the ASCE standard method and tabulated the performance
ratings of various types of mechanical aerators used in aquaculture ponds. Paddlewheels,
propeller-aspirators, vertical splashers and pump sprayers were generally
found to have SAE ratings over 1 kg O2/kW h. The spiral paddlewheel design
promoted by Boyd as having an SAE of 3-kgO2/kW h was much more efficient than
the Taiwanese paddlewheels that dominate the world market.
Increasing salinity tends to reduce surface tension, causing smaller diameter
bubbles and droplets. This provides a greater interface surface area, a, and so kLa
is expected to increase with salinity. Fast et al. (1999) measured the effect of salinity
on the oxygen transfer of paddlewheels, finding that increasing dissolved solids up
to 11 ppt effectively enhances mass transfer about 50% above the freshwater
condition.
Gnezdiloff (1999) found the efficiency of a typical Taiwanese paddlewheel might
increase when speed was reduced below the nominal 100 rpm. Peterson and
Patterson (1999, 2000) explained that operation at faster speed results in backsplashing.
Linear regression curves for the paddlewheel tested by Boyd (1998) were
developed for 610 and 910 mm diameter spiral wheels with speeds in the range of
75–125 rpm, which may have been entirely above the speed of backsplashing, and
missed potentially interesting effects at or below backsplashing breakpoint speed.
In this paper we document experiments aiming to determine the relationship
between speed and performance for the typical paddlewheel designs in the Eastern
Hemisphere. These data provide aquaculturalists an indication if performance
varies between manufacturers, and how they will behave if speed controlled with a
variable frequency inverter.
the ASCE standard method and tabulated the performanceratings of various types of mechanical aerators used in aquaculture ponds. Paddlewheels,propeller-aspirators, vertical splashers and pump sprayers were generallyfound to have SAE ratings over 1 kg O2/kW h. The spiral paddlewheel designpromoted by Boyd as having an SAE of 3-kgO2/kW h was much more efficient thanthe Taiwanese paddlewheels that dominate the world market.Increasing salinity tends to reduce surface tension, causing smaller diameterbubbles and droplets. This provides a greater interface surface area, a, and so kLais expected to increase with salinity. Fast et al. (1999) measured the effect of salinityon the oxygen transfer of paddlewheels, finding that increasing dissolved solids upto 11 ppt effectively enhances mass transfer about 50% above the freshwatercondition.Gnezdiloff (1999) found the efficiency of a typical Taiwanese paddlewheel mightincrease when speed was reduced below the nominal 100 rpm. Peterson andPatterson (1999, 2000) explained that operation at faster speed results in backsplashing.Linear regression curves for the paddlewheel tested by Boyd (1998) weredeveloped for 610 and 910 mm diameter spiral wheels with speeds in the range of75–125 rpm, which may have been entirely above the speed of backsplashing, andmissed potentially interesting effects at or below backsplashing breakpoint speed.In this paper we document experiments aiming to determine the relationshipbetween speed and performance for the typical paddlewheel designs in the EasternHemisphere. These data provide aquaculturalists an indication if performancevaries between manufacturers, and how they will behave if speed controlled with avariable frequency inverter.
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