There is heat exchange but it is not externally noticeable because the reaction is happening at the ambient temperature of the tank. The space vacated by the condensing vapor easily matches the volume of the incoming liquid.
The tank is normally vented while being filled. The 80% or "bleeder" valve is usually opened during the process.
Wouldn't the tank be warm when done? That energy has to go somewhere.
I think he means "in his home town/area".
Believe what you wish. But you should be happy that your bottles are filled with liquid as if they were not they would empty so quickly that use would not be practical.
It will get to around 119° F. / 48°C next week there in Pahrump. Does that mean they cannot fill any propane tanks there during the day?
I don't know, I'm not there now. When I was forced to stay there over the summer during the Covid lockdowns the little 5000 btu air conditioner in my insulated shed/man cave kept it at 70 degrees during the hottest temperatures. I just hung out in there during the heat of the day when the a/c in the RV could no longer keep up. Give me a comfy chair, small cooler, TV and computer and I'm set.
Have you seen the "vent" or "spitter", as the Fixed Liquid Level Gauge is often called, go from vapor to liquid when the tank hits the 80% level? The change in sound alone as the liquid rapidly expands is a good indicator if the sudden cloud of propane gas didn't catch your attention. The transition from liquid to gas is nearly instantaneous. The pump that pressurizes the tank to 150+ PSI, depending on the ambient temperature, obviously isn't that fast when reversing the process. The few minutes it takes to refill various size tanks or cylinders though, is more than enough to reduce the small amount of gas remaining in the vessel being refilled. And consider that 20% of the gas is not reduced to liquid, but remains in the gaseous state in the headroom above the liquid.
Here is what AccuWeather says for Pahrump. See 7-7, 2024. Of course, a week off could be inaccurate. 119°, if it happens, will be Pahrump's record high by two degrees.
That "bleeder valve" is actually the "Fixed Liquid Level Gauge", and is not used to vent the tank other than the small amount that escapes until the liquid reaches the 80% of the water capacity point where the refiller shuts off the flow. On DOT cylinders, some states/municipalities require using the Fixed Liquid Level Gauge, while others require filling by weight. In practice, it's not uncommon to see refillers just fill until the OPD valve kicks off the flow, although that's not allowed by any responsible authority. That method is also used at times when refilling the permanent ASME tanks permanently installed on RV's without opening the Fixed Liquid Level Gauge as they should. The simple Fixed Liquid Level Gauge is far more reliable than the mechanically operated OPD.
We open the Fixed Liquid Level Gauge valve when filling tanks but often the OPD valve kicks in before the FLLG shows liquid venting.
Right. We can quibble over the term "vent" but It is open during the filling process and will relieve internal tank pressure until the liquid reaches the 80% level.
Actually it won't relieve internal pressure. The tank pressure is determined by the vapor pressure at a specific temperature. Opening a vent to let some vapor out just makes more liquid propane boil off to maintain the tank's pressure. No different than what happens when you release propane vapor into the system via the regulator.
How do you fill the built in tank at home? Around here it's usually high school kids running the stations. OK to run cash registers but I'm a little leary about their mechanical skills.
The tank will fill just as well with the "vent" closed as it will with it open. The refiller just won't know it's full until the OPD trips at the 80% level. The "vent" is much too small to relieve any significant internal pressure. The point is, there is no need to relieve any internal pressure when refilling. The tank will fill just as fast with or without the Fixed Liquid Level Gauge open.
The vent(Fixed Liquid Level Gauge) begins to spew liquid when the liquid level reaches it.
Yes, that's its "full" indicator. Having it open has nothing to do with whether it will fill or not though.
Both filling methods are correct depending on the tank size and local/state regulations.
