Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.

On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection. Heat transfer into and
out of is probably easier (less lossy) as well.

--
Cheers
Dave.

"Dave Liquorice" wrote in message
ll.co.uk...
On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection.

But isn't what is used with the commercial heat stores
used in houses etc.

Heat transfer into and
out of is probably easier (less lossy) as well.

Its harder than using air with a fan which is what
is normally used with the commercial ones. And
the problem with leaks is eliminated too.

On Tuesday, 7 July 2015 20:09:46 UTC+1, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

They're cooked at somewhere around 1000C. In operation not that hot usually The limit is going to be insulation temp limit & loss.


NT

On Tue, 07 Jul 2015 20:35:59 +0100 (BST), "Dave Liquorice"
wrote:

On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection. Heat transfer into and
out of is probably easier (less lossy) as well.

Yup, but volume is a prob. 1000L of water wll store about 5kWh at my
required temps. Bloody big tank! Hoping maybe bricks will make the
whole package smaller*.

*Yes.. and then a safe way to extract the heat... ideas?*

"Simon Cee" wrote in message
...
On Tue, 07 Jul 2015 20:35:59 +0100 (BST), "Dave Liquorice"
wrote:

On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection. Heat transfer into and
out of is probably easier (less lossy) as well.

Yup, but volume is a prob. 1000L of water wll store about 5kWh at my
required temps. Bloody big tank! Hoping maybe bricks will make the
whole package smaller*.

Yes, that and the lack of a leak problem is why the commercial
ones don't use water, they use metal bricks in my case.

*Yes.. and then a safe way to extract the heat... ideas?*

The usual thing is air moved with a cylindrical fan.

On Tuesday, 7 July 2015 21:50:10 UTC+1, Simon Cee wrote:
On Tue, 07 Jul 2015 20:35:59 +0100 (BST), "Dave Liquorice"
wrote:

On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection. Heat transfer into and
out of is probably easier (less lossy) as well.

Yup, but volume is a prob. 1000L of water wll store about 5kWh at my
required temps. Bloody big tank! Hoping maybe bricks will make the
whole package smaller*.

*Yes.. and then a safe way to extract the heat... ideas?*

water, oil, fan

I assume you're already storing what you can in the already present large masses eg floor slab


NT

On Tue, 07 Jul 2015 21:50:02 +0100, Simon Cee wrote:

Water at 4.187 kJ/l/K is hard to beat and being a fluid
distributes
the the heat through it's body by convection. Heat transfer into
and
out of is probably easier (less lossy) as well.

Yup, but volume is a prob. 1000L of water wll store about 5kWh at my
required temps.

What are your "required temps" 5kWh doesn't sound like a particulary
large big delta T for 1000l of water.

Wanders off to pre-existing water heating spread sheet:

1000 l, 5 K delta T, = 4187 * 1000 * 5 = 20,935,000 J = 5.65 kWhr

Only 5 K? Water based store would normally work over about 50 K (40
to 90 C) thus 1000 l stores nearer 60 kWhr.

Bloody big tank!

Only a 1 m cube, or 2m high 80 cm dia, will weigh a tonne (literally)
but rocks are denser... Dismantled a night storage heater a while
back the blocks are surprisingly heavy for their size

Hoping maybe bricks will make the whole package smaller*.

You need to know their thermal capacity, and your operating delta T.
The dismantled heater would have stored a maximum of 21 kWhr (ie 3 kW
for 7 hours on E7) in a box overall 30 x 24 x 9" but with inadequate
insulation as it would be fooking hot in the morning with room also
well warm. So it should have been shut down and only leaking a small
amount of heat.

*Yes.. and then a safe way to extract the heat... ideas?*

With hot (2 to 300 C maybe) rocks convecting or forced air is about
all I can think of.

--
Cheers
Dave.

On 07/07/2015 20:09, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.

Their working temperature was never hot enough and their heat capacity
woefully inadequate at least for houses when electric storage heaters
were common. Phase change eutectic salt mixtures are the least bad
option if you want to get optimum performance of heat capacity per unit
mass. The snag is that they tend to degrade or separate with time.

--
Regards,
Martin Brown

On Tuesday, 7 July 2015 22:58:05 UTC+1, Dave Liquorice wrote:
On Tue, 07 Jul 2015 21:50:02 +0100, Simon Cee wrote:

Hoping maybe bricks will make the whole package smaller*.

You need to know their thermal capacity, and your operating delta T.
The dismantled heater would have stored a maximum of 21 kWhr (ie 3 kW
for 7 hours on E7) in a box overall 30 x 24 x 9" but with inadequate
insulation as it would be fooking hot in the morning with room also
well warm. So it should have been shut down and only leaking a small
amount of heat.

