Temperature Estimates Goal Seek Dialog
Applicability: Cranium, Synapse (core versions 0315+)

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 temperatures shown below are all 20 degrees apart. Each temperature was entered as a goal value and the compositions were varied until the goal value was matched.

Dialog Controls

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 temperature by varying pressure, or as initial guesses, if you plan to seek your goal temperature by varying composition values.
Pressure Value Control: enables you to enter a pressure value. This value is either used as a fixed value, if you plan to seek your goal temperature by varying composition, or as an initial guess, if you plan to seek your goal temperature by varying pressure.
Independent Variable Control: enables you to specify either pressure 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 temperature 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.
Example: Seeking a goal temperature
  1. Open the MKS Sample Knowledge Base document. (Open a "working" copy or create a copy of the document (see here) if you are just experimenting with this functionality.)
  2. Make sure the current units are: wt% for composition; kPa for pressure, C for temperature. (See documentation on the Property Units Dialog for details on changing units.)
  3. Change to the Mixtures Chapter and navigate to the '1-Propanol + Water' mixture. (See the Navigation Overview documentation for details on navigating chapters and pages.)
  4. Scroll down to the Phase Equilibria Section and click the left mouse button on the property control. (See the section's documentation for additional details.)
  5. The Properties Dialog is activated. Select 'VLE, Bubble Point - f(T,P,X)' as the property and 'Temperature Estimates' as the values type.
  6. Now click the left mouse button on the Section's large table control. The application activates the Temperature Estimates dialog. (See documentation on the Phase Equilibria Temperature Estimates Dialog for additional information.
  7. Click the left mouse button on the dialog table's first row and press the Goal Seek button. The application activates the Goal Seek Dialog.
  8. Enter the values and selections shown in the image below then press the dialog's Start Seek button.
  9. Pressing the Start Seek button begins the solution process. During the process, the application will update the independent variable, the X1 Composition in this example, estimate the property value, and compute the difference between this estimate and the goal value. For example, after the first iteration the compositions will have changed and the Goal Values will have been updated.
  10. After the second iteration, the estimated value will be closer to the goal value.
  11. Finally the iterations will converge onto a solution.
  12. Pressing the Goal Seek Dialog's OK button will store the state variables and estimated value into the Temperature Estimates dialog.
  13. Pressing the Temperature Estimates dialog's Save button will store this estimated value into the current document.
Tip: Estimate some values first

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.

Related Documentation
Topic Description
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.