Abstract: An air heater mounted in an elongated ventilation slot located beneath a window of a land, sea or air vehicle has a plurality of self-regulating ceramic heater tablets having a positive temperature coefficient (PTC) positioned between two metal strips and fastened thereto in thermally and electrically conductive relation.Heat exchangers comprising sheet metal fins with baffles are secured in electrically and thermally conductive relation to the opposite sides of the strips so that the baffles introduce turbulence into the air flowing over the strips. Other metal strips having electrical terminals are thermally and electrically connected to the fins opposite the first named strips for energizing the heater tablets. The PTC tablets are spaced to define flow passages therebetween so that the air flowing through the ventilation slot passes over the heat exchangers, plates and tablets for rapidly withdrawing heat from the tablets.

Abstract: A heating device for fuel or other fluid, in particular to prevent solidification of paraffin constituents in diesel oil, comprises a housing (1) with an inlet (14) and an outlet (15) for the fuel, and a number of metal plates (3, 4) inside the housing. Tablets or heater elements (5) made of a ceramic material with a positive temperature coefficient (PTC) are fastened on the metal plates so that heat and electricity is conducted. To improve the heat transfer one or more turbulators (6; 6a, 6b) are placed between two of the above-mentioned metal plates, (3, 4) provided with PTC tablets. Passages (16, 17) are present to make the infed fuel flow from the inlet (14) over the first metal plate, through a turbulator and over the second metal plate to the outlet (15).