Variable Pressure Infusion Modification Results: a Paper - Page 3

Beginner and pro baristas share tips and tricks.
HBchris
Posts: 198
Joined: November 20th, 2015

Postby HBchris » Sep 13, 2016, 5:10 pm

For anyone that knows or can check, what is the flow rate (grams / sec) of various machines such as: vesuvius, Strada, Hydra MVP.
when at 1 bar? 2 bar? 3 bar?

As I know pressure and flow are directly related. Lower pressure would result in lower flow.

Just curious to see how that compares to Slayer, which has a pre-brew flow rate (usually set between 1 - 2g per second).

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shawndo
Posts: 862
Joined: January 10th, 2010

Postby shawndo replying to HBchris » Sep 13, 2016, 6:00 pm

I was thinking about this recently and how that may/may necessarily not vary per machine based on the headspace group design.

I was told that the Slayer is factory set at 40 grams per 30 seconds. When pulling a shot, that might result in something like 4 bars after 20 seconds in a slayer. For consistency, say you are using a dose that has an idea "nickel test" result.

If I set my needle valve also to 40g/30seconds, I might not be able to fill up the headspace in the same amount of time so I might not be able to reach 4 bars after 20 seconds with the same dose volume.

So to be consistent between machines, which measurement should be targeted? Flow rate or pressure ramp rate?
Hopefully that ramble made sense....
Darmok and Jalad at Tanagra

Mrboots2u
Posts: 474
Joined: December 25th, 2013

Postby Mrboots2u » Sep 14, 2016, 6:59 am

HBchris wrote:For anyone that knows or can check, what is the flow rate (grams / sec) of various machines such as: vesuvius, Strada, Hydra MVP.
when at 1 bar? 2 bar? 3 bar?

As I know pressure and flow are directly related. Lower pressure would result in lower flow.

Just curious to see how that compares to Slayer, which has a pre-brew flow rate (usually set between 1 - 2g per second).

For the Vesuvius will depending on the pump accelation set and the jet
I have a smaller jet in mine and pump speed at 340 its 90 g in 30 seconds fir 2 bar ( lowest it will go )
if i set the pump speed lower say to 100 then i can get 83g for 2 bar

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CorvusDoug
Posts: 72
Joined: August 31st, 2016

Postby CorvusDoug » Sep 16, 2016, 4:47 pm

HBchris wrote:For anyone that knows or can check, what is the flow rate (grams / sec) of various machines such as: vesuvius, Strada, Hydra MVP.
when at 1 bar? 2 bar? 3 bar?

As I know pressure and flow are directly related. Lower pressure would result in lower flow.

Just curious to see how that compares to Slayer, which has a pre-brew flow rate (usually set between 1 - 2g per second).


Our Hydra MVP has the following water debit rates with an empty bottomless portafilter inserted (18g VST basket):
Stage I (pre infuse): 3mL/sec
Stage II (ramping): 3.5mL/sec
Stage III (full pressure): 3.8mL/sec

The main factor affecting flow rate of espresso between these 3 stages is the dispensing pump pressure. For our machine:
Stage I: line pressure (around 3.5 bars I think)
Stage II: 7.5 bars
Stage III: 9 bars
Corvus Coffee Roasters - Denver, CO www.corvuscoffee.com

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radudanutco
Posts: 141
Joined: October 18th, 2012

Postby radudanutco » Sep 17, 2016, 7:59 am

HBchris wrote:For anyone that knows or can check, what is the flow rate (grams / sec) of various machines such as: vesuvius, Strada, Hydra MVP. when at 1 bar? 2 bar? 3 bar?
As I know pressure and flow are directly related. Lower pressure would result in lower flow.
Just curious to see how that compares to Slayer, which has a pre-brew flow rate (usually set between 1 - 2g per second).


I've never seen for these machines, a chart with pressure and flow rate profiles above the puck, where it counts eventually...

I imagine the flow rate as being dependent of the hydraulic resistance between the rotary pump output (constant pressure) and the atmospheric 0 bar pressure (gauge) as reference; among the flow restrictors on the circuit, the main one is the puck itself;
the puck resistance is the highest in the circuit and soon after wetting, it closes the chamber space (headspace, or the cylinder chamber) so the flow rate is the maximum above the puck - 0 bar phase; after a time interval, depending of the flow rate upstream, the volume is filled enough to have a pressure ramp until the (variable) puck resistance comes into play, as the puck becomes saturated;
from now on comes the brewing flow, and the flow rate depends on the puck resistance and the distribution of pressure fall among the restrictors on the water circuit;

please correct me, as this is my limited and simplified image of the process, considering my experiments with my modified Strega (dimmer, group heater PID-ed, PI pressure gauge); no experience with high end professional machines;

and btw, with hybrid, vibe pump machines, like Strega, pressure and flow rate are inversely related...
so, i.e. after a 5s zero bar stage - puck soaking, of filling the cylinder chamber with the maximum pump flow rate of more than 10 ml/sec, follows a pressure ramp in which the flow rate from the pump is decreasing to less than 3 ml/sec as the OPV is opening, and the process enters next stage of spring pressure extraction; this variable flow rate stage could be beneficial for a smooth flow start through the puck; or at least for an added forgiveness...
full kind of variations follows: for ex., stop the pump when maximum pressure reached, and wait for a slower decrease in pressure until 4 bar (the saturated puck is permeable), then lift the lever on springs, but retaining the lever to maintain approx. the same flow rate; that would mean a slow PI, then a ramp to max pressure (kind of a spike), then decrease and approx. a steady low;

 
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