SIMULATION OF BOILING HEAT TRANSFER AROUND MICRO PIN-FIN HEAT EXCHANGER: PROGRESS AND CHALLENGES Page: 2 of 2
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reduced average bubble size and shorter
retention time, i.e. the time for the vapor
phase sticking on the pipe surface. The
smaller average steam bubble size and
shorter bubble retention time will
enhance the overall thermal efficiencyAUl
T, 1
11Fig. 1 Schematic of inline arrangement
of micropin-fins on the exterior surface
of heat exchanger tubes.
Computational Problem Details
As a preliminary step, a simple
computational model was generated
using a commercial package
GAMBITTM. The heat conduction in the
solid is solved using transient heat
conduction equation using a commercial
package FLUENT . A periodic
arrangement of micropin-fins containing
four in-line cylindrical fins (Fig. 1) was
modeled. Material properties of the
metal were selected corresponding to
Nickel and the fluid was selected as
water. For the preliminary calculations,
the far field coolant temperature was set
at 300K and the fin base temperature
was set at 370K. The governing
equations for the mass, momentum and
energy transport were solved in the fluid
in a conjugate heat transfer mode. The
results were presented for a case with the
quiescent fluid surrounding the
micropin-fins. The computational mesh
comprised of unstructured arrangements
of around 100,000 tetrahedral finite
volumes.
Results and Discussion
For the steady state, temperature
distribution is expected to be mostlylinear in the quiescent surrounding fluid
conditions (Fig. 2). In the future, several
studies will be conducted to simulate
different geometric arrangements,
different fin cross-sections, and realistic
operating conditions including phase-
change with boiling by adding
complexities in simple steps.
300 310 320 330 34D 35D 360
* 2~
Fig. 2 Contours of temperature field
around four micropin-fins.
Conclusion
Boiling at microscales is a challenging
problem for the computational models as
well as the resources. A hierarchical
methodology is needed to incorporate
the nano/microscale physics with the
macroscale system performance.
Acknowledgements
This study was sponsored by a grant from
U.S. Department of Energy, Award No. DE-
FG52-05N27041.
References
1. Tien, C.-L., Majumdar, A. and
Gerner, F.M. Microscale Energy
Transport, Taylor and Francis (1998)
216-218.
2. Faghri, M. and Sunden, B. Heat and
fluid flow in microscale and nanoscale
structures, WIT Press (2004) 173-224.
3. Dhir, V.K. Phase Change Heat
Transfer- A perspective for the future,
Rohsenow Symposium on Future Trends
in Heat Transfer, MIT (2003).
4. Kandilkar, S.G. Heat Transfer
Mechanisms During Flow Boiling in
Microchannels, J. Heat Transfer, 126
(2004) 8-16.
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Tyagi, M.; Maha, A.; Singh, K. V.; Li, G. & and Pang, S.S. SIMULATION OF BOILING HEAT TRANSFER AROUND MICRO PIN-FIN HEAT EXCHANGER: PROGRESS AND CHALLENGES, article, July 1, 2006; Baton Rouge, Louisiana. (https://digital.library.unt.edu/ark:/67531/metadc874271/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.