PERFORMANCE EVALUATION OF A PADDLEWHEEL WATER CIRCULATOR WITH DIFFERENT BLADE SHAPES IN A SPLIT-POND TEST SYSTEM  

The catfish industry, the dominant aquaculture sector in the U.S., has confronted increased feed costs and competition from foreign imports. This has led to the development and implementation of alternative production technologies, like the split-pond system (SPS), in an attempt to increase yields and profitability. With the current success seen by early adopters of the technology, the SPS technology is becoming more prevalent in the southern U.S. for the production of hybrid catfish and has further driven interest in the technology. The primary benefits of the SPS compared to traditional earthen ponds are from water circulation and mixing. The performance of paddlewheels varies according to operational parameters and physical features of the waterwheel. The shape of blades on paddlewheels is a primary determinant of performance. As paddles pass through the water column and generate water flow forward, edge turbulence by the paddles occurs. Thus, a certain amount of water slips behind the paddles, entailing energy loss. Thus, this study seeks to evaluate the pumping efficiency of slow rotating paddlewheels with various blade shapes used in modular culvert based split pond systems in an attempt to provide insight into design characteristics and their impact on the mechanical efficiencies of SPS.

Two 0.1 ha ponds were retrofitted at the Aquaculture Research Station at the University of Arkansas at Pine Bluff with a culvert based modular paddle wheel SPS. Three different blade shapes were tested at varying rotational velocities (1, 3, 5, and 7 rpm) and water depths (0.8, 1.0, 1.2 and 1.4 m). Each treatment combination was tested 24 times, while recording the following parameters: slip factor rate, power consumption, water flow rate and water head build-up. Data will be analyzed to provide insight into the affect of varying design characterizes on the pumping efficiency of a modular culvert based SPS.

Results indicate that blades with greater surface area provided greater efficiency than those with less surface area. Designs which added walls, enclosing the side of the paddle wheel, to reduce water slip behind the paddle did not translate to increased efficiency. Detailed analysis of engineering data is currently ongoing.