Experimental study of the flow of solutions of cellulose nitrate in a tube rotating about its own axis

Abstract

An experimental study is made of the flow of solutions of cellulose nitrates in a stationary tube and a tube rotating about its own axis. Comparison of the results obtained from experimental and theoretical studies shows that they agree well with one another. Key words: non-Newtonian fluid, cellulose nitrate solutions, tube rotating about its own axis, experimental and theoretical studies.The non-Newtonian flow of a fluid in tubes rotating about their own axis was described mathematically in [1, 2] for two cases of the behavior of the medium near the solid boundary: attached flow and boundary-layer slip flow.Since it is difficult to determine the radial V r , tangential V ϕ , and axial V z velocities of such a flow experimentally, in order to confirm the adequacy of the mathematical model in describing the actual flow we designed and built an experimental unit that makes it possible to do the following: measure the pressure of the fluid on the wall of a tube rotating about its own axis at different angular velocities; maintain a constant angular velocity for the rotation of the tube or vary this parameter while measuring it and the rate of flow of the fluid.The unit (Fig. 1) includes a thin-walled tube 1 of corrosion-resistant steel with an inside diameter of 26 mm and a length of 1100 mm. To prevent vibration and deformation of the tube during its rotation, it was installed on three supports 2 and 3 and rotated inside long bearing assemblies that included two radial roller bearings.To measure the piezometric head of the fluid, plugs 6 with a thin elastic base (membrane) were inserted into bosses 4 welded to the tube every 260 mm of its length. The base of the plugs was 10 mm in diameter and ranged from 0.2 to 0.4 mm in thickness. Strain gages 5 were stuck to the inside surface of the plug. The gages sensed the elastic strains in the membrane as the medium flowed along the through portion of the tube. The gages had two terminals, each of which was secured to the clips of multichannel mercury current pickup 7. This arrangement made it possible to simultaneously transmit electrical signals from four rotating gages connected so as to form the bridge circuit of extensometer 8, which was powered from dc source 9.The output signal from the current pickups was sent to flat switch 10, which received an electrical signal from each of the four gages in succession for recording by millivoltmeter 11.To balance the bridge of the extensometer, a fifth, compensating gage was diagonally mounted on top of calibration beam 12 of calibration unit 13. The latter unit was connected to extensometer 8 through switch 11.The hydrodynamics of flow of anomalous fluids was studied inside a stationary tube (ω = 0) and a rotating tube. The speed of rotation of the rotating tube was measured with stroboscope 15 and was regulated with a speed box. The rate of flow of the medium was measured volumetrically with a graduated vessel.

Special Aspects of Nitrocellulose Molar Mass Determination by Dynamic Light Scattering

“…Viscometry is the main method for determining the viscosity average molar mass in industry. The method is simple and does not require advanced equipment [ 25 , 26 , 27 , 28 ]. The polymerization degree of cellulose nitrates determined by the viscometric method, most commonly, is a mean value of several separate fractions.…”