# Heat Problem

1. Aug 31, 2006

### ecid

Hallo... everyone... straight to the problem, ok!

I'm now building an egg incubator box, sized 100cm cubic. And i provide its heat with a set (4 pieces) light bulb.
And now, what i like to know is:
Any equation or formula to determine how long it took to warm up the whole box?

Thanks...

2. Aug 31, 2006

### Integral

Staff Emeritus
This is a non trivial question with no closed form answer. The best way to determine the time and temperature is to turn on your lights and time it. If it is located in a area subject to air currents or non uniform lighting the time to reach a temp and the final temperature reached will change with your environment.

3. Aug 31, 2006

### Danger

I'm not sure about exact formulae. It would depend upon the type of bulbs (purpose-designed incubator bulbs or regular incandescent), and their wattage. Either way, you have to determine first how much of the rated wattage is converted to heat rather than light. I don't really know how you would do that other than maybe measure the surface temperature of each bulb. Even then, I think that it would be kind of 'iffy'. This strikes me as a trial-and-error sort of situation.

edit: Oh, hi Integral. I didn't see you sneak in.

4. Aug 31, 2006

### Cyrus

We could do a rough estimation if you told us the start and stop temperatures and did a simple energy balance.

5. Aug 31, 2006

### ecid

Re..:

I use ordinary bulb, i'm not sure which wattage is the best, maybe 15 watt?
Purpose-designed incubator bulbs? Just heard of that... any info about that?

Start/stop temperature?

6. Aug 31, 2006

### Cyrus

Is this for a middle school project or something?

7. Aug 31, 2006

### Danger

Pretty much just 'heat lamps', such as you might find in a hotel bathroom. They're designed to radiate primarily in the infrared band. The ones that we used about 40 years ago were shaped like regular bulbs, but I think that nowadays they're mostly reflector types.

8. Sep 1, 2006

### ecid

Re Heat

cyrusabdollahi Is this for a middle school project or something?

none of those above...

9. Sep 1, 2006

### ecid

not really, actually it's my final.
i'm majoring electrotechnik, and i've never faced with non-electric problem such as that, and i was wondering if there any equation or formulae to deal with it?
I know, the best solution is trial and error, measuring the temperatur in the box until it reached max value, where the temp rising stopped. isn't right?

10. Sep 1, 2006

### rcgldr

Is this a cube, or an open top box with no significant circulation of the surrounding air? It needs to be an open box for the eggs to receive fresh air. I hope you don't plan on putting real live eggs in that box. Real incubators use thermostats or the equivalent (someone looking at temperatures and making adjustments). 100cm^3, so the box is only 4.64 cm's long per side?

The temperature will stabilize when the differences in temperature inside and outside the box balances out with the heat flow resistance factor. I'm not sure if the heat flow resistance will vary with temperature, for example, the box in a 60 degree Farenheight environment versus the same box in a 120 degree environment. My guess is that the temperature curve would be similar to part of a hyperbola, with an asymptope at the peak temperature.

Last edited: Sep 1, 2006
11. Sep 1, 2006

### ecid

re :...

a closed (hopely cacuum) cube, which i installed 4 12V fan, and a simple ventilation system is also made.

That's the plan... real live and fertil egg, i use microcontroller-operated temperature sensor and it also controlling the heating system.
The size of the box :
width : 121 cm
height : 158 cm
length : 100 cm

12. Sep 1, 2006

### ecid

cacuum = vacuum

13. Sep 1, 2006

### rcgldr

What is the goal temperature for the incubator, and what do you plan to do when the chicken hatches? It needs a "mother" to imprint on in the first 5 minutes. Not a fan of experiments involving live animals just for a class.

14. Sep 1, 2006

### Danger

Good point, Jeff. I would really like to see Moonbear weigh in on this. She can probably advise a way to deal with this with minimal trauma to the 'subjects'.