How many nitrogen gas cylinders are needed for a pressure-relief tank truck?
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At room temperature, the pressure in the tank truck must be maintained at 0.4 MPa, and nitrogen cylinders are used for gas-phase unloading. How many 40L standard nitrogen cylinders are required? Please provide the specific volume calculation, thank you!
How large is a tank truck? What is the pressure in a 40L nitrogen gas cylinder?
Tank truck: 25 m³; gas cylinders are generally filled at 15 MPa
Ignoring the effects of initial pressure and temperature changes, a rough estimate gives (25*0.4)*1000/(15*40) = 16.67 (bottles)
This post was last edited by minizero on 2018-10-15 at 11:39. It differs slightly from the comments above: due to volume expansion, calculations should be done using absolute pressure. The cylinder should still have at least 0.4 MPa left (i.e., an absolute pressure of 0.5 MPa). Therefore, the calculation can be roughly done as follows: ((25*0.5)*1000)/(14.9*40-0.5*40) = 21.7 cylinders. Discussions are welcome
No matter how accurate the calculations are, it seems useless to dig anyway – what if there’s a leak? Right? Prepare 200 bottles of gas; if the pressure is not sufficient, fill them with air. Bro, I know you guys don’t lack money. :lol.
Oh, right. You’re right; I forgot about absolute pressure. . . . .
Ignoring the temperature changes, if x bottles are needed, then (25 + 40*x/1000)*0.5 = 15.1*40*x/1000. Solving this equation gives x = 21.404. It’s been a long time since I’ve worked on problems like this; I used to practice such calculations a lot in high school, so my estimate is correct.