Or other machines with steam or piston pressure have only one boiler: the bottom of the boiler is hot water for brewing coffee, and the top provides steam. However, in order to make steam, the whole boiler must be heated to boiling, so that hot water close to boiling point can burn coffee powder, lose the aromatic oil hidden in coffee powder, and extract doubly bitter coffee.
Because the water for making coffee is heated in a large boiler, it will not be fresh if it is left in the boiler for too long, and the temperature difference of hot water will increase because of the use of steam, because the difference of steam quantity also increases the temperature difference of hot water for making coffee.
In order to improve the temperature difference, Ernesto valente built the world's first FAEMA in 1960, with the pump as the pressure source.
In E6 1, the heating method of the water for brewing coffee is changed so that the water for brewing coffee does not directly contact the heat source, but a method similar to waterproof heating is used.
Fermat
The middle of E6 1 boiler (hereinafter referred to as the outer boiler) is a pipeline (hereinafter referred to as the inner pipe), and fresh cold water is introduced into the inner curved pipeline by a pump.
When the pump pushes fresh cold water through this pipe, the cold water will be heated by the hot water of the external boiler, but it is surrounded by the pipe, so the fresh water will not touch the hot water of the external boiler. The reason why the internal water pipe is bent is to let the cold water have enough time to contact the external boiler and become the hot water temperature just suitable for brewing coffee.
Because there is hot water circulating in the boiler, the temperature of each cup of coffee is very close, whether it is one cup per hour or one hundred cups at once.
This can not only reduce the temperature difference, but also give consideration to the freshness of water, and the hot water of the external boiler is only used to generate steam for making milk bubbles, not for brewing coffee.
This is the principle of single boiler heat exchanger. Today, more than 30 years later, the internal structure and principle of most Italian coffee machines are still very close to FAEMA E6 1.
It can be inferred from the above explanation that the greater the capacity of the external boiler, the lower the temperature difference of hot water for brewing coffee, and the more it can reduce the temperature difference caused by using steam.