Typically you first enter state variable values and then request the application to generate an estimated property value. Sometimes, the opposite process is desired - you specify a desired property value and ask the application to estimate the state variable values that would generate that estimate.
For example, the estimated bubble point pressures shown below are all 10 kPa apart. Each pressure was entered as a goal value and the compositions were varied until the goal value was matched.
The Goal Seek dialog has controls for entering state variables and performing the goal seek operation.
|Components Controls: displays the current mixture's components.
|Compositions Controls: enables you to enter composition values. These values are either used as fixed values, if you plan to seek your goal pressure by varying temperature, or as initial guesses, if you plan to seek your goal pressure by varying composition values.
|Temperature Value Control: enables you to enter a temperature value. This value is either used as a fixed value, if you plan to seek your goal pressure by varying composition, or as an initial guess, if you plan to seek your goal pressure by varying temperature.
|Independent Variable Control: enables you to specify either temperature or composition as the independent variable, i.e., the variable that will be varied to achieve the goal value.
|Residual Composition Control: if you select a composition as the independent variable, then you must select a second composition as the residual variable. As the independent composition variable is varied, this residual composition will be assiged a value to ensure the total of the compositions equals 1 or 100, depending upon the units selected.
|Property Control: displays the property being estimated.
|Tie Line Control: enables you to enter any short text string for the estimate's tie line. Typically, tie lines are entered as TL001, TL002, TL003, etc.
|Goal Control: enables you to enter your goal pressure value.
|Value Control: displays the value estimated at the current state variables. This value should start approaching the goal value as the solution process proceeds.
|Delta Control: displays the difference between the goal value and the current estimated value. This value should approach zero as the solution process proceeds.
|Start Seek Button: pressing this button starts the solution process.
|X Total Button: pressing this button activates the Residual Composition Dialog. This dialog shows the total of all entered compositions and suggests a residual value if only one composition value is missing. See documentation for the Residual Composition Dialog for details.
It is sometimes necessary to have a very good initial guess in order to find a successful goal seek solution. One way you can often get a good initial is by estimating some values at state variable conditions near those you expect for goal value.
You can use these estimated values as your initial guess by simply selecting them in the Estimates Dialog and pressing the Goal Seek button. The selected state variables will be assign to the Goal Seek dialog's controls.
|Getting Started using Synapse
|provides a quick tour of Synapse's capabilities including examples of chemical product design.
|Getting Started using Cranium
|provides a quick tour of Cranium's capabilities including a discussion of structure editing.
|Estimating Chemical Properties
|a short video demonstrating how to estimate the physical properties of chemicals using either Synapse or Cranium.
|Estimating Mixture Properties
|a short video demonstrating how to estimate the physical properties of mixtures using either Synapse or Cranium.