# Using concentric pipes as an inductive heater

• EzeTom
In summary, the engineer is thinking of building an inductive heater that uses two concentric pipes to conduct current. He saw one of these heaters in a furnace in Europe and thought it might be a fun project to build at home. He does not know the frequency of the driver board or the power requirements. He wants to try a proof of concept prototype using 1" diameter and .625 OD pipes with a wall thickness of .125". The temperature he is looking for is around 300F.
EzeTom
Hi Everyone,

I am a mechanical Engineer, playing in the electrical word :)

I was thinking about creating an inductive heater, that was based on 2 concentric pipes, with a current flow path that is from the inside pipe, through to the outside pipe, and utilizing an induction power supply to do so. I saw this style of heater in a lead melting furnace on a recent trip to Europe, and I thought it might be a fun project for me to build at home. (the furnace was a crucible with a "heating stick" inserted into it.

Does anyone have any suggestions as to the math, and science behind this? I see on ebay there are many inductive heater power supplies for sale, however I am certain there will be some impedance matching/ Frequency/ Voltage parameters that will need to be optimized, I only tool a couple of electrical classes in school, and from what I gather, this sort of heater arrangement is basically a very "lossy" transmission line.

Any thoughts?

I think we need a better picture of the type of heater you suggest. Please post a link.
Are the concentric pipes the “heating stick” you refer to ?
Does conduction between tubes only take place at the tip of the tubes ?
Is the gap between the tubes used for water cooling ?

Baluncore said:
I think we need a better picture of the type of heater you suggest. Please post a link.
Are the concentric pipes the “heating stick” you refer to ?
Does conduction between tubes only take place at the tip of the tubes ?
Is the gap between the tubes used for water cooling ?
Thanks for the reply,

what I was thinking of is using something similar to this, but with 2 pipes - you can double the wattage (using transformer oil or something inside to conduct the heat from the inside to the outside. The below link is using a copper (non mag) conductor on the inside, and then using a magnetic pipe to create the "heater" via the return high frequency current that drives to the "skin" of the steel pipe. ( Induction-Resistance Heating)

http://www.valin.com/documents/Skin_Effect_Slides.pdf

I bought one of these on Ebay, http://www.ebay.com/itm/H-Voltage-Power-Supply-ZVS-Tesla-Coil-Driver-board-Marx-generator-Jacobs-ladder/141931226883?_trksid=p5411.c100167.m2940&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140131123730%26meid%3Dac08e617be664148bb7fa53db57effd4%26pid%3D100167%26rk%3D6%26rkt%3D15%26sd%3D172001795203

But I am not really sure how to calculate if this will be suitable, or if I need some sort of impedance matching transformer to ensure all of the power is dissipated in the steel pipe... Any ideas ?

Last edited:
The circuit board shown on eBay is printed with DC 12V-30V / 10A. The maximum power input is therefore 30V * 10A = 300W. The maximum output power available must therefore be less than 300 watt.

1. You have given us no idea of the physical size of the tubes involved, or the external thermal insulation and heat losses.

2. You have given us no idea of the temperatures you require. Even if transformer oil is cooled and circulated continuously, it will break down at temperatures that will melt lead.

You will need some form of output transformer, the secondary of that will be the load.

Id like to just try a proof of concept prototype - maybe using some pipes 1" and .625 OD? with 0.125" wall? and perhaps 6" long? The temperature I am looking for is around 300F. - for the initial test, It will just be in air, so I would suspect 300 ish watts should apply some significant heat...

I don't know what the frequency of the driver board from Ebay is, I guess I will have to wait to have it arrive to measure it...

Do you have any ideas how I can begin to calculate what I would need to do, to balance the load in the pipes, with the power supply?

Just thought I would bump this.

## 1. What is the principle behind using concentric pipes as an inductive heater?

The principle behind using concentric pipes as an inductive heater is electromagnetic induction. When a high-frequency alternating current is passed through the inner pipe, it creates a magnetic field that induces an electric current in the outer pipe. This current creates heat due to the resistance of the material in the outer pipe.

## 2. What are the advantages of using concentric pipes as an inductive heater?

There are several advantages to using concentric pipes as an inductive heater. Firstly, it is a highly efficient method of heating as it directly heats the material inside the outer pipe. It also allows for precise control of the heating temperature and can be easily scaled for different heating requirements. Additionally, it does not require any direct contact between the heater and the material being heated, making it safer and cleaner to use.

## 3. What types of materials can be heated using concentric pipes as an inductive heater?

Concentric pipes as an inductive heater can be used to heat a wide range of materials, including metals, plastics, and liquids. The material being heated needs to be electrically conductive for the process to work effectively. However, even non-conductive materials can be heated indirectly by placing them inside a conductive container, such as a metal can, which is then heated by the concentric pipes.

## 4. Are there any limitations to using concentric pipes as an inductive heater?

One limitation of using concentric pipes as an inductive heater is that it is not suitable for heating large volumes of material. It is more suitable for smaller, localized heating applications. Additionally, the material being heated needs to be in direct contact with the outer pipe for the process to be effective. This may not be possible for certain shapes or sizes of materials.

## 5. How does using concentric pipes as an inductive heater compare to other heating methods?

Compared to other heating methods, using concentric pipes as an inductive heater is considered to be more energy-efficient and precise. It also does not require any fuel or open flames, making it a cleaner option. However, it may not be as suitable for heating larger volumes of material as other heating methods, such as furnaces or ovens.

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