Abstract: A flow-through, chamber-in-chamber, nanocavitation apparatus having an elongated housing with an inlet and an outlet. A working chamber disposed between the inlet and the outlet includes alternating radial and central flow guides disposed concentrically in the working chamber about a central axis. A first radial flow guide is disposed proximate to the inlet and all radial flow guides have a radial opening adjacent to an inner wall of the housing. A first central flow guide is disposed proximate to the outlet and has a central opening about the central axis. The alternating concentric nature of the flow guides promotes alternating generation and collapse of cavitational features, all while promoting the efficient exchange of heat between hot zones and cooler regions of adjacent flow guides.