Investigation of Thermal Conductivity of a Polymer Solution as Function of Shearing Rate

Abstract

A novel research apparatus is developed to measure the fluid thermal conductivity while in shearing flow, and to determine its dependence on the shearing itself, contrary to the current state-of-the-art of measuring thermal conductivity under the condition of motionless fluid. A concentric cylinders’ apparatus was developed to provide controlled heat transfer in the radial direction, orthogonal to the circumferential fluid velocity, thus virtually preserving pure conductive heat transfer mode. The measurement and control are accomplished and integrated by using a computerized data acquisition system and a comprehensive virtual instrument, developed using the LabVIEW application software. It was found that the thermal conductivity of a Newtonian fluid, such as distilled water, was virtually independent of the fluid motion, as expected. However, for non-Newtonian fluids such as 1000 and 2000 wppm aqueous polyacrylamide (Praestol) solutions, there was up to 10–20% increase of thermal conductivity in the operating shear rate range (40 ≤ γ ≤ 510 sec−1) at 27°C average fluid temperature.