Current passage tubes in conductive polymer composite for fluid heating

This communication reports the design and testing of a tubular heat exchanger in conductive polymer composites (CPC) using the ohmic effect (current passage tube). The weak inertia and the good thermal efficiencies of such a device are fully suitable for water or thermo-sensitive products heating. The materials of the extruded tubes are obtained by blending an insulating thermoplastic polymer matrix with a conductive filler like carbon black nano particles. The electrical resistivity of the composite can be adjusted by the nature and content of the filler. Consequently, an electrical transformer is no longer needed for the electrical input of the heat exchanger. The results presented deal with two different poly(propylene) tubes. The first one is filled with carbon black only, whereas short carbon fibres are added in the second one. First, the effect of the filler content on the electrical and thermal conductivities is quantified. Then, the coupling of the electrical and thermal phenomena is studied. Experimental tests, performed with and without water flow inside the tubes, were completed on a device developed in our laboratory. These experiments were performed under direct current to show the thermal and electrical behaviours of the tubes. The numerical simulation of the temperature profile in the thickness of the pipes corresponds well with the experimental results.