Click here for an example,
here for an input file and
here for the GROUND coding,
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* TACT - THERMAL ANALYSIS OF COOLING TOWERS *
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TACT is a computer program developed specifically for the
simulation of natural-draught cooling towers. It is a
derivative of the PHOENICS code, which
bases its predictions on solving the fundamental equations
of fluid flow.
Where is the need?
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Cooling towers normally require a significant portion of the
capital invested in any new plant, and therefore any
reduction in number or size of towers can potentially lead to
a large saving in initial cost. This can be achieved by testing
the tower for various environmental scenarios in order to
determine the most practicable and efficient design, so
avoiding the traditional method of "over-design" to account
for all eventualities.
Cooling-tower operators can benefit from optimal
performance, by reducing running costs and by establishing
the best control strategy.
Safety and environmental concerns can be alleviated by
demonstrating all possible scenarios and situating towers to
minimise environmental impact.
Why TACT?
---------
TACT enables the user to represent the cooling tower fully
in 3D, rigorously taking into account all features of its
physical design, such as:-
1"""Internal and external tower geometry;
1"""Fill characteristics;
1"""Resistance of the fill zone, eliminator, sprinklers,
struts & supports;
1"""Local wind patterns, in speed, direction, temperature
& humidity;
N?' Non-uniformities in fill & inlet water flow rates;
1"""Departure from conventional tower shapes.
TACT: Thermal Analysis of Cooling Towers
By fundamental representation of the physical processes of
heat transfer and fluid flow which encompass the external
environment as well as that inside the tower, TACT provides
a complete prediction of both internal and external air
conditions and interactions.
TACT Menu System
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The TACT menu system has been developed to match
practitioners requirements whilst consistently using plain
English.
The menus are accessed by a branch-type structure and all
defaulted values are set to describe a realistic tower size
and condition which you can modify to your own
requirements. Options can be chosen by mouse or
keyboard, and a graphical capability enables the
visualisation of the tower during set-up phase.
Flow Visualisation
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To post-process results, TACT can use one or the other of
the two stand-alone packages from the PHOENICS
computational suite.
AUTOPLOT is the graph plotting package. This program
enables you to trace profiles of wind pressure, velocity,
temperature, water vapour concentration and all other
results derived from TACT. It can also be used to plot results
from multiple TACT runs, in order to display trends from
parameric studies.
PHOTON is the visualisation package which enables you to
view wind vectors and contours of properties in colour, thus
enhancing the presentation of results for clear and concise
interpretation.
(Picture: Tower performance as a function of wind speed,
for various water distributions)
(Picture: Vapour contours plotted through the centre plane
of a cooling tower)
(Picture: Wind vectors plotted on a horizontal lane at basin
level)
TACT Menu Display
TACT: Thermal Analysis of Cooling Towers
TACT can be used to optimise the design of new cooling
towers by way of parametric studies; and performance
improvements of existing ones from changes in fill design or
water distribution can be tested.
Results provided by TACT predictions can include
performance related data such as:-
1"""Air temperature distribution and water vapour
concentrations in and around the tower.
1"""Water temperatures within the tower.
N?' Outlet water-temperature.
N?' Evaporative water losses.
N?' Air flowrate through the tower.
N?' Thermal performance of the tower as a whole.
On the other hand...
Most contemporary models are too simplistic for reliable
predictions of cooling tower performance, mainly due to
their reliance on one- or two-dimensional representation of
the geometry. Anything less than a three-dimensional
model will not account correctly for local wind patterns that
can have a profound effect on cooling rates. Before TACT
there was no rigorous three-dimensional model.
Many existing models are based on expiricisms derived
from measured data. These seldom hold true for other
cooling towers of different size and capacity, or that operate
in a different environment.
Main features of TACT
---------------------
* Ease of use
* TACT has a user-friendly menu which provides a
straightforward and concise method for data input.
* No specialist computer or mathematical knowledge is required.
Geometric Features
------------------
TACT provides a full three-dimensional representation of
the cooling tower. The menu permits the user, who may be
a designer or operator, to prescribe and modify details of
the tower layout, such as location and characteristics of the
air inlet, fill zone, eliminator, sprinklers, struts, supports and
rain zone which can all be studied in detail.
* Mesh Generator
TACT works by solving balance equations for conservation
of mass, momentum and energy across discrete, multiply
linked, cell subdivisions which together form the entire
calculation domain. The collective subdivisions which
constitute the computational mesh conform to a non-
orthogonal curvilinear coordinate system which is
generated automatically by TACT.
* Turbulent Characteristics of the Flow
TACT uses an effective viscosity method for the
representation of turbulence in the air, which influences air
movement and energy transfer processes both inside and
around the cooling tower.
* Buoyancy Effects
TACT includes buoyancy forces determined from
differences in local air density, which in turn are accurately
linked to air temperature and humidity.
* Prevailing Wind
TACT employs an atmospheric boundary-layer profile in
order to represent the effect of the approaching wind on
tower performance. This can be adjusted for different wind
speeds, directions and ground effects.
On-line Help and Documentation
------------------------------
TACT comes complete with a comprehensive on-line help
facility and carefully-prepared documentation which provide
the user with clear instructions on how to apply the software
and achieve a solution quickly and effectively.
Consultancy Service
-------------------
CHAM offers a consultancy service. If users prefer, CHAM
engineers will perform all the TACT calculations, supplying
the results to the client, with advice as to how they should
be interpreted.
The CHAM consultancy service can also perform CFD
analyses of many other classes of equipment and
processes of interest to engineers. CHAM engineers are all
highly qualified professional engineers and scientists,
experienced in many disciplines associated with the
application of advanced Computational Fluid Dynamics to
modelling of fluid-flow, heat transfer and chemical reaction
for industry.
(Picture: Perspective view of a water vapour plume)
Availability of TACT
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TACT is available for use on most computer software
including PCs, workstations and super computers.
It can be purchased under annual or perpetual schemes.
Licence fees depending on the computer type/power.