Vaporization Propane without LPG vaporizer
Vaporization Propane without LPG vaporizer
(OP)
Good Morning.
I'd like to know how I can estimate the rate of vaporization without a vaporizer or without applying the heat directly to the tank.
This is the case:
I have a propane tank that storage saturated propane. When the regulator let de vapour above the liquid to go out, the system lost the equilibrium and part of the liquid have to vaporize to reach the equilibrium again. The liquid takes the energy from itself and so, the temperature inside the tank drops.
my question:
how i can size the tank to let the system vaporize as many liquid as vapour is going out (without any external device)?
I'd like to know how I can estimate the rate of vaporization without a vaporizer or without applying the heat directly to the tank.
This is the case:
I have a propane tank that storage saturated propane. When the regulator let de vapour above the liquid to go out, the system lost the equilibrium and part of the liquid have to vaporize to reach the equilibrium again. The liquid takes the energy from itself and so, the temperature inside the tank drops.
my question:
how i can size the tank to let the system vaporize as many liquid as vapour is going out (without any external device)?





RE: Vaporization Propane without LPG vaporizer
You have several variables to consider:
1. As you use propane the amount of liquid decreases. Your heat transfer I suspect is primarily through the wetted area of the tank so as the tank level decreases your heat transfer may becomed limited. You may need to have external finned piping to ensure your heat transfer area.
2. The 'minimum' hot side temperature you want to design for
3. The minimum pressure and thus temperature you can accept the propane vapor at.
Natural convection is going to transfer heat from the ambient air to the heating surface.
The same concept is used for vaporizing liquid N2 for plants where no external heating medium or energy is used, ambient air is used with finned pipes to vaporize the liquid nitrogen.
RE: Vaporization Propane without LPG vaporizer
I had read that the area of the tank must be large enough to vaporize. I thought that area was the interface area (the area between the liquid and its vapor)and that is why i thought the energy was taken from the liquid itself and later compensated from the ambient (it is the same process but different order). In this case, the rate of vaporization depends only of the velocity to achieve the equilibrium (the amount of vapor leaving the tank) and the convection heat transfer will set the temperature inside the tank.
What do you think about it?
----
My consumption isn't continuous, so the vaporization is just for a few minutes (five or six). That is why I don't want use any kinf of external advice for the vaporization, but I am going to evaluate the use of fins .
RE: Vaporization Propane without LPG vaporizer
Let's say you had an equilibrium vapor/liquid at some pressure and temperature. You suddenly draw out vapor and drop the vapor space pressure to half of its original pressure. The liquid is still at its original temperature and its vapor pressure is now greater than the pressure in the vapor space. Some of the liquid vaporizes using its own internal enthalphy causing the liquid's temperature to drop. Enough liquid vaporizes until the liquid's vapor pressure and the pressure in the vapor space are the same.
RE: Vaporization Propane without LPG vaporizer
RE: Vaporization Propane without LPG vaporizer
RE: Vaporization Propane without LPG vaporizer
RE: Vaporization Propane without LPG vaporizer
He wants to ensure a sufficient supply of propane vapor.
RE: Vaporization Propane without LPG vaporizer
In short, I think there could be a lot of tanks with enough volume for my normal consumption, but only a few of them will be have the required geometry for this operation.
RE: Vaporization Propane without LPG vaporizer
Although lot of useful and guiding accurate info is given to you by our learned/experienced professional Colleagues.
I feel to alert you for a somewhat serious(potential)hazard of negative pressure inside(vacuum as indicated indirectly by Compositepro in the 27th June 14:42 Hrs post)
This may endanger the containment's mechanical integrity if proposed storage containments(vessels,Bullets or spheres) are not designed for vacuum!
Hope this helps with way forward on process design safety.
Best Regards
Qalander(Chem)
RE: Vaporization Propane without LPG vaporizer
Thank you for the alert. I am going to take into account the vacuum inside the tank.
Best Regards,
L.
RE: Vaporization Propane without LPG vaporizer
RE: Vaporization Propane without LPG vaporizer
With little or no big fresh liquid inflow in comparison to the eat-up rate(s)(leaving aside any heat energy inputs).
In-effect this may create low pressure,low temperature conditions with a possibility of some partial vacuum;that needs to be taken care-off.
Best Regards
Qalander(Chem)
RE: Vaporization Propane without LPG vaporizer
Another question related:
In the tank I have propane liquid & vapor in equilibrium. Then, when the propane begin to flow, due to pressure difference, some liquid vaporizes to reach the equilibrium again. If the amount of heat from the atmosphere isn't sufficient, the temperature and the pressure in the tank drops until the heat transferred from atmosphere can maintain certain temperature or until the pressure reach the atmospheric pressure.
Assume that the temperature and the pressure drops only a little and the propane flow stops. In that point the propane will take heat from the atmosphere, due to temperature difference,and the temperature will increase. However, as you have a fixed volume, the pressure in the tank will also increase.
My question is: it would reach the original pressure?
(If I had a pressure indicator in the tank I would see the original pressure again?)
I think that it is possible if the amount of liquid is sufficient, but it "sounds" strange, and I can not "play" with a real propane tank in order to verify this :).
Regards,
Lij
RE: Vaporization Propane without LPG vaporizer
If you stop vapor flow, then tank will rise to ambient temperature and the pressure will rise to the vapor pressure at that temperature. This will be your "original" pressure if you are at you original temperature.
RE: Vaporization Propane without LPG vaporizer
I used to have to deal with a similar problem when putting Freon in a large bus. The liquid would become so cold after a while that there wasn't enough pressure to drive any more gas into the system to continue charging it, so I would put the jug right in the exhaust flow path and it would heat the tank enough to keep the pressure up. Fortunately the charging point was right ajacent to the engine exhaust. Without doing that, I would have had to wait for the cycle that Compositepro describes above to bring the pressure back up enough to continue.
rmw
RE: Vaporization Propane without LPG vaporizer
At a loading dock in north Texas in the winter, we could not load the trucks from a single 30,000 gallon tank during the winter without adding steam heat to the tank. With 3 bullets opened to the loading dock loading at 350 gpm, the tanks would get enough solar and atmospheric heat transfer to not cavitate the pumps. 2 30,000 gallon tanks were on the border line.
RE: Vaporization Propane without LPG vaporizer
This has been a great help for me.
Regards,
Lij