calculating number of cartridge heater to heat a block

[gpignanelli]

I am working on a project that requires a block of aluminum (69" x 60" x 21") to be heated to 350 degrees Fahrenheit in 1 hour. I also must maintain the 350 degrees for 8 hours. We will be using cartridge heater with thermal-couples to heat the block of aluminum. What I like to know is the calculations needed to figure out how many cartridge heaters we will need and what the wattages of the cartridges need to be. Again the goal is to heat the block 350 degrees fahrenheit in 1 hour and maintaing the temp for 8 hours.

Thanks for the help.

 

[chicopee]

Is the Al.block solid or hollow?;partially, partly or insulated, or bare? exposed to tranquil or moving air or some other medium?;is heating internal or external to the block? how is it supported? what is the initial temperature before heating. Did I miss anything else?