With regard to its function as a differential pressure flowmeter, the movable tube flowmeter of the straight flow type previously reported by the present authors may be considered to correspond to the Venturi meter while the movable orificeflowmeter, here reported, corresponds to an orifice meter.
An orifice meter should be considered to be composed of not only the orifice plate but a part of the tube including the pressure taps should also be included as an essential component. Similarly, in the movable orifice flowmeter, the short tube connected movably by a bellows to the fixed pipe should also be considered.
From the viewpoint of measuring principle, however, the movable orifice flowmeter is a kind of a movable tube flowmater of the straight flow type, in which the movable tubewith a smaller diameter becomes extremely short. Therefore, the true flow rates are obtained by the movable orifice flowmeter without the need of a discharge coefficient.
The results of experiments with the trial flowmeters show good agreement with the theory.
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