*Yes.. and then a safe way to extract the heat... ideas?*

With hot (2 to 300 C maybe) rocks convecting or forced air is about
all I can think of.

You can alays heat water if you limit the rate of heat flow to said water.


NT

On 07/07/15 21:44, wrote:
On Tuesday, 7 July 2015 20:09:46 UTC+1, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

They're cooked at somewhere around 1000C. In operation not that hot usually The limit is going to be insulation temp limit & loss.


NT

I built a barbecue out of night storage blocks.

I got them to dull red heat once


--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

On Tue, 07 Jul 2015 22:55:26 +0100, Martin Brown wrote:

Phase change eutectic salt mixtures are the least bad option if you want
to get optimum performance of heat capacity per unit mass.

Phase change is the way to go if you can handle it. 1 kg of liquid
water @ 100 C to water vapour at 100 C requires 2,270,000 J compared
to heating 1 kg of liquid water from 0 to 100 C of 418,700 J

--
Cheers
Dave.

I think the most inefficient part of my storage heaters is insulation. In my
view all around the sides and bottom of the heat store should be much
better insulated than it is, and th vents when closed should also use some
kind of insulation to keep the bricks warm without wasting it.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Dave Liquorice" wrote in message
ll.co.uk...
On Tue, 07 Jul 2015 20:09:39 +0100, Simon Cee wrote:

Any idea what temp they get up to? Max temp for long term use?

At a guesstimate well over 100 C.

Investigating heat-store possibilities. Doing some sums.

Water at 4.187 kJ/l/K is hard to beat and being a fluid distributes
the the heat through it's body by convection. Heat transfer into and
out of is probably easier (less lossy) as well.

--
Cheers
Dave.

On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric heat
capacity to water.

On Wednesday, 8 July 2015 10:01:08 UTC+1, Brian-Gaff wrote:
I think the most inefficient part of my storage heaters is insulation. In my
view all around the sides and bottom of the heat store should be much
better insulated than it is, and th vents when closed should also use some
kind of insulation to keep the bricks warm without wasting it.

There are fan-assisted storage heaters which operate in the way you describe, but they're very bulky and expensive.

Height: 66cm
Width: 99m
Depth: 26cm

Weight: 223kg

costs £620 plus VAT.

https://www.tlc-direct.co.uk/Products/ERADL4024.html

Owain

On 08/07/15 11:35, Robert wrote:
On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric heat
capacity to water.

I expect the bricks could go a lot hotter - but you are going to impair
the heating element at some point and safe containment is going to
become more of a problem. Last think a storage heater needs to do is
rupture and drop red/white hot bricks all over its combustible surroundings!

"Robert" wrote in message
...
On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric heat
capacity to water.

But are easy to use over a much bigger temperature range and
so occupy much less volume and don’t have a leak problem.

"Tim Watts" wrote in message
...
On 08/07/15 11:35, Robert wrote:
On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric heat
capacity to water.

I expect the bricks could go a lot hotter - but you are going to impair
the heating element at some point

That gets red hot and works fine like that, just like it does in an oven.

and safe containment is going to
become more of a problem.

You certainly need better insulation.

Last think a storage heater needs to do is rupture and drop red/white hot
bricks all over its combustible surroundings!

They don’t rupture. The bricks are basically blocks of metal
and even if they crack they aren't going anywhere.

On 08/07/15 12:23, ratsack wrote:


"Tim Watts" wrote in message
...
On 08/07/15 11:35, Robert wrote:
On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric heat
capacity to water.

I expect the bricks could go a lot hotter - but you are going to
impair the heating element at some point

That gets red hot and works fine like that, just like it does in an oven.

and safe containment is going to
become more of a problem.

You certainly need better insulation.

Last think a storage heater needs to do is rupture and drop red/white
hot bricks all over its combustible surroundings!

They don’t rupture. The bricks are basically blocks of metal
and even if they crack they aren't going anywhere.

I know "they" don't.

I am merely pointing out that designing for say, white heat, is going to
make the whole containment problem *much* harder. And let's say you do
design for white heat - and the insulation fails locally creating a
hotspot. You now have the conditions to warp or even melt the load
bearing structure. So yes, it could rupture.

There's clearly a reason 600C is a popular design choice, and 1000C is not.

On 08/07/15 12:23, ratsack wrote:

They dont rupture. The bricks are basically blocks of metal
No, they sare not anything like blocks of metal.

Idiot.

and even if they crack they aren't going anywhere.


