Sorry, I haven't qualified my question: I mean a tank under aeration, with a mass transfer coefficient KLa and a dissolved gas saturation concentration of Cs. Both these parameters are dependent of temperature, but a temperature rise will increase KLa and conversely decrease Cs. However, they do not necessarily cancel each other out, and so we need a temperature correction for each of these. Traditionally, the correction factor of KLa is a number theta = 1.024, but this is known to be very approximate. Just wonder who has a better method in calculating the oxygen mass transfer at different temperatures?
The relationship between the dissolved oxygen concentration (DO) and the equilibrium partial pressure at the contacting gas phase is given by Henry's law. DO is often measured with a Clark polarographic oxygen electrode, which calibration and conversion from percent saturation to molarity is addressed at § 2.2.1 (pp. 11-12) of the signalled reference.
You may want to consider the Shumpe et al. correlation for the 'salting out' effect on gas solubilities in aqueous solutions, which has been often used concerning to gases dissolved in biomedia (e.g. O2); Cf.: A. Shumpe, "Gas solubilities in biomedia", in: Rehm, H. J.; Reed, G. (Eds.), "Biotechnology", Vol. 2, Chap. 10, VCH, Weinheim (Germany), 1985; for a modelling application, you may check the following reference (pp. 13-16).
The KLa mass transfer coefficient also contributes to determine DO of the aerobic fermenter. The air to fermenter's media mass-transfer rate of oxygen (Na) should be dependent on the local oxygen deficit: Na = KLa·(Cs-C). Here, Cs is the DO that would apply for saturation of the fermenter's broth and C is the measured DO. A mean concentration difference can be defined (ΔCm) after accepting some convenient mixing model, so that: KLa = OTR / ΔCm, where OTR stands for oxygen transfer rate. Agitation should contribute for KLa. Such a modelling-based approach implicitly takes into account other variables that may influence KLa; including temperature (T) or pH. Further details on this kind of approach, were given at the following reference (MSc Thesis):
Thesis Controlo do Oxigénio Dissolvido em Fermentadores para Minimi...
Thank you very much, Carlos. Do you think you can send me an English version?
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