MacroFlow: General Flow Systems

MacroFlow enables accurate prediction of the system-level thermo-fluid behavior in a variety of engineering applications. The easy-to-use and integrated Graphical User Interface (GUI) allows quick network construction, solution control, and postprocessing. The component library in MacroFlow is both comprehensive and flexible to enable network analysis of a large variety of engineering systems. Further, a comprehensive database of fluids allows analysis of gas and liquid systems. The heat transfer capability is very complete so that the temperature distribution throughout the system can be predicted for a variety of thermal boundary conditions. Finally, the solution methodology is very efficient, robust, and accurate to ensure reliable use of MacroFlow for system-level design. MacroFlow can be used for the analysis of:

• Steady or unsteady behavior
• Compressible (up to choking) and incompressible flow
• Heat transfer with the surroundings by convection and radiation
• Real gas properties
• Mass and energy sources

MacroFlow is a productivity tool. It use for the design of flow systems shortens the design cycle, improves the quality of the final design, and reduces the time to market.

MacroFlow provides a unified visual environment for the construction, solution, and evaluation of complex flow systems. The powerful graphical user interface facilitates easy construction of networks, allows flexible control of the solution procedure, and provides graphical display of the results. It enables users to analyze complex flow systems quickly and efficiently.

To further facilitate network construction, libraries of commonly encountered components, fluids, and units are included in MacroFlow. The flow system is then constructed through mouse driven selection, placement, and connection of the components within the graphical work environment.

Solution control parameters, such as relaxation factors, convergence criteria, and matrix-inversion procedure can all be specified through dialogs or pull-down menus. This provides the user with the ability to easily optimize the solution approach for a specific problem.

MacroFlow provides flexible post processing through a variety of means, including x-y plots, bar charts, tables, directly on the network, and animation. As with all input fields, units for post processing can be selected from the provided library or user-defined. Once a custom unit has been defined, it is dynamically updated throughout the entire program and added to the unit library.

An extensive component library is provided with MacroFlow, which includes the following:

• pipes, ducts, and logical connections
• elbows, tees, wyes, and crosses with arbitrary angles
• fans, pumps, and blowers
• nozzles, exhausts, and intakes with and without screens
• screens and orifices
• air filters and ultra-high purity gas filters
• diffusers and expanders
• plenums and tanks
• valves, including pressure, timing, ball, swing, gate, and many more
• generic resistances
• customizable node
• available for Windows 95/98/NT/200/XP operating systems

All specific information corresponding to a component is user specified through component dialogs, making network construction simple and easy. Additionally, each component can be customized through a variety of user- defined correlations.

Productivity of the thermo-fluid design of gas and liquid flow systems is further enhanced by including component databases from leading vendors of Gas Filters(Entegris, Mott), Heat Exchangers(Lytron),Cold Plates(Lytron),Quick Disconnect(Aeroquip), Fans(Dynamic Air Engineering, Comair Rotron, JMC Products),Air Filters(Universal Air Filter), and by providing facilities to extend these databases with user-defined characteristics. 

A library of over fifty common fluids and gases is provided with MacroFlow. These fluids occur in a variety of engineering applications such as electronics cooling, semiconductor processing, and fuel delivery systems. These properties are taken from various handbooks such as Thermodynamic Properties in SI by W.C. Reynolds, and Matheson Gas Data Book by Carl Yaws.

Any other desired operating fluid can be specified through a number of options.

• Density - Ideal Gas Law, Compressibility Factor, or a polynomial expression
• Viscosity - Power Law, Sutherland's Law, or a polynomial expression
• Specific Heat - polynomial expression
• Thermal Conductivity - polynomial expression
• Thermal Expansion Coefficient - polynomial expression
• If the above options are inadequate, a piecewise-linear input mode is available, whereby values of any material property can be expressed in tabular form.

Any user-defined fluid property can be saved in the database of fluid properties for ongoing use.

MacroFlow uses the technique of Flow Network Modeling (FNM). In this technique, a flow system is represented as a network of components and flow paths. Then, the specific network characteristics are defined by the user, through tab-dialog input. These component characteristics include volumes, flow resistances, heat transfer coefficients, and any other required properties, all of which can vary with time.

