Satish Lele

Pressure / Vibrations
Flow-induced vibration (FIV) of power and process plant components is a relatively unregulated technology by industry codes and standards. To a large extent FIV is an operational problem that has relatively little direct impact on public safety. Yet flow-induced vibration is often viewed as too mysterious one for the average practicing engineers to understand. The investigating method of predicting the vibrations of stable tubes and rods in response to external turbulent flows is important. At any instant of time, the surface pressures will exert a net lateral force on the rod and make turbulence-induced vibration. The vibration of the fuel rods contacting with the spacer grid makes scratch and damage on the cladding cover that results radioactive material release. A spacer grid with mixing vane and ribbed tube are designed to make high turbulence for higher heat transfer rate and critical heat flux (CHF) enhancement, that induces more vibration in the channel.

Many studies have been carried out on gas–liquid two-phase flow, because heat transfer enhancement is an important theme in order to improve performance of heat exchangers and steam generators. The bubble departure from the tube wall is retarded in sub cooled flow boiling and low-quality region under micro gravity. Therefore, it is necessary to positively remove the bubbles near the wall surface, because departure from nucleate boiling (DNB), in which there is a shift to film boiling from nucleate boiling, is apt to occur. When DNB occurs, the wall temperature rises rapidly. For this purpose, it is possible to improve the heat transfer coefficient and the critical heat flux pressing against the wall surface of the liquid phase and the droplet by the centrifugal force due to the swirl flow. When a swirl flow generator such as a twisted tape and a wire coil is inserted into a circular tube, the realization is possible. However, an increase of the energy consumption in the entire system including the pumping poser of the heating medium is generated, because the flow resistance also increases.

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