Froth heaters

A froth heater, comprising:

• an outer case defining an inner cavity, an inlet in fluid communication with the inner cavity, and
• an outlet in fluid communication with the inner cavity;
• and
• a heater core inserted into the inner cavity and configured to form a flow path between an inner wall of the outer case and the heater core between the inlet and the outlet, wherein the heater core includes a core cavity configured to receive a heater therein to heat the heater core,
• wherein the heater core includes a plurality of channels defined on an outer diameter thereof including a first channel and a second channel, wherein the flow path is defined by the inner wall of the outer case and the plurality of channels, wherein the plurality of channels are circumferentially defined around the heater core, wherein the first channel includes circumferential rings in fluid communication with adjacent circumferential rings via one or more axial passageways defined through dividing walls of the first channel, wherein the circumferential rings are defined in a first axial fraction of the heater core, wherein the second channel includes a spiral channel is-defined at least in a second axial fraction of the heater core.