Is there anyone who understands mass flow meters? Please take a look
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The company installed mass flow meters at the location where liquid ammonia is filled, and found that in the unfilled state the density indicated 6.14 with a temperature of 17.5; once filling began, the density dropped sharply, fluctuating between 4.9 and 5.0. The outlet pressure is 1.3 Mpa. By comparing this with the saturated vapor pressure of liquid ammonia, it can be seen that at a temperature of 18 degrees, the saturated vapor pressure is only 0.8 Mpa. Under these conditions, liquid ammonia shouldn’t vaporize, right? Is there anyone who can discuss this?
Is there a flow indicator before filling? Generally, before using a mass flow meter, the medium needs to be introduced into it, and then the inlet and outlet stop valves are closed to perform zero-point calibration.
No, the flow rate indicates 0 kg/H
According to the manufacturer’s explanation, it is mainly due to the vaporization of liquid ammonia that causes a sharp change in density
The instrument manufacturer replied that there is no problem; it is caused by the vaporization of the medium. Your understanding of the vaporization of liquids is incorrect. Liquids, especially volatile ones, do not vaporize only at temperatures where a certain saturated vapor pressure is reached; that phenomenon is called boiling. As long as the environment can provide sufficient heat, volatile liquids can vaporize at any temperature, of course to some extent. However, for liquid ammonia in pipes, partial vaporization leads to deviations in mass measurement.
Liquid nitrogen has a density of over 800 kg/m³; the initial density of 6.14 can be disregarded or ignored. The density is very low during filling; it must have vaporized.