Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Patent
1997-07-02
1998-10-20
Biegel, Ronald L.
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
7386118, 73644, G01F 0166
Patent
active
058249150
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a volume flow meter for flowing media that works on the transit time principle, with a conduit measurement section, two ultrasonic transducers arranged at opposite ends of the conduit measurement section that send ultrasonic signals into the flowing medium and/or receive them from the flowing medium and a control and evaluation circuit, wherein the control and evaluation circuit measures the transit time of the ultrasonic signals between the ultrasonic transducers to determine the volume flow through the conduit measurement section.
Since the known volume flow meters on which the invention is based have proven very good when used in the industrial sector, many other applications have recently been developed for these volume flow meters, particularly applications in which the flowing medium has clearly high temperatures. Here, their use in the area of oil extraction is mentioned only as an example. Since piezo crystals are generally used as the basic component of the ultrasonic transducer in the known volume flow meters, the possibilities of using the known volume flow meters are limited to a temperature range up to 120.degree. C., but at the most 150.degree. C. At higher temperatures, the ultrasonic transducers regularly used are subject to problems or are completely dysfunctional.
SUMMARY OF THE INVENTION
The task of the invention is, therefore, to develop and design the known volume flow meters in such a way that they can be used even when the flowing medium is at high temperatures and in such a way that they have superior measurement precision.
The volume flow meter in the invention for flowing media that works on the transit time principle, in which the task introduced and described above is solved, is characterized by the fact that the ultrasonic transducers send ultrasonic signals into the flowing medium via thermally insulating ultrasonic waveguides. The invention guarantees that the high to very high temperatures in the flowing medium are far from being reached on the ultrasonic transducer because of the thermally insulating ultrasonic waveguide placed between the flowing medium and the ultrasonic transducers. In one suitable design of the thermally insulating ultrasonic waveguide, for example, temperatures of up to 1000.degree. C. are possible for the flowing medium without affecting conventionally--and hence inexpensively--designed ultrasonic transducers.
One first advantageous embodiment of the invention of the volume flow meter is that the ultrasonic waveguide is designed in the form of a rod. The rod-shaped design of the ultrasonic waveguide guarantees that even materials with higher heat-conducting coefficients, but even better other material parameters, particularly with regard to the required ultrasonic waveguide properties, can be used as the starting material to produce ultrasonic waveguides.
A particularly big difference between the temperature of the flowing medium and the temperature of the ultrasonic transducer can be guaranteed in the volume flow meter according to the invention by the fact that a cooling device is provided to cool the ultrasonic waveguide. Here, both active cooling devices, like water or air cooling, and passive cooling devices are conceivable.
An especially advantageous design for the volume flow meter in the invention is one in which the ultrasonic waveguides have at least one cooling rib. This passive cooling device is particularly advantageous since it requires no other installation expense and is extremely trouble-free.
Finally, it has also proven particularly advantageous to produce the ultrasonic waveguides of stainless steel. Ultrasonic waveguides produced in this way are inexpensive, have a relatively low heat-conducting coefficient and have good ultrasonic wave-conduction properties.
The invention's design of the volume flow meter necessitates conversion of the method for determining volume flow according to the transit-time principle, which can be used in a volume flow meter designed according to the
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Boer Andre H.
Hujzer Arie
Biegel Ronald L.
Krohne A.G.
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