Helical Ribs Research Articles

Characteristics of Hydraulic Capsule Transport. Influence of Capsule Surface Geometry.

In order to realize the core flow without using wheels, we experimentally investigate effects of helical ribs caved in a side surface of the capsule. The capsule has 4 ribs of 3mm height or 5mm height. The angle of rib coiling the capsule outer diameter is varied five kinds. The diametrical clearance between the pipe and capsule is 4mm for capsule used. When the capsule mass is small, the capsule velocity is faster then the average water velocity. When an inlet pressure head becomes lower, the capsule of 5mm rib height moves lower than the water flow, although the capsule of 3mm rib height still moves faster than that. When the capsule mass becomes large, the capsule velocity becomes lower than the water flow as well. But the capsule velocity is increased when the angel of rib becomes large. Finally, we observed that the pattern of pressure difference at the popeline is influenced by the capsule surface geometry and the capsule mass.

Prediction of flow over helically ribbed surfaces

Fully developed, steady flow through an annulus with a multistart, helical-ribbed inner cylinder is numerically predicted and compared with available data. To facilitate comparison, the transverse-ribbed case is included. It is predicted that substantial differences exist between turbulent flow over helical ribs and that over transverse ribs. The predictions clarify the experimental finding that helical-ribbed cylinders can be expected to have better pressure drop and heat transfer characteristics than transverse-ribbed cylinders. For this work the AERE Harwell code FLOW3D Release 2 was used.

Investigation of annular liquid film flow in tubes with helical ribs and wires. Experimental correlation and cause of the entrainment-suppression effect.

The entrainment rate of liquid droplets in a two-phase annular mist flow is investigated in the helically ribbed and wired tubes with the aim of suppressing the droplet entrainment to improve evaporative heat transfer in various steam generators of the one-through type. The results show that the entrainment rate in the tubes is lower than that in smooth ones. An experimental correlation is introduced between the suppression rate of the entrainment and the parameters including liquid and gas flow rates and the shape of the ribs or wires. The decrease in number of disturbance waves is supposed to be the main cause of the entrainment suppression and is brought about by the direct interaction between the disturbance waves and the helical ribs or wires.

Investigation of annular liquid film flow in tubes with helical ribs and wires. Suppression of droplet entrainment with the aim of improving evaporative heat transfer.

The entrainment rate of liquid droplets in a two-phase annular mist flow is investigated in the helically ribbed and wired tubes with the aim of suppressing the droplet entrainment to improve evaporative heat transfer in various steam generators of the one-through type. The results show that the entrainment rate in these tubes is lower than that in smooth ones. Large disturbance waves on the surface of the liquid film flow in the tubes are also smoothed, which may be a reason for the entrainment-suppression effect. The effect can be correlated with three nondimensional parameters. The pressure drop of two-phase flow through the tubes is influenced by some factors as well as by the hydraulic diameter of the tubes.

An experimental study on solid‐liquid flow through rectangular ducts

AbstractReduction in energy consumption has been the main concern of the workers in the field of solid‐liquid flow. Investigators have tried to achieve this objective in various ways. Two of the well‐known methods are: the addition of polymer solutions to the solid‐liquid mixture and the fitting of helical ribs inside regular circular pipes. In the latter case, the reduction is considerable, but it results in a very low rate of transportation. Chiu and Seman have reported considerable reduction of head loss in a square duct when compared to the flow through a circular pipe.In the present work, an experimental study has been underaken to compare the head loss for solid‐liquid flow in a circular pipe, with that for rectangular ducts of four different aspects ratios (width/height ratios), keeping the cross‐sectional area of each one of them to be the same. When the perforance of a circular pipe is compared with that of the other rectangular ducts, it seems that the square duct shows a better performance in the low operating range of velocity, whereas the rectangular duct of aspect ratio 1.5 presents a still better performance, from the energy requirement point of view, for practically the entire velocity‐range within which the experiment was conducted.

Turbulent flow in helically ribbed pipes

AbstractVelocity profiles, turbulence intensities and Reynolds stresses were determined in pipes containing three helical ribs equally spaced on the pipe wall. Pitch to diameter ratios of 8 and 11 were used. The fluid considered was air and measurements were made with X wire probes calibrated for pitch and yaw effects.The ribs appeared to affect the axial flow via the tangential component which reached a maximum below the ribs in most cases. Evidence of increases in mixing length near the wall and decreases in the central core was obtained. These are in agreement with recent theoretical predictions of other workers. Turbulence intensities were not significantly altered when normalized with the usual friction velocity.

Turbulent flow in helically ribbed pipes

AbstractVelocity profiles, turbulence intensities and Reynolds stresses were determined in pipes containing three helical ribs equally spaced on the pipe wall. Pitch to diameter ratios of 8 and 11 were used. The fluid considered was air and measurements were made with X wire probes calibrated for pitch and yaw effects.The ribs appeared to affect the axial flow via the tangential component which reached a maximum below the ribs in most cases. Evidence of increases in mixing length near the wall and decreases in the central core was obtained. These are in agreement with recent theoretical predictions of other workers. Turbulence intensities were not significantly altered when normalized with the usual friction velocity.

The structure of reaction wood as indicated by scanning electron microscopy

Scanning electron microscopy was used to investigate the structure of normal and reaction wood of Cupressus arizonica Greene, Pinus canariensis C. Sm., and P. radiata D. Don. The wood of P. radiata was examined before and after various chemical treatments. These included chlorine water-sodium hydroxide, glacial acetic acid-hydrogen peroxide, sodium hydroxide-sodium sulphide, 17.5 % sodium hydroxide, 78 % phosphoric acid, 72 % sulphuric acid, 1 % osmic acid, and 2% potassium permanganate. The helical ribs of the S2 layer in reaction wood cells appeared to be multistranded. Warts tended to become fewer and restricted to the grooves in the S2 layer during the change-over from normal to reaction wood cells. The origin and chemical composition of the warts and associated membrane are considered.