Estimation of Heat Transfer Coefficient from Universal Expression of Tangential Velocity at Boundary Layer Edge on Side Wall of a Fully Turbulent Agitated Vessel

Abstract

The heