quar wrote:What I'm really looking for is a way to use the thermo adapter to replace my current technique of flushing 2oz past the end of the water dance and then waiting 40 seconds or so, much like Dan's technique in the HX Love article.
My approach using the thermocouple / thermometer adapter is different than Eric's. His instructions say to install the probe at a depth equal to the turn towards the exit:
This gives a good approximation of the actual brew temperature and the reading is not volatile. However, I prefer the probe deeper because the reading changes more quickly, allowing me to flush more accurately. This approach works very well with the type T thermocouple / Fluke 54-II combination because they react rapidly, though it's not bad for the thermometer adapter despite its slower response time. More recently I've been using the thermometer adapter exclusively and Jon / RegulatorJohnson's "blind flush" technique, excerpted below from
Need hints on using E61 thermocouple adapter:
HB wrote:RegulatorJohnson wrote:maybe i should have called it the "simulated shot" instead of the "backflush cooling flush" ?
I tried this technique on the Vibiemme Domobar Super and it works
very well! The "blind flush" drops the temperature more slowly than an unimpeded flush, which plays to the strengths of a E61 thermometer adapter versus the thermocouple adapter. Less water in the driptray, less refilling and emptying.
As the unofficial keeper of heat exchanger nomenclature, the techniques to-date are:
- Flush and rebound - from the original HX Love article, a flush followed by a 30-45 second wait while the heat exchanger recovers.
- Flush and go - for fast recovery HX machines, this is a flush followed by the extraction within 10 seconds.
- Flush and wait - Eric's flush to well below the target temperature, then waiting for the thermosyphon to re-establish itself until the thermometer adapter reading matches the desired brew temperature.
- Blind flush - Jon's "flush until you're close, and then flush with blind basket" approach above; requires Eric's thermometer/thermocouple adapter.
I believe the particulars of Jon's approach will vary from machine-to-machine because of the tuning of the return versus direct flow from the thermosyphon during an extraction. That is, the water reaching the brewhead isn't only from one leg of the circuit:
Although this diagram depicts a one-way street, there's no shutoff solenoid blocking the return (blue) leg during an extraction, so the water reaching the group will be a mixture of the water that's passed by way of the heat exchanger (red) and some that's pass through the return (blue) leg. If I understand correctly what's happening, Jon's "blind flush" is forcing the water to rapidly circulate, thereby equalizing the system's thermal balance without expending water. Neat idea, Jon!
Jon's approach makes it much easier to nail the flush precisely because the temperature drops in "slow motion" compared to an unimpeded flush. One caveat though: It works exceptionally well on E61 HX machines like the Vibiemme Domobar Super that have over-pressure valves venting from the cold side of the HX, I assume because the turbulence drives the thermosyphon and equalizes the group temperature. The Quickmills vent the OPV from the hot side of the HX; I don't have one to test, but I assume their temperatures will drop more rapidly as a consequence.
Perhaps Quickmill owners with the thermometer adapter would benefit from a hybrid approach? That is, flush until the flash boiling stops, drop in a blind basket, continue with a "blind flush" to the target temperature. Remove the blind basket, drop in the prepared basket, wait maybe 10 seconds for good luck, pull. Anyone willing to try it?
by quar on Thu Dec 20, 2007 10:04 pm 
