Heat Plate in Air to Melt Plastic

[rjsfocus]

I am setting up a system where a rectangular plate is heated by a set of heater cartridges, producing about 4000 watts. This plate is in free convection air. It is used to melt plastic at regular invervals. I am trying to model the system so we can estimate temperatures of the plate to control the system better, by using Simulink. I am having trouble linking several equations together though. I can figure out the temperature and time it takes to reach the temperature, in a vacuum at least, through Q=CM(Tf-Ti), and q=Q/t. The heaters are heated like a convection oven, electricity is either supplied or stopped, based on the temperature of the plate.
What I am looking to do is find the temperature of the plate during a cycle, such as when temperature is roughly steady state, but is then decreased when energy is transfered to the plastic, and to air as well if I can. Does anyone have any idea how to calculate the temperature drop when it hits the plastic, and then how long it takes for the temperature to increase? I feel it is similar to say a fridge, it runs at a constant temperature until an item is put into it. The temperature drops and then rebounds.
Thanks for any help that can be provided.
Rich

[Kelly_Bramble]

Sounds like you need to separate the calculation tasks.

First

temperature and time it takes to reach the temperature

Second

but is then decreased when energy is transfered to the plastic, and to air as well if I can

Third

then how long it takes for the temperature to increase

[rjsfocus]

Good start so far. Let's start simple. I have 4000 watt going to the plate of volume v and area a, in air of T. How can I find the temperature the plate will reach?

[Kelly_Bramble]

Any heat transfer book will provide and fundamental equation for:

4000 watt going to the plate of volume v and area a, in air of T. How can I find the temperature the plate will reach?

Or, you can look here.

https://www.engineersedge.com/heat_t...le_content.htm

https://www.engineersedge.com/heat_t...conduction.htm

https://www.engineersedge.com/calcul...ace__10050.htm

https://www.engineersedge.com/calculators.htm