Hi all,

 

I'm a beginning ME student and I have a project that requires me to heat a liquid (around 16 ounces) to around 120-140 degrees F. My idea is to place an electrically heated coil powered by a dynamo. My question is: what kind of voltage would i need to supply with my dynamo to achieve this kind of temperature?

 

Also, I researched some kinds of resistive wires that I could use and most said to use the same kind of wire that is used in appliances like toasters. Is there a better way to go about this?

 

THANKS!

You must know one of the main laws of electricity:

 

[math]V=I*R[/math]

 

What's the formula for resistance in a wire?

What's the formula for power (as a function of V,I and R (pick two out of 3))?

 

Those were highschool formulas for me - so I expect that you know them too... and since this seems homework to me, I won't tell you

If I know the resistance of the wire, I am able to derive a formula for the power it will deliver (in the form of heat)... and with that you can calculate how long it will take to heat your liquid.

Please realize that if you suspend a coil (wire) in water, you might severely decrease its resistance (since you effectively shortcircuit it by the water, which is conductive).

 

After that it's just a matter of insulating the liquid so that all the heat stays in it. With a perfect insulation, you will reach the desired temperature regardless of the power.

Well it is homework but not of the textbook type. I'm designing a product for my mechanical engineering class that will take a current sent through a resistive wire to heat the liquid. The concept is to create something that takes human input energy and converts it to something usable. So its not a problem that I'm trying to get someone else to do for me, just need some guidance on it

 

And I guess I didn't explain my setup very well. My idea is to attatch the coils to the underside of a metallic cup so that it inducts the heat better, not to suspend them in the liquid itself. So I was wondering what kind of wire I should purchase and the motor as well, keeping in mind that I only have a certain amount of space. (About 8-12 cubic in.) Also, I researched some of the materials and I think I need to also purchase some capacitors to store the charge and then discharge it across the wire at once rather than a continuous charge (without capacitors) that I think wouldn't be able to deliver the necessary amperage.

 

...basically I'm in need of some general guidance from someone to know how to tackle my concept for my project. If you have any other questions as to what I'm trying to accomplish, just ask me and I'll try to tell you what I'm thinking.

Edited September 30, 200916 yr by hjel0743