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For a heat exchanger to be manufactured, a series of materials
processing steps must be executed. Intricate designs and increasingly
tight manufacturing conditions may not necessarily be in full
accord. In such cases, serious problems in manufacturing may
prevent a designer from getting the most of its product, or
may lead to failing altogether. A number of issues related
to such problems have been considered within the program instituted
at the UK Center for Manufacturing and under the guidance
of Dr. D.P. Sekulic. Two such R&D problems are as follows:
1. Modeling of the transient 3D behavior of a compact heat
exchanger during manufacturing
2. Thermal integrity of fin-tube bonds for multilouver fin
- extruded microchannel tube configuration
1. Modeling of the transient 3D behavior of a compact heat
exchanger during manufacturing
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The sequence of instantaneous temperature fields in a
compact heat exchanger core (source: Sekulic, D.P., Salazar,
A., Gao, F., Rosen, J.S., and Hutchins, H.F., Local
Transient Behavior of a Compact Heat Exchanger Core During
Brazing, Int. Journal of Heat Exchangers, Vol.
4 (2003) pp. 91-108. A segment of an assembly (multilouver
fins and extruded tubes) indicates the locations of thermocouples
installed on a sample during brazing - data presented
in the attached graphs.)
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Temperature history during manufacturing by brazing and the
deviations of predicted and measured temperatures at listed
locations (Sekulic, D.P., Salazar, A.J., Gao, F., Rosen, J.S.,
and Hutchins, H.F. Experimental Heat Transfer, Fluid Mechanics,
and Thermodynamics 2001, Vol. 1, Edited by G.P. Celata,
P.Di. Marco, A. Goulas, and A. Mariani, Edizioni ETS, Pisa,
2001 pp. 803-808.)
2. Thermal integrity of fin-tube bonds of a multilouver fin-extruded
microchannel tube configuration
A selection of fin-tube joints from actual heat
exchanger. Notice poor and/or pathological joints (source: H.
Zhao, A. J. Salazar, D. P. Sekulic, Influence of topological
characteristics of a brazed joint formation on joint thermal
integrity, ASME-IMECE 2003, Washington D.C., November 2003.)
A designer assumes that all the joints in a real heat exchanger
are characterized by a selected fin efficiency. In an actual
heat exchanger, this is far from being true. In the following
plot, a distribution of evaluated fin efficiency in an actual
heat exchanger has been presented and contact resistances
modeled. Very few fin-tube joints have the prescribed thermal
integrity. ( Source: H. Zhao, A. J. Salazar, D. P. Sekulic,
Influence of topological characteristics of a brazed joint
formation on joint thermal integrity, ASME-IMECE 2003, Washington
D.C., November 2003.)
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