Only one feed and one product
stream are allowed for the unit. An Input Error is generated if a user
tries to import a keyword file that specifies more than one feed or product
stream.SimSci RESET Unit -- Add-on Unit Operation
Description
The purpose of the RESET unit is to allow you to reset the product stream enthalpy datum using the thermodynamic method specified within the unit. Assume the product of one unit operation feeds a second unit operation. Further assume the enthalpy basis in the thermodynamic method sets of these unit operations is different and inconsistent with the other unit. In such cases, a discontinuity in the enthalpy calculations occurs due to the difference in enthalpy basis. The purpose of the Reset unit is to perform an orderly transition from one enthalpy basis to the next. This avoids calculation difficulties that otherwise would arise due to the discontinuity in the enthalpy data.
Usage
Only one feed and one product
stream are allowed for the unit. An Input Error is generated if a user
tries to import a keyword file that specifies more than one feed or product
stream.
Starting with version 4.1, PRO/II
issues a warning message whenever the thermodynamic method of a unit operation
is different from the thermodynamic method of any of its feed streams.
This warning message applies to all unit operations except for the RESET
unit, the BLEND unit and any Refinery Reactor Model Unit Operations. Because
these units require different thermodynamic methods, such a warning is
not appropriate for them.
Thermodynamic System
In addition of available thermodynamic systems user can select ‘Determined from Connectivity’ option, with this option thermodynamic system will be applied during simulation and it will be same as downstream unit thermodynamic system. “Determined from Connectivity” option will be selected as default when user adds new Reset Unit.
Thermodynamic Reset Basis
The feed stream pressure is always kept constant. The user is required to specify a second quantity to be held constant. The choices are listed below. New product stream conditions will be calculated based on the option specified. “Automatic” option will be selected as default when user adds new Reset Unit.
The available calculation options are as follows:
Automatic –
When feed stream is in single phase, flash the feed stream with constant temperature with product stream thermodynamic. If resulted stream is in same phase continue with constant temperature flash for thermodynamic reset. If resulted stream phase changed use ‘Constant Degrees Over/Under Saturation or Constant Vapor’ basis for thermodynamic reset.
In all other cases use ‘Constant Degrees Over/Under Saturation or Constant Vapor’ basis for thermodynamic reset.
Constant Temperature
Constant Enthalpy
Constant Degrees Over/Under Saturation or Constant Vapor
Dew Point
Bubble Point
Automatic thermodynamic reset basis selected as default when user adds new reset unit.
