The vibration of Heat Exchange Tubes due to hydrodynamic fluid coupling is an international problem for Nuclear fuel assemblies etc. on account of frequent failure of Heat exchanger tube, which causes not only expensive repair but a great loss to the plant. Thus, several studies in this field have been made so far. But here, a study of three circular cylindrical tubes in a liquid is done on the analytical approach. The author also describes the various parameters for maximum efficiency of heat transmission from Heat Exchanger's, which is defined as; nH =F (G/R, V) = Heat transmission efficiency of the heat exchanger, where G=gap between two adjoining tubes, R= Radius of cylindrical tubes (if considered of same diameters) and V= fluid flow velocity and geometry of tubes. The relations amongst the above parameters are yet to derive to solve this problem.

The Friction Stir Welding (FSW) is a latest process of Advanced Welding Technology and was invented in 1991 by The Welding Institute (TWI) at Cambridge, in United Kingdom. In 1995, Friction Stir Welding has been used in production applications by introducing welding of extrusions to form paneling for marine applications in Europe and USA. Since then, the process has been commercialized in many other applications including rail car, automotive, aerospace, heavy truck, medical applications, etc. In this book a detailed emphasis is given about historical developments, types of welding processes, working principles of friction stir welding, design feature of FSW tools, processing on aluminium alloys and application in various industries. Author has also tried to place the opinions of researchers as to what they say about the latest techniques of Friction Stir Welding.