RandomTask Senior Member Joined: 30 Jan 2013 Posts: 62 Location: Saskatchewan, Canada Expertise: I love coffee
Grinder: Barratza Encore Drip: Behmor Brazen Roaster: Behmor 1600
Posted Thu Feb 27, 2014, 9:32am Subject: Re: What is the best water flow rate for water drip coffee maker?
Since no one else has attempted to answer this question, I will do my best. The more technical users on the forum may chime in with a better answer.
From everything I've read, there is no "mass flow rate" listed as optimum for coffee extraction. There is guidelines stated for contact time; how long the water is in contact with the grounds, not how quickly the water is pushed through them. Tempurature is as, if not more, imporant than contact time, as water should be between 92°C - 96°C through the enitre brewing process.
The SCAA guidelines for brewers state: "For a brewer at maximum coffee and water capacity, the minimum technical requirement is for the water contact time with the coffee grounds shall be more than 4 minutes but less than 8 minutes for all brewers operating under standard temperature and pressure at the manufacturers stated design voltage, depending on grind." with a quantity of grinds of ~55g/litre of water.
All the details of what the SCAA consideres a "certified" brewer can be found on their certified brewer program here.
Unfortunately, your optimum flow rate is going to be based off of the quanty of water held by the brewer so that it dispense all of the water within the 4 minute window.
I could not give you a direct answer for what the mass flow rate is, but I advise you could use a normal coffee maker to calculate it out. For example, you could add 1 liter water to a drip coffee maker and observe the full time it used. Of course, you need to do it more than once and try to use more than one coffee machine. Then The volume divided by the seconds, you will get the mass flow rate of water for the drip coffee maker
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