Abstract: An ohmic heater comprises at least two electrodes contained within a vessel such that the electrodes lie along the length of the vessel. The vessel has inlet and outlet ports in the top and bottom through which a fluid to be heated flows, passing through the vessel along the length of the vessel. The electrodes are equally spaced about the axis of the vessel and when in use, are each connected to a single phase of a power supply, such that the total voltage at any point in time at the electrodes is near or at a neutral potential of the electric power supply. Electrically conductive guard rings are positioned around the inner periphery of the inlet and outlet ports of the vessel and are connected to the neutral potential of the electric power supply by electrical connectors. A leakage current monitor is interposed between guard rings and the neutral potential to enable current leakage from said heater to be monitored.

Abstract: An apparatus for heating an electrically conductive fluid ohmically by passing an electric current through the fluid between electrodes spaced along a pipe through which the fluid flows. The pipe has an electrically insulating internal liner and is cooled, e.g. by cooling water flowing through a cooling jacket between inner and outer skins of the pipe. The inner skin supports the liner and is perforated to allow intimate cooling of the liner. The cooling prevents heating of the fluid in a layer immediately adjacent the internal liner to such a temperature that the medium would foul the liner.

Abstract: A heater for liquid foodstuffs has a pipe through which the foodstuff flows and electrodes spaced along the pipe to drive a heating current through the foodstuff. In the embodiment, the electrode is a platinum coated cylinder arranged transversely in an enlarged part of the pipe so that electric current flows to the electrode only over a smooth surface portion, entirely within the edges of the exposed electrode surface.

Abstract: A method of disrupting vapor films formed in film boiling in boilers, in which method transient electrical discharges are effected either in the boiler liquid or in a body of liquid in acoustic communication with the boiler liquid. The electrical discharges are effected at one or more selected locations in the boiler to produce shock waves which act on surfaces of the boiler liquid space where vapor films are to be disrupted. By disrupting such vapor films there is enabled an improvement in the heat transfer rates per unit area across the interface between the fire space and the liquid space of a boiler. There are also disclosed various arrangements in boilers for generating these shock waves. Electrical discharges may be effected between a pair of electrodes mounted in the boiler or between an electrode and an adjacent wall of the boiler, and several mounting configurations for electrodes in boilers are described.