Momentum, heat, and mass transfer analogy for vertical hydraulic transport of inert particles

Abstract

Wall-to-bed momentum, heat and mass transfer in the vertical liquid-solids flow, as well as in the single phase flow, were studied. The aim of this investigation was to establish the analogy among those phenomena. Also, effect of particle concentration on momentum, heat and mass transfer was studied. The experiments in hydraulic transport were performed in 25.4 mm I.D. cooper tube equipped with a steam jacket, using spherical glass particles of 1.94 mm in diameter and water as a transport fluid. The segment of the transport tube used for mass transfer measurements had internal coating made of benzoic acid. In the hydraulic transport two characteristic flow regimes were observed: turbulent and parallel particle flow regime. The transition between two characteristic regimes (Y* = 0), occurs at a critical voidage ε ≈ 0.85. The vertical two-phase flow was con­sidered as the pseudofluid, and modified mixture-wall friction coefficient (fw) and modified mixture Reynolds number (Rem) were introduced for system characterization. Experimental data show that the wall-to-bed momentum, heat and mass transfer coefficients, in vertical flow of pseudofluid, for the turbulent regime are significantly higher than in parallel regime. Wall-to-bed, mass and heat transfer coefficients in hydraulic transport of particles were much higher than in single-phase flow for lower Reynolds numbers (Re lt 15000), while for high Reynolds numbers (Re gt 15000), there was not significant difference. The experimental data for wall-to-bed momentum, heat and mass transfer in vertical flow of pseudofluid in parallel particle flow regime, verify analogy among these three phenomena.

U ovom radu prikazani su rezultati eksperimentalnih ispitivanja prenosa količine kretanja, toplote i mase zid-fluid u vertikalnom hidrauličkom transportu inertnih čestica i pri strujanju fluida u cevi istog prečnika. Eksperimentalna ispitivanja vršena su istovremenim merenjem potrebnih parametara za definisanje navedenih prenosa. Cilj ovih ispitivanja bio je određivanje koeficijenata prenosa pri vertikalnom hidrauličkom transportu inertnih čestica i uspostavljanje analogije tri prenosa. Eksperimentalni sistem predstavljala je vertikalna transportna cev prečnika 25,4 mm snabdevena omotačem za zagrevanje parom, kao i segmentom transportne cevi prepariranim rastopom benzoeve kiseline. Kao fluid korišćena je voda, a vršen je transport staklenih sfernih čestica prečnika 1,94 mm. U rezultatima su prikazani dobijeni koeficijenti trenja, prelaza toplote i prelaza mase. Korišćenjem koncepta pseudofluida, pokazano je postojanje analogije prenosa količine kretanja, toplote i mase u transportnoj cevi za paralelni režim strujanja.