# Calculation Options Dialog

This dialog displays information about the current network, and allows you to specify calculation settings for the current network and globally for all networks. To display the Calculation Options Dialog: ▪Select the Options | Calculation menu item. ▪Right mouse-click on the Data Palette to display a context menu and select 'Calculation...'. ▪Press F2. This dialog has up to seven tabbed pages depending on the modules in your license. Current Network The tab Current Network shows read-only information about the current network file you have open. Convergence Criteria The Convergence Criteria tab allows you to adjust the calculation convergence criteria. Warning: Unless you have a valid reason for doing so, it is not recommended that you adjust these settings. At the limit the solver can exit before full convergence has occurred, this means inaccurate answers. You can always talk to our support team (support@fluidflowinfo.com) if you have a network that is difficult to converge. The Convergence Criteria tab: Global Settings The Global Settings tabbed page shows the settings that are global to all calculations made by FluidFlow. This tab allows you to set global constants used in the calculation. Atmospheric pressure is defined as 101325.00 Pa a. It should be noted that a value of zero should not be used for atmospheric pressure as this will lead to convergence issues. In general, it is not recommended that you adjust the value of 101325.00 Pa a. Note, you can allow the software to adjust atmospheric pressure at boundaries and pressure controllers for elevation. When selected, FluidFlow allows for an appropriate height correction to gauge pressure at a given elevation. You can also choose include other settings for your network as follows: Inclusions Include Viscosity Correction Factor for Centrifugal Pumps: If you are modelling a liquid with a viscosity higher than 4.3 centistokes, FluidFlow makes a correction to the performance data according to the method described in the Hydraulic Institute (HI) Standards. This correction will only occur if the option has been enabled from the "Global Settings Tab" of the Calculation Options dialog AND the fluid viscosity is within the range of 4.3 - 3300 cSt as outlined in the Hydraulic Institute (HI) Standards. Include (Implicit) Reducers/Expanders for Control Valves: If you are modelling a system which includes control valves and you insert a control valve which has connection sizes which are smaller/larger than the connecting pipes, FluidFlow will automatically include a reducer/expander as necessary. This will only occur if this option has been enabled from the "Global Settings Tab". Convergence Aids Automatically close sprinklers, open pipes, open resistances on backflow: When solving a network, FluidFlow will initialize all boundary pressures in the system. If the system includes a sprinkler, open pipe or open resistance node, the pressure at these nodes is atmospheric and flow from these nodes can only occur out of the network. If however there happens to be an error in the model arising from data entry, etc., in solving the conservation of mass, energy and momentum equations, there can be conditions whereby the pressure (1 ATM) at these nodes is higher than at other points in the system. This would indicate that flow would therefore arise from these nodes when in reality, we know that this is not the case. If we therefore enable this option, we will get a warning for the respective boundary node where the likelihood of backflow has arisen and flow in that direction will be prevented from occurring. Automatically use "Ignore Pressure Loss" status for unstable tee junctions: If we are modelling a system where we encounter an unstable condition at a tee junction, the software will revert to ignoring the pressure loss for the respective tee junction if this option is enabled. Heat Transfer - Pipe Heat Loss Outside Coefficient Users can choose from two options to estimate the outside coefficient in pipe heat loss/gain calculations: Option 1) ASTM Standard C680 Correlation and Option 2) Use VDI Heat Atlas Correlations. The Global Settings tab: Gas The Gas tab allows you to set either STP (Standard Temperature and Pressure 15°C and 101325 Pa) or NTP (Normal Temperature and Pressure 0°C and 101325 Pa) for gas volume reference conditions. It is essential that careful consideration be given to the correct reference gas volume flow units prior to building your gas model. You can also choose from three different options for the inclusion of the Joule Thomson effect in your gas calculations: 1.Include Joule Thomson Effect in "Ignore Heat Loss/Gain" model. This option is switched ON by default which means the J-T effect is included in gas calculations where the Heat Loss Model for a pipe has been set to "Ignore Heat Loss/Gain" on the Data Palette. 2.Include Joule Thomson Effect in "Fixed Transfer Rate" model. This option is switched OFF by default which means the J-T effect is excluded in gas calculations where the Heat Loss Model for a pipe has been set to "Fixed Transfer Rate" on the Data Palette. 3.Include Joule Thomson Effect in "Do Heat Loss Calculation" model. This option is switched OFF by default which means the J-T effect is excluded in gas calculations where the Heat Loss Model for a pipe has been set to "Do Heat Loss Calculation" on the Data Palette. For gas pipelines with heat loss where condensing may occur, we have two entries we can make: 1.Assume that the pipe has a steam/vapor trap arrangement. This means that if condensing occurs in the pipeline, all liquid is removed and the vapor leaves the pipe at saturated conditions. This is reflected in the calculated results for the outlet conditions of the pipeline. 2.Assume that the pipe has NO steam/vapor trap arrangement. This means that if condensing occurs, a two-phase mixture will leave the pipe. This is also reflected in the calculated results for the outlet conditions of the pipeline. The Gas tab: Two Phase The Two Phase page allows you to select the two phase pressure loss correlation. Available methods are shown below: Slurry The Slurry page allows you to set pressure loss correlations and constant values to be used in slurry flow calculations. Pulp & Paper Stock The Pulp & Paper Stock page allows you to set pressure loss correlations to be used in pulp and paper stock flow calculations.