Vacuum Pump Power Consumption Dialog

This dialog is displayed when the user clicks on the Setup button of the following tabs:

● Vessel Operations: Vent/Emissions Tab

● Reaction Operations: Vent/Emissions Tab

● Cont. Stoich. Reaction in a Photobioreactor: Vent/Emissions Tab

● Agitated Tank Operations: Vent/Emissions Tab

● Tray Drying: Oper. Conds Tab

● Freeze Drying: Oper. Conds Tab

● Mixing & Drying: Oper. Conds Tab

● Granulation: Oper. Conds Tab

● Drum Drying: Oper. Conds Tab

● Rotary Drying: Oper. Conds Tab

Note that this button is available only if an operation vents gas and the operating pressure (or pressure control setting, for a “Vent/Emissions” tab) is less than the specified ambient pressure through the flowsheet’s Reference Conditions dialog. Then, a vacuum pump is needed in order to vent that gas. From this dialog, the user may choose among different options for specifying the power consumption of a vacuum pump used for this purpose.

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this dialog. The table also displays their default values and their generally acceptable range:

Variable	Default Value	Range

● Suction Temp. (^oC) The temperature at vacuum pump inlet. It is assumed equal to the temperature of evacuated gas.	25.0	Positive
○ Power Type Indicates the power type that is used by the operation. Click on the list box to bring up a list of available power types in order to select one.	<Std Power>	Any Power Type
◙ Set Total Power (kW) The total power consumption for the operation (per cycle, if the procedure is set to operate in batch mode).	0.0	Positive
◙ Set Specific Power (kW/(m³/h) The power consumption per unit of suction rate for the operation. This is calculated by dividing the Total Power by the Suction Rate.	0.0	Positive
◙ Set Power Per Equipment Unit (kW) The power consumption per equipment unit for the operation (per cycle, if the procedure is set to operate in batch mode). This is calculated by dividing the Total Power by the number of equipment units.	0.0	Positive
○ Efficiency (%) The efficiency of the selected compression model (isothermal or isochoric). Usually, the efficiency of isothermal compression in liquid ring vacuum pumps is 25%-40%. A suitable efficiency for isochoric compression in a roots vacuum pump is 83%.	30.0	(0,100)
● Suction Rate (L/h) The volumetric flow rate at vacuum pump inlet. It is assumed equal to the volumetric flow rate of evacuated gas plus the volumetric flowrate of the air leak.	0.0	Positive
● Suction Pressure (atm) The pressure at vacuum pump inlet. It is assumed equal to the pressure of evacuated gas.	0.0	Positive
● Exit Pressure (atm) The pressure at vacuum pump outlet. It is assumed equal to the ambient pressure (specified at the flowsheet level).	1.0	Positive
● Air Leak Rate (STP) (L/h) The volumetric flow rate at the program’s standard temperature and pressure (STP) conditions of air leaking into the vacuum pump.	0.0	Positive

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

The following list describes the available specification choices in this tab; for more details on how these are implemented, see Vacuum Pump Auxiliary Equipment Calculations.

•Power Consumption Options...

You may choose among four different options for specifying the power consumption: you may set the total power, or set the specific power (which is defined as the total power divided by the total suction rate), or set the power per equipment unit (which is defined as the total power divided by the number of equipment units), or let the program calculate the power consumption based on a selected compression model (see below).

•Compression Model Options...

You may either select isothermal compression or isochoric compression. Compression in a liquid ring vacuum pump is isothermal, while compression in a roots vacuum pump is isochoric.