Abstract: A heating device generates heat by working a liquid in a closed container with a rotating stack of finely perforate square plates and recovering the heat from the thus heated liquid. In one embodiment a stack of a multiplicity of flat square plates radially offset one from another is rotated in an oil bath in a container under an inner perforate non-rotating cover over which is a similar non-rotating cover that is imperforate. The thermal energy developed through the mechanical working of the liquid is transferred to the main liquid bath and is then removed, as for example, by circulating air or a liquid around the outside of the container with the thus heated air or liquid being used to heat a house or the like.