Hydrogen: Hydrogen is generally lighter than air as it has a molecular weight less than that of oxygen, nitrogen, and carbon. Therefore, as long as there are no currents (winds) in the area, hydrogen will rise to the highest point in an enclosure, fairly rapidly, 1/2 as fast as water falls. Conservation of mass rules in physics also tell us that if one thing leaves, something else must take it's place. This brings us to the first couple rules for venting hydrogen. Since air has a density so little, as long as we don't create a vacuum, one vent can run at speeds a bit faster than the other. The weight of Hydrogen creates the force that allows it to rise...
Vents must go up. - No matter how you try, you will not successfully vent hydrogen through the bottom of a box.
Good practice to reduce bends. - No bends more than 45° and your vent will flow freely.
Intake and Output tubes. - One vent tube should vent the hydrogen upwards, the other shall bring in fresh air to the bottom of the box or enclosure.
Intake and Output tubes of metal. - copper is best as sparks are reduced, and heat dissipation is good.
Lifeline and SunXtender AGM Batteries gas 10% by volume, over the course of a charge or discharge. To determine this, we measure your batteries. Please input the number of batteries, and size of one of them below to determine gas dissipation.
Worst case is a short circuit, batteries discharge as fast as they can, 10 minutes max! So we need to allow that much gas out in less than 10 mins.
Solve flow rate equation, Bernoulli's Equations, for Pipe Diameter:
To evacuate the gas from the above discussion, Cu In of gas, in under 10 minutes, accurately, is a series of differential equations, calculus, and big math. To make things, easy, we'll use a linear equation instead, but lose a touch of accuracy. So far we have defined our time, and volume, we only need a rate to determine the pipe size.
We know our flow rate is 1/2 of gravity, in reverse (hydrogen is only 1/2 as light as air) = 16 ft/s2.
Differentiated equation from a water operators handbook:
For a Tank:
t = (H / (C x A)) x (h * 12 / (8 x g))^0.5
Where
t = time in seconds = 10 mins, or 600 seconds for this.
h = height of h2 in our battery box we'll say is 1
H = Cubic inches of Hydrogen
C = Orface coef. (0.7 to 0.91) I use 0.81 for a pipe penitrating the tank wall.
A = area of orface in sq in
h = height of vent pipe above outlet in ft
g = acceleration constant (2304 in/sec)
And result in the following for our H2 Evacuation Problem:
Minimum Vent Radius: or
Minimum Vent Diameter: or
Divide by 5 for inside pipe diameter:
inch Inner Vent.
Add inside pipe radius, to external pipe radius to get final pipe size for vent. Final External Pipe Diameter: inch External Vent Pipe
Calculator for educational purposes only.
Generally a 5:1 or 4:1 ratio of external pipe to internal pipe is adequate.
Remember to use a minimum difference .5 inch pipe sizes.
(small installs usually a .75 inch pipe and .1875 inch pipe vent setup).
Please check all building codes, NEC, and math prior to installation.
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Hydrogen: Hydrogen is generally lighter than air as it has a molecular weight less than that of oxygen, nitrogen, and carbon. Therefore, as long as there are no currents (winds) in the area, hydrogen will rise to the highest point in an enclosure, fairly rapidly, 1/2 as fast as water falls. Conservation of mass rules in physics also tell us that if one thing leaves, something else must take it's place. This brings us to the first couple rules for venting hydrogen. Since air has a density so little, as long as we don't create a vacuum, one vent can run at speeds a bit faster than the other. The weight of Hydrogen creates the force that allows it to rise...
