Abstract The use of a liquid level sensor made it possible to measure changes in gas hold-up over time stirred tank during unsteady mixing. These results were subjected Fourier series analysis and model was proposed. It allowed one determine the value hold-up, which can be useful for characterizing mixing as comparison steady characteristic frequency also determined, corresponds about twice osc...

Rotary disc contactor (RDC) has been widely used for liquid-liquid extraction owing to its advantages such as high operational flexibility, efficiency, throughput, as well as low driving power and capital cost. As a key variable in liquid-liquid extraction columns, hold-up has been discussed in the literature in three categories: static, dynamic and total hold-up.1 Static hold-up refers to that...

Causal and Noncausal discrete{time transfer functions for some discrete{time system with zero order hold (ZOH), rst order hold (FOH) or ideal sampler are distinguished and described. In the case of ZOH or FOH the discussed notions are essential for the system with a continuous time plant described by the rational proper transfer function with the order of numerator equal to that of the denomina...