Bubble Generation

Small air bubbles, 100 |im or less, are formed by injection of supersaturated pressurized recycle water into a flotation tank using specially designed nozzles. The process of bubble formation involves two steps: nucleation and growth. During the first step the large pressure difference across the nozzle produces bubble nuclei spontaneously. Air bubbles grow at a fixed number of nucleation centres due to air transferred from the water. As the excess air is transferred from the dissolved to the gas phase, the bubbles grow in size. Additional bubble growth may occur as the bubbles rise due to a decrease in hydrostatic pressure or coalescence.

Measurements of bubble sizes for DAF systems indicate that bubbles maintain a steady-state size range of 10-100 |im. A reasonable estimate of average bubble diameter is 40 |im. The steady-state size depends on the saturator pressure and the injection flow rate. The injection flow must provide a rapid pressure drop and be sufficient to prevent back-flow and bubble growth on pipe surfaces in the vicinity of the injection system. To ensure small bubbles, pressure differences (saturator gauge pressures) of 400-600 kPa are recommended.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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