In order to create a heat source. I've made a little aluminum CPU emulator. It will create up to 50Watts of heat. This device is composed of two 10 Ohm resistor connected in parallel. Each resistor is capable of 25Watt of heat. They're secured to the aluminum plate by a bracket. However, one design flaw is that the legs are also made of aluminum, which can get extremely hot (up to 150C) with the resistors.

Finished Product