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Session 2659

Instrumentation with Computerized Data Acquisition for an Innovative Thermal Conductivity Apparatus

M. Kostic Northern Illinois University Error! Bookmark not defined., DeKalb, IL 60115, USA

Abstract. An innovative method and a novel research apparatus are being developed to measure the thermal conductivity of a non-Newtonian fluid while it is subjected to shearing flow, and to determine its dependence, if any, on shearing itself. This is contrary to the current state-of-the-art of measuring thermal conductivity under the condition of motionless fluid, to avoid convective heat transfer influence on the results. The emphasis here is given to the apparatus’ instrumentation and computerized data acquisition design and its educational demonstration as a purposeful and typical application example, while a detailed description of the mechanical design and test results will be presented elsewhere. 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. The designed system accomplishes the following objectives: (a) acquire measured data with high speed and accuracy; (b) interactively process/analyze measured data for immediate use or store it for future post-processing; (c) provide interactive and accurate, feed-back process control - motor speed and guard-heating power, and (d) interactively display data in graphical and/or numerical forms. In addition, this system allows for easy modification and enhancement of virtual (software) instruments by modification of software programs.

1. INTRODUCTION It is known that high molecular polymeric solutions and other rheologically complex non- Newtonian fluids are affected by shearing flow: becomes fiber-like, non-uniform and non-isotropic. An innovative method and a novel research apparatus are being developed to measure the thermal conductivity of a fluid while it is subjected to shearing flow, thus measuring the thermal conductivity as a function of temperature and shearing parameters themselves [1-14]. Such measurements are essential because the fluid (changing) structure and anisotropicity are flow-induced and dependent. To increase control of the parameters and accuracy, the flow should be isometric (laminar and one-dimensional) and heat transfer should be only in the transverse direction to the fluid velocity, i.e., orthogonal to it, to prevent interference from convective heat transfer. The emphasis here is given to the apparatus’ instrumentation and computerized data acquisition design and its educational demonstration as a purposeful and typical application example, while a detailed description of the mechanical design and test results will be presented elsewhere [15-16].

The measurement and control are accomplished and integrated by using a computerized data acquisition system and a comprehensive so called “virtual instrument,” developed using the LabVIEW application software. The motor’s rotational speed is measured by a tachometer-sensor and controlled by a voltage-varying DC motor through a built in, solid-state, servo power-amplifier circuitry. The main heater is powered and controlled by a high-quality DC power supply, while

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Kostic, M. (1997, June), Instrumentation With Computerized Data Acquisition For An Innovative Thermal Conductivity Apparatus Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6624