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Heat Transfer Analysis in Wire Bundles for Aerospace VehiclesDesign of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.
Document ID
20160011474
Document Type
Conference Paper
Authors
S L Rickman
(Langley Research Center Hampton, Virginia, United States)
C J Iannello
(Langley Research Center Hampton, Virginia, United States)
Date Acquired
September 26, 2016
Subject Category
Space Transportation And Safety
Report/Patent Number
NF1676L-23364
Meeting Information
14th International Conference on Simulation and Experiments in Heat Transfer and its Applications(Ancona)
Funding Number(s)
WBS: WBS 869021.03.05.01.20
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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