Freezing Core

With the Force Furnace you can smelt blocks and items similar to a vanilla furnace but twice as fast.
The furnace can be upgraded by applying an Upgrade Core of choice into the Upgrade slot on the top left. (Once an upgrade is applied taking it out will void it)

The Speed Core will increase the furnace speed fivefold.

The Heat Core will increase the furnace efficiency by twofold, allowing you to smelt twice the amount of items/blocks with the same amount of fuel.