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EN
The paper presents the results of studies on local resistance coefficients (ζ). The study used pipe aerators with filling made according to the Polish patent PL235924. The hydraulic investigations were performed in real working conditions of a water treatment plant in a testing rig built in the Scientific and Research Water Station of the Warsaw University of Life Sciences (SGGW). The investigation encompassed two plastic pipe aerators of an internal diameter 101.6 and 147.6 mm with steel Białecki rings of 12 and 25 mm in diameter. Measurements of pressure difference (Δp) in the investigated aerators were performed at volumetric water flows (Q) selected from the range 2-20 m3∙h-1 with the interval 2 m3∙s-1. The values of ζ were determined according to the PN-EN 1267:2012 standard. The investigation showed that the ζ depends both on an internal diameter of the plastic pipe aerator and the diameter of Białecki steel rings. The values of ζ increase with a decrease of the internal diameter of the pipe aerator and a decrease of the ring diameter.
EN
The topic of failures and water losses in the urban-rural water supply network was discussed. The purpose of the work was to assess the level of real water losses and the failure rate of the urban-rural water supply network in 2010-2016. The article’s introduction contains the information on the types and causes of breakdowns in the water supply network. The life cycle of the leakage from its inception to its removal was also described. Next, the methodology and indicators for assessing actual losses in the water supply network were presented according to the guidelines of the International Water Association (IWA), i.e. ILI, CARL, UARL, RLB and water balance. The material and methods chapter describes how to calculate the failure rate. On the basis of the literature review, a method of assessing the failure of the water supply network and the level of actual water losses was presented. The research part presents the results of the water losses indicators values and assesses them against the literature data for the entire urban-rural system. The results of the failure of the water supply of the urban area and the rural area were also presented and compared with the literature data. A method of calculating limit values of the failure intensity index for the entire water supply system was also proposed. The changes in the intensity of failure occurrence during the year were presented. The object described in the studies achieved the A rating according to the classification of ILI and RLB values throughout the entire analysis period (2010–2016). Failure intensity in the analyzed period exceeded the average values calculated for water supply networks in Poland many times. The values in individual cases exceeded the limit values specified in the literature.
EN
The increasingly frequent use of computer simulations for the calculations concerning the water supply systems requires accounting for the demand patterns. Determining the coefficients of daily and hourly non-uniformity is indispensable for the correct designing or modernization of pipes in the water supply network. The first goal of article was to obtain the non-uniformity index for the preparation of hydraulic models in rural water systems called "N" system and "CWK" system. In this article, the authors present the results of the water consumption analysis in two rural water supply systems. The article presents the water consumption non-uniformity factors calculated over the course of a year, a month and a day. The article also included the calculated water demand curves over the course of a day, showing the variability of water demand with characteristic morning and evening water consumption peaks and changes of the consumption curve in the prospective development of the water supply network, where industrial consumers would become the main water consumers. The research material consisted of the water consumption measurements in two rural water supply networks situated in northeastern Poland, taken over the years 2010-2017. The article also shows the water demand curves in the studied rural water supply networks for every day of the week. The values of minimum and maximum hourly non-uniformity coefficients were compared to the mean value of these coefficients. The changes in the values of minimum and maximum hourly coefficients with respect to the mean value for the given hour may differ from -89% to +85% for hours of minimum demand. The changes in the values of minimum and maximum hourly coefficients with respect to the mean value for the given hour may differ from -16% to +30% for hours of maximum demand.
EN
The study analyzed 8295 daily rainfalls recorded in Wrocław from 1960 to 2017. The frequency of daily precipitation in a year was determined in nine categories: from very weak (less than 1.0 mm) to disastrous (over 100 mm). In addition, the precipitation trends were determined by linear regression and the Mann-Kendall test. Analysis of the variability of the number of days with precipitation of particular categories showed a statistically significant downward trend for moderately strong precipitation (10.1-20.0 mm). In case of other categories of precipitation, the tests did not show statistically significant changes.
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