Images reveal that atmospheric particles can undergo liquid–liquid phase separations

4.27.19

This a youtube video detailing how a gas mass flow controller works. First the gas that flows into the flow controller go through four stages of conditioning. These conditioning stages get rid of any turbulent flow and other irrigularities that could arise due to upstream conditions. You need laminar flow to have linear and accurate results. The laminar flow element creates a pressure drop that makes a very small proportion of the gas flow take a different route than the bulk flow. These individual gas molecules travel through a very thin wire that (stainless steel capillary tubing) that is where the sensing actually takes place. The capillary sensor works as follows. The stainless steel tube is precisely wound with two platinum wires that measure the resistance through the capillary tube. The resistance changes with the temperature profile and when the sensor is not ini use the temperature profile looks symmetric. Once gas flows in the tube the gas molecules carry heat with them and shifts the temperature profile towards the downstream coil. This then changes the capillary resistance. The onboard digital electronic measure the difference in resistance and translate these values to a mass flow reading. The signal is directly related to the mass flow rate of the gas and the gas in the capillary rejoins the bulk gas flow. This laminar flow is nearly perfect. The mass flow signal is relayed to the direct acting valve. This valve controls the precise mass flow rate.

This is my first blog post and didn't know just how complicated these sensors actually could be. Gas mass flow devices are critical, because most of the time the volume of product or speed of the product doesn't matter as much as the actual mass traveling through the pipe. Mass flow rate devices are also not affected by temperature and pressure so there is less possibility of measurement error. Almost all processes from transporting gasoline to brewing beer require that the operators know exactly how much product is going from one point to another.