FLUID VELOCITY MEASUREMENT USING LASER TECHNIQUE

Abstract

One of the important measurements in chemical industrial units is the measuring of the fluids velocity in different stages of industrial process. Determination of this parameter is important for controlling the heat and mass transfer. Hence, the present study is designed for this purpose by employing laser technique. A specific system was constructed using laser light. It consists of two He-Ne lasers ( power of 1 mW and 632.8 nm wavelength) and a detection system. The fluid system involves a centrifugal pump to change the fluid velocity. Two fluids were employed; water and gasoil. The detection system consists from a special electronic circuit essentially built to detect the laser beams with a time counter. The experiments were carried out at different fluid velocities. The velocity measurements determined by laser system were based on the basic principles of the velocity which is the linear change of distance as function of time. In the first run of the experiment with water, the water flows in the glass tube create air bubbles which change the laser intensity incident on the detector. When the intensity in the first detector changed the electronic circuit started up the counter and then the counter stopped by the intensity changed in the second detector. The velocity obtained was affected by the 4 bubble size, but it gave similar results wh en the experiment was repeated for the same velocity with different distances. Two tubes with 1 cm and 1.6 cm outside diameter were used in these experiments. In the second run of the experiments with gasoil, the work was done without pump so it made the flow control poor and caused scattered results. The obtained results showed significantly accurate results and a high sensitivity of the system for any small change in the fluid velocity.