A tolerance of 1.0
×10−4 was used for convergence.
The computer simulations were carried out on SGI® Onyx®
3800 with InfiniteReality3 Graphics (at the National Supercomputing
Center for Energy and the Environment NSCEE at UNLV) and
the computer runs would take between 4 and 7 h of CPU time to
completely converge. The k–ε model is known not to perform well
in unconfined flows, flows with large additional constraints such as
large temperature gradients in the direction of flow. In this study
though it is to be noted that our simulated flow study is basically
of the confined type (internal flow) adding to that that our flow
thermal conditions are assumed “isothermal” with no temperature
gradients. In addition to that we also based our use of this model
and its accuracy on previous results of papers where similar general
conditions (confined flows and no thermal gradients) existed and
for which these numerical simulations yielded reasonable quantitative
agreements with the experimental data for those situations.
These three studies are: The first paper on which we based our use
of the model and its accuracy is [7] which involved the study of liquid
flow in a ball valve for different partial openings of that valve
where good agreement was shown with previously obtained experimental
data. The second [8] involves the flow and pressure drop for
air flow in an elbow (with and without flow vanes) was simulated
and compared to experimental results from the literature to yield
good quantitative comparisons. Finally the last study is [9] where
the study of air flow through an air handling unit was made and
compared with experimental data from the literature (for an identical
flow geometry) and where favorable comparisons of previous
experimental data was shown to exist. These three papers used the
k–ε model that is used for the present paper with the same identical
empirical constants provided by the software STAR-CD as default
values.