A Correlation of the Minimum Thermal Resistance at Soldered Joints

Abstract

mixture of silicone oil and lampblack distributed over the model surface in a random dot pattern. Oil-flow patterns on the vertical wedge surface are shown in Fig. 2 for /3 angles of 5° and 10°. In both symmetrical and asymmetrical cases, the flow can be divided into similar regions. *S-shaped lines (area 1) indicate a vortex near the corner (see Ref. 4 for a more detailed discussion of this vortex). A featherlike pattern (area 3) is separated from the s-shaped pattern by a thin oil accumulation line (area 2). Outside of the feather pattern a region of strong crossflow terminates in a heavy oil accumulation line (area 4), and beyond this the flow gradually approaches two-dimensional, undisturbed wedge flow. Near the top of the wedge the flow is not two-dimensional due to the projection of the wedge into the tunnel-wall boundary layer. One significant difference in the symmetrical and asymmetrical oil-flow pattern occurs in the region between area 1 and the corner juncture. For the ft = 10° case, the flow appears to be approximately radial from the tip of the model; for the ft = 5° case, the flow is turned toward the corner juncture. A possible explanation for this effect is that the vortex on the horizontal wedge moves toward the corner as ft decreases. Isoheating lines obtained from sequential photographs of the melting point boundary are shown in Fig. 3 for the ft = 10° corner. Data are presented as ratios of local to maximum heating measured on the vertical surface. The previously discussed flowfield regions from Fig. 2 are also shown. From a comparison of Figs. 2 and 3 it is apparent that the maximum heating is associated with the vortex in the near corner region.