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 ohmic heating apparatus for heating flowable media which is flowing through a conduit comprises electrodes exposed to the flowing media and supply means connected to the electrodes and to the media to pass a heating current through the flowable media. The electrodes are made of a material of closed microporosity having a resistance to surface fouling. The material of closed microporosity is preferably made of vitreous carbon.

Abstract: A heating apparatus for heating an electrically conductive flowable medium includes a pipe having a conductivity no greater than that of the medium and a pair of electrodes projecting in a cantilever fashion into the pipe at spaced locations therealong and each having a noble metal plated surface exposed to the flowable medium. Each electrode is sealed to the wall of the pipe with a flat-faced aspetic seal formed between a flat end face of the elctrode and a cooperating flat face on the pipe wall. The electrodes may be hollow, fluid cooled and have a rounded free end made of an electrically non-conducting material on which is mounted a temperature or pressure sensor. The exposed electrode surface may be partially coated with an electrically insulative material to confine heating current flow to a particular surface portion of the electrode.

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 compressor for a heat pump using a condensible gas as a working fluid has a lubricant temperature controller comprising a heater for the lubricant in the sump, the heater being controlled by differential pressure responsive means comprising the vapor pressure above the lubricant in the sump with a pressure obtained from a sensor bulb in the sump oil, the bulb containing a solution, in a lubricant of a refrigerant, the refrigerant preferably being the same as the working fluid of the heat pump.