Air can be entrapped in water and wastewater systems under a variety of conditions, and if such air is not managed properly, it can impose considerable operational penalties. To avoid these problems and the dangers associated with air pockets, several air management strategies have been routinely suggested. However, the devastating consequences of air pockets frequently documented in the literature imply the need for further development in this area. Improving air management obviously requires a thorough understanding of the current strategies and their shortcomings. This paper overviews the sources of air in pipes and key consequences associated with its presence. Current measures for managing air in water pipes are reviewed and critiqued. Finally, knowledge gaps that limit the efficient application of current air management strategies to real world problems are identified, and suggestions for future development are presented.
Elevated high points along a pipeline profile are the most common places where air vacuum valves (AVVs) are installed. This paper uses basic water hammer theory to semianalytically explore the effects of such AVVs. A simple frictionless reservoir-pipe-reservoir system with an exaggerated intermediate high point is considered with a sudden flow curtailment assumed upstream. Key design parameters such as the maximum air pocket volume, the duration of air pocket growth and collapse, and the maximum magnitude of the pressure spike resulting from water column rejoinder are semianalytically developed for various high point locations. The magnitude of the reduced pressure wave created by the refraction at the high point, and both its vertical and horizontal position, are demonstrated to crucially determine system performance. Numerical examples are compared with the semianalytical expressions to highlight the accuracy of the derived expressions. The effect of friction is later introduced to help reveal friction's influence on air valve performance.
Zir co nium al loys, are usu ally used as fuel clad ding ma te ri als in VVER (wa ter-cooled, water-mod er ated en ergy re ac tor) type re ac tors, mainly, due to their low neu tron ab sorp tion cross-sec tion, de sir able me chan i cal prop er ties, and good cor ro sion re sis tance un der re ac tor op er at ing con di tions. Dur ing ex po sure to wa ter at high tem per a ture, wa ter re acts with zir conium al loys, which re sults in the pro duc tion of an ox ide layer. The en tire area of cor ro sion along with the ac com pa ny ing ab sorp tion of hy dro gen in the zir co nium metal ma trix has attracted a lot of at ten tion when the per for mance of the core com po nents as well as the op er ation of the re ac tor is em pha sized. The growth of the zir co nium ox ide layer plays a de struc tive role in de creas ing ther mal ef fi ciency of the re ac tor by re strict ing the in let tem per a ture and chem i cal prop er ties of the cool ant. The pres ent study aimed to de velop a com puter code to pre dict long-term wa ter side cor ro sion weight gain, ox ide thick ness and de ter mine the concen tra tion of ab sorbed hy dro gen in VVER-1000 re ac tors dur ing nor mal op er at ing con ditions. The pro posed model can be uti lized to es ti mate the pre-tran si tion and post-tran si tion cor ro sion weight gain and the ox ide thick ness in op er at ing con di tions.
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