immersion circulator

:  an electrical appliance used for sous vide cooking that is immersed in a container of water and that circulates and heats the water to a precise, consistently maintained temperature Known as an immersion circulator, it is a six-inch metal box with a digital temperature readout and a shiny coil that thrusts deep into the stockpot, simultaneously heating and circulating the water with a powerful little pump. — Jeffrey Steingarten