Paddle Wheel Speed Research Articles

Intake Pipes Evaluation: Comparison between Paddle-Wheel and Hot-Wire Anemometry Methods

The aerodynamic behaviour of the intake pipes of direct injection diesel engines has usually been quantified by means of swirl number and the discharge coefficient. In order to validate these parameters an experimental method based on the hot-wire technique has been applied to the steady flow rig where the former parameters are measured. This method allows the measurement of the three components of the velocity referred to an orthogonal coordinate system by placing the probe parallel to these three directions. The results obtained are presented and analysed in this paper. The comparison between the two measurement techniques has been done in terms of discharge coefficients, angular momentum flux and paddle-wheel speeds, calculated by integration of the measured velocity field in the case of the hot-wire results. The comparison between the values of the angular momentum flux allows the conclusion to be made that some of the hypotheses assumed by the paddle-wheel method are not accurate.

Design and peroormance of paddle wheel aerators

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 O 2 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 O 2 h −1) and SAE (2·7–2·9 kg O 2 kWh −1) and were much more efficient than other aerators used in channel catfish farming.

Evaluation of plastic pipe, paddle wheel aerators

Paddle wheel aerators made of polyvinyl chloride (PVC) pipe had standard aeration efficiencies (SAE) of 2·0–2·6 kg O 2 kWh −1 when paddle wheel diameter was 71–81 cm, paddle wheel speed was < 90 rev min −1, and paddle depth was < 15 cm. The standard oxygen transfer rate (SOTR) was low (1·15–1·85 kg O 2 h −1 per 1-m length of paddle wheel). To supply enough oxygen for large ponds, PVC paddle wheels would be impractically long, and, even then, values for SOTR per unit length of paddle wheel and SAE would be lower than those obtained for steel paddle wheels currently used in aquaculture. PVC paddle wheels might have application in small ponds and especially in mariculture ponds where construction of noncorrosive material would be beneficial.