--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 08/07/2015 08:23, Dave Liquorice wrote:
On Tue, 07 Jul 2015 22:55:26 +0100, Martin Brown wrote:

Phase change eutectic salt mixtures are the least bad option if you want
to get optimum performance of heat capacity per unit mass.

Phase change is the way to go if you can handle it. 1 kg of liquid
water @ 100 C to water vapour at 100 C requires 2,270,000 J compared
to heating 1 kg of liquid water from 0 to 100 C of 418,700 J


Yes but then you have a pressure vessel and the possibility of releasing
all the energy suddenly.

On 08/07/2015 13:44, newshound wrote:
On 08/07/2015 08:23, Dave Liquorice wrote:
On Tue, 07 Jul 2015 22:55:26 +0100, Martin Brown wrote:

Phase change eutectic salt mixtures are the least bad option if you want
to get optimum performance of heat capacity per unit mass.

Phase change is the way to go if you can handle it. 1 kg of liquid
water @ 100 C to water vapour at 100 C requires 2,270,000 J compared
to heating 1 kg of liquid water from 0 to 100 C of 418,700 J


Yes but then you have a pressure vessel and the possibility of releasing
all the energy suddenly.

That is why it is usually the melt from solid to liquid that is used for
energy storage or eutectic molten salt energy transport.
A few candidates online in this paper:

http://www1.eere.energy.gov/solar/re...0_ualabama.pdf


--
Regards,
Martin Brown

On Wed, 08 Jul 2015 13:44:25 +0100, newshound wrote:

Phase change is the way to go if you can handle it. 1 kg of liquid
water @ 100 C to water vapour at 100 C requires 2,270,000 J
compared
to heating 1 kg of liquid water from 0 to 100 C of 418,700 J

Yes but then you have a pressure vessel and the possibility of releasing
all the energy suddenly.

Phase change is the way to go *if you can handle it*. B-)

--
Cheers
Dave.

lots of great replies and info - too many to thanjk individually. so
thaanks all.

"Tim Watts" wrote in message
...
On 08/07/15 12:23, ratsack wrote:


"Tim Watts" wrote in message
...
On 08/07/15 11:35, Robert wrote:
On 08/07/2015 07:38, Tim Watts wrote:
On 07/07/15 20:09, Simon Cee wrote:
Any idea what temp they get up to? Max temp for long term use?
Investigating heat-store possibilities. Doing some sums.

tia.


600C

http://www.esru.strath.ac.uk/Documen...3/Becerril.pdf

Useful article.
Bottom line magnetite heat storage bricks have a similar Volumetric
heat
capacity to water.

I expect the bricks could go a lot hotter - but you are going to
impair the heating element at some point

That gets red hot and works fine like that, just like it does in an oven.

and safe containment is going to
become more of a problem.

You certainly need better insulation.

Last think a storage heater needs to do is rupture and drop red/white
hot bricks all over its combustible surroundings!

They don’t rupture. The bricks are basically blocks of metal
and even if they crack they aren't going anywhere.

I know "they" don't.

I am merely pointing out that designing for say, white heat, is going to
make the whole containment problem *much* harder.

In practice it isn't, because its much easier to do than when using
water, essentially because there is no possibility of a leak.

And let's say you do
design for white heat - and the insulation fails locally

That doesn’t happen and it is trivially easy to ensure that it doesn’t.

creating a
hotspot. You now have the conditions to warp or even melt the load bearing
structure. So yes, it could rupture.

No it can not.

There's clearly a reason 600C is a popular design choice, and 1000C is
not.

Just because the insulation is more practical/economic at the lower
temperature.

"The Natural Philosopher" wrote in message
...
On 08/07/15 12:23, ratsack wrote:

They dont rupture. The bricks are basically blocks of metal
No, they sare not anything like blocks of metal.

Mine are.

Idiot.

and even if they crack they aren't going anywhere.

"Chris Hogg" wrote in message
...
On Thu, 9 Jul 2015 05:18:46 +1000, "ratsack"
wrote:



"The Natural Philosopher" wrote in message
...
On 08/07/15 12:23, ratsack wrote:

They don't rupture. The bricks are basically blocks of metal
No, they sare not anything like blocks of metal.

Mine are.

Some storage heaters have metal 'boxes' full of granular ceramic
material such as bonded magnetite. Yours may be this type.

Mine aren't boxes of anything, they are clearly cast 'bricks' of some
sort of metal that are fairly irregular on the outside to provide
channels for the air that is used to get the heat out of the pile of
'bricks'

There is no way that can ever fail catastrophically, the worst that could
happen is one cracks and that crack would be completely harmless.

There are fusible links that handle a failed thermostat so it doesn't
heat forever. The heating elements and fusible links are easy to
change if they do fail and I have changed a couple in the 40 years
I have had it.