Modelon's Heat Exchanger Library - Overview presentation from 2014

1. An overview
HEAT EXCHANGER LIBRARY
1

2. • Heat Exchanger Library
 Key features & capabilities
• Model approach and fidelity
 Heat exchangers
 Stack example
 Air side interface
• Library contents
 Package overview
AGENDA

3. • Modelica library by Modelon
• Geometric, segmented heat
exchanger models
• Several flat tube and louvered fin
designs
• Inhomogeneous flow and
temperature distribution
• Heat exchanger stacking
• Coupling to CFD data
• Prescribed air flow, or driven by
pressure gradient – also for
inhomogeneous distributions
HEAT EXCHANGER LIBRARY

4. • Geometric models of flat tube heat
exchangers
 Geometric friction and heat transfer
correlations
• Air side interface allows heat exchanger
stacking
• Automatic area fraction calculations on
flow segment level
• 2D – discretized and lumped flow source
and sensor components
• Plug-and-play compatible with other
Modelon libraries for thermal
management
KEY FEATURES

5. Geometries considered
MODELING APPROACH
Horizontal Vertical

6. Coolant path discretization: Unique temperature exposed to the wall in
each segment. Several segments per pass and multiple layers are
accounted for.
Example: 2-layered, 3 passes per layer, 4 coolant segments per pass.
COOLANT SEGMENTATION

7. CHANNEL GEOMETRIES
Several geometries are possible.
• Free flow area, heat transfer area, etc. calculated automatically
• Geometric friction and heat transfer correlations included

8. The air flow through each segment assumes uniform flow and
temperature. This interface is coupled to the heat exchanger geometry
and segmentation, i.e. not suitable as external connector interface when
building stacks.
AIR SIDE INTERFACE

9. 1D-3D COUPLING
Distribution Cmin/Cmax NTU = 0 NTU = 5
Interpolated Non-Uniformity Non-Uniformity
A0 0.2 0.820 0.818 0.846
A1 0.2 0.859 0.856 0.874
A2 0.2 0.959 0.950 0.958
A3 0.2 0.998 0.991 0.993
A0 0.4 0.815 0.769 0.850
A1 0.4 0.860 0.831 0.900
A2 0.4 0.961 0.948 0.956
A3 0.4 0.998 0.993 0.995
A0 0.6 0.814 0.750 0.821
A1 0.6 0.862 0.810 0.862
A2 0.6 0.962 0.946 0.949
A3 0.6 0.998 0.991 0.991
A0 0.8 0.815 0.811 0.809
A1 0.8 0.864 0.844 0.840
A2 0.8 0.963 0.946 0.938
A3 0.8 0.998 0.989 0.989
A0 1 0.816 0.810 0.808
A1 1 0.866 0.845 0.842
A2 1 0.964 0.971 0.945
A3 1 0.998 0.999 0.998
HXL Simulation Ranganayakulu Paper
Non-Uniformity
Model compares well with published
reference results (analytic FEA)

10. Example: Two heat exchangers without common edges. Partly covered by
an obstacle causing lower flow rate through a segment.
Air flow straigth through the heat exchanger stack is assumed.
STACK EXAMPLE (IN LIBRARY)
Front view Side view
Passes in red

11. We introduce the concept of stream tubes. The segment edges are
aligned with the component boundaries and depend on component size
and position only. For each stream tube, uniform flow rate and pressure
drop is assumed. The temperature distribution is independent of the
stream tubes.
STREAM TUBES
Stream tubes
Indicated in solid or dotted

12. STACK MODEL
In the Stacks package, there are different
templates and experiment to get a better
understanding of how to use the Stack
components.

13. STACK MODEL
The stack can now be built by directly connecting
components. The component connectors are
independent of the internal component
segmentation and includes the flow bypassing
the component.

14. STACK EXPERIMENT MODEL
The air side boundary conditions may be:
• Upstream flow and downstream pressure, or
• Upstream and downstream pressures per stream tubes
• Upstream temperature profile
Segmentation is defined on top
level, and is automatically
propagated to all components
The stack is
parameterized by the
component geometries
and positions

15. HEAT EXCHANGER
There are two
subsections to the heat
exchangers:
• Flat tubes
• Plate

16. • Cross-flow
• Support one phase
and two phase
• Connected to the
surrounding air on the
air side
HEAT EXCHANGER FLAT TUBE

17. FLAT TUBE MODEL
External connector: Flow
segmented by stream tubes, high
resolution temperature profile, full
stream field represented (not
limited by HX outer edges)
Discretized wall
Replaceable
components

18. • Plate with counter
flow or concurrent
flow
• Often uses
pressurized media
HEAT EXCHANGER PLATE

19. PLATE MODEL
Replaceable
components
Discretized wall

20. Default test cases, to set
up your own experiments
• Initial values
• Steady-state init
• Sources
• User interaction
components
TEST BENCHES

21. BASIC COMPONENTS

22. • MATLAB
• Python
• Excel
BATCHED SIMULATION
Experiment settings
Parameter modifiers
Output of the experiment
at the stop time

23. BATCHED SIMULATION
• Monte Carlo on the HX effectiveness multipliers (uniform distribution between 0.6 & 1) and the flow
rate scaling factors (normal distribution with mean 1 and std dev 0.1)
• Constant Speed drive cycle at 120 kph with fan off and 50% grill opening (trade-off identified earlier)
• Steady-state coolant temperature decreases with increasing HX effectiveness factor. Same trend
with the flow rate scaling factor.
• Coolant temperature however remains relatively steady over a range of values of both the HX
effectiveness and flow rate scaling.

24. info@modelon.com
www.modelon.com