[b]Numerical Modeling of Cross Flow Compact Heat Exchanger
with Louvered Fins using Thermal Resistance Concept[/b]
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INTRODUCTION
As the engine power density continuously increases and
additional heat sources such as intercooler for boosted
intake air charge, HVAC system, oil cooler and EGR
cooler, are commonly used, thermal loads to the vehicle
thermal management system have been significantly
increased. On the other hand, the engine room is more
crowded than ever in order to accommodate additional
convenience and safety related equipments in the
limited engine room space


STRUCTURE AND DESIGN PARAMETERS OF
COMPACT HEAT EXCHANGERS
As illustrated in Fig. 1, the compact heat exchanger
(CHE) is made of four major components, coolant inlet
tank, outlet tank, pressure cap and core. Coolant tanks
are positioned either on top and bottom of the core as
shown in Fig. 1 or located on the left and right sides of
the core. The coolant circuit is usually pressurized using
pressure cap to increase the boiling point of the coolant
in many applications, which allows higher operating
temperature. The major sub-components of the core are
the coolant tubes and the fins


FINITE DIFFERENCE METHOD
Grid System
In this study, the inlet air velocity was assumed to be
uniform and the temperature variations between the
tubes were also assumed to be negligible. Therefore
only a single fin and tube assembly was discretized as
shown in Fig.3 and the heat exchanger performance
was calculated by multiplying the performance from a
single tube by the number of tubes.


NUMERICAL MODELING
In order to develop a numerical model with the predictive
capability for various design parameters of the heat
exchanger, Finite Difference Method (FDM) with
staggered grid system was employed in this study. The
heat exchanger core was divided into small control
volumes along the tube as shown in Fig. 3. FDM
enables us to take into account the significant air
temperature increase as well as the local variations of
the properties and the heat transfer coefficient.


THE EFFECT OF CORE ASPECT RATIO AND
SIZE
The objective of this study is to develop a heat
exchanger model that has the capability to predict the
heat exchanger performance depending on the design
parameters without relying on experimental data. The
predictive capability of the model was demonstrated with
two different case studies.


CONCLUSION
A numerical modeling methodology using Finite
Difference Method with staggered grid system based on
the thermal resistance concept has been developed for
the compact heat exchanger with louvered fins and flat
tubes. With physics based modeling approach, the
model can predict the effect of detailed design variable
and geometry changes on the heat rejection
performance.