Surface diffusion in thin film couples
Abstract A study has been made of surface diffusion in the evaporated thin film couple Ni-Au. Structural changes within the diffusion zone were examined by electron microscopy in situ . Apart from a slight migration of the layers, crystallization was quite pronounced. The results obtained by means of an electron microprobe analyser showed that the diffusion rate was higher than in the bulk.
Abstract In this study, the influences of the changes in fin geometry on heat transfer and pressure drop of a plate fin and tube heat exchanger are investigated, numerically. A computational fluid dynamics (CFD) program called Fluent is used in the analysis. The segment of one tenth of fin is used in the modeling, due to symmetrical condition. The results of heat transfer, static, and total pressure drop values of ten different fins are tabulated and the normalized values of them are, also, given for the comparison of the models. The distance between fins is found to have a considerable effect on pressure drop. It is observed that placing the fin tube at downstream region affects heat transfer positively. Another important result of the study is that increasing ellipticity of the fin tube increases the heat transfer while it, also, results in an important reduction in pressure drop.