Heating/Cooling Curve for Flash Drum
The heating/cooling curves for the internal stream of a flash unit can be evaluated by isothermal and fixed-enthalpy methods. The temperature, pressure, and enthalpy ranges are between the inlet and the outlet stream conditions for the selected flash unit and are retrieved by PRO/II automatically.
Note: For each flash entry in the Heating/Cooling Curve Main Window, PRO/II will perform only one type of calculation. If both isothermal and fixed-enthalpy calculations are required for the same flash unit, you have to duplicate the flash entry in the main window and then select one method for each entry.
Usage
From the Heating/Cooling Curve Main Window, select the desired flash unit in the unit operations table. Push the corresponding Enter Data button to display this window.
Evaluation Condition
Isothermal Calculation
Select the first option to perform isothermal flash calculations with equal temperature and pressure increments. The pressure and temperature ranges lie between the inlet and outlet conditions of the flash unit under consideration. In the case of multiple feed streams, the inlet conditions are taken as the average inlet temperature and the lowest feed stream pressure.
Fixed-enthalpy Calculation
Select the second option to perform fixed-enthalpy flash calculations with equal enthalpy and pressure increments. The enthalpy range lies between the total feed and total product streams enthalpies. The pressure range is between the lowest feed stream pressure and the flash drum pressure.
For both calculation types, the first point for the curve is calculated at the inlet conditions. The number of increments for the temperature/pressure/enthalpy ranges is equal to the value specified in the Number of Evaluation Points field minus one.
Report options
You can request the results printout to contain additional data such as Liquid Activity Coefficients, K-Values, etc., by selecting the appropriate options. These selections will apply only to the curve for which you are entering the evaluation data. The first of these options (liquid activity coefficients, etc.) will produce meaningful results only if a liquid-activity K-value method is chosen in the thermodynamic data section of input.
Number of Evaluation Points
The temperature, pressure, and enthalpy ranges are divided equally into the number of evaluation points where the flash calculations are performed. The default value is eleven. Note that the first evaluation point is at the unit inlet conditions.
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