Temperature distribution measurement and control of extrusion process by tomography

Abstract

Polymer extrusion molding is an important process in the polymer manufacturing industry. It is crucial to measure and control the temperature of polymer melt. Although different techniques, such as thermocouple, infrared and ultrasonic, have been attempted to measure the temperature, there is no suitable means so far to measure the internal temperature in a cross section of a polymer extrusion process, and hence the process is operated by trail-and-error. Electrical capacitance tomography (ECT) is a non-intrusive and non-invasive technique to obtain permittivity distribution of a cross section. Because the permittivity is a function of temperature for a certain material, if the extrusion chamber is fully occupied by polymer, the temperature distribution can be derived from the permittivity distribution, which can be obtained by ECT. This paper reviews the existing methods to measure the temperature of polymer melt first. The approach and the key issues to measure the temperature distribution based on ECT will be discussed in detail.

E5.3 - Suitability of ECT for Non-invasive Temperature Monitoring in Fixed-bed Reactors

“…The method has already been investigated in the context of temperature measurement in the production of plastic pellets and in a polymer extrusion machine [3,4]. In the field of reaction engineering, the method has already been used to identify flow regimes in fluidized beds [5].…”

Applications of Electrical Capacitance Tomography for Research on Phenomena Occurring in the Fluidised Bed Reactors

“…This possibility was noticed for example in (Tapp et al, 2003) but without a broader analysis of the problem. It is noteworthy that simple mapping of determined permittivity of the substance into the corresponding temperature is only possible in homogeneous environment (Yang et al, 2008). Although it excludes the possibility of determining the temperature field in the fluidised bed using ECT tomography in its basic form; this may be the basis for its modification.…”

“…Dependency of both ' and " of the bed material on temperature is known for many substances (Chełkowski, 1993;Yang et al, 2008) but can also be obtained experimentally (Thorp et al, 1987). Measurement of dielectric characteristic as a function of frequency of the applied voltage is known as dielectric spectroscopy (Asami, 2002).…”

Non-invasive temperature monitoring in fixed-bed reactors by electrical capacitance tomography

“…If for example the temperaturepermittivity relationship of a material is known, the temperature distribution in the material can be estimated from the reconstructed permittivity distribution. With this in mind, experiments have already been carried out to investigate the extrusion temperature in polymer injection molding machines and to monitor the cooling process of plastic pellets after production [16,17]. Another study focused on estimating the temperature field of a flame from combined conductivity and permittivity measurements [12].…”