Dynamics of a Pipe Subjected to Internal and Confined External Flow

We consider a hanging cantilevered pipe conveying water within a water-filled container; the upper portion of the pipe is surrounded by a rigid cylindrical tube of larger diameter, forming an annular fluid-filled region around the pipe. Two flow configurations are investigated : (a) water enters the pipe at its clamped end and flows downwards, discharging at its free end into the container; the fluid exits the container by flowing upwards in the annulus and out; (b) the reverse flow arrangement: water enters the system at the upper end of the annulus and exits by flowing upwards in the pipe. The dynamics of the system is studied theoretically and experimentally for both configurations. The analytical models utilized are outlined and the experiments are described. Theory and experiment find that the system loses stability at sufficiently high flow velocity by flutter or static divergence.

Experimental Research on Pressure Drop to Optimize Twisted Strips with Holes in Tubes of Condensers

In order to reduce the pressure drop increase caused by self-rotating plastic twisted-strips in heat transfer tubes of vacuum condensers in thermal power plant, the twisted strips structure is optimized. There are holes distributed in twisted strip uniformly. The holes diameter and interval are optimized through experimental research. The results show that when holes diameter is less than 6mm, holes can reduce the pressure drop increase at low flow velocity while the pressure drop with holes is greater than that without holes at high flow velocity. The holes diameter is 4~5mm when the pressure drop is the lowest. The pressure drop with holes is always larger than that without holes when holes diameter is more than 6mm. The pressure drop will increase as holes interval decreases at high flow velocity, while it will reduce at low flow velocity.