Optimization and Computational Fluid Dynamics - Department of ...

20 Gábor Janiga
y
Tinlet = 293 K
000 111
000 111
000 111000
111
000 111
vinlet =0.03 m/s
x
000 111
000 111
Twall = 353 K
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Periodic
Periodic
Fig. 2.1 Schematic description of the tube bank heat exchanger configuration considered
in Case A
optimal results for a micro heat exchanger based on different multi-objective
optimization methods.
The optimal spacing problem with three chips in an enclosure is reported
in [51]. The optimal location of heat sources was investigated by da Silva
et al. [70] for forced convection and in [71] for natural convection. The latter
was examined by Dias and Milanez [17] using Genetic Algorithm (GA) to
find the optimal location. Staggered finned circular and elliptic tubes in forced
convection are studied by Matos et al. [56]. Bello-Ochende et al. [10] analyzed
cylinders in cross-flow with up to three different sizes in row configurations
for maximizing the heat transfer density.
Nevertheless, optimization based on an arbitrary positioning of the tubes
in a cross-flow heat exchanger could not be found in the literature. This will
be considered now. In Case A, parallel EA are coupled with a CFD code and a
two-dimensional model of a cross-flow tube bank heat exchanger is considered.
One possible simulated configuration is shown in Fig. 2.1. Air enters the
domain at Tinlet = 293 K and is warmed up by passing between the tubes
in which a warm fluid flows in the corresponding practical application. The
tubes are supposed to have a constant outer wall temperature, Twall = 353 K.
The outlet is at atmospheric pressure.
The optimization problem consists of finding the best locations of the
tubes to increase heat exchange while at the same time to limit the pressure
loss. The two corresponding numerical parameters to optimize are the
average temperature difference ∆T and pressure difference ∆P. Thesetwo
objectives are obviously interrelated. If the exchange surface increases, the
heat exchange will be favored and the temperature difference between inflow
and outflow will be also enhanced. But, simultaneously for a given air flow
rate, the pressure loss will increase and the heat exchanger loses efficiency.
Outlet