water heating v time taken

water heating v time taken

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Discussion

Pvapour

Original Poster:

8,981 posts

252 months

Thursday 3rd July 2014
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consistent ambient temp & at sea level

does the temperature of water being heated by a constant force rise at a constant rate or does it accelerate as the temperature of the water rise? Ruling out evaporation so volume staying the same.

jet_noise

5,630 posts

181 months

Friday 4th July 2014
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Dear P,

searching for "water heating curve" suggests it's constant,

regards,
Jet

Russian Rocket

872 posts

235 months

Friday 4th July 2014
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is it on a conveyor belt?

tapkaJohnD

1,930 posts

203 months

Friday 4th July 2014
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Lvapour,
There is a quantity known as the "specific heat" or "specific heat capacity" of any material. It's quoted in calories per kilogram per degree C (or F, if you must). That for water is, by definition in the International System of Units (aka metric system), ONE calorie per ONE kilogram per ONE degree C. It is thus that the quantity "Calorie" is defined, and it is a constant. There would be little point in such a standard if it wobbled about all over the place at different temperatures!

You may be confused by the "Latent Heat of Melting" and the "Latent Heat of Vapourisation" (I note your user name), which show that much heat may be applied to melting or vaporising material, inc. water, that will not change its temperature while either solid or liquid remain.

John

mike_knott

339 posts

223 months

Saturday 5th July 2014
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Pvapour,

If the 'constant force' is a constant rate of energy input then the water temperature will rise at a variable rate as the specific heat capacity of water varies with temperature.

If the 'constant force' is an energy source at a constant temperature then the rate of temperature rise will fall as the differential temperature between the 'constant force' and the water will also fall.

Mike...

Pvapour

Original Poster:

8,981 posts

252 months

Monday 7th July 2014
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thanks gents, some great explanations there thumbup

Mr2Mike

20,143 posts

254 months

Monday 7th July 2014
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mike_knott said:
Pvapour,

If the 'constant force' is a constant rate of energy input then the water temperature will rise at a variable rate as the specific heat capacity of water varies with temperature
Worth noting that the effect is quite small, only ~0.8% over the range 0C to 100C. For many practical purposes it can be treated as constant.