Heat Transfer with Die Heater

May we assume that there is a bore hole in the center of the Al block?

Or, do we heat it from the outside?????????

Sorry Lyn, I missed the obvious, depending on how many I use, there will be 1 or more and the heater put in with heat sink paste.

Tony

~3 min...

... depending on how much heat goes elsewhere than into the aluminum.

Well yes it would have to be in an insulated sleeve of some sort...Maybe like a small table top kiln oven made to close fitting spec....

Thanks SolarEagle and Tornado

How much will it shorten the time using 2 and up to 4, 500W heaters. A 200x100 face will be exposed to the 20°C ambient and an extractor fan for fumes will cool that face slightly.

Tony

With 4 you could probably cut it to under 30 sec....

Thank you SolarEagle, that wraps it up.

Thanks nick name and ozzb, I used the formula from ozzb, (thank you) and reached 5.4 minutes with 500W, we decided on 3 at 50mm centres due to other considerations. As the small parts will be swapped hot, 2 minutes initial heat is not huge. When I've built it I'll, I'll report back.

Tony

The soft I have does not accept a flux as input. I had to imagine a way to simulate a constant flux and I found it so the following picture is the temp distribution after 120s with a flux of 500 W/heater. The distance between heaters is 50 mm same as you choose.

As you see results are convergent.

As you also see is a more uniform temperature over the width.

Making use of symmetries the picture represents only a quarter of the plate.

Reality is that between heater and wall there is an air layer and air is a good thermal insulation. Due to this the time will be longer but same order of magnitude.

Thanks for that nickname.

I will use a thermal paste when I insert the heaters.

We are not sure what temperatures we will require, but it will be 120°C - 160°C range, from your simulation I would need to place the thermostat sensor close to the centre.

I'm assuming the temperature would stabilise after a few minutes. As aluminium conducts quite well.

Tony

You are right but not only the conductivity is in the game the parameter is the thermal difusibility = k/(ρ*cp) i.e. the specific hea and the specific weight have a negative impact on the speed with which heat travels across the body.

My simulation gives you an indication about the temp differences along the width so knowing the thermostat position you will know approximatively which temp is where.

q = m x C x (Tf - Ti)

q = amount of heat energy gained or lost by substance

m = mass of sample

C = heat capacity (J ^oC^-1 g^-1 or J K^-1 g^-1)

T_f = final temperature

T_i = initial temperature