Developing Aeraters and Designing Supply Pipes

Sufficient studies have not been made as yet on the system of hydroponics flooding and circulating solution in growing vats. In the present study, the author developed a simple aerator of superior function, designed a supply pipe of equal delivery, (the solution-delivery to multiple growing vats in the existing system is unequal), and improved the existing supply risers.<BR>The results obtained are summerized as follows:<BR>(1) The aerater (No.5 in Fig. 4), which is attached to a portion of the supply riser, was developed. In general, the greater the solution flow and the smaller the cross sectional area in the throat portion, the more air is mixed, and this air mixing apparatus is not stopped up structurally.<BR>(2) The mixing ability of aerater No.5 is superior to the existing aeraters provided the flow rate is greater than 15 l/min (Fig. 5 & 7). If it drains off at 2 cm below the solution surface, the surrounding fruit vegetables are protected from the effect of spray and their roots are completely shaded.<BR>(3) The ratio of the flow at the first and the distal outlet of the 31 mm supply pipe (total length 40m) was 2. 65 (Table 1) in the existing system, and the quality of the tomatoes in the distal growing vat was inferior to the first.<BR>(4) For new supply pipes, the pipe size can be determined from. Eq.(17) by selecting a value for the solution-delivery variable k.<BR>(5) For existing supply pipes the method of supplying the solution equally by varying the height lof the supply riser has been devised (Eq.(3) & Fig. 10 & 12). Good results were obtained in real-life experiments in which two samples were grown varying the riser height only in one case and both the riser height and the supply pipe diameter in the other (Table 4 & 6).