1998 Volume 46 Issue 534 Pages 393-397
A transportation system with low pressure drop using spiral flow has been developed. With this system, ceramic balls were transported at the rate of 190kg/h in a 15.0m long pipeline that was composed of a 5.0m vertical section and a 10.0m horizontal section with 34.0mm diameter. The pressure drop was dramatically decreased by about 40% from 6.91×102 [Pa/m] to 3.88×102 [Pa/m] as compared with the typical method. The particles movement was observed at the vertical section to discuss the low pressure loss. The particles moved as rotating without touching the inner pipe wall. The device to produce spiral flow is a nozzle with an annular slit, attaching to the conical cylinder. Pressurized fluid is forced through the side of the device into the buffer area and then through the angled annular slit into the conical cylinder. Due to the Coanda effect of this annular jet attaching to the nozzle wall, the flow downstream develops a spiral structure with steep axial velocity distribution and high stability that is much more ordered than typical turbulent flow. To accomplish the high performance transportation, particles should not touch the pipe inner wall. The requirements can be responded by the steep axial velocity profile and swirling motion of the spiral flow with large free vortex region.
