Please calculate the flow rate based on the flow calculation sheet
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This is a flow calculation sheet for an orifice plate. According to this sheet, the maximum pressure difference is 40 kPa, corresponding to a flow rate of 60,000 Nm3/h. The transmitter’s range is also 40 KPa. For example, if the transmitter current is 8 mA, which corresponds to 25%, taking the square root of that value and then multiplying it by the flow rate of 60,000 gives a flow value of 30,000 Nm3/h; calculating using the formula below also yields 30,000. Is it necessary to apply any temperature compensation to this value? If temperature difference compensation is applied, is the unit after compensation still Nm3/h?
It depends on the operating conditions; if they are the same as those in the design, no compensation is needed. If there is a significant difference, then compensation is required, with the unit still being NM3/H
Gases have different densities at various temperatures and pressures; accurate measurement requires temperature and pressure compensation.
In my humble opinion, the flow rate measured by a differential pressure flow meter represents the flow rate under the actual operating conditions. The flow rate values given in the calculation sheets are merely the design-condition flow rates converted to standard-condition values. If the actual operating conditions are identical to the design conditions, then the standard-condition flow rates correspond one-to-one with the differential pressure values. However, if there is a difference between the actual and design conditions, temperature and pressure compensation is necessary to ensure accurate flow rate measurement. It should be noted that the target for compensation is the design conditions, not the standard conditions. In other words, the actual operating conditions are first converted to design conditions, and then, based on those design conditions, the flow rate is converted to a standard-condition value through the calculations.
If density is used for calculation, no further compensation is required.