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Manufacture of Pressure-Sensitive Products
Published in István Benedek, Mikhail M. Feldstein, Technology of Pressure-Sensitive Adhesives and Products, 2008
Microperforating can be used to transform some carrier materials in a porous web. Such microporous webs are needed for medical tapes, condensed water-free packages, etc. (see also Applications of Pressure-Sensitive Products, Chapter 4). Various methods are used for perforation, such as hot needles, liquid or gas jet, ultrasons, high-frequency laser, and electrostatic microperforation. Hot needles are used for PE and PP films and nonwovens. The hole diameters produced by this technology are 200–500 pm. On such machines webs with a width of 1,500 mm can be processed with a speed of 10–30 m/min. Gas and liquid jets are used for perforating soft webs (foam, nonwovens, board). Thermoplast-like polyolefins and PVC can be cut with ultrasons. High-frequency cutting is limited to thicknesses of 5–30 pm. Laser perforating is used for narrow webs. It allows running speeds of 600 m/min and is used mainly for fine paper. The hole diameters produced using this method are 50–200 μm.
Protection for Downstream Migrants
Published in Charles H. Clay, P. Eng, Design of Fishways and Other Fish Facilities, 2017
Screens other than wire mesh have also been used for preventing entry of fish. Thin steel plates with perforations of various sizes and shapes are available commercially. Some of the shapes of perforation available are round, square, hexagonal, and slotted. These are available in various plate thicknesses and in materials other than steel, such as copper, brass, zinc, etc. In general, perforated plates will have a lower coefficient of discharge than a wire screen with equivalent size of mesh opening, and will thus have a greater head loss. They are not generally used for fish screens except in special cases, such as where a mechanical wiper is attached to keep the screen free from debris.
Numerical investigation of heat transfer augmentation and frictional loss characteristics in heat exchanger tube with the use of novel perforated rectangular cut twisted tape
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Figure 5 depicts the temperature counters at the cross-section of pipe in case of PT, with STT and PRCTT at Re = 4000. It is perceived in the contours that in PT, large temperature gradients are presents, that is, temperature of fluid near the solid surface is higher and lower toward near the center. When STT is inserted in the tube, it disrupts the velocity and thermal boundary layer and augment the intensity of turbulence of the flow. Proper mixing of fluid occurs due to high intensity of turbulence in flow which leads to reduction in temperature near the tube wall and decrease in average temperature of cross-section. This reduction in temperature leads to higher rate of heat transfer. Further introduction of RCTT reduces the rate of heat transfer by very small amount. Due to rectangular cuts, turbulent mixing increases tries to intensify the rate of heat transfer but perforation in the tape give the passage for the flowing fluid to pass which reduces the turbulent effect up to certain limit which leads to reduce in rate of heat transfer by small amount. The main advantage of perforation is reduction in frictional losses due to extra passage for the flow.
Response of perforated H-pile subjected to coupled lateral displacement history and axial loading
Published in Australian Journal of Structural Engineering, 2023
Hrishikesh N. Shedge, Manoj Kumar
The HP 10 × 42 pile is developed with six unique sets of perforation geometries at its zone of local buckling. The perforations are made in a manner in which their impact on the hysteretic response of HP 10 × 42 under coupled axial and lateral cyclic displacement history will be significant. The location of local buckling zone is found by observing the response of the unperforated specimen. The Figure 3 shows that local buckling of flange occurs in a zone ranging from 25 mm to 175 mm from the bottom face of the H-pile. The area of perforation on each flange is 5000 mm2 and is kept constant throughout the study. The selection of dimensions for perforation is based on maintaining the area of perforation as constant. The perforations are broadly divided into two categories based on their shape: square/rectangular perforation and circular perforation. Figure 4 highlights the geometric details of perforations made according to their respective shape and number.