Why is it that when you run water from the hot tap, it initially makes more
noise as it it running through the pipe/tap while the water is cold (having
cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold water
versus hot water, and that cold water has more bubbles of dissolved air?

On Wed, 15 Jun 2016 13:54:05 +0100, Chris Hogg wrote:

On Wed, 15 Jun 2016 12:51:58 +0100, "NY" wrote:

Why is it that when you run water from the hot tap, it initially makes
more noise as it it running through the pipe/tap while the water is cold
(having cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold
water versus hot water, and that cold water has more bubbles of
dissolved air?

Almost certainly it's due to the drop in viscosity of the water with
temperature. Between 15C and 60C the viscosity drops by a factor of
three, and although I'm not particularly familiar with turbulence and
Reynolds Numbers, I assume that it will be less turbulent, and less
noisy in the pipe, as a consequence. See http://tinyurl.com/gs2axet I
know from my own experience that pouring recently-boiled water from a
kettle sounds quite different to pouring cold or warm water. It sounds
softer.

Yes, it's the first indication that I've forgotten to boild the kettle in
the first place!

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
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On 15/06/2016 14:01, Chris Hogg wrote:
On 15 Jun 2016 12:55:25 GMT, Bob Eager wrote:

On Wed, 15 Jun 2016 13:54:05 +0100, Chris Hogg wrote:

On Wed, 15 Jun 2016 12:51:58 +0100, "NY" wrote:

Why is it that when you run water from the hot tap, it initially makes
more noise as it it running through the pipe/tap while the water is cold
(having cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold
water versus hot water, and that cold water has more bubbles of
dissolved air?

Almost certainly it's due to the drop in viscosity of the water with
temperature. Between 15C and 60C the viscosity drops by a factor of
three, and although I'm not particularly familiar with turbulence and
Reynolds Numbers, I assume that it will be less turbulent, and less
noisy in the pipe, as a consequence. See http://tinyurl.com/gs2axet I
know from my own experience that pouring recently-boiled water from a
kettle sounds quite different to pouring cold or warm water. It sounds
softer.

Yes, it's the first indication that I've forgotten to boild the kettle in
the first place!

LOL! You too!

....followed by a lack of colour around the tea bag!

Peter

On 15/06/2016 13:55, Bob Eager wrote:
On Wed, 15 Jun 2016 13:54:05 +0100, Chris Hogg wrote:

On Wed, 15 Jun 2016 12:51:58 +0100, "NY" wrote:

Why is it that when you run water from the hot tap, it initially makes
more noise as it it running through the pipe/tap while the water is cold
(having cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold
water versus hot water, and that cold water has more bubbles of
dissolved air?

Almost certainly it's due to the drop in viscosity of the water with
temperature. Between 15C and 60C the viscosity drops by a factor of
three, and although I'm not particularly familiar with turbulence and
Reynolds Numbers, I assume that it will be less turbulent, and less
noisy in the pipe, as a consequence. See http://tinyurl.com/gs2axet I
know from my own experience that pouring recently-boiled water from a
kettle sounds quite different to pouring cold or warm water. It sounds
softer.

Yes, it's the first indication that I've forgotten to boild the kettle in
the first place!

Glad to know its not just me that usually realises I have just made it
with cold water just by the sound alone ;-)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Bob Eager wrote:
On Wed, 15 Jun 2016 13:54:05 +0100, Chris Hogg wrote:

On Wed, 15 Jun 2016 12:51:58 +0100, "NY" wrote:

Why is it that when you run water from the hot tap, it initially makes
more noise as it it running through the pipe/tap while the water is cold
(having cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold
water versus hot water, and that cold water has more bubbles of
dissolved air?

Almost certainly it's due to the drop in viscosity of the water with
temperature. Between 15C and 60C the viscosity drops by a factor of
three, and although I'm not particularly familiar with turbulence and
Reynolds Numbers, I assume that it will be less turbulent, and less
noisy in the pipe, as a consequence. See http://tinyurl.com/gs2axet I
know from my own experience that pouring recently-boiled water from a
kettle sounds quite different to pouring cold or warm water. It sounds
softer.

Yes, it's the first indication that I've forgotten to boild the kettle in
the first place!

Your kettle must have a well insulated handle!

--
Mike Barnes
Cheshire, England

"Mike Barnes" wrote in message
...
Yes, it's the first indication that I've forgotten to boild the kettle in
the first place!

Your kettle must have a well insulated handle!

The handle of my kettle is fairly well insulated and doesn't get warm when
there's hot water in the kettle. However there's enough heat radiated off
the kettle (or enough conducted through the surrounding air) to feel whether
there's hot water in the kettle.


