On Thu, Feb 17, 2011 at 8:45 AM, Jed Rothwell <jedrothw...@gmail.com> wrote:
> Joshua Cude <joshua.c...@gmail.com> wrote: > > >> With 1 kW, you can raise the temperature of the water at 300 mL/min about >> 50C to give 65C or so, definitely too hot to touch. >> > > That is true, but the power was not 1 kW. It was 400 W. It was 1 kW at the > beginning of the experiment, but a flow calorimeter or hot water heater > cools down rapidly at these flow rates, so a few minutes after the power > falls to 400 W, the water would be lukewarm. > > In Japan, most kitchen and bathroom sink water heaters are the instant, > on-demand type that heat up the water as it flows through. Essentially, they > are flow calorimeters. A recalcitrant old gas fired one that I use often > goes off and stays off as the water is flowing. The water cools down > instantly. (Come to think of it, that's kind of dangerous. We should > probably get it replaced.) > > - Jed > > I meant to add that these flow through water heaters are designed to have low thermal mass (so they heat up quickly), and the flow rate of a tap is much higher than in Rossi's experiment.
