Dali flow tube

Dali Flow Tube - The advantage is this type of flowmeter is that it has a permanent head loss of only 5 % of the measured pressure differential. This is the lowest pressure drop of all orifice meter designs. Flow ratios as high as 1 10 (e.g., 1.0 to 10 kg/s) can be measured within + 2% of actual flow. Dali flow mbes are available in different materials and diameters up to 1500 mm. 

O. Miner. The Dali flow tube. Instrument Engineer, April 1957, pp. 45-49. 

The flow sensors most commonly employed in the industrial practice are those that measure the pressure gradient developed across a flow constriction. Then, using the well-known (from fluid mechanics) equation of Bernoulli, we can compute the flow rate. Such devices can be used for both gases and liquids. The orifice plate (Figure 13.5a), venturi tube (Figure 13.5b), and Dali flow tube are typical examples of sensors based on the foregoing principle. The first is more popular due to its simplicity and low cost. The last two are more expensive but also more accurate. 

Figure 4.2 The micro-Flow Tube Reaetor/Mass Spectrometer instrument. 1 — heated gas inlet/vacuum feedthrough, 2 — hot zone of flow tube, 3 — multiion source block, 4 — ion guide, 5 — quadrupole mass spectrometer, 6 — ion guides, 7 — reaction cell, 8 — quadrupole mass spectrometer, 9 — daly detector... 

In view of the complexity of the pipework, it was difficult to prejudge the likely accuracy of the overall prediction. Total flows were measured by Dali tubes situated in the main downcomers to the pumps over a range of thermal powers ranging up to 300 MW. The predictions were within the scatter of the measured points. At full power the comparison was as shown in Table 3. 

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