FLOWTECH Acrylic Body Tube Variable Area Flow Meters (Rotameters) are intended for general in line metering applications (i.e. for Gas & Liquid) where operating conditions are with the limitations of Acrylic Body metering tubes. These are the principle of Variable Area. The float moves freely up and down tapered Acrylic body Tube with fluid flow from bottom to top. The float takes up a position where buoyancy forces and the float weight are balanced in proportion to flow rate. The Vertical position of the float as indicated by scale is the measure of the instantaneous flow rate.
PRINCIPAL OF ACRYLIC BODY ROTAMETER:
When fluid or gas flows through a taper tube containing a float, a pressure difference of P1and P2 is created between upper and lower side of the float. The float moves upwards by a force obtained by multiplying the pressure differential by the maximum cross sectional area of the float.
Due to taper tube, as the float moves upwards, the fluid passing area increases as a result of which the differential pressure decreases. Upward movement of float stops when the dead load is dynamically balanced by the differential pressure. Tapering of metering tube is so designed that the vertical movement of the float becomes linearly proportional to the rate of flow and the scale is provided to read the position of the float, thus giving birth to flow rate indication.
Based on Bemoulli's theorem, the principle mentioned above can be theoretically expressed as follows.