An LPG cylinder works by storing Liquefied Petroleum Gas (LPG) under pressure, which is then released as a gas for use in appliances.
Inside an LPG cylinder, the gas exists in both liquid and gas forms. The liquid LPG settles at the bottom, while the gaseous LPG is at the top. When you connect a device, like a stove, and turn it on, you open a valve at the top of the cylinder. This allows the gaseous LPG at the top to escape through the connected regulator and supply the appliance.
Here's the core process based on how the cylinder replenishes the used gas:
- Gas Usage: As the gaseous LPG is used up by the appliance, the pressure within the cylinder starts to drop slightly.
- Liquid Evaporation: To maintain the pressure and continue supplying gas, the liquid LPG at the bottom of the cylinder begins to evaporate (turn into gas).
- Thermal Energy Source: This evaporation process requires energy, specifically thermal energy. The liquid LPG draws this energy from its surroundings – primarily the metal walls of the cylinder and the ambient air outside.
- Replenishment: Cylinder Gas is present in both liquid and gas forms. When the device connected to the bottled gas starts to be used, the gaseous LPG at the top is depleted. The liquid LPG at the bottom evaporates to replace the depleted gas using the thermal energy it draws from its surroundings. This continuous evaporation ensures there's a steady supply of gaseous LPG at the top until most of the liquid is gone.
This constant conversion from liquid to gas is why an LPG cylinder might feel cold to the touch when it's being used, especially at a high rate, as it's drawing heat from its environment.
Think of it like a boiling pot: the liquid water turns into steam (gas) when heated. In an LPG cylinder, the "heating" comes from the surrounding environment's temperature.
Key Points:
- LPG is stored under pressure, allowing it to exist as a liquid at relatively low temperatures.
- Only the gaseous phase is used by appliances.
- Liquid LPG evaporates to replace the gas that is used, a process requiring thermal energy.
- This evaporation continues until the liquid level is very low.
This simple yet effective mechanism allows a large amount of energy (stored as liquid) to be conveniently transported and used as a gas fuel.
