The grooved pipe is a kind of pipe with rolling grooves, which are usually round grooved pipe, oval grooved pipe, etc. The grooved pipe is named because it can see the obvious grooves in the cross section of the pipe. Such pipes can cause fluids to flow away from the wall surfaces of these turbulent structures to generate flow detachment zones, and form vortices of different strengths and sizes. It is these vortices that change the flow structure of the fluid and increase the turbulence in the near-wall region, thereby increasing the convective heat transfer film coefficients of the fluid and the wall.
a. Rolled grooved tube Rolled grooved tube is a horizontal or spiral groove with a certain pitch and depth rolled from the outside of the circular tube according to the design requirements. A convex horizontal rib or spiral rib is formed on the inner wall of the tube, as shown in the right .
Such a groove on the outer wall of the pipe and a protrusion on the inner wall can simultaneously enhance the heat transfer of the fluid on the inner and outer sides of the pipe, and are particularly suitable for strengthening the heat transfer of the single-phase fluid inside the pipe and enhancing the pipe External fluid vapor condensation and liquid film boiling heat transfer.
b. Spiral grooved tubes are available in single-pass and multi-pass spirals. After forming the spiral groove tube, there is a groove with a certain spiral angle, and the tube has corresponding convex ribs. The spiral groove should not be too deep, the greater the deep flow resistance of the groove, the larger the spiral angle, the larger the heat transfer film coefficient of the groove tube. If the fluid can rotate along the groove, the number of threads has little effect on heat transfer.
c. The grooved tube is continuously rolled with variable cross-section. A lateral groove intersecting at 90 ° with the tube axis is formed outside the tube, and a lateral convex rib is provided inside the tube. After the fluid flows through the convex ribs in the tube, no spiral flow is generated, but an axial vortex group is generated along the entire cross section to enhance the heat transfer. The horizontally threaded pipe also has a great strengthening effect on the film boiling heat transfer of the fluid in the pipe, which can increase the boiling heat transfer coefficient by 3-8 times.