Talking of kettles, ours has a switch which only latches in the on position
if there's mains to the kettle. It then switches itself off when the kettle
has boiled. About a year ago the latch mechanism failed, so I've been
holding it down with a cork heat mat whenever I want to use the kettle, and
I've kept thinking "I really *must* buy a new kettle". Then lo and behold
the other morning it latched into place, for the first time in a year, and
has worked properly (even switching off when the kettle boils) ever since. I
wonder what went wrong that has since righted itself. I'd assumed that a
plastic lug had broken off inside the switch mechanism, but evidently it was
nothing so fatal and final!

On Thu, 16 Jun 2016 09:29:08 +0100, Mike Barnes wrote:

Bob Eager wrote:
On Wed, 15 Jun 2016 13:54:05 +0100, Chris Hogg wrote:

On Wed, 15 Jun 2016 12:51:58 +0100, "NY" wrote:

Why is it that when you run water from the hot tap, it initially
makes more noise as it it running through the pipe/tap while the
water is cold (having cooled down in the pipe) compared with when the
water runs hot?

Is it something to do with the amount of air that can dissolve in
cold water versus hot water, and that cold water has more bubbles of
dissolved air?

Almost certainly it's due to the drop in viscosity of the water with
temperature. Between 15C and 60C the viscosity drops by a factor of
three, and although I'm not particularly familiar with turbulence and
Reynolds Numbers, I assume that it will be less turbulent, and less
noisy in the pipe, as a consequence. See http://tinyurl.com/gs2axet I
know from my own experience that pouring recently-boiled water from a
kettle sounds quite different to pouring cold or warm water. It sounds
softer.

Yes, it's the first indication that I've forgotten to boild the kettle
in the first place!

Your kettle must have a well insulated handle!

It does. Bloody great Bosch thing.



--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

Your kettle must have a well insulated handle!

It does. Bloody great Bosch thing.



Made in China?

On Thu, 16 Jun 2016 09:08:18 +0000, DerbyBorn wrote:


Your kettle must have a well insulated handle!

It does. Bloody great Bosch thing.



Made in China?

Yes. But it gets a lot of abuse, and soldiers on.

I guess Bosch pay the Chinese a bit more to make a kettle, then the other
kettle 'manufacturers' do.



--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 16/06/2016 09:58, NY wrote:
"Mike Barnes" wrote in message
...
Yes, it's the first indication that I've forgotten to boild the
kettle in
the first place!

Your kettle must have a well insulated handle!

The handle of my kettle is fairly well insulated and doesn't get warm
when there's hot water in the kettle. However there's enough heat
radiated off the kettle (or enough conducted through the surrounding
air) to feel whether there's hot water in the kettle.


There isn't on my kettle, its insulated.
Its about the only way to make them more efficient.

On Wednesday, June 15, 2016 at 12:51:40 PM UTC+1, NY wrote:
Why is it that when you run water from the hot tap, it initially makes more
noise as it it running through the pipe/tap while the water is cold (having
cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold water
versus hot water, and that cold water has more bubbles of dissolved air?



Is it because the the viscosity (mu) of water is bigger when it is hot? That would mean the Reynolds number (v.rho.d/mu) is higher (more turbulent) when the water is cold and smaller (laminar) when it is hot.

Robert

On Thursday, 16 June 2016 15:33:39 UTC+1, RobertL wrote:
On Wednesday, June 15, 2016 at 12:51:40 PM UTC+1, NY wrote:
Why is it that when you run water from the hot tap, it initially makes more
noise as it it running through the pipe/tap while the water is cold (having
cooled down in the pipe) compared with when the water runs hot?
Is it something to do with the amount of air that can dissolve in cold water
versus hot water, and that cold water has more bubbles of dissolved air?
Is it because the the viscosity (mu) of water is bigger when it is hot? That would mean the Reynolds number (v.rho.d/mu) is higher (more turbulent) when the water is cold and smaller (laminar) when it is hot.

Or perhaps that the surface tension of hot water is much lower which will
change the behaviour of bubbles?

John

On 15/06/2016 12:51 PM, NY wrote:
Why is it that when you run water from the hot tap, it initially makes
more noise as it it running through the pipe/tap while the water is cold
(having cooled down in the pipe) compared with when the water runs hot?

Is it something to do with the amount of air that can dissolve in cold
water versus hot water, and that cold water has more bubbles of
dissolved air?


I noticed the difference in sound when making a brew and knowing the
water is cold by the sound. Obviously, density.