Is the flow rate measured by this float-type flow meter under standard conditions?
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Dear teachers, there is a float flow meter on site for measuring compressed air flow rate. The gauge indicates 25°C, pressure of 0.6 Mpa, density of 1.29 Kg/m3, and the unit is Nm3/h. Is the flow rate measured under standard conditions? Can it be understood in this way: when the process conditions are such that the compressed air pressure is 0.6 Mpa and the temperature is 25°C, the measured flow rate represents the flow rate under standard conditions, and no conversion is necessary – the manufacturer has already made the conversion.
Traffic? Not necessarily; it depends on whether the flow rate conditions under measurement match the standard conditions. -
At 25°C, with a pressure of 0.6 Mpa and a density of 1.29 Kg/m3, this value represents the Nm3 volume at which the flow meter is calibrated by the manufacturer. It refers to the volume of gas at 0 degrees Celsius and 1 standard atmosphere; to determine the flow rate under the actual temperature and pressure conditions on site, there is a calculation formula used
However, according to the formula for rotameters, flow rate has no direct relationship with the temperature and pressure of the medium (although changes in temperature and pressure can affect the density of the medium, small changes in density are likely to have little impact on accuracy)
According to the operating temperature and pressure specified in the table header, the corresponding standard cubic value can be measured directly.
. The scale is in square units. The values of 25℃, 0.6Mpa, and 1.29Kg/m3 on the header represent the nominal operating conditions; in other words, the scale corresponds to the conditions at 25℃, 0.6Mpa, and 1.29Kg/m3. The N in Nm3/h refers to the nominal operating condition. That is, the operating condition used as a comparison benchmark, which is what is commonly referred to as standard conditions. Note: The nominal operating condition is different from the true standard condition. The standard state refers to a condition of a temperature of 273.15 K (0°C) and a pressure of 101.325 KPa. In engineering, standard conditions actually refer to nominal operating conditions, with many being based on \"normal temperature\" and \"normal pressure\" as benchmarks. For example, some materials exhibit different properties under standard conditions compared to those under operating conditions; therefore, in engineering practice, a nominal operating condition that deviates from standard conditions is specified. In engineering terms, “20T cooling water” usually refers to room temperature water (20°C or 25°C), rather than water at 0°C.
As shown in the figure, the flow rate is 71 cubic meters per hour. I once asked the manufacturer about this issue, and the reply was that the value in the gauge has already been converted to standard cubic feet, and it is displayed directly as standard cubic feet
Since the unit indicated is Nm3/h, this refers to standard conditions, with a temperature of 0°C (273.15 Kelvin) and a pressure of 101.325 kPa (1 standard atmosphere, or 760 millimeters of mercury). This value represents the flow rate of the actual gas. There are also so-called operating conditions, which correspond to a temperature of 20°C and 1 atmosphere; the temperature and pressure indicated on the gauge are, in my understanding, the temperature and pressure at the time of instrument calibration, while the scales are based on the converted standard conditions.