The Heat Exchanger

It’s good to start with a definition:

A heat exchanger is a device used to transfer heat between a solid object and a fluid, or between two or more fluids. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. Heat Exchangers are widely used in commercial and the industrial sector.

(Definition from Wikipedia – https://en.wikipedia.org/wiki/Heat_exchanger)

Heat Exchanger – Coffee Machine

In this article we want to explain how the Heat Exchanger type of espresso machine actually works. This type of machine is really very simple, although often people seem to believe it’s much more complicated than it is, especially the mystical “heat exchanger”. As usual on Bella Barista, we like to keep it simple:

Let’s first start with an explanation of the “Heat Exchanger (HX)”, a very fancy term for a copper tube that passes through hot water. In the picture below, we have built one, and as the cold water flows through the copper tube, immersed in a container of hot water, it gets heated up.

So the HX is really very simple and it is probably clear that the temperature of hot water exiting the heat exchanger depends on a number of things

• How hot the water in the container (boiler) is
• The surface area of the copper tube (or to put it simply, how long it is)
• The temperature of the water when it enters the copper tube
• How fast the water flows

For more information on how the Heat Exchanger works inside the espresso machine, view this article.