Flow measurement of extremely low-temperature media
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I would like to ask whether the flow rate of liquid nitrogen at -200°C can be measured using an equilibrium flow meter Can carbon steel or stainless steel be used for the material of the guide tube? What kind of transmitter can withstand such low temperatures?
It’s possible. Generally, the temperature inside the storage tank is around -196 degrees Celsius, but the temperature in the pipes is not that low. The pressure transfer tubes are made of stainless steel, and once the pressure is transmitted to the transmitter through these tubes, the temperature becomes less low.
For ultra-low-temperature media, especially gases liquefied at very low temperatures, low-temperature vortex flowmeters should be used as much as possible; this helps to reduce pressure losses and avoids maintenance and calibration issues associated with the use of pressure conduits for installing differential pressure elements. All major meter brands offer low-temperature vortex flowmeters, which can be used for liquid nitrogen, liquid oxygen, and similar substances.
The pressure tap connected to the orifice plate does not need insulation; otherwise, liquid nitrogen would vaporize. The temperature is only slightly lower than room temperature, and the transmitter is also at a temperature close to room temperature, so there are no issues with its use. Orifice plates can also be used; otherwise, the process pipelines would not be functional.