AN EXPERIMENTAL AND ANALYTICAL STUDY OF HEAT TRANSFER TO POLYMER SOLUTIONS IN TURBULENT PIPE FLOWS UNDER CONSTANT WALL HEAT FLUX (VISCOELASTIC, NON-NEWTONIAN).

摘要

Scope and Method of Study. The main objectives of this study were to experimentally determine the momentum and heat transfer characteristics of drag reducing turbulent pipe flows and to develop and establish a semi-empirical equation for heat eddy diffusivity based on the experimental results. The measurements of friction factors, heat transfer coefficients and apparent viscosities were conducted for the solutions of Separan AP-273 and WSR-301 with concentrations of 10 to 1000 ppm flowing turbulently in the test sections of 0.436 inches and 0.739 inches under the constant wall heat flux condition. The critical Weissenberg number for heat transfer was studied using Separan AP-273 solution of 1500 ppm and Separan AP-30 solution of 3000 ppm. An attempt was made to develop a heat eddy diffusivity expression for turbulent viscoelastic pipe flows in terms of friction drag reduction ratio and Weissenberg number which could be determined from the measurements of pressure drop and rheological properties.;Findings and Conclusions. The addition of polymers to turbulent pipe flows produced drastic reduction in friction drag and heat transfer as compared with the solvent flows. This reduction was more pronounced with the increase of polymer concentration and the decrease of pipe diameter. However, this was limited by the maximum reduction asymptotes for friction drag and heat transfer. For the same concentration, Separan AP-273 was proved to be more effective drag reducer compared with WSR-301. All the experimental results were presented in terms of the apparent Reynolds number and Weissenberg number. This study confirmed the critical Weissenberg number for heat transfer for Separan AP-273 solutions. Ws(,ch) = 200-250, suggested by the previous works and further demonstrated that this value is applicable to other polymers. A scaling law for pipe diameter and polymer concentration was proposed and verified. An empirical correlation for heat transfer was derived with the use of friction drag reduction ratio and Weissenberg number. The proposed heat eddy diffusivity expression was proven to predict the experimental data within the maximum error of 30% for various polymer solutions with wide range of concentrations.