1. The apparatus comes installed with a slab assembly. The main Heater and a radial guard heater are placed between copper plates. 

2. The specimen in the form of slabs of equal thickness are placed on either sides of heaters and cooling plates through which water is circulated are on the other Sides of the specimen. 

3. The radial guard heater ensures all heat of the main heater to pass axially through the specimens which is collected by cooling plates.

4. By finding out the temperatures and Heat input, thermal conductivity of specimen can be calculated. The test set up is surrounded with an enclosure with insulation inside to provide undisturbed Surroundings.