A SIMPLE FLOW INDICATOR P. J. APICE Barren Division, Allied Chemical and Dge Corporation, Edgewater, New Jersey
A SIMPLE flow indicator can easily be constructed with a small piece of glass tubing and a few inches of wire. This flow indicator provides a means for the visual observation of the flow rate of water circulated through a water-cooled condenser. The system operates in accordance with Bernoulli's principle: When a fluid is in steady flow, its pressures will be high wherever its velocity is low and, conversely, its pressure will be low wherever its velocity is high. The insertion of a piece of glass tubing into the rubber tnbing connected t o the outlet of a condenser creates a constriction within the column of flow and presents an application of this principle. This constriction causes an increase in flow velocity and a decrease in pressure. This results in air being channeled by a piece of wire, inserted between the glass and rubber tubing, into the condenser flow causing a hnbble-stream. Any change in flow rate will produce a corresponding change in the bubble formation and speed of travel. A visual observation of the huhble-stream is all that is needed to insure that proper water flow is being maintained. For the indicator to function properly, a steady flow must be maintained through the tnbing, and the indicator should be placed on the outlet, or upper, side of the condenser in order that no hydrostatic pressure is acting against it. The glass tubing used for the indicator should have the following approximate dimensions: length, 17 cm. ;
'VOLUME 35, NO. 1, JANUARY,
1958
inner diameter, 8 mm.; wall thickness, 1 mm. A piece of corrosion resistant wire 5 to 7 em. long and 1 to 1.5 mm. in diameter provides the air channel hetween the glass and rubber tubing. Bend about 1 cm. of one end of the wire into a sharp hook and place the hook over the end of the glass tube. Insert the glass tube with wire in place between two pieces of rnhber tubing connected to the outlet side of the condenser, as shown in the figure. At least 12 cm. of glass tnbing should he visible. Adjust the rate of water flow and observe the bnbble-stream in the glass tube. Any deviation from this observed huhble-pattern is indicative of a change in the rate of flow through the system.
