Flux thermique et coefficients de transfert global et partiel d'un échangeur à ailettes spiralées en graphite

Abstract

Heat flux and global and partial heat transfer coefficient in an exchanger with helicoidal graphite fins. A new evaporation technique consists of letting a stream of liquid flow along an helicoidally fins. The fins that are rolled in spirals around a heated vertical tube through with a hot fluid is circulated. The tube and fins are manufactured one bloc of impregnated graphite. Because of the great complexity of the geometry of this exchanger and the flow on its fins. the determination of he thermal transfer coefficient by external convection is difficult to obtain by a direct calculation. It is indirectly determined here by Wilson's method which is based on two stages: one is experimental and the other is theoretical. In this article, we determine the quantity of exchanged heat and the coefficient global of the thermal transfer of this exchanger/evaporator during the heating, also, we determine the different partial resistances during the heating, as well as the coefficient of convection between the external wall of the fin and the solution to heat. The procedure, proposed in this work, has allowed to validate the equation proposed by Wilson.