Power Generation in a Straight Flow Steam Turbine-Generator: Oper. Conds Tab

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab. The table also displays their default values and their generally acceptable range. Note that due to how the variables are used in the modeling equations, the range of acceptable values may be further reduced; for more details, see Power Generation in a Steam Turbine-Generator: Modeling Assumptions & Constraints.

Variable	Default Value	Range

○ Exhaust Pressure (atm) The pressure of the outlet stream. If a condensing turbine is used, it is equal to the operating pressure of the condenser.	1.0	Positive
◙ Operating Temperature of Condenser (^oC) The temperature of the outlet stream when a condensing turbine is used.	100.0	Positive
○ Cooling Agent Name Indicates the cooling agent that is used in the condenser. Click on the list box to bring up a list of available cooling agents in order to select one.	<Cooling Water>	Any Cooling Agent
● Inlet Temp. (^oC) The inlet temperature of the cooling agent.	25.0	Positive
● Outlet Temp. (^oC) The outlet temperature of the cooling agent.	30.0	Positive
● Rate (kg/h) The mass flow rate of the cooling agent.	0.0	Positive
● Cooling Duty (kcal/h) The heat transfer rate of the cooling agent.	0.0	Positive
○ Heat Transfer Efficiency The heat transfer efficiency of the condenser.	90.0	0-100
● Operating Throughput per Unit The mass flow rate of feed at each equipment unit.	0.0	Positive
○ Setup Time The amount of time (per cycle) spent before each operation is carried in preparation for the actual execution of the operation. It may involve actions like cleaning, vacuuming, setting up of equipment, etc. which the user opted not to model explicitly.	0.0	Positive
◙ Process Time (min) The actual duration of the operation (per cycle). It can be either set by user or set by a master-slave relationship.	60.0	Positive
○ Ignore Labor? Check this box to ignore labor for this operation. This option is used only if the process time is set by a master-slave relationship.	Yes	Yes/No

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 Power Generation in a Steam Turbine-Generator: Modeling Calculations.

•Turbine Type...

If a back pressure turbine is selected, the specified exhaust pressure must be greater than or equal to ambient pressure.

If a condensing turbine is selected, the specified exhaust pressure may be less than the ambient pressure.

•Expansion Calculation...

By default, the isentropic work is calculated analytically (“Analytical Isentropic Expansion Model” option). Optionally, if the working fluid is steam, the user may choose to calculate the isentropic work based on steam enthalpies before and after the expansion, calculated based on a built-in steam calculator (“Built-In Steam Calculator” option).

•Operating Temperature of Condenser...

If the operating temperature is set by the user, the user may specify a value that is less than or equal to the saturation temperature of the working fluid at the specified exhaust pressure.

If the operating temperature is set equal to the saturation temperature, the operating temperature will be calculated by the program so that it matches the saturation temperature of the working fluid at the specified exhaust pressure. If the “Built-In Steam Calculator” option is selected, the saturation temperature of steam at the specified exhaust pressure is calculated based on the built-in steam calculator.

•Duration Options...

In Rating Mode, you can set the process time (and the setup time), allow the process time to be calculated (based on the throughput and rating power of the units), or allow the duration to match exactly the duration of another operation either in the same procedure or in another procedure. In Design mode, you must either specify the process time (and the setup time) or allow the duration to match exactly the duration of another operation (either in the same procedure or in another procedure) in order for the program to calculate the required power (per step and per unit).

a) If you choose to match the duration of this operation with the duration of another operation,

b) You introduce a master-slave relationship between the two operations. The program will match the setup-time, the process time and the turnaround time of this compressing operation (the 'slave') with the corresponding times of the reference operation (the 'master' operation). For more on master-slave relationship, see The Scheduling Tab.