new features in version 2.9

version 2.9 of macroflow incorporates new capabilities in the preprocessor and the component library� that enhance its ability to analyze a wider variety of flow systems encountered in many applications including liquid-cooled electronics systems and semiconductor processing. in the following discussion, a summary of these enhancements is provided for users of earlier versions of macroflow.

preprocessing

• enhanced library of gases and mass flow rate units – semiconductor processing involves use of inert and reacting gases. the fluid property database of macroflow has been significantly enhanced to include the fluid properties (density, viscosity, thermal conductivity, specific heat, and volumetric expansion coefficients) for a variety of gases that are used in semiconductor processing applications. further, for each gas, units of standard volumetric flow rate (sccm, scfm, slpm), which actually represent the mass flow rate, are included in the units library. the enhanced library of gas properties and mass flow rate units enables analysis of compressible flow in a wide variety of gas delivery systems in semiconductor applications.
• initial conditions – when macroflow is used to perform unsteady analysis, a uniform initial pressure and temperature throughout the systems can now be specified using the initial conditions option in the model menu. this option is activated automatically and only when the model requires transient analysis (e.g. due to time-varying mass flow rate, boundary pressure, and transient filter clogging). by default, the initial conditions are set equal to the ambient conditions. when heat transfer is inactive, only the initial pressure can be specified with the initial temperature being equal to the ambient temperature.
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• enhanced component libraries from leading vendors – an important capability in macroflow is the availability of a library of component characteristics from the leading manufacturers. version 2.9 includes characteristics of quick disconnect products offered by eaton aeroquip (www.aeroquip.com) and ultra high-purity filters offered by entegris (www.entegris.com) and mott corporation (www.mottcorp.com). with this, users can conveniently perform detailed system-level analysis of liquid flow distribution and cooling systems that involve standard qds and analyze gas delivery systems involving gas filters in semiconductor processing applications.

solver

• fan heat sink – impingement heat sinks are commonly used for localized cooling of cpus that produce high heat dissipation in a small volume. such a heat sink consists of a fan mounted directly on the top of the heat sink. macroflow allows modeling of the flow paths through a fan heat sink where the flow enters at the top of the heat sink and splits into lateral streams after impinging on the base. the flow split can be unequal depending on the flow resistances downstream of each lateral branch. note that the fan that creates the flow has to be set up separately upstream of the heat sink. the standard and user defined options enable analysis in the following manner.

  standard – the standard option allows analysis of a plate fin heat sink based on the geometrical characteristics and the thermal conductivity of the heat sink. the flow resistance correlations determine the loss in pressure along each of the two fluid streams that starts at the top of the heat sink and flows out of the side faces. macroflow determines the heat transfer coefficient over the fin surfaces, the corresponding fin efficiency, and hence the resulting thermal resistance of the heat sink. by specifying the heat dissipation at the base of the heat sink, macroflow also determines the average temperature over the base of the heat sink.

  user defined – for a heat sink geometry different than the plate-fin heat sink, the user can specify the resistance characteristics for the flow stream that starts at the top of the heat sink and exits from the side surface of the heat sink. user also specifies the thermal resistance of the heat sink. macroflow then calculates the total flow entering the heat sink, the flow split, and the average temperature of the base of the heat sink.

• quick disconnect – quick disconnects are used in liquid distribution and cooling systems for convenience in isolating components or subsystems without allowing any leakage. the flow path within a quick disconnect is complex so that the flow resistance characteristics may depend on the direction of the flow. thus, the flow characteristics can be specified as being independent of or dependent on the flow direction. each resistance characteristics can be specified as dimensional polynomial or piecewise linear function of the flow rate (volumetric flow rate or mass flow rate) along with the reference density and viscosity at which the characteristics are measured. these characteristic can then be automatically adjusted for changes in density or viscosity of the fluid relative to their reference values. macroflow also contains a library of quick disconnect products offered by aeroquip (www.aeroquip.com).
• flow map – liquid cooling systems used in defense electronics and avionics applications operate under largely varying ambient conditions. since the properties, especially the viscosity, of the commonly-used coolant fluid varies significantly with temperature, the flow resistance characteristics of the components are significantly affected by change in temperature. a commonly used method of describing the flow resistance behavior is to express the pressure drop as a two-dimensional function of flow rate (mass or volumetric) and temperature. the heat load absorbed by the fluid as it flows through the component is also specified. the temperature used in the representation of the characteristics can be the inlet temperature, the average temperature, or the exit temperature. note that, such a component characteristics is valid for a specific fluid because the effect of variation of fluid properties with temperature comes indirectly through the dependence of pressure drop on the temperature. when used in the analysis of a system, user has to ensure that the fluid properties are consistent with those used to create the flow map characteristics.