Brew Temperature HX prototype

[hbuchtel]

This is a continuation of the Conti marries Achille thread over in the lever machines forum. As this prototype is powered by a vibe pump (rather then a lever as originally planned) I thought it would be more appropriate to continue it over here.

Basically it is a heat exchanger machine with the boiler (kettle) at brew temperature rather then steam temp. The ~2.5 liter kettle is only there to provide heat for the long HX tube coiled inside it.

Here are the original drawings and a few pictures of the functioning machine-






The pump and manual pressure valve are off to the left, and the PID and electromagnetic relay are off to the right.


A few technical details:

Group from Gaggia Espresso
2.5 liter galvanized steel kettle
1000W heating element
5 meters of ID6mm nylon tubing (rated at 120C, 3.0Mpa)
no-name vibe pump

This afternoon I got my grind and dose right and had the most extrordinary ristretto I've ever had... no exaggeration... the first sip was like a sunrise, gone in a moment then a slow wash of... no words for that flavor! The aftertaste wasn't pleasant, perhaps the temp was a bit low or there was a bad bean...

Here is a video of the shot. You can see the pressure up in the left hand corner, I held it at about 9bar. It was 15.5g of a mix of Colombian, mokha, and mandheling (the last of my greens!) pulled at 100C (un-calibrated) in a CMA double basket. (Warning- the vibe pump makes a racket... turn your volume down!)


And the shot. Probably not much crema by the standards of the folks here, but it looks good to my lever-trained eye!


Enjoy!

Henry

[old442]

I don't understand the thermosyphon line in the drawing. There is no thermosyphon loop as shown.

[espressme]

Congratulations Henry!
You have gone a lot further than most in scratching the itch for a better method of brewing.
Once the test bed works consistently, I await the package!
Cheers
Richard

[hbuchtel]

I don't understand the thermosyphon line in the drawing. There is no thermosyphon loop as shown.

Hello Kurt, the thermosyphon line is there, though hard to see... in the last photo the white tube is visible coming from behind the group and attaching low on the front side of the kettle (rather then at the bottom as in the drawing).

The thermosyphon works because the Gaggia groups have a hole (originally the water inlet) coming from the back of the group through to the inside of the group (see pic below). I drilled a small hole (see the first photo in the original post) in the kettle at the opposite corner from this hole so the water would wash over the surface of the group. I really don't know how much this helps, but it should help to keep the group closer to the temp of the water in the kettle.



Hello Richard! Any plans to make one of these yourself? I'm sure you could do a much better job then me! (ps thanks again for 'donating' that PF to the project!)

Henry

[espressme]

Hi henry,
I hope your health is better!
At the moment I am a couple weeks behind on custom work and have too many projects to try it. Your solution works and others will benefit when they try it. Maybe my pet project will use some of your Idea!
thanks from all of us!
sincerely
Richard

[hbuchtel]

Hi Richard, my health is very good, thanks, which I think has more to do with being on vacation then anything else

I'd love to hear from anybody about directions to go with this project from here... on the list is an OPV, a 3-way group, a SS kettle, and getting the equipment together to do some of the temp testing that people have done on other temp-stable machines (like Jeff did on the PID'd Alexia).

About the 'package,' I'm thinking marble sides to replace the wood, then a single sheet of SS wrapping around from the group to the back of the machine. I still don't know where to put the temp management equipment, or whether to keep the pump and reservoir separate from the rest of the machine. . .

. . . but for now she is sitting there making great espresso!

Henry

[barry]

other than bodging convenience, is there any reason you've used plastic tubing instead of a more thermally conductive metal tubing?

[hbuchtel]

other than bodging convenience, is there any reason you've used plastic tubing instead of a more thermally conductive metal tubing?

Good call. I'd never looked up the numbers before, turns out nylon is way lower then any kind of common metal (.25 vs 46 for steel and 401 for copper). I made the choice basically for convenience, but copper tubing (ID?) would be a good choice for the next one. I can't think of any reason why I would want a lower conductivity...

I don't think it is an issue with this model, because it takes 15+ minutes to warm up the 2.5 liters of water and without a 3 way valve I have to wait a long time between shots anyway. However, I'd like to be able to use a smaller kettle and make shots faster, so copper tubing would be a better choice.

Any thoughts on TC placement? Right now it is in a steel sheath coming in from the top, about 5cm away from the element and off to one side (ie not directly above the element). If I recall correctly, the displayed temperature has not fallen during a shot...

Henry

[timo888]

... it takes 15+ minutes to warm up the 2.5 liters of water ... I'd like to be able to use a smaller kettle and make shots faster, so copper tubing would be a better choice.

Any thoughts on TC placement? Right now it is in a steel sheath coming in from the top, about 5cm away from the element and off to one side (ie not directly above the element). If I recall correctly, the displayed temperature has not fallen during a shot...

Bravo, Henry.

With the current 2.5L kettle, how much time is required to raise or lower brew temp 2 degrees?

Can you divide the kettle into cubic regions and sample the temperature for each, to get a sense of how much temperature variation there might be within the kettle? Shooting from the hip, I'd place the TC closest to where the brew water enters the group.

Regards
Timo

[hbuchtel]

Bravo, Henry.

With the current 2.5L kettle, how much time is required to raise or lower brew temp 2 degrees?

Can you divide the kettle into cubic regions and sample the temperature for each, to get a sense of how much temperature variation there might be within the kettle? Shooting from the hip, I'd place the TC closest to where the brew water enters the group.

Regards
Timo

Hi Timo! I think what I could do is put a couple of the TC sheaths at various points in the kettle, then drop the TC in one at a time. I'm not really sure what I should be looking for, but it would be good to just collect some more information.

Unfortunately I'll be traveling for the next 2 weeks, so I'll have to leave it as it is for now. French press for 2 weeks!

