Joule Heating Project: Maximizing Glycerol Vaporization

• SinguIarity
In summary, Eric is working on a project to create a heating coil to vaporize glycerol on a portable device. He did some research and decided to use a resistive heating element that gets him 30 watts. He wants to minimize heat loss and use low thermal conductivity containment materials. He also wants to use a coil that reaches the desired heat relatively quickly. His goal is to obtain this power and minimize loss. There are several issues that he needs to address, such as the power supply and load balancing the batteries.
SinguIarity
Hi all, some background info, thanks for reading and helping!

I'm working on a project, the portable device is to vaporize glycerol(300 C). In an attempt to maximize vapor production, I've decided to skip the experimentation and calculate the optimal specs for each part. Also pardon my vocabulary, computer science major with about 5 hours of research done in resistance heating and general electrical engineering.

These are the limits on the circuit board:
PWM (Pulse Width Modulation) output, up to 5 amps
Variable Volt: 3~6.0V
(2) 1200mAh 18350 batteries
1.2ohm minimum coil
20mm maximum length of coil

My goal is to create a heating coil that will vaporize as much glycerol as possible on this board. I did some research and people say the lower the ohms the more heat is released so is it safe to assume we should stick to a 1.2ohm coil? We also want it to have as much surface area as possible, to heat up more liquid. The preferred heating wire is 28awg Kanthal A1. We also need the coil to reach the desired heat relatively quickly(0-2 seconds). So would it be better to use a lower gauge wire so we can put in more wraps and get a longer coil? Or should I stick with the common build of 10 wraps around a needle for around 1.5ohm. What would be the best coil design and wire material and wire type(round vs ribbon/flat).

Cheers,
Eric

Your maximum power seems to be (6V)(5A)=30 Watts. 30 Watts electrical power in a resistor is also your heating power.

Your goal seems to require you both obtain this power and minimize loss.

So use a resistive heating element that gets you 30 Watts. Set your adjustable power supply to full voltage. If you’re really clever you might use some of the waste heat from the power supply to preheat the glycerol.

Minimize heat loss using low thermal conductivity containment materials. Dribbling down a coil using the vaporized glycerin itself as your first insulation layer may be best. Glycerin is very viscous---at least it is at room temperature. At room temperature its volumetric tension (called surface tension) should separate it into droplets protruding perhaps 1 mm from the surface on fine wire. If you use a coiled heating element keep the windings about 3 mm apart. Experiment.

This isn’t electrical engineering. Its geometry and materials.

I don’t know where 1.2 Ohms comes from… You need 1/1.2 = .83 Ohms. So use about 8,8 Ohms unless your power supply gets upset with it.

Search “American Wire Gauge” to get 8.8 Ohms. I see about 25 cm of 40 gauge copper wire which looks problematic. It's far too flimsy. Use Nichrome instead.

Good luck.

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[edited due to an error regarding resistance change with temperature]

1.2 ohms is 6V/5A, so 1.2ohms is the correct answer. Not sure where Rena got 0.83 and 8.8.

Kanthal 28 AWG Gauge A1 Wire is 5.27 Ohms/ft Resistance (Kanthal A-1 is a ferritic iron-chromium-aluminium alloy (FeCrAl alloy) for use at temperatures up to 1400°C (2550°F).)

The first issue is whether the wire can handle 5 amps without fusing. (I didn't find the fusing current)

Also, you are discharging the 1200mah batteries at 5 amps. You need to know what you are doing with respect to load balancing the batteries both for charging and discharging. (do you have a circuit that takes care of that?)

The mechanical design question is how to expose the most wire to the chemical. I assume that would be to make the coil a flat disc and drop the chemical directly on the wires. I don't know about residue and cleaning though. You can use a single wire or multiple longer wires in parallel to get the desired resistance

This has good info starting at page 80 http://www.kanthal.com/Global/Downloads/Materials%20in%20wire%20and%20strip%20form/Resistance%20heating%20wire%20and%20strip/S-KA026-B-ENG-2012-01.pdf

Last edited by a moderator:
meBigGuy said:
1.2 ohms is 6V/5A, so 1.2ohms is the correct answer. Not sure where Rena got 0.83 and 8.8.

Yes, you are quit right. I don't know where-from either.

I would approach this project by first understanding the principles behind Joule heating and how it relates to vaporizing glycerol. Joule heating is the process by which electrical energy is converted into heat energy in a conductor, such as a heating coil. In this case, the goal is to maximize the amount of heat generated in order to vaporize the glycerol efficiently.

Based on the provided information, it seems that the main factors to consider in this project are the resistance of the coil, the voltage and current limits of the circuit board, and the desired heating time. It is true that a lower resistance coil will generate more heat, but it is important to find a balance between heat production and safety. A coil with too low of a resistance could potentially draw too much current and damage the circuit board or batteries. Therefore, it is wise to stick to the 1.2ohm minimum coil specified for the circuit board.

In terms of coil design, there are a few options to consider. Using a lower gauge wire will allow for more wraps and a longer coil, which can increase the surface area and potentially produce more heat. However, this also means that the coil will have a higher resistance. On the other hand, using a higher gauge wire will result in a lower resistance coil, but with a shorter length and potentially less surface area. The best approach would be to experiment with different wire gauges and coil designs to find the optimal combination for this specific project.

As for the wire material, Kanthal A1 is a good choice as it is known for its high resistance and ability to withstand high temperatures. Flat or ribbon wire can also be considered for their larger surface area compared to round wire. However, it is important to keep in mind that the wire material and type may also affect the overall resistance of the coil.

In conclusion, the key to maximizing glycerol vaporization in this project would be to find the right balance between resistance, surface area, and heating time. This can be achieved through experimentation and careful consideration of the different factors involved. It is also important to keep safety in mind and not exceed the limits of the circuit board and batteries. Good luck with your project!

1. What is Joule heating and how does it relate to the project?

Joule heating is the process by which an electric current flowing through a conductor produces heat. In this project, Joule heating is used to heat the glycerol and maximize its vaporization in order to create a more efficient and effective heating system.

2. What is the purpose of maximizing glycerol vaporization?

The purpose of maximizing glycerol vaporization is to increase the efficiency of the heating system. Glycerol has a high heat capacity and can store a significant amount of thermal energy, making it a valuable resource for heating applications. By maximizing its vaporization, we can utilize this energy source more effectively.

3. How is the project being conducted?

The project is being conducted by using an electric current to heat the glycerol and increase its temperature. This is achieved by passing the current through a conductor, such as a resistor or heating coil, which is in contact with the glycerol. As the glycerol heats up, it vaporizes and can be used for various heating purposes.

4. What are the potential applications of this project?

This project has potential applications in various heating systems, such as space heating, water heating, and industrial processes. It can also be used in renewable energy systems, as glycerol is a byproduct of biodiesel production, making it a sustainable and eco-friendly energy source.

5. What are the potential benefits of using glycerol for heating?

Using glycerol for heating has several potential benefits. It is a renewable and sustainable energy source, as it is a byproduct of biodiesel production. It also has a high heat capacity, making it more efficient than traditional heating methods. Additionally, using glycerol for heating can reduce carbon emissions and contribute to a greener future.

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