Example : Numerical Consistency of ES_StableIF97 Steam Table Functions in Region 1
This example shows how to use the Function and Unit Forms by showing the actual preparation work of the numerical consistency of ES_StableIF97 steam table functions in Region 1. The results of this example are used as a part of the Numerical Consistency of ES_StableIF97 Steam Table Functions.
The above is the copy of IAPWS-IF97 document. The Table 5 includes the sample test values provided by IAPWS for Region 1 Basic Equation, i.e. Eq. (7), for the user's computer-program verification.
This Example 1 shall show the verification process of ES_StableIF97 AddIn.
Unit Legend Embed
In order to show the usage of Unit Legend, the verification shall be performed by the use of Unit Legend instead of direct input of unit numbers into each steam table functions..
In A1 cell, the title of the sheet is made, i.e. "IAPWS-IF97 Table 5 Verification". In A3 cell, "Unit Legend" is written. After that, A4 cell is selected and then ES_StableIF97 AddIn Units Form is invoked as shown below by clicking the Form's toolbar button, or the Form's menu.
After the Unit Form is invoked, the units in Unit combo boxes are selected coinciding with IAPWS-IF97 units. For Pressure unit, "bar a" is selected instead of "MPa" because the Unit Form does not have "MPa" pressure unit. 1 MPa = 10 bar a.
Check the "Embed or Locate <ESStb> Unit Legend" check box. Since A4 cell has already been selected before the Unit Form is invoked, the text box of "Anchoring Cell Address of <ESStb> Unit Legend" is already filled in with "$A$4" as shown below.
And then check "Absolute Cell Address for Unit Cell" check box and select "Embed" option button, as shown below.
For details about how to use Unit Form, please refer to this.
If the user wants to select another anchoring cell, he has to click "Cell Select" button. Then, the Unit Form disappears and an input form shown below pops up for user's selection of a cell in an Excel sheet.
If the user clicks "OK" button in the input form, the input form disappears and the Unit Form appears again
In the Unit Form, if the user clicks "OK" button, an Unit Legend is embedded as shown below.
Temperature and Pressure Input by Unit Conversion Functions
For this verification work, temperature and pressure are required as input arguments. If the temperature and pressure are input into MS Excel cells as numbers, they do not respond to unit number change of the Unit Legend. As an example, if the user inputs 300 K temperature into the temperature cell as "300", the cell value "300" is not changed even though the user changes the unit number in the Unit Legend.
In order to make the temperature and pressure respond to the unit number change of the Unit Legend, they should be input by the Unit Conversion Functions of ES_StableIF97 AddIn.
In order to input Temperature 300 K by the Unit Conversion Function, invoke the ES_StableIF97 AddIn Function Form as shown below, then ;
Then, click "Embed" button. The function is embedded as shown below. Temperature has been input by the function ES_CvtT.
Pressure is also input by the function ES_CvtP in same way.
Steam Table Function Embed
In order to embed the ES_StableIF97 function for v, specific volume at 300 K, 3 MPa(= 30 bar a), invoke the ES_StableIF97 AddIn Function Form as shown below, then ;
Then, click "Embed" button. The function is embedded as shown below. It is seen that the specific volume, v(= 1.00215168E-03), calculated by ES_StableIF97 is just same with the Table 5 test value.
Other properties of the Table 5 test values are calculated by the same procedure performed for the specific volume above, and shown below.
It is seen that the property values calculated by ES_StableIF97 functions are just same with the IAPWS-IF97 Table 5 test value.
Property Unit Change
Change the integer numbers of <Unit No.> cell C8 and C9 of Unit Legend to zero. Then <Unit> cell strings are changed automatically to "kcal/kg" and "kcal/kg-K". In the picture below, it is seen that the Unit String Function of "ESStb_SUnitStr" of ES_StableIF97 AddIn functions was embedded into cell B9. The function was embedded automatically when the Unit Legend was embedded. In other <Unit> cells, relevant Unit String Functions were embedded. Therefore, the user changes the integer numbers of <Unit No.> cells, the <Unit> string changes automatically.
Since the water property functions embedded in "F", "G" and "H" columns have the <Unit No.> cell addresses for Unit Number, the enthalpy and entropy values of the three columns are changed automatically when the integer numbers of <Unit No.> cells are changed. Below it is seen that the enthalpy and entropy values are changed from "kJ/kg" and "kJ/kg-K" unit values to "kcal/kg" and "kcal/kg-K" unit values.
The picture below shows temperature and pressure unit number change to "oC" and "kg/cm2 a" respectively. It is seen that other property values are not changed, even though the temperature and pressure values shown were changed to those of new units. They must not be changed, because actual temperature and pressure values were not changed and only the showing values were changed.
Unit Legend Locate
If the user opens this example workbook later, he has to Locate the existing Unit Legend in order to use same units. When the user starts Excel; opens this example workbook; and invokes "ES_StableIF97 AddIn Function" form, popped up is the message box below .
This message box is popped up because in the last use of the Form, the "Cell Address Input for Unit Number" checkbox was checked. Please note that ES_StableIF97 AddIn Forms remember their last settings and come with their last settings whenever they are invoked.
Since this is the first time Excel starts with this workbook and the "Cell Address Input for Unit Number" checkbox was checked in the last use, the program asks the user whether to Embed or Locate Unit Legend.
Since this example has its existing Unit Legend, let's select "Yes' button and invoke "ES_StableIF97 AddIn Unit Form.
And then, click "Cell Select" button and invoke an input form. Then select "A4" cell in Excel sheet and click "OK" button in the input form to change the text of "Anchoring Cell Address of <ESStb> Unit Legend" text box to "$A$4", and click "Locate" option button. Then the values of the "Unit No." and "Cell Adrs" labels are automatically coincided with those of the existing Unit Legend, as shown below.
If the user embeds steam table functions after this, the functions shall have same unit numbers or cell addresses with the existing Unit Legend.
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