Thermal measuring and testing – Thermal testing of a nonthermal quantity – Of fluid volume
Patent
1984-09-28
1986-08-05
Frankfort, Charles
Thermal measuring and testing
Thermal testing of a nonthermal quantity
Of fluid volume
374 45, 73 55, G01N 2500
Patent
active
046039791
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a procedure and a means for measuring the flowing friction of liquid substances with high internal friction and viscosity, such as molten plastic mix for instance.
Plastic extruders, or extrusion presses, are used to manufacture a huge variety of plastic components, such as tubes and pipes, sewer pipes of PVC, cable insulations of polyethylene, etc. In the extrusion process the granular raw material is placed under high pressure (200 bar) and high temperature (about 190.degree.-230.degree. C.) with a screw press and heating resistances. The molten plastic mix is then pressed through the nozzle or tool, being at the same time formed to become for instance a hollow tube, e.g. a sewer pipe. As a result of the high pressures and temperatures, quite remarkable amounts of energy have to be expended in extrusion processes. In the lack of reliable measuring pick-ups the extrusion process could not be fully optimized up to now. Optimization requires a reliable feedback as basis for control, but a continuously operating control loop could not be successfully implemented heretofore. This is because it has been found that measurement of temperature and pressure alone is not sufficient to base the control on. The state of the melt mass can be estimated to a certain degree by measuring the velocity of ultrasound through the mass, but this too does not disclose the height of friction in the extruder.
In order to optimize the energy consumption, one ought to know the amount of friction energy in the extrusion process. If the raw material is comparatively coarse hard PVC, the contribution of friction is assuredly high. Furthermore, the friction may also significantly depend on the degree of smoothness of the extruder walls. Although on the other hand conjectures are presented to the effect that the wall roughness has no effect on friction for the reason that close to the wall the velocity of the melt mass is low at all events. The flow profile of the melt mass is very poorly understood for the reason that practical measurements are very awkward.
SUMMARY OF THE INVENTION
We have in connection with a hard PVC manufacturing process made the following experiment. During extrusion pressing in progress, the operation of the extruder was stopped and the development of the temperature in the interior of the extruder was observed. Within less than one minute, the temperature had gone down about 10-15 degrees. This means that friction accounted for a fraction of this magnitude of the temperature of the melt mass, because when the mass stops moving, the friction energy falls out while the other kinds of heating remain in effect. The temperature reading was restored to its previous value about 10 seconds after restarting. This experiment demonstrates the high significance of friction in the temperature measurement.
The objects of the present invention are attained with the aid of a measuring sleeve shaped in a specific way and in which the melt mass is conveyed through a stepwise narrowing nozzle in such manner that its velocity stepwise increases in accordance with Bernoulli's law. The friction of the mass will thereby gradually increase as its velocity increases. When the temperature of the melt mass is measured in each reduced zone, the contribution of the friction terms can be assessed with the aid of thermometers alone. Since in each zone the pressure also changes as the velocity changes, it may also useful to measure the pressure in each zone. The advantages of a measuring sleeve of this kind is that its installation after the press section is easy; it is a completely passive measuring member; it interferes minimally with the flow; nothing but simple measuring pick-ups are used therein; and its price is quite moderate. Owing to the high pressures and frictions, high forces are produced which act on the temperature pick-ups and pressure pick-up inserted in the flow, but temperature and pressure pick-ups specially appropriate for use on extruders are available which to
REFERENCES:
patent: Re17841 (1930-10-01), Zimmerli
patent: 1586948 (1926-06-01), Connet
patent: 2023568 (1935-12-01), Albersheim et al.
patent: 3841147 (1974-10-01), Coil et al.
patent: 3930399 (1976-01-01), Munk
patent: 4067230 (1978-01-01), Ball
patent: 4425790 (1984-01-01), Bice et al.
patent: 4527417 (1985-06-01), Pravda
Luukkala Mauri
Matilainen Aarre
Frankfort Charles
Will Thomas B.
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