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GPS-X Technical Reference

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117 Suspended Growth Models<br />

Elevation above sea level: Specifies the elevation above sea level.<br />

Standard air conditions (U.S. (air temp 20°C, 36% humidity)/ European (air temp<br />

0°C, 0% humidity/User-Defined): If the aeration method is diffused, this switch selects<br />

which standard conditions are used to calculate the standard air flow used within <strong>GPS</strong>-X<br />

and displayed as an output. If user-defined standard air is selected, the user must enter<br />

the properties of their air in the Properties of User-Defined Air sub-section. The userdefined<br />

air option provides the user with a method of specifying pure oxygen.<br />

Properties of User-Defined Air Sub-Section<br />

Mole fraction of oxygen in user-defined air: When user-defined standard air has been<br />

selected, this parameter specifies the oxygen mole fraction of the user-defined air. The<br />

default value is 1 which is consistent with pure oxygen.<br />

Density of user-defined air: When user-defined standard air has been selected, this<br />

parameter specifies the density of the user-defined air. The default value is 1,429 mg/L<br />

which is consistent with pure oxygen.<br />

Molecular weight of user-defined air: When user-defined standard air has been<br />

selected, this parameter specifies the molecular weight of the user-defined air. The<br />

default value is 32 g/mole, which is consistent with pure oxygen.<br />

Exponent in blower power equation: When user-defined standard air has been<br />

selected, this parameter specifies the value of exponent K in Equation 6.28 for the userdefined<br />

air. The default value is 0.284, which is consistent with pure oxygen.<br />

Physical Form – Layout Wide Settings<br />

When global conditions are being used for oxygen solubility or it is necessary to change<br />

global physical constants important to aeration, the relevant physical data is accessed by<br />

selecting System > Input Parameters > Physical. The available parameters are shown in<br />

Figure 6-6 and are detailed below.<br />

Oxygen Solubility (Layout-Wide Settings) Sub-Section<br />

Most of the parameters in this sub-section of the layout-wide physical form are duplicates<br />

of the local versions discussed earlier. The one exception is as follows:<br />

Barometric pressure at sea level: Specifies the pressure at sea level. The default value<br />

is 101.325 kPa.<br />

<strong>GPS</strong>-X <strong>Technical</strong> <strong>Reference</strong>

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