A heat transfer assembly for transferring heat from a heat generating device to a circulating fluid, said heat transfer assembly comprising an evaporator device having at least one microchannel formed therein, in thermally conductive contact with said heat generating device, a condenser device, actuating means and manifold means for circulating said fluid between said evaporator device and said condenser device, wherein said heat transfer assembly further comprises a bubble generator capable to create bubbles in said at least one microchannel at a controlled frequency.