Applications of sealed sources in chemical engineering. V

The absorption radiometric method (241Am) was used for determining the thickness of liquid flowing through an inclined pipe 2000 mm in length and 25 mm in diameter, with an inclination of 1.2 and 3deg. The results obtained using this method and measurements using a needle which closes an electric circuit when it comes into contact with the surface of the liquid, were used for assessing the correctness of the published theoretical solution of gravity flow of a liquid with free surface through a circular channel. The absorption method determines the thickness of the layer contactlessly and integrally in the area given by penetration of a cylinder corresponding in diameter with the collimated beam and so the difficulties are avoided connected with the mean layer thickness determination when using the needle method. This is advantageous mainly in the laminar mode with an undulating surface and in the turbulent area. The measurements confirmed that the tested theoretical relations apply under conditions for which they were derived with adequate accuracy. (author)