A convective heat transfer system for use with a fluid with particles, including a fluid channel having a wall and being capable of transferring the fluid, and a field emitter operable to emit a time-varying field into the fluid channel such that, when the fluid is in the channel, the time varying field affects a portion of the particles to change the rate of heat transfer between the channel and the fluid. The fluid can be a slurry with suspended field reactive particles. The system can include a plurality of field emitters located along the walls of the fluid channel, to vary the field and manipulate the distribution of the particles within the slurry, thereby changing the heat transfer characteristics of the system. The field can be an electric field or a magnetic field. The fluid channel can be disposed in a heat transfer system.