Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 12/01/2009 21:30:04

Title: Coffee brewing problem
Post by: syhprum on 12/01/2009 21:30:04

When I prepare my morning coffee I require one liter of water at 100°C, I can obtain this in two ways I either fill the kettle from the cold tap at 10°C or I runoff three liters of water from the hot tap until it runs at 50°C and then fill the kettle from this.
Assuming the water in the hot tap has been heated from 10°C and as the cost of gas for heating the hot water is 25% per Kwh compared to the electricity which is the most economical?

Title: Coffee brewing problem
Post by: lyner on 12/01/2009 21:47:15

You drink too much coffee, anyway, syphrum.

Title: Coffee brewing problem
Post by: RD on 12/01/2009 22:27:42

If the hot tap water comes from a copper tank it will have an increased amount of copper salts in it compared to the cold tap water. The copper salts may taint the taste of your coffee.

[The cold water is delivered in copper pipes but because it is cold less copper salts will be dissolved in it than in the hot water]

Title: Coffee brewing problem
Post by: DoctorBeaver on 12/01/2009 22:39:12

Oh tut! You should never use boiling water for coffee. Use water slightly off the boil to bring out the full flavour.

Title: Coffee brewing problem
Post by: dentstudent on 13/01/2009 08:03:24

Go and buy a nice bean-to-cup machine, and all your coffee worries will be over. I did, and mine are!

Title: Coffee brewing problem
Post by: syhprum on 13/01/2009 08:20:52

I did not cook the figures but merely took typical ones but when I did the arithmetic I found the cost of either procedure to be the same.
I know of course water needs to be 95°C but not having a thermostatically controlled kettle it is easier to heat it to 100°C and then add a little cold.