Confusions about dry air, wet air, and flow rate
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When using a flow meter, does the displayed flow rate generally represent the flow rate of dry air or wet air? I’ve never understood this; according to the consultation with the metrology institute, it’s about calibrating the system device, and the flow rate refers to the flow rate of dry air. So, is the density displayed in real time by the secondary instrument considered to be the density of moist air? To calculate the dry air flow rate, it is the density of wet air minus the density due to moisture; this value equals the density of the dry portion in the wet air multiplied by the volume, and that gives the dry air flow rate. I beg the experts to tell me something. I’ve been confused for a week.
The parameters measured for flow rate are merely the volumetric or mass flow rate per unit of time. Determining the specific contents of various substances within this volume is something that will be dealt with later. If dry gas is needed, the volume occupied by moisture must be removed. But this is only relative. I don’t know why the calculations are so precise. For reference.
If wet air flows through the flow meter, then what is measured is the standard cubic flow rate of the wet air. If the air is drawn from the ambient atmosphere by a fan for delivery, to determine the flow rate of dry air it is necessary to subtract the amount of water vapor contained in it from the measured flow rate of wet air, based on the current atmospheric temperature and relative humidity. Under normal room temperature conditions, the difference is only a few percentage points; in summer or when humidity is high, it’s sufficient to increase the flow rate slightly. If air is transported after being pressurized by a compressor, and cooling as well as conventional gas-liquid separation for water removal are carried out after pressurization, the amount of water vapor to be deducted must be determined based on the temperature and pressure conditions during cooling and condensation, as well as whether measures are in place to remove water mist.
Thank you. I was busy lately and didn’t get a chance to reply. Sorry