Heat transfer calculations in a Lab furnace

[matsci1]

Greetings All,

I am a PhD student in a physical chemistry department. Our research group would like to build our own high termperature ovens for preparing samples. Nothing fancy, just a controled rise in temperature to a given setpoint, hold it there for a designated amount of time and the cool down. The controllers that will do this are inexpensive and also the relays and thermocouples...that is not a problem. The question is about heat transfer and power.

We will be using Kantahl resistance heating wire. It is serviceable to 1350°C and we have a 230V, 16 Amp service to the normal labortory outlet. The question is how much power input to heating chamber should we design to reach temperature "X" in a heating chamber of volume "Y". The volume we have in mind is about 2700 Cubic Centimeters (15cm X 15cm X 12cm). This can all be calculated through the heat transfer equaitons and knowing the R factor of the insulation, surface area...etc.
Does anyone know of some softwear that can simplify this process?

Thank You,
MS1

[ed_denu]

I can't help with the software you requested, but can I ask a question or two and point out a few things you probably already know.

Most of the discussions on this thread deal with building PC or similar type ovens that typically reach 400-550F. I doubt you will find anyone attempting to build an oven this tiny that can reach 1300C. The obvious problem would be to find material that can withstand this high of a temperature. Fiberglass or even mineral wool, the two most common insulating materials used would not.

There is an excel ss referenced in the sticky above that computes wattage necessary to reach specified temperatures, but I doubt that it factors in all the specifics of reaching the temperature you note.

If you are unsuccessful in finding the calculations you need, have you considered just using a ramp/soak pid controller with a TC, and letting it hit and maintain the temperature set points you enter, without a concern over knowing the heat loss?

I'd really like to see a picture of this tiny oven when you get it complete.

[CarWiz]

Go to the Kanthal website and download their alloy reference manual. The information you seek is there. The formulae starts around page 71.

Kanthal - Manufacture of Heating Systems, Resistance Wire, Appliance Wire, Heating Material