Design characteristics of venturi aeration system

Abstract

The crucial phenomenon of air and water mixing together is called aeration. The venturi aeration is mainly responsible to transfer air directly through the atmosphere into the flowing water attribute to its simplicity and reliability. A water tank of 1000 litres capacity having dimensions 100 × 100 × 100 cm3 was used to conduct the experiments for aeration for the purpose of studying the characteristics of venturi aeration system design. Venturi having three significant sections i.e. inlet, constricted and outlet section, used as a differential pressure producer basis on Bernoulli’s theorem where the middle section of the venturi often called as constricted section is responsible for the energy conversion, which transfers oxygen by aspirating air into the constricted section and producing interfacial area between the air and water. On the basis of dimensional analysis, non-dimensional numbers associated with geometric, dynamic and process parameters were analysed. The non-dimensional geometric parameters like throat length (tl), hole distance from beginning of throat (hd), throat hole diameter (th) were optimized and additionally conducted at constant flow rate (vw=0.396 m/s). To assess the performance of designed venturi, the selection of different tl as 20, 40, 60, 80 and 100 mm, with varying number of holes inserted, depends on the tl and keeping th constant at 2 mm. The SAE values were initiated more with increasing tl. The maximum SAE values was obtained with maximum number of holes open as 6.200 × 10-3 kg O2/kWh for 100 mm tl. A constant flow rate was maintained to construct the equations for the prediction of venturi aeration system’s characteristics via simulations. For the purpose of simulations different geometric conditions of the venturi design system were considered. The simulation equations developed for tl based on the Re and Fr are subjected to 12.655 × 10-5 > Re > 2.531 × 10-5 and 1.251 < Fr < 6.256, respectively. It was also concluded that from the non-dimensional study, the simulation equation developed for NDSAE based on the tl be valid and subjected to 3.890× 103< NDSAE <0.215× 103.