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ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

INFLUENCE OF RHEOLOGICAL PROPERTY CHANGES ON FRICTION AND CONVECTIVE HEAT TRANSFER IN A VISCOELASTIC POLYACRYLAMIDE SOLUTION

Get access (open in a dialog) DOI: 10.1615/IHTC6.1460
pages 329-333

Résumé

Previous measurements of heat transfer and pressure drop in low concentrations (25-200 wppm) of high molecular weight polymers in aqueous solutions were time dependent, even at a fixed flow rate apparently reflecting the continuing degradation of the polymer by shear stress. At high concentration of the order of 2000 wppm the pressure drop and heat transfer are unchanging with time, which has been interpreted as evidence that no degradation is occuring. To get insight into this process, an aqueous polyacrylamide solution of 2500 wppm concentration was studied in a 2.21 cm inside diameter tube. The solution was circulated in turbulent flow in a closed loop for 550 hours continuously. The pressure drop and the flow rate were measured periodically and samples of the solution were collected for rheological measurements on a Weissenberg Rheogoniometer.

It was found that the pressure drop and, inferentially, the heat transfer stayed essentially unchanged at a fixed flow rate up to 500 hours before the pressure drop began to increase gradually.

The rheological measurement indicated that the shear viscosity at high shear rate measurements (above 1000 sec−1) remains unchanged during the tests. However, the normal force, and zero shear rate viscosity both decrease with time. It therefore appears that there exist a threshold value of the dimensionless ratio of the elastic and viscous forces, above which no change in pressure drop and heat transfer occur.