Charge Factor

A container must have space for vapor as well as liquid. As the temperature rises, the liquid expands. The space filled with vapor decreases. At a certain point, there will only be liquid in the container. Beyond this, even a slight increase in temperature causes high pressure to build up in the container as the liquid tries to continue expanding even though there is not enough space for it. The forces that result are strong enough to rupture the container. To prevent a container from being overfilled, the regulations regarding compresses gasses specify how many kilograms of refrigerant that may be added to a container per liter of interior volume. The product of multiplying this charge factor by the internal volume of the container is the permissible capacity. The figure for refrigerant used in vehicles is 1.15 kg/liter.