Regarding the flow rate of nitrogen
Thread Content
I have a rather basic question for everyone. In the tables of typical flow rates for fluids, the flow rate at 0.6 MPa is given as 10–20, while for nitrogen gas at 1.0–2.0 MPa the flow rate is 3–8. However, for nitrogen gas at 5.0–10.0 MPa, the flow rate becomes smaller, ranging from 2–5 m/s. What’s the reason for this? Isn’t the flow rate proportional to pressure, just like in steam? Is it because of liquid nitrogen? We are now going to use nitrogen to fill the interior of the equipment for protection, in order to displace the air inside. What pressure of nitrogen should be used? How should the flow rate be determined?
4 kilograms of nitrogen should be used.
The reason why the flow rate is lower at higher nitrogen pressures is that, during transportation through the pipes, pressure drops due to resistance in the pipes. Friction within the pipes causes the temperature of the nitrogen to rise, leading to an expansion of its volume and an increase in volumetric flow rate, which in turn increases the flow speed as well. It’s just my personal understanding; I hope experts can give some guidance
1. The flow rate of nitrogen gas is primarily determined by resistance considerations； 2. The higher the pressure, the greater the density. If the flow rate remains the same, the resistance will be much higher; to keep the resistance from being too high, it is necessary to reduce the flow rate ； 3. It has nothing to do with liquid nitrogen ； 4. Nitrogen protection is used; generally, the nitrogen sealing pressure is 0.02–0.05 MPa, and no specific requirement exists for the flow rate, with thorough displacement being the key principle ；
The higher the nitrogen pressure, the greater the density according to Clapeyron’s equation. Since the mass flow rate of nitrogen required by the process is constant, it is necessary to reduce the volume flow rate; with a fixed pipe diameter, this means reducing the flow velocity.
If nitrogen is used for protection in atmospheric-pressure storage tanks, high pressure can cause damage to the equipment. A pressure range of 0.02~0.05 MPa is appropriate
If nitrogen is used for protection of equipment at atmospheric pressure, a higher pressure requires stricter sealing requirements for the equipment; 8 KPa is sufficient.
A slight positive pressure under nitrogen protection is sufficient. Generally, the pressure in normal-pressure containers should not exceed 0.1 MPa.
We use nitrogen protection at ±50 Pa
For nitrogen sealing in pressure vessels at normal pressure, pressure reduction is required; the nitrogen pressure used for such sealing must not exceed the designed pressure, and it must also be lower than the setting pressure of the safety valve. 0.6 MPa is usually sufficient.
May I ask LZ, in which book or manual did you find the range for the nitrogen gas flow rate? Thank you