Henry

EDIT Sorry, forgot to answer your question about changing the temp. I just tried it, and it took a bizarre 8 minutes to get from 100 to 102C. I think this has less to do with the amount of water and more to do with my PID, which I assume was programmed to control industrial equipment... which might explain why it was being so cautious.

[arriflex]

Never underestimate the insulative characteristics of plastics and teflon! As I mentioned in the parent thread, the thermal coefficients of a highly conductive plastic versus a low conductivity metal are nearly 100:1. What I'm trying to say is that your long time for a temperature change is not solely dependent on the PID tuning. Another way around a low coefficient is to increase the velocity of the fluid inside and or outside your tubing.

Anyway, it is very exciting to see this picking up steam. har har. I just happened to be dreaming about modifying my Pavoni, now having spent half a year with it and really getting the hang of it (and its limitations). But then, why screw up a production machine when I've got a machine shop to start from scratch!

I can't wait to see this continue to get refined, and keep dreaming about doing something too. I will caution against the use of marble, however... Natural stone is not particularly tolerant of temperature differentials of this magnitude, especially when placed under stress.

Now off to find an old group...

arri

[timo888]

Another way around a low coefficient is to increase the velocity of the fluid inside and or outside your tubing.

Something to cause the heating water to circulate? Like a combination lava-lamp/espresso machine?

Regards
Timo

[arriflex]

Touché

[hbuchtel]

I will caution against the use of marble, however... Natural stone is not particularly tolerant of temperature differentials of this magnitude, especially when placed under stress.

Thanks for the heads-up! I was thinking of marble mostly 'cause it is cheap and easy to find around here... I'll have to look for other options.

I was just thinking that there might actually be an advantage to using the less-thermally-conductive nylon tubing, which is that the water in the tube will be protected from eddies of hotter and cooler water within the kettle... when the element comes on, for instance. Of course, simply keeping the element off during the shot would take care of most of this problem...

This is assuming that the main goal is be able to pull a single shot with a constant intrashot temperature, rather then pull shots quickly.

I'm about to put the machine together again (better this time )... Then it is time to work on my barista skills, which, if they could be expressed as a number, would be a lot less consistant then this machine I've made...

Henry

[hbuchtel]

Phew! I think anybody who has restored or re-built an espresso machine can sympathize when I say that I spent the entire afternoon and evening chasing down leaks... but I'm done! Thank goodness for whoever invented plumber's teflon tape!

I managed to fit all the electronics and plumbing inside the case and added an OPV, so things are looking and working better. Photos tomorrow!

Henry

[hbuchtel]

Excellent shots this afternoon. Especially surprising 'cause they were from a lightly roasted Yunnan arabica that my Caravel was unable to make anything drinkable from!

Here are the photographs-


the plumbing-
vibe pump lower left ->
adjustable OPV middle right ->
valve + pressure gauge upper left ->
fitting to HX.


the electronics-
PID and electromagnetic relay front center
shot timer (+unused PID) taken from Precisia lower right


My barista skills fell apart for this shot- it started blonding v. early


'Dats all folks! Classes start monday so this is probably how it'll look for a while. To sum up, it was cheap, took little skill to make, and makes great espresso! Make one yerself!

Henry

[Designer]

What an amazing project! Henry.

-Keven

[caeffe]

Now that's what I call Home-Brew!

Congratulations and thanks for sharing. One of these days, I'll have to try something like this ....

[arriflex]

Oh so nice to see someone getting physical! I'd love to find some time to start bending tubing and such.

Details? What about it do you like, dislike, will you do differently ('cause we know you'll be at it again!) and such?

Does anybody have recommendations for finding or even deciding on a group/portafilter combo? I've been perfectly content with my itty-bitty Pavoni, but would like to go just a bit bigger for the home-built.

BTW, in looking at ideas for the pump, I wonder how a pneumatic cylinder might fare with appropriate plastics inside, they're sure cheap enough to try...
(Caution, link is to a 14mb pdf) http://www.bimba.com/pdf/catalogs/FL_OriginalLine.pdf

Tanx for the PIX!

arri

[hbuchtel]

Details? What about it do you like, dislike, will you do differently ('cause we know you'll be at it again!) and such?

Hello Arri, sorry for the late reply!

I'm basically very happy with the machine as it is now. I hope the future will bring a 3-way valve, copper HX tube, stainless steel kettle, and a lever or rotary pump, but I'm finding that as it is it totally satisfies my daily espresso needs. In the future I'd like to have two versions, a portable 'laptop' with everything together in one package, and a 'desktop' with outboard lever/pump etc. Maybe the latter could be hung on the wall...

What I love the most is being able to split 22g in the synesso triple (thanks again Richard!) to make capps for me and my wife! Having the OPV and shot timer is a big help, as I can steam while the shot is running.

Not having a 3-way valve is an irritant, mostly because I have to wait a long time before I can clean up (>2 minutes for most shots). It also limits my hosting ability I recently decided not to ask a couple friends over just because there would be four of us altogether and I didn't want to serve drinks in two rounds.

I'm looking for another brand of group that would fit my needs. Basically all single boiler groups would work, but I've got my sights set on one of the 'magical' groups... Elektra semiautomatica for example... (by the way, if anybody living in Canada wants to buy an appropriate group w/ 3-way send me a pm).

Sadly, the weakest part of the equation is still me... I had my technique pretty well worked out for my Caravel but still have a way to go on this machine! It is getting better though.

Funny, what I'm having the most trouble with is getting my pre-conceptions (ie flat-line=better or 92C=92C) out of the way and just tasting what is in the cup! I find keeping my eyes tightly shut helps a bit

Henry

FYI-> brewing at 80C/170F? OK!