Abstract
Trash racks are the first element mounted in inlet channels of hydraulic structures. Their primary task is to capture coarse pollutants flowing in the riverbed/river channel and protect water facilities downstream. With the use of these devices, it is possible to separate coarse suspended matter, branches carried with the current, floating plastic elements, etc., which undoubtedly contributes to a trouble-free flow through culverts or channels and prevents hydroelectric power plant turbines from failure. An important issue here is also to ensure the proper operation of trash racks, particularly in respect of hydraulic structures whose task is to convert water energy into electricity (hydropower plants). Proper operation of trash racks minimizes losses arising from obstructing the free flow of water through accumulated waste or, in the wintertime, through icing. Incorrect work in this area entails specific head losses, and consequently leads to economic harm. In the paper, the resistance values of trash racks were analyzed at small hydropower plants (SHPs) operating at low temperatures, determined under laboratory conditions, with the occurrence of frazil ice and ice. The results indicate that the added ice into the channel resulted in the formation of a cover in front of the trash racks with an average thickness of about 0.02 m. The accumulated ice increased the head losses up to 14%. The range of the ice cover depended on the weight added ice and reached 0.6 m in analyzed cases.
Highlights
The process of ice formation in rivers is more complex than in lakes, primarily due to the movement of water itself and the phenomenon of turbulence, which causes the water to supercool evenly throughout its depth profile
The phenomenon of river ice jams caused by ice occurrence includes multiple interactions between hydrodynamic, mechanical and thermal processes and justifies the development of river ice research [2,3], all the more so since its negative consequences affect society, hydropower, ecology and the environment [2,4,5]
6,59 determination of ice jam duration and intensity should take into account, i.e., the river gradient, anthropogenic factors and characteristics of a
Summary
The process of ice formation in rivers is more complex than in lakes, primarily due to the movement of water itself and the phenomenon of turbulence, which causes the water to supercool evenly throughout its depth profile. Supercooling of river water, this involves only a few hundredths of a degree Celsius or even less, allows ice particles to adhere to each other, because in such conditions they are not stable and can aggregate actively. Such a process causes major problems with, e.g., water intakes [1]. Most data on the formation of river ice Energies 2020, 13, 1775; doi:10.3390/en13071775 www.mdpi.com/journal/energies
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