A consistent method of defining the transient thermal contact conductance is developed. With this method the heat flow is calculated numerically between two, three-dimensional heat flux tubes in perfect contact over an area less than the nominal cross-sectional area. This total heat flow is matched to that of a one-dimensional model using an applied interfacial conductance. This applied conductance represents the constriction of the heat flux tube geometry. This definition is consistent with respect to variation in time and geometry, and it does not use the material resistance explicitly. Behavior of the transient contact conductance with respect to contact-to-nominal radius ratio (a/b), nominal radius-to-length ratio (b/c), and material combination is determined. The results agree well with applicable analytical, experimental, and other numerical results. Calculated data shows that for a/b less than 0.01, the half-space assumption is valid for bodies in contact. For b/c values of less than one, there is no further affect on the contact conductance as b/c gets smaller. Assumptions about the heat flux and temperature contact conditions were evaluated. Calculated data shows that the constant heat flux assumption with respect to time will result in large error, and constant heat flux with respect to radius is appropriate at very short time. Constant temperature assumptions are better for the long time to steady state time regime, and large error will occur if steady state values of the contact conductance are used in transient analysis. Calculated data is presented as a dimensionless parameter versus dimensionless time for parametric study and application to engineering analysis.
Transient thermal contact conductance of dissimilar bodies with finite geometry
1998
8 Seiten, 28 Quellen
Conference paper
English
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