Tutorial - Page 11

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Sub-problem 2.4: Establish an approximate total pressure drop value for nitrogen-water downflow at 10 bars (1.3 mm glass beads; G=1 kg/m²s)

1) Open Case problem I.mr.

2) Add the new specifications to the problem.

Select the Reactor tab. The qualitative specifications on the Packing type and Packing material turn insignificant since the choices have been reduced to Beads for the Packing type and Glass for the Packing material (it means that all 169 data sets deal with glass beads). This fact can be observed when the combo box, which provides a list of components for the corresponding field, disappears.
Check the Packing nominal size box, change the units from m to mm, and select the corresponding Value field . In the dialog window, write 1.3 in the left box with a 5% extension in the right box. Press OK, then Execute. A total of 74 data sets remain in accordance within the problem specifications.

Select the Fluids tab to set the liquid and gas compositions. The composition setup can be done using two approaches, either from the liquid phase or gas phase point of view. Select Add in the Liquid phase panel. The following dialog window will be presented to the user. It exhibits all single components, either a gas or liquid at room conditions, reported for the 74 data sets. Select Water, highlighting it in blue, and press OK. Do not execute.

Comment: When starting a new query, the user should always specify the fluids composition at the end, if possible. Otherwise, the component list for the whole integrated databank is rather long. This is why a Search engine is provided based on four categories, being the usual Name, the most common Synonym/ (or Name if the synonym is not available), Acronym (if possible) and chemical Formula (if possible).

The water and gas compositions remain to be set. In the Liquid phase panel, select (unspecified) in the Composition field . The ensuing dialog window gives the composition of water (Water) in the liquid phase and the composition of other liquids (Liquid phase: Others) as well. The last field gives the complete gas phase composition (Gas phase). It looks that one gas/liquid combination involving water is present for the reduced list (74 data sets). Highlight the composition (Water - Water (100%); Gas phase - Nitrogen (100%), and press OK, then Execute. The list will be reduced to 38 lines from Hasseni and Pommier.

Comment: After selecting a liquid, the user can highlight one or several gas/liquid compositions in either one of the five tables (mol. %, vol. %, wt %, mixed or all). The user can not select, for example, one line from the mol. % table and another from the vol. % table. This is why the all table was formed, which contains all compositions from the 4 previous tables. Go here for a small example on how to use fluids composition table.

3) Select the Plot button . The Plot creator dialog window will appear.
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4) To specify the X-axis value, click on the knob corresponding to Operating conditions in the Horizontal axis panel. Highlight Gas mass flow rate.
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5) To specify the Y-axis value, click on the knob corresponding to Hydrodynamics in the Vertical axis panel. Click on the knob corresponding to Total pressure drop, and highlight Experimental.
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6) To specify the discriminate value, choose the Advanced tab. Click on the knob corresponding to Operating conditions, and select Pressure. Press OK.

7) To discriminate the diagram in terms of pressure, select the Discriminate series button . Choose the Value discrimination option. The minimum and maximum values for the discriminate (pressure - 38 data sets) is presented (Min value: 10 bar; Max value: 100 bar). Enter a large number (i.e. 1000) in the Number of classes box. Press OK.

8) Lets say the diagram contains thousands of points, making it difficult to perceive individual points of interest. It is possible to draw only specific series in order to alleviate the diagram. For that matter, right click on the legend. The following dialog window will be presented to the user. Unselect all the series in the Draw field, except the one of interest (10 bar). Press OK, and all series for 50, 90 and 100 bar will be removed from the diagram, but still in memory.

Comment: The Draw on top option enables the user to draw the specified serie over the others. It is especially handful when the diagram contains several data points. This option will be used in a later example.

9) Save this problem as Case problem 2.4.mr in a folder of your choice.

CONCLUSION: Based on the latter diagram, it can be concluded that the total pressure drop for nitrogen-water downflow at a gas mass flow rate approaching 1 kg/m²s through 1.3 mm glass beads operated at 10 bars should approximate 70000 Pa/m or 70 kPa/m.

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