Power Factor
Another informative measurementfor oil evaluation is file power factor. This indicates the amount of energywhich is dissipated, as the molecules align themselves in an electrical field, becauseof the frictional resistance as the medium. Thus, as viscosity increases, thepower factor takes on more
importance, since highviscosity media oilier much greater sources of frictional resistance than thelower viscosity materials.
This comprises a very convenientdetermination since in the evaluation of the dielectric constant on balancingthe A.C. bridge, the resistance as well as the capacitance must be balancedand, therefore, two determinations are made at one time. Figure 4 presents thepercent power factor change for the polymerized and the oxidized oils.
Examination of the arithmeticplot of viscosity power factor shows that for a n y given viscosity the powerfactor of the oxidized oil samples is considerably greater than that of thepolymerized oil. Consequently, power factor is mainly dependent on two variables:viscosity and oxygenated structure, the latter of which apparently contributesmore. This could very well be another tool to be used to great advantage in thestudy of oxidation and oxidative polymerization during the processing of dryingoils.
Summary
Three physical test methods fordrying oils have been described. They are:
1. Molecular weight terminations in cyclohexane for thermally polymerizedand
oxidized oils. Results have beencompared with those obtained in benzene. Theoretical and factual reasons havebeen
givenfor the a p p a r e n t validity of average molecular weight determinations incyclohexane.
2. Dielectric constantdeterminations for treated oils. It has been shown that the dielectricincreases as an oil is oxidized but flint no increase in dielectric occurs
thermal polymerization. The dielectric constantis mainly
a function of the oxygenatedstructure of the oil.
3. Power factor determinations. Thepower factor increases on polymerization an(t on oxidation. The values obtainedfor any given viscosity are considerably greater for the oxidized samples.
Molecular weight and dielectric constant determinations have been usedto advantage in our plants and laboratories. Our knowledge on power factordeterminations, however, is as yet not extensive but it is felt that with morebackground data on this constant a potentially meaningful tool for oil evaluationcan be developed.| 欢迎光临 英语听力论坛 (http://bbs.tingroom.com/) | Powered by Discuz! 7.2 |