Flowmeter

1. An acoustic flowmeter comprising a flow tube including an inner elongate member in the flow tube to define at least one flow passage for the flowmeter, in which the inner elongate member comprises multiple flights or divisions extending the length of the flow tube to form multiple flow passages defined by a wall of the flow tube and the multiple flights or divisions.

2. An acoustic flowmeter comprising a flow tube with an annular flow passage, in which the annular flow passage is defined by generally cylindrical wall of an outer body and an inner elongate core body held in position within the said flow passage by one or more generally radially extending support arms projecting inwardly from the said outer body.

3. An acoustic flowmeter as claimed in claim 2 , in which two acoustic transducers are located axially spaced along the said annular flow passage.

4. An acoustic flowmeter as claimed in claim 3 , in which the said acoustic transducers are mounted on the said outer body.

5. An acoustic flowmeter as claimed in claim 3 , in which the said acoustic transducers are mounted on the said inner elongate core body.

6. An acoustic flowmeter as claimed in claim 2 , in which the acoustic transducers are connected to control means operable to effect a transit time differential determination of the flow rate of the fluid.

7. An acoustic flowmeter as claimed in claim 6 , in which the said control means are operable to excite the said acoustic transducers in a continuous, simultaneous manner or in sequence whereby to transmit and receive acoustic signals alternately, each transducer being connected to receive acoustic signals when the other transducer is being excited to transmit them.

8. An acoustic flowmeter as claimed in claim 2 , in which the said generally radially extending support arms have feathered leading and trailing edges whereby to provide minimal disruption to the streamline flow of fluid in the said annular passage.

9. An acoustic flowmeter as claimed in claim 2 , in which there are provided connector means at each end of the said annular flow passage whereby to connect the flow passage to conduits of an external fluid circuit.

10. An acoustic flowmeter as claimed in claim 6 , in which the said connector means taper from one end to the other whereby smoothly to vary the flow cross section of the fluid path entering and leaving the said annular flow passage.

11. An acoustic transducer as claimed in claim 2 , in which the said central core body has a tapered portion at each end thereof.

12. An acoustic transducer as claimed in claim 8 , in which the said tapered portions at each end of the said central core body extend into connector means at each end of the said annular flow passage whereby to connect the flow passage to conduits of an external fluid circuit.

13. An acoustic flowmeter as claimed in claim 2 , in which two acoustic transducers are located axially spaced along the or each flow passage.

14. An acoustic flowmeter as claimed in claim 10 , in which the said acoustic transducers are mounted on an outer body of the flow tube.

15. An acoustic flowmeter as claimed in claim 10 , in which the said acoustic transducers are mounted on the said inner elongate member.

16. An acoustic flowmeter as claimed in claim 13 , in which the said control means are operable to excite the said acoustic transducers in a continuous, simultaneous manner or in sequence whereby to transmit and receive acoustic signals alternately, each transducer being connected to receive acoustic signals when the other transducer is being excited to transmit them.

17. An acoustic flowmeter as claimed in claim 3 , in which the said acoustic transducers are mounted on the radially extending support arms.