Maximal oxygen transfer rate

Evaluating this unit in vitro, Clark and Mills found the maximal oxygen transfer rate to be 34 ml/min at a gas-to-blood flow ratio of 8 1 and at 1500 ml/min blood flow (Figure 5). 

Since the oxygen is sparingly soluble gas, the overall mass-transfer coefficient KL is equal to the individual mass-transfer coefficient KL. Our objective in fermenter design is to maximize the oxygen transfer rate with the minimum power consumption necessary to agitate the fluid, and also minimum air flow rate. To maximize the oxygen absorption rate, we have to maximize KL, a, C - CL. However, the concentration difference is quite limited for us to control because the value of C L is limited by its very low maximum solubility. Therefore, the main parameters of interest in design are the mass-transfer coefficient and the mterfacial area. 

Proton translocations accompany these cyclic electron transfer events, so ATP synthesis can be achieved. In cyclic photophosphorylation, ATP is the sole product of energy conversion. No NADPFI is generated, and, because PSII is not involved, no oxygen is evolved. The maximal rate of cyclic photophosphorylation is less than 5% of the rate of noncyclic photophosphorylation. Cyclic photophosphorylation depends only on PSI. 

Simulated distributions of gas hold-up, mass transfer coefficient, and dissolved oxygen concentrations in a mixed impeller system (J Rushton turbine, 2 pitched blade impellers) are shown in Fig. 16. At a stirrer speed of 100 min" and a gassing rate of 0.224 m s , the simulated voliune averaged values of gas hold-up and volumetric mass transfer coefficient are Eg = 0.17 and kiU = 532 h , respectively. The value of the volumetric mass transfer coefficient shows a reasonable agreement with /Cifl = 610 h" estimated from the empirical equation suggested by van t Riet [62]. As illustrated in Fig. 16, the gas hold-up is maximal close to the ring sparger. 

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