High Temperature Flow Meters: How do I measure the flow of liquids at elevated temperatures ?
I well remember my physics teacher dropping a piece of sodium into a bath of water and being mesmerised by the pyrotechnics. In its solid form sodium is a soft silvery-white metal which is highly reactive with a lot of chemicals. However, in its liquid form it is used in cooling circuits as it has unique physical and thermal properties. High temperature flow meters exist which can measure this liquid metal at temperatures up to 600°C and possibly above. The flow of other materials commonly required to be measured at elevated temperatures included bitumen, molten sugar and sulphur in the construction, food and chemical industries. In all cases using high temperature flow meters, it is important to conserve the heat in the liquid to prevent it sticking to the internal surfaces and damaging the pipework and other equipment. Maintaining the temperature is also important as the transport properties of the fluid can change dramatically with even small temperature changes.
Titan High Temperature Flow Meters
For slightly above ambient applications insulating pipes is often sufficient to maintain the transport properties of the fluid. By comparison, high temperature flow meter applications (>50°C) require other techniques to be used such as heat tracing elements and water or oil heating jackets. In these high temperature flow meter system the sensing element has to be able to withstand these temperatures but the electronics usually cannot and are therefore mounted some distance from the main body to maintain a thermal bridge. Likewise associated materials commonly used in flowmeters such as paint, seals and cabling could be subject to operating outside their design envelope thus alternatives have to found.
Currently the highest elevated temperature flowmeter – Titan has manufactured operates at 200°C. This bespoke system was an oval gear flowmeter for metering engine oil in an F1 racing car testbed. Other flow technologies such as electromagnetic and Coriolis can also be adapted for higher temperature applications.