[colbertn]

Hello, I am trying to formulate an algorithm that will calculate the approximate time it takes a base metal to get up to a curing temperature.  I have calculated how much energy it will require using the change in temp, mass, and specific heat.  Now I can't figure out how to calculate how much energy is being absorbed by a constant temperature gas oven to figure out how long it will take to absorb that much energy? Anyone have any ideas about how to do this?
Thanks

[curiouscat]

Give us details. Numbers. Sketch.

[Enthalpy]

Is there any equilibrium? Uniform temperature? If you mean: the heat absorbed to bring the gas to the temperature, it's computed from the gas' specific heat at constant pressure, Cp - provided this specific heat varies reasonably little over the temperature range.

[colbertn]

Well, for example, most of the parts I am trying to get up to temperature are aluminum, with a specific heat around 0.22 BTU/lb-F.  If I am trying to take it from room temp, I'll call 70 degrees F, to a cure temp of 400 degrees F, I am increasing 330 degrees F.  By my calculations, this should require approximately 72.6 BTU's for a one pound part.  Now the question is, using a gas oven, which is already starting at a 400 degree air temperature, how long does the part need to be in that oven to absorb 72.6 BTU's of heat energy and therefore have a base metal temperature of 400 degrees?  What factors do I need to figure out to calculate this.  I want a spreadsheet with an algorithm where, after entering the starting and final temperatures, selecting the metal (specific heat), and entering the part weight, it will automatically give a time estimate for the base metal heat up.  Any help would be appreciated!  Thanks

[Corribus]

I'm no chemical engineer, but I assume the thermal conductivity of your materials (one of which in this case is air) will be important. Thermal conductivity is itself temperature (and I assume pressure) dependent, so that will have to be taken into consideration. Also keep in mind that ovens can heat by more than one mechanism - e.g., both convection and irradiation - so this may be important depending on what your equipment is.

[curiouscat]

In addition to what @Corribus wrote:

How thick is your slab & what geometry? The tricky part in these problems is temp. inside the part is hardly uniform. Do you want to wait until the whole part comes up to 400 F uniformly? At the end heat transfer from 400 F air to 400 F metal will become very slow due to the low deltaT available.

Is there radiant heat transfer too? Or only via the air? And is there a circulating fan? How is the part supported? Will heat transfer be through only one face or all?