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alpha

a

[-]

Factor that describes the ratio of k_La in the media as compared to the k_La in water/air under identical conditions of power and gas flow rate.

beta

b

[-]

Factor that describes the ratio of dissolved oxygen saturation in deactivated media as compared to that of water/air under identical conditions of temperature and pressure. In a fermentation, the microorganisms must be disabled for this determination.

Shaft Deflection near bottom

d_SHAFT.BOT

mm

Deflection in the shaft near the bottom of the reactor, tank, vessel, or fermenter.

Shaft deflection near top

d_SHAFT.TOP

mm

Deflection in the shaft near the top of the reactor, tank, vessel, or fermenter.

Tank deflection at side

d_TANK.SIDE

mm

Deflection in the side wall of the reactor, tank, vessel, or fermenter. This is a sign that the tank wobbles.

Baffle thickness

D_BAF

mm

Thickness of the baffles.

Blade thickness(i)

D_i,BLADES

mm

Thickness of the the blades of the i-impeller.

Top head thickness

D_TOP

mm

Thickness of the top dish. Often found on data describing the ASME pressure testing of the tank.

Longitude relative to front

F_BAF

deg

Position of the first baffle from the front in CCW-direction. If the baffles are not placed symmetrically around the tank, list their positions separately.

Longitude relative to front

F_COIL

deg

Position of first coil or bundle from the front. List them if not symmetrical. Irrelevant for helical coils.

Longitude relative to front

F_SP

deg

Position of the sparge pipe relative to the front in degrees.

Avg Shear Rate

g^·_i,AVG

1/s

Average impeller shear rate for the i-impeller.

Max Shear Rate

g^·_i,MAX

1/s

Maximum impeller shear rate for the i-impeller.

Newtonian Viscosity

h

cPs or mPas

Although most fluids and slurries exhibit non-Newtonian flow characteristics, this is a characteristic viscosity that a company has used to date to describe the viscosity of their fluids.

Viscosity factor

hF

Factor that reduces the k_La as viscosity increases. It is a constant for viscosity < 25.

Rotational direction

j

Rotational direction of the shaft, either clockwise (CW) or counter clockwise (CCW) as seen from the top-down.

k_La Impeller Factor

kF

Ratio that describes how well an impeller system is, based on k_La as compared to a standard single impeller system at the same P/V and Qg. All single impeller systems have the same k_La at the same P/V and Qg.

Theta

q

Constant that describes the deviation of k_La based on different temperatures. The standard temperature is 20^oC. Most reported Theta-values vary between 1.016 and 1.047.

Henzler's ThetaMix(95%)

q¹_{i,MIX,HENZLER}

[-]

Henzler’s ThetaMix number (95%) for a single mixer in a standard tank for the i-impeller.

Henzler's Mult-Imp ThetaMix(95%)

q^M_{i,MIX,HENZLER}

[-]

Modified Henzler’s ThetaMix number (95%) for multiple impellers in a tank for the i-impeller for the i-impeller.

Recirculation Time

q_RECIRC,i

s

Recirculation Time. Time for the average packet of fluid to return to the place it started from for the i-impeller.

Unaerated Density

r

kg/m3

Density of the media without any gas pockets. This should be the density at the operating temperature.

Density of unaerated water at temperature

r_H2O

kg/m3

Density of water at the operating temperature.

Average gassed density of the media

r_LIQ,G

kg/m3

Density of media at the operating temperature taking the entire gassed volume into account.

Total MixTime(95%) for all impellers

t_MIX,95

s

Mixing time based on 95% degree of blending.

95% Blend Time for bottom impeller

t_MIX,B,95

s

Mixing time based on 95% degree of blending for just the bottom impeller (or single impeller).

95.0% Blend Time for bottom impeller

t_MIX,B,x

s

Mixing time based on the degree of blending, x, for just the bottom impeller (or single impeller).

Total MixTime(95.0%) for all impellers

t_MIX,x

s

Total mixing time based on the degree of blending, x, and the e_AVG.

Degree of mixing (blending) desired

x

%

Point at which the reactor, tank, vessel, or fermenter is considered mixed. 100% would take indefinitely long by definition. Typical values are 90%, 95% or 99% mixed.