How to convert flow rate
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For the same orifice plate, the flow transmitter ranges from 0-60 KPA, corresponding to a flow rate of 0-500 NM3/H. The orifice plate was designed based on a gas molecular weight of 20.3, a pressure of 0.422, and a temperature of 87.7. For some reason, the gas being measured now has a molecular weight of 28, the same pressure of 0.422, but a temperature of 15 degrees; in this case the flow rate indicated is 120 NM3/H. What is the actual flow rate? How to calculate it? How is the differential pressure value of an orifice plate calculated? Why does 500 correspond to 60 KPA?
Is it not very dependent on temperature? What if the medium changes from another gas to N2, or vice versa? Also, how is this nominal flow rate calculated when setting the differential pressure for the orifice plate? Isn’t it always based on the operating conditions during normal use?
This post was last edited by HEJIYUER on 2021-2-6 23:18. In SQT, the ratio of operating density to design density is used (which takes into account the parameters MW, P, and T). The differential pressure measured at the orifice plate is related to the volumetric flow rate under operating conditions; the operating flow velocity is used in the calculations. However, the input unit is KG/NM3, which is surface data; the program still needs to convert it to the actual volumetric flow rate. Although you have changed the medium, the transmitter’s range remains unchanged (the differential pressure under the new operating conditions is still 60 KPA). Therefore, this conversion does not require considering the differential pressure value.