefficient, is known as the Ackermann correction factor7 for the effect of mass transfer on hent transfer. Note that the tmal flux of enthalpy to the vapor-liquid interface is ihe sum of the condnetiva flux and the enthalpy carried by the tmasferring molecules... 

A more detailed treatment using a logarithmic driving force for vapor flux and the concept of the humidity potential coefficient O while accounting for the influence of the moisture vapor flux on the transfer of heat to the surface, namely, the Ackermann correction Luikov number Lu, which is essentially the ratio of the Prandtl number Pr to the Schmidt number Sc, has also been introduced. 

Ackermann correction, (dimensionless) relative humidity (dimensionless)... 

There are six sublimation studies and two vaporization studies from which an enthalpy of formation for Hf(g) could be derived. A plot of these vapor pressure data, log p vs 1/T, reveals considerable discrepancy between the various studies. In the liquid region, the vapor pressure values of Koch et al. (1 ) and Ackermann and Rauh (2) are in close agreement. The pressures of the former study are 5% higher at 2500 K but become 10% lower at 2800 K. The measured temperatures in the former study ( ) were adjusted (i.e., the pyrometer reading) by Koch et al. ( ) so that at the observed melting point the temperature would be 2500 K. The sample purity was not stated. In the latter study (2) the reported vapor pressures were corrected pressures (assuming ideal solution) from a eutectic of Hf and W. The Hf sample had a measured melting point of 2464 K the purity was not reported. 

Methods for correcting for grain-size effects in studies on heavy metal concentrations in estuarine and coastal sediments have been discussed by Ackermann (1980). There is, unfortunately, no one standard method for particle-size normalisation and a wide range of techniques are in use (Table 2.3). The method which often involves the least effort is the correction which uses comparison with rubidium (Rb) as a conservative element (Ackermann, 1980). This technique relies on the fact that Rb has a similar ionic radius to potassium (K) and so substitution of Rb for K will take place in clay minerals. Furthermore, Rb is present in the sand fraction in very much smaller concentrations than in the clay or silt fraction and concentrations of the element in sediments are rarely influenced by anthropogenic activity. Another advantage of the use of Rb is that it is often routinely analysed by X-ray fluorescence along with a suite of pollutant trace metals. 

Ackermann, F. (1980) A procedure for correcting the grain size effect in heavy metal analyses of estuarine and coastal sediments. Environmental Technology Letters 1, 518-27. 

Correction of Grain Size by Conservative Element Content in Relation to Cesium (Ackermann, 1980). A Regression Line and Correlation to Percentage of Fraction <20 nM in Sediment Samples from Ems Estuary. B Correction of Zinc Contents in a Sediment Core from Ems Estuary. 

In Eq. 14.191, xg is the mass flow fraction of the gas (i.e., rhglm), cpg is the specific heat of the gas, and dTgldim is the local slope of the equilibrium condensation curve (see Fig. 14.25). hg is calculated for the gas phase flowing along by itself and should be corrected for mass transfer effects using the Ackermann [202] correction factor ... 

Heat and mass transfer have an influence on each other, which can be taken into account by the Ackermann [5] correction factor E for the heat transfer stream... 

The ionization energy Ej = 72300 cm (9.0 eV) has been derived from the two-member 5d ns D3 series [3]. From the appearance potential (8.82(4) eV) of Pt+ ions, measured by electron impact, Rauh and Ackermann [4] have derived 8.89 eV as maximum value of the ionization energy and deduced Ej=8.61 eV after correction for ionization to excited states of the ion [4]. 

---