The FNM methodology is fast because it does not attempt to calculate the detailed variation within a component but it utilizes overall component characteristics. This results in a small number of equations that describe the flow and heat transfer over the entire system which can be solved in a rapid manner. Further, since the component characteristics are empirically determined, the predicted behavior of the system is very accurate.

Conservation of mass, momentum, and energy are enforced over the various components and connections. A pressure-correction based solution method is developed for the analysis of the discretization equations that describe conservation of mass, momentum, and energy over an unstructured network. A direct solution method with Newton-Raphson linearization is used for their solution. The resulting solution method is very fast (solution in less than a minute) and robust.

Results of analysis of a network model can be examined in a variety of ways as described below:

• Plots – Predicted variations of various physical quantities can be plotted as Bar Charts or Line Graphs. The appearance of the plots can be customized by specifying the plot color, axis titles, axis range, and font/orientation/format of the captions.
• Tables – Numerical values of predicted quantities can be listed in tabular format in any user-specifiable units.
• On-Screen Display of Results – Specific physical quantities of interest can be listed directly on the screen for chosen components to enable convenient examination of the system performance.
• Animation – The flow of the fluid through the system can be visualized as an animation of colored balls through the network model. Flow animation provides quantitative information because the speed of the dots is proportional to the local flow rate or velocity and the dots are colored according to the local temperature or pressure.
• Export of Plots and Tables – Both the plots and the workspace can be exported as pictures of a suitable format (bmp, gig, jpg, png, tif) to a user-specifiable file for inclusion in reports and presentations. Similarly, tables can be exported as files of csv format for reading into Excel spreadsheets for further processing of data.

In order to facilitate easy creation of the list of components for which results are to be examined using on-screen display, user can visually select the components by first highlighting them on the network before creating plots, tables, or on-screen display of results. The list of components can, of course, be further modified within the individual dialogs. This capability virtually eliminates the need for selecting components by their names, which can be cumbersome for large networks.

MacroFlow is applicable to systems that exhibit any combination of steady, unsteady, incompressible or compressible thermo-fluid behavior. Therefore, MacroFlow can be used to analyze the thermo-fluid behavior of a virtually limitless variety of flow systems. For example, MacroFlow has been used to model:

• gas and liquid delivery systems in semiconductor processing applications
• intake and exhaust manifolds of internal combustion engines
• automotive oil-lubrication systems
• ventilation and cooling systems
• filtration systems
• mufflers
• electronics cooling scenarios
• pipe networks
• heat exchangers
• coolers and dryers
• gas supply systems
• cryogenic systems and many more...

MacroFlow is particularly well-suited for the analysis of ultra-high purity gas delivery systems and liquid delivery systems in Semiconductor Processing applications. Thus, it enables analysis of gas sticks that include valves, mass flow controllers (MFCs), and ultra-high purity gas filters. Simulation of the unsteady behavior of gas flow systems can also be performed in an efficient manner to study time scales for purging processes that involve charging and discharging phenomena. In order to facilitate the ease of setting up models for gas delivery systems involving compressible flow, MacroFlow contains the following two important features:

• A comprehensive library of properties of various inert and reactive gases used in semiconductor processing
• A library of the characteristics of gas filters offered by Entegris and Mott

MacroFlow also enables rapid and accurate analysis of liquid delivery systems involving flow of various liquids through systems that include tubes, pumps, valves, elbows and mixing chambers.

MacroFlow is being actively used at leading semiconductor tool makers for designing gas delivery systems (e.g. gas sticks, supply lines) and liquid delivery systems (e.g. supply and distribution manifolds for corrosive liquids).

MacroFlow was used to optimize an automobile air-conditioning compressor system, by investigating the effect of valve timing, chamber volume, orifice geometry, and operating fluid on volumetric performance.

For a proposed avionics cooling system, MacroFlow was used to select cooling fans and blowers, and to optimize their placement. This MacroFlow model was then used to assess the impact of fan/blower failure on the operating temperatures of essential components.

Exhaust system of an automobile needs to be designed to reduce the noise while minimizing the engine back pressure. MacroFlow was successfully used to evaluate the relative performance of a single and dual exhaust system for a passenger car.