Liquid hydraulic time constant

In this equation Tl can be considered to be a liquid hydraulic time constant. /I is a dimensionless combination of Ti and rv . = -(tv/Tl) and describes the influence of the vapor flow on the hquid flow (dLjdv) in order to give the same hold-up. represents the... 

The liquid hydraulic time constant ( 3) is included by using a linearized form of the Francis weir formulation, and 3 is set to 6 s. 

Equation (5.32) is a simple linear relationship between the liquid holdup on a tray, M , and the liquid flow rate leaving the tray, L . The parameter P is the hydraulic time constant, typically 3 to 6 seconds per tray. 

As expected, the hydraulic time constant is completely determined by the term from Eqn. (16.52) which describes the mass above the weir. Thus it depends largely on the liquid flow and the hold-up fraetion. The equation for Tk becomes ... 

Sample volumes can be measured In any of three general ways (a) by means of a probe aspirating the liquid at a constant rate, (b) by using mechanically or hydraulically actuated, high-precision syringes for a preset time and (c) by weighing the liquid. 

The continuous-flow nonsteady state measurements can be made after the reactor has reached steady state, which usually takes at least 3 to 5 times the hydraulic retention time under constant conditions. Then an appropriate amount of the compound to be oxidized (e. g. Na2S03) is injected into the reactor. An immediate decrease in the liquid ozone concentration to c, 0 mg L-1 indicates that the concentration is correct. Enough sulfite has to be added to keep cL = 0 for at least one minute so that it is uniformly dispersed throughout the whole reactor. Thus a bit more than one mole of sodium sulfite per mole ozone dissolved is necessary. The subsequent increase in cL is recorded by a computer or a strip chart. The data are evaluated according to equation 3-24, the slope from the linear regression is - (2/,/Vj + KLa(03)). 

One of the most important uncertainty about in-situ parameter concerns materials intrinsic conductivity. They can vary by one or even two order of magnitude. This is quite important because, according to equation 3, darcean liquid flow is directly proportional to this parameter. Theoretically, if the conductivities ratio between the EB and the site remains constant, and, if darcean water flux is dominating, the saturation time should be proportional to EB intrinsic conductivity. To check this, three hydraulic calculations were performed, with EB intrinsic conductivity of respectively lO , 10 ° and... 

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