HCurve - General Information

Heating/Cooling Curves - Technical Information

The Heating/Cooling curve module is not a unit operation as such, but rather, supplemental calculations which are performed after the flowsheet calculations have been completed.

The heating/cooling curve module generates heating or cooling curves for any process stream in the flowsheet, including some unit operation internal streams that undergo heating or cooling. Optionally, the heating/cooling curve module also performs Additional Calculations including physical, critical, thermodynamic, transport, and petroleum properties.

Calculation Method

The heating/cooling curves are generated by a series of equilibrium flash calculations performed at specified equal increments of temperature, pressure or enthalpy. You may select the number of points where the flash calculations are to be performed, or use the default eleven (making ten equal intervals). Any optional properties, if requested, are also calculated at these points.

You may select isothermal and/or fixed-enthalpy calculations. Isothermal calculations are performed by a series of flashes at equal temperature and pressure increments. Fixed-enthalpy calculations are performed by a series of flashes at equal enthalpy and pressure increments. Additional points are reported in both cases if phase boundaries are crossed. For flowsheet streams, Bubble point and Dew point calculations can also be performed. Bubble and Dew point temperatures may be computed to correspond to a pressure grid, or the pressures may be computed to correspond to a given temperature grid.

Process Stream Curves

When generating heating/cooling curves for process streams, you must provide the ranges over which the flash calculation is to be performed. The stream component properties can be studied over pressure and temperature ranges different from the actual stream conditions.

Unit Operations' Internal Stream Curves

Heating/cooling curves can be generated for the flash, heat exchanger, and column unit operations' internal streams. For these units, the endpoints for the calculations are at their internal combined feed and product stream conditions. For exchangers, you may select both hot and cold side streams for curve generation. For columns (including side columns), the condenser, reboiler, and pumparound heaters/coolers may be selected. The temperature, pressure and enthalpy ranges are retrieved from the units automatically by PRO/II to generate the heating/cooling curves. However, for Columns, Simple Heat Exchanger, Rigorous Heat Exchanger, ACE, and LNGHX, you can specify a pressure range over which the calculations will be performed.

The applicable thermo method is automatically retrieved from the respective units when the Heating/cooling curve calculations are performed. For example, if Heating/cooling curve is configured for simple Heat Exchanger, the thermo method specified on hot and cold sides of the heat exchanger is retrieved and used in Heating/cooling curve calculation. For calculating Heating/cooling curves for streams, the thermo method specified by the user in heating/cooling curve unit is considered.

HTFS Interface

The PRO/II - HTFS link is implemented through the Excel interface to create the .PSF files that can be imported into HTFS. This is an easy interface to transfer PRO/II data into .PSF files.

Plots

Plots for calculated curves can be generated by selecting the Output\Generate plot command. Also, the plot data can be exported to spreadsheet-compatible applications from the Plot window using the File\Export command from its menu bar. See Plot Overview for more details.

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