The propane cylinder is full of mostly liquid propane, with propane vapor in the remainder of the volume. As you use the stove, the vapor is let out to burn, which lowers the pressure of the tank. As a response, some of the liquid propane turns to vapor. In order to make this phase change, the propane absorbs heat from the surroundings (this can be measured as the latent heat of vaporization).
So the tank gets cold because the liquid propane is using heat to vaporize.
When matter changes phase from a liquid to a gas, it requires energy. That’s why we sweat – when the sweat evaporates, it pulls energy from our bodies, cooling us off. Here, the propane in your tank is stored in a liquid form. As you use the propane, it changes from liquid to gas, little by little (with the gas coming out of the heating element, allowing you to cook your chili). As it changes from liquid to gas, it takes energy from the tank vessel, which becomes cold. That then causes water vapor from the air to condense onto the cold surface, where it then freezes. —> frosty tank
Gases all obey a universal law that relates pressure, volume, mass, and temperature. You can take any amount of gas & put it in any size contain, while having it at any temperature or pressure. You can then change any of those values, but in doing so will change the others. Increase the temperature, but keep the amount & container the same size and the pressure goes up. This is why you don’t put pressurized containers, like spray cans, into a fire.
In your case the pressure is slowing going down, but not as fast as the amount of gas is leaving. The volume is also fixed. That means the only other thing that can change is the temperature.
Of course, there’s also the propane changing from a liquid to a gas. Gas is more energetic than a liquid, so converting a liquid to a gas takes energy.
Hey there,
When you use a propane stove, the liquid propane in the tank turns into a gas. This process takes energy, which comes from the heat of the surrounding air. If the air is cold enough, the heat transfer can cause the tank to get so cold that water vapor in the air condenses on the tank and freezes, forming frost.
This is especially common in cold weather when the temperature difference between the propane tank and the surrounding air is large. To prevent frost from forming, you can try to keep the propane tank warm, either by placing it in a warmer location or by wrapping it in a blanket or towel.
Propane is a gas at room temperature. It is compressed into a liquid when it’s put into cylinders. Pressurizing a gas, crushing it into a smaller space, causes it to heat up. The cylinders then return to ambient temperature slowly over time.
When you use the cylinder, it is releasing gas. Lowering the pressure of the gas lowers its temperature for exactly the same reason as above (raise the pressure, raise the temperature; lower the pressure, lower the temperature). The stove generates heat by letting the gas expand out from the cylinder and then burning it. The cylinder becomes cold as it vents gas. You’re venting gas fast enough to cause frost to form.
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