How do flow restrictors achieve a lower temperature?

[espressobsessed]

How do they physically achieve a lower temperature when you use a smaller size.

For example, we've opted for the 2mm restrictors on our commercial HX in lieu of the stock 3mm... temp data suggests the smaller restrictors are the ideal size for providing consistent shot temps.

thanks in advance,
jimmy

[HB]

I'm a little confused. Are you referring to a thermosyphon flow restrictor (similar in purpose to the one on the Faema E61 Legend below)? Or the gicleur valve?

[barry]

fwiw, a gicleur isn't a valve, it is an orifice.

some thermosyphon systems have a gicleur in the thermosyphon to control the rate of flow through the thermosyphon.

[espressobsessed]

I mean the thermosyphon flow restrictor...

or more specifically, the restrictors that came on my rancilio classe 8.

Although, the Nuova Simonelli Aurelia claims to achieve temp stability through the use of inline gicleurs.

So I too am confused.

[HB]

To elaborate on Barry's answer, a thermosyphon looks like this:


Hotter water (red) rises to warm group, cooler water (blue) falls and is reheated by steam boiler; repeat

The flow restrictor is introduced in the lower return pipe (blue) to "tune" the group's idle temperature by slowing the circulation. The barista's proper flushing practice prior to pulling the shot and the group's thermal inertia attenuates the HX's temperature fluctuations. It's an efficient design that can deliver good shot-to-shot temperature stability, though not with the same level of simplicity as the "look ma, no hands" dual boiler design.

[espressobsessed]

interesting...

Simple enough.

I had always envisioned the restrictor being infront of the group, not after, which wouldn't have made sense, because it would effect extraction.

It's funny though, why the Classe machines from rancilio would even come with the larger 3mm restrictors. It would seem you'd need to place steady work cycles on it to actually get things semi-stable (from the data I saw).

Although, having talked with Alex von der Lippe, it seems stainless groups are a new thing for the classe machines (none of his classe 8s are stainless, he believes).

So now I am curious the how the thermic properties of stainless will effect the shot temperatures.

Thanks Dan!!