FLUID HEATER WITH FINITE ELEMENT CONTROL

An ohmic heater for heating a conductive fluid includes electrodes (14) and spaces (20) between the electrodes. A controller (52) selectively connects the electrodes to a power supply (36) during a succession of actuation intervals so as to form conduction paths, each including two live electrodes connected to different electrical potentials, and the fluid in one or more spaces. The controller models fluid passing through the spaces as a series of finite elements moving through the spaces. Before each actuation interval, the controller estimates the expected results of actuating various possible conduction paths, including the estimated temperature of the fluid in the conduction paths and the estimated currents passing through the live electrodes. The controller selects a set of conduction paths for which the estimated results meet a set of constraints, and actuates only the selected conduction paths during the actuation interval.