HCurve

Usage

• First, select one stream by highlighting it with the mouse cursor on the main PFD.

• Then use this command to display the PRO/II Hot Key - Heating/Cooling Curves main data entry window. (Another path to this feature is the HCurve item on the Tools menu.)

The Stream ID is defaulted in the Stream ID static text field. In all cases, only one stream (or one unit operation) is selected. Currently in PRO/II, curves on selected unit operations is not supported.

The curve specification fields are identical to those in the HCURVE unit operation, and the functionality is identical. Only a single curve is allowed. No provision is made to input additional curves.

The thermodynamic method set may be declared in the last field on the left of the form. This drop-down list box lists all Thermodynamic method sets active in the simulation. The method of the selected stream should be selected as the default.

Generating A Report

Once the type of curve and all required data are defined by the user, calculations may be initiated in one of two ways:

1. Press the "Show Plot" button. This action initiates two actions:
   Action 1: The curve data is passed to routine GUHCAL which calls to perform the calculations. If a fatal calculation error occurs, an appropriate message is displayed in a dialog box. Pressing OK returns to this form.
   Action 2: If no fatal error occurred, the Plot Options WINDOW is opened and the focus passes to that window.

2. Press the "Show Table" button. With no further user interaction, the tabular data for Temperature, Pressure, and Enthalpy at all calculated points are displayed in numeric tabular form. There are 3 columns: Temperature, Pressure, and Enthalpy.

Using the Plots Form

This form is displayed after the user pressed the "Plots" button on the main form, which executed the calculations with no errors.

Four plots initially are provided:

1. Temperature vs. Enthalpy: Temperature is scaled on the left Y-axis and Enthalpy appears on the X-axis. Text and an icon on the button illustrate this.

2. Temperature & Pressure vs. Enthalpy: Temperature is scaled on the left Y-axis. Pressure is scaled on the right Y-axis. Enthalpy appears on the X-axis. Temperature and pressure are plotted independently against enthalpy.

3. Temperature vs. Pressure: Temperature on the Y-axis, Pressure on the X-axis.

4. Pressure vs. Temperature: Pressure on the Y-axis, Temperature on the X-axis. This is the complement of plot (3) above.

On pressing one of the buttons, the plot is displayed in a separate non-modal window. Functionally, the plot action mimics existing behavior in the BVLE hot key.

After the plot is displayed, the user may return to this form and press another button to display another plot.

Since all the Temperature, pressure, and enthalpy data are always available, regardless of the type of curve being calculated, all the plots are always available.

After displaying all the desired plots, the user clicks the Cancel button to return to the main form, where the curve definition data may be altered to create a new curve. Then, the Show Plot and Show Table buttons can again be used to display the new data. The user exits from the main window of the HCURVE hot key feature by clicking the Cancel button.

Suitable defaults need to be formulated to characterize the curve to generate. The curve should be of type ADIABATIC DUTY, DP=0.0, where DUTY is set to the enthalpy of the stream (i.e., DUTY = Ht). This is suggested only as the easiest obvious default; a more meaningful default should be requested from the thermodynamics group. Also default POINTS=11, and activate the KPRINT option.

Thermodynamic System

The Thermodynamic Method entry is defaulted to the thermodynamic method set associated with the stream, or to the default set. The Print Option entry is defaulted to Summary, and the PLOT option is active.

Note: HCURVE hot key functionality can be applied to streams only. Hot Key functionality is available to users in demand mode. In this mode, the user does not lay down the feature as part of a PFD for a flowsheet. Rather, the feature begins execution immediately upon activation of a "hot key". Upon termination of execution of the feature by the user, all data associated with the current instantiation of the feature is lost. No changes are made to the existing keyword or GUI implementation of these features. All these features are already fully supported through key words. HCURVES are fully supported in the PROVISION Graphical User Interface (GUI).