Design and peroormance of paddle wheel aerators
ABSTRACT An apparatus was constructed for testing the influence of paddle shape and depth and paddle wheel speed and diameter on oxygen-transfer characteristics of paddle wheel aerators. Paddles triangular in crosssection were more efficient than other paddle shapes. Standard oxygen transfer rate (SOTR) increased with increasing paddle depth and paddle wheel speed while standard aeration efficiency (SAE) declined. For a particular depth and speed, SOTR increased with increasing paddle wheel diameter. The greatest SAE (2·96 kg O2 kWh−1) was achieved with a 91 cm diameter paddle wheel with triangular paddles operated at 77 rev min−1 and 12·5 cm paddle depth. Three companies made floating, 7·5 kW electric paddle wheel aerators according to design specifications developed in this research. These commercial aerators had high values for SOTR (18·8–21·8 kg O2 h−1) and SAE (2·7–2·9 kg O2 kWh−1) and were much more efficient than other aerators used in channel catfish farming.
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ABSTRACT: Chalcogenide glasses are known for their large transparency in the mid infrared, which includes the two atmospheric windows lying from 3–5 μm and 8–12 μm. Chalcogenide single mode fibers present numerous potential applications in the IR field, such as military countermeasures, LIDAR spectroscopy and spatial interferometry. Two routes can be considered for the elaboration of a single mode fiber. The first method consists in preparing a classical step index fiber (SIF) with a core-clad configuration. This procedure is based on two glass compositions (core and clad) with compatible thermal and optical properties and having a refractive index difference allowing the single mode propagation. The second route is based on the design of a microstructured optical fiber (MOF) in which the guiding function is ensured by the refractive index contrast between the core glass and the air contained in the capillaries surrounding the core. Two kinds of fibers exhibiting single mode propagation were fabricated; the first one is a SIF with a 22 μm core diameter and the second one is a three rings of holes MOF. The geometry of the MOF shows a d/Λ around 0.35 and a 40 μm core diameter. In both cases the optical losses in the 2 to 12 μm region were measured and compared.Research Highlights► Two designs were investigated: step index fiber and microstructured fiber. ► Single mode propagations were observed at 9.3 µm for both fibers. ► Attenuations from 2 to 12 µm of the single mode fibers cores are measured.Journal of Non-Crystalline Solids 01/2011; 357:2480-2483. · 1.72 Impact Factor
- Journal of Environmental Engineering-asce - J ENVIRON ENG-ASCE. 01/2009; 135(7).
- Journal of Environmental Engineering-asce - J ENVIRON ENG-ASCE. 01/2005; 131(8).