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SOLVER TECHNOLOGY |
Perhaps the most fundamental requirement for a solver is that the answers are
both accurate and reliable. In particular, it's critical that the solver
represents all of the important physical effects. Finally, it should converge
easily and with minimal user intervention for a wide range of forced and natural
convection problems. |
FLOTHERM carries out a full, 3-dimensional solution of
the 'Navier-Stokes' equations which govern fluid flow and heat transfer. This
includes the effects of:
- conduction
- convection (air movement)
- thermal radiation
- air viscosity
- turbulence and
- buoyancy effects.
The solver is based on finite volume techniques
meaning that the solution is fully conservative for mass, energy and momentum.
And, based on many years of experience, we've been able to come up with
optimized solution parameters to suit a wide range of electronics thermal design
problems.
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HIGHLY EFFICIENT GRIDDING |
The grdding system employed must be appropriate to the system that you're
analyzing. Many gridding systems are designed for smooth meshing around
relatively low numbers of curved objects such as aerofoils or pipe bundles or
through combustion chambers. But the inside of a computer or a router or a
telecomms rack doesn't look like that! Most electronic systems are cluttered
with hundreds, sometimes thousands of irregular objects. And this means that a
gridding system is needed which is efficient both in terms of its memory
requirements but also solution speed.
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FLOTHERM's gridding system was developed to meet just
those needs. Highly memory efficient and optimized for fast solution in
cluttered systems, the grid is automatically generated from a series of
object-associated grid constraints and user-defined grid patches. Although the
number of nodes may be larger than those for an unstructured grid, the
efficiency of the scheme is such that memory requirements are much lower
(sometimes an order of magnitude), and solutions are much more efficient and
much faster for typical electronics problems. Proven over 10 years of hard work
in demanding day-to-day design work, the gridding system has proven to have no
match. |
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AUTOMATIC RADIATION VIEW FACTOR CALCULATION |
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In some applications, the effect of thermal radiation can be a significant
factor. Sometimes this can be beneficial, perhaps by dissipating heat to the
environment. At other times it can be harmful, for example by absorbtion of
solar radiation. In particular, natural convection systems and portable products
such as mobile phones and laptop computers need to take radiative losses into
account. But one of the characteristics of many electronics systems is the
small, irregular and cluttered cavities that exist within. And this makes the
manual calculation of radiation exchange factors a demanding task.
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FLOTHERM includes powerful functionality for the
automatic calculation of radiation view and exchange factors. The analyst
identifies which surfaces are involved in the radiative exchanges, and the
FLOTHERM Exchange Factor Calculator determines the view and exchange factors
taking into account:
- multiple reflections between surfaces
- complete and partial shading; and
- automatic surface subdivision.
Combined with the use of libraries of surface finish properties, this
provides an extremely powerful capability for the thermal analyst worried about
Thermal Radiation.
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ORTHOTROPIC CONDUCTIVITY |
A number of the materials found in electronics
applications exhibit different thermal conductivities in different coordinate
directions. The most common examples are PCB's (Printed Circuit Boards) and the
substrates of some IC packages, but it is also a concern for some composite
materials. The magnitude of the effect can also be quite large. For example, the
in-plane conductivity of a typical 4 layer PCB can be as much as 2 orders of
magnitude higher than the through-plane conductivity.
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FLOTHERM allows for the effect of orthotropic
conductivity by giving the user the ability to set different conductivity in
different coordinate directions. In addition, when defining a PCB, the in-plane
and through-plane conductivities are calculated directly from user specified
board details removing a layer of calculations from the user. |
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ADVANCED FAN MODELING |
Fans are a common and critical component in many systems. But they can be
complex to model accurately since an analysis should include the effect of:
- non-linearities in the fan curve
- the effect of fan swirl
And, although manufacturers publish fan characteristics in their data books,
accurate information about fan swirl is difficult to find.
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FLOTHERM includes fan operating point calculation for
both linearised and non-linear fan characteristic curves. Any number of fans can
be included and FLOTHERM will calculate the operating point of each, reporting
this back to the user through tabulated output. The fan curves can be input by
hand, or read in from a library file supplied by the manufacturer.
 FLOTHERM also allows the user to define the swirl from a fan, or to
employ a built-in empirical correlation based on joint research with PAPST GMBH
and members of the DELPHI Research Consortium.
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MONITOR POINTS |
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FLOTHERM provides a system of 'monitor points' which
can be used to check on the progress of the solution as it moves towards
convergence. Created and positioned with the mouse, monitor points can also be
attached to geometrical assemblies so that they become, in effect, computational
probes which can then be passed from user to user or re-used in subsequent
analyses |
