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Low thermal mass material

RUTHOM

New Member
Hi,

I want to reduce a consummation of 1500W for furnace based on hot air recycling to minimum consummation. Actually, it can do temperature ramp up to 300ºC and to cool until to 40ºC in 4min. I want to maintain the same situation, but to reduce the wattage to a consummation of a battery. Some body could help?

Hi,

Please, just all of I want is to know if it is possible to gate god results working with a heating element of 300-600w, doing ramps from 25 up to 200-250ºC with less than 100VDC.
On the picture, You will see a heating element of 1700w, 220V/230V, VAC 15-20A

Eii! I really need a help, I will be very grateful to receive inputs about this subject!
 

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unclejed613

Well-Known Member
Most Helpful Member
it's difficult to understand what you are trying to accomplish. you might want to buy a spool of nichrome wire and make your own heating elements (or find an old toaster and use it's heating elements). nichrome wire begins at a low resistance cold, and the resistance increases as the wire heats up. without knowing exactly you are trying to heat (air, water, other materials), then i really can't give you very specific answers. the specific heats of different materials vary all over the place...
 

RUTHOM

New Member
Hi
Many thanks for your response!

The idea is to make a air oven which can work with a low voltage(12V, 24V, ….).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Hi
Many thanks for your response!

The idea is to make a air oven which can work with a low voltage(12V, 24V, ….).
Presumably you are aware that you NEED high wattage?, using low voltages doesn't mean you can use less power, it just makes you need massive current to compensate. There are good reasons why you don't get battery powered heaters.
 

RUTHOM

New Member
Yes you're right! But working with portable and miniaturized instruments is also a good reason! I was really searching through internet and I didn't find air heaters with moderate wattage and reach 300ºC. It is a way to investigate?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Fine resistance wire is readily available, it's commonly sold for "vapes" - artificial cigarettes etc.
You can get various alloys from 0.1mm upwards.

Temperature is not a problem - you can make a small element that will glow red hot while running on a single AA cell - but power, how much mass of something it can heat, is a very different thing.

More power input means you can heat move mass and/or heat the mass faster

The key question is: What, exactly, are you wanting to heat up - the material - the mass - the volume etc.
 

RUTHOM

New Member
In a 100mm*200mm*18mm metallic cube SS with a recycling air ventilator inside. To get 250ºC stable.
 

Les Jones

Well-Known Member
Most Helpful Member
From your post #7 it sounds like your device is a closed system. If you have perfect thermal insulation (Which is not possible in practice.) you need the energy to raise the thermal mass from it's original temperature to it's desired temperature. The required POWER depends on how quickly you need this to happen. (As energy is power times time.) Once you have reached the desired temperature no more energy is required to maintain the temperature WITH PERFECT INSULATION. So in the real world you can't have perfect insulation so energy is being lost through the insulation. So you need to input power to compensate for this loss. So reducing this power requires increasing the thermal resistance and / or the amount of insulation material. If you did not cover heat when you did science at school an analogy would be charging a capacitor. With a capacitor with no leakage resistance once it is charged up to a voltage it remains at this voltage. Think as the thermal insulation like the leakage resistance of a capacitor. This is not a perfect analogy at the energy stored in a capacitor is 1/2 x C x V^2 but the heat energy is thermal mass x temperature rise. (Thermal mass is mass x the specific heat of the material.) I hope the helps you to understand your problem better.

Les.
 

RUTHOM

New Member
Hi Les,

I highly appreciate your inputs, of you all! The science have made big advances, but don't care about simple things like to take a cup of coffee in some where on pick-nick day with a coffee maker cordless(With a battery, I mean).
 

Les Jones

Well-Known Member
Most Helpful Member
There is nothing new about the information I posted. It was about 60 years ago I was taught that at school. As for a cup of hot coffee for a pick-nick. Using a thermos flask will weigh less than the weight of the Li-On required required to heat the water.

Les.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The relevant science is "Conservation of energy", one of the most fundamental principles.

If you want to heat a certain mass of something by a certain number of degrees, whether it's a complex chemical or pot of water, you have to put the appropriate number of watt-seconds of power (= joules) in to it, regardless of the power source.

That can be slow or fast, high wattage for a short time or lower wattage for a longer time, but the amount of power or energy needed must come from somewhere.


You can boil a jug or cup of water with a low voltage element - 12V ones have been available for many years.
They are normally intended to run from a vehicle "cigar lighter" power connection, but there is no reason they could not be used from a 12V battery pack, if it were big enough.

Example:

You would need a battery pack that can provide 12 to 15V at a minimum of ten amps for probably 10 - 15 minutes, to boil each cup quantity of water.

A large four cell drone battery pack (eg 5AH) could run it and make two or three cups of coffee.

It's possible, just not convenient. That's why gas is so often used for small heating appliances and tools, as the energy "storage" in a small can of gas is vastly higher than the best similar size battery made so far.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Hi Les,

I highly appreciate your inputs, of you all! The science have made big advances, but don't care about simple things like to take a cup of coffee in some where on pick-nick day with a coffee maker cordless(With a battery, I mean).
That's probably where you're going wrong, such a thing isn't really 'that' simple as already explained by others - and science hasn't made any recent 'advances' in such things, as it's quite simple to understand and nothing has changed. The only 'advances' are in battery technology, and that's not really advanced very far - there are far more efficient ways for portable energy systems.
 

crutschow

Well-Known Member
Most Helpful Member
simple things like to take a cup of coffee in some where on pick-nick day with a coffee maker cordless(With a battery,
Even the best present batteries do not store sufficient energy to do that with a reasonable sized battery.
A cup of water takes a lot of energy to heat from room temperature to coffee drinking temperature.
 

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