Flash Types
A flash calculation type is selected based on your choice for the first and second specifications in the Flash Main Window. The following is a list of available flash calculation types and the specifications required to select them.
Adiabatic Flash (ADIA)
This type of Flash is selected when you choose either temperature or pressure (first specification) and duty (second specification). The corresponding pressure or temperature is then calculated. You can specify that the enthalpy change between the feed and products is to be zero (duty = 0), or supply a value for the duty.
Isothermal Flash (ISOT)
This type of Flash is selected when you choose temperature and pressure (one of them for the first specification and the other for second specification). The duty to maintain the specified isothermal condition will be calculated.
General Dew Point Flash (DEW)
This type of Flash calculation is performed when you select either pressure or temperature (first specification) and dew point (second specification). The corresponding equilibrium temperature or pressure at the dew point and the required duty are calculated. If the feed contains a mixture, the first dew point is selected.
Water Dew Point Flash (DEWWATER) (not for electrolyte models)
In hydrocarbon/water systems with the water decant option, you can select the water dew point instead of allowing the system to pick the first dew point. To choose this type of flash you need to select either pressure or temperature (first specification) and the water dew point (second specification). The equilibrium temperature or pressure at this dew point and the required duty are calculated. This flash type is not available if VLLE thermodynamic method is being used.
Hydrocarbon Dew Point Flash (DEWHC) (not for electrolyte models)
In hydrocarbon/water systems with water decant option, you can select the hydrocarbon dew point instead of allowing the system to pick the first dew point. To choose this type of flash you need to select either pressure or temperature (first specification) and the hydrocarbon dew point (second specification). The equilibrium temperature or pressure at this dew point and the required duty are calculated. This flash type is not available if VLLE thermodynamic method is being used.
Upper Dew Point Flash (UPPERDEW) (not for electrolyte models)
In systems having retrograde region in the phase envelope, there may be two dew points at exactly the same temperature. Using the UPPERDEW flash type ensures calculating results for the dew point at the higher pressure. By default, the flash chooses the dew point at the lower pressure.
Bubble Point Flash (BUBB)
When you select either pressure or temperature (first specification), and Bubble point (second specification) this type of flash calculation is performed. The corresponding temperature or pressure at the bubble point conditions and the required duty are calculated.
Isentropic Flash (ISEN) (not for electrolyte models)
This flash simulates isentropic operations, in which the calculations follow a line of constant entropy. You have to select temperature or pressure (first specification) and isentropic process (second specification) for this type of flash calculation. The corresponding pressure or temperature and the required duty are calculated.
Stream Specification Flash (TPSPEC)
When you choose either pressure or temperature (first specification) and supply a value for a Generalized Performance Specification for the product stream (second specification) this type of Flash is selected. The corresponding temperature or pressure is then determined through iteration, until the desired specification is achieved. You can supply a tolerance level ( Absolute or Relative) to speed this convergence. The required duty for the flash operation is also calculated.
Vapor Mole Frac Flash (FRAC)
This type of Flash is selected when you choose either temperature or pressure (first specification) and Vapor Mole Fraction (second specification). The corresponding temperature or pressure is then determined through iteration, until the desired specification is achieved. The required duty for the flash operation is also calculated.
Related Topics