Patent ID: 7050706

Claim:
An apparatus for heating fluid comprising passageway means defining a flow path for the fluid to be heated, upstream fluid temperature measuring means to measure the temperature of fluid to be heated, a plurality of sets of electrode means in or forming the flow path and between which said fluid passes, said sets of electrode means including at least first and second electrode sets along the fluid flow path, said first electrode set and said second electrode set both having at least one pair of electrodes between which an electric current is passed through the said fluid to heat the fluid during its passage along the flow path, first downstream temperature measuring means downstream of the second electrode set, fluid flow rate measuring means, and electrical control means to supply and control electrical power to the electrodes of each set, said control means having processing means to relate current flow and applied voltage in response to measured upstream and downstream temperatures and fluid flow rate to determine desired power input to the fluid from each electrode set to achieve a desired fluid temperature downstream of the second electrode set.