A STUDY OF THE DEPOSITION OF FINE PARTICLES IN COMPACT PLATE FIN HEAT-EXCHANGERS

The main purpose of this study was to investigate the performance of p lain fin heat exchangers (PFHE) under particulate fouling for a wider application potential. A simulated PFHE was subjected to accelerated f ouling tests with aluminium oxide (6 mu m) and ferric oxide (3 mu m) p articles suspended in water. Both plain fin and wavy fin corrugations were used. Experimental tests were performed under non-heating (30 deg rees C) and heating (105 degrees C) conditions. In all tests, the depo sition/time curves showed an asymptotic behaviour. Deposition rates we re higher under heated conditions. Under isothermal conditions, the de position appeared to be governed by mass transfer from the bulk suspen sion to the wall surfaces and the particle deposition was mainly due t o the effect of Brownian diffusion. The theoretical predictions of mas s transfer coefficients from a convective mass transfer correlation we re in general in reasonable agreement with the mass transfer coefficie nts obtained from experimental data. The effect of surface temperature was to increase the bulk temperature, therefore the diffusivity of th e depositing species. Increasing the bulk temperature from 8 degrees C to 60 degrees C also increased the deposition rate. The wavy fin heat exchanger showed higher deposit weights compared with the plain fin a nd the pressure drop was also higher. Increasing the fluid flow veloci ty (Re up to 2500), increased the deposit weight onto the plain lin ge ometry. For the wavy fin geometry, beyond Re > 1500, the deposit weigh t started to decrease.