Analysis of natural vaporization in LPG tanks

At standard atmospheric pressure and temperature, the main components of liquefied petroleum gas (LPG)—propane and butane—exist in gaseous form. Moderate pressurization converts LPG into liquid form, which is suitable for storage in cylinders and tanks. When gas is required for consumption, the valve at the top of the tank opens, pressure drops, and the liquid LPG vaporizes. This natural vaporization process relies on ambient heat from the surroundings, which is transferred through the walls of the LPG tank. The natural vaporization rate depends on several factors, such as the ambient temperature, the surface area of the tank in contact with the liquid (i.e., the filling percentage), the exact composition of LPG, and the design and positioning of the LPG tank. When natural vaporization rates cannot meet the gas demand, as in the case of colder climates and large commercial applications, an additional LPG vaporizer is necessary. The literature's data on natural vaporization in LPG tanks are incomplete and ambiguous, often limited to the most prevalent conditions. This leaves engineers and designers in doubt on whether an LPG vaporizer is actually required. Therefore, the aim of this study is to provide an exact calculation procedure for the natural vaporization in LPG tanks that is capable of taking into consideration different ambient conditions, propane–butane mixtures, LPG tank designs, and the system's working conditions. Aboveground and underground installations, as well as horizontally and vertically positioned LPG tanks, are also accounted for in the present study. The analysis reveals that LPG vaporizers are necessary in situations of high demand, low-temperature environments, limited tank size, and when using butane-heavy LPG mixtures.