Ribbed tubes

The extension of these PECs to two-phase heat transfer is complicated by the dependence of the local heat transfer coefficient on the local temperature difference and/or quality. Heat transfer and pressure drop have been considered in the evaluation of internally finned tubes for refrigerant evaporators [14] and for internally finned tubes, helically ribbed tubes, and spirally fluted tubes for refrigerant condensers [15]. Pumping power has been incorporated into the evaluation of inserts used to elevate subcooled boiling critical heat flux (CHF) [16, 17]. A discussion of the application of enhancement to two-phase systems is given by Webb [373],... 

FIGURE 11.12 Comparison of heat transfer characteristics of smooth and ribbed tubes with once-through boiling of water [95],... 

J. W. Ackerman, Pseudoboiling Heat Transfer to Supercritical Pressure Water in Smooth and Ribbed Tubes, J. Heat Transfer (92) 490-498,1970. 

The use of ordinary surface roughness elements tends to reduce the critical heat flux. However, by introducing helical and fin-form deformations on the tube surface, it is possible to induce swirl and turbulence in the flow, which promotes transfer of the liquid phase to the surface and thus gives enhancement. An example of work of this kind is illustrated in Fig. 15.135, which shows results obtained by Nishikawa et al. [329] using rifled and ribbed tubes. 

Commercial Production of Pile Parts. The main pile parts for which the commercial facilities have been incompletely developed are the uranium bars or tubes, the aluminium ribbed tubes for lining the graphite, the assembling of the rods and sheaths and end caps, and the graphite blocks. 

There has been some little difficulty in getting the aluminium ribbed tube but it now appears that Wolverine and maybe others will attempt to extrude, draw, or roll the tubes with integral ribs. As an alternative, it is possible to weld separate ribs inside the tube. Sciaky Brothers have expressed their assurance that this process is entirely feasible, although it is still preferable to have extruded or drawn ribs. 

Fabrication technology for fuel elements to achieve reliable operation Ribbed tubes for fuel elements fabricated from EP-823 steel Available mastered at an industrial scale... 

Lee and Haller (1974) found heat flux and tube diameter to be the important parameters affecting the minimum mass flux limits to prevent pseudo-film boiling. Multilead ribbed tubes were found to be effective in preventing pseudo-film boiling. 

Ackerman, J.W., 1970. Pseudoboiling heat transfer to supercritical pressure water in smooth and ribbed tubes. Journal of Heat Transfer, Transactions of the ASME 92 (3), 490—498 (Paper No. 69-WA/HT-2, pp. 1-8). 

Dryout or boiling transition may occur during the sliding-pressure startup of the once-through reactor as seen in Fig. 1.21 [43, 44]. Ribbed tubes and spiral tapes have been used for the supercritical boilers to improve the critical heat flux. The... 

Satisfactory performance is obtained with tubes having helical ribs on the inside surface, which generate a swirling flow. The resulting centrifugal action forces the water droplets toward the inner tube surface and prevents the formation of a steam film. The internally rifled tube maintains nucleate boiling at much higher steam temperature and pressure and with much lower mass velocities than those needed in smooth tubes. In modern practice, the most important criterion in drum boilers is the prevention of conditions that lead to DNB. 

Frame surface cooled (using the surrounding medium) The primary coolant is circulated in a closed circuit and dissipates heat to the secondary ccxilant. which is the surrounding medium in contact with the outside surface of the machine. The surface may be smooth or ribbed, to improve on heat transfer efficiency (as, in a TEFC or tube venulated motor (Figures 1.19 and 1.20) 4 ... 

Rippen-. ribbed costal, -fell, n.. -haut, /. (costal) pleura, -glas, n. ribbed glass, -heiz-korper, m. ribbed (or finned) radiator, -rohr, n. ribbed or finned pipe or tube, -trichteri m. ribbed funnel. 

Figure 10-1OM. Finned tube with internal ribs enhances heat transfer inside as well as outside the tubes. (Used by permission High Performance Tube, Inc., Finned Tube Data Book. )...

We use variants of profile extrusion to produce tubing -with diameters of less then 1 mm and pipes with diameters exceeding 1 m, Wall thicknesses can vary from a few tens of micrometers up to several centimeters. Extruded window and door frames are more complex than pipes. Such profiles are largely hollow with internal ribs and fins that reinforce and divide the interior into two or more channels. We use solid rubber profiles in applications such as door seals and windshield wipers. We can produce foamed extrudates by incorporating a blowing agent, such as butane or carbon dioxide, into the polymer in the molten state. As the polymer exits the die, its internal pressure drops and the dissolved gas expands to form bubbles within the product. Examples of foamed extrudates include pipe insulation and automobile door gaskets. 

The shade assembly (intended to shield the bombardier from the glare) consists of an asbestos orFiberglas shade(G), shade wire, 8 steel tubing ribs (F) springs, and a shade frame clamped to the base block end of the illuminant assembly. A shade retainer support (B) into which a steel fuze adapter and its plastic shipping plug (A) fits, completes the flare assembly... 

Filtration can be accelerated by using funnels with ribbed walls (Fig. 17a) or with a long tube having a loop (Fig. 175). A filter fits tightly against the upper edge of the funnel and the ribs, which ensures more rapid flowing down of the liquid and a small vacuum. In the second case, the loop plays the role of a siphon, when it is filled, the liquid rapidly flows down, and a rarefied space forms in the tube. 

Webb, R.L., Eckert, E.R.G. Goldstein, R.J. (1971) Heat transfer and friction in tubes with repeated-rib roughness. International Journal of Heat Mass Transfer, 14, 601-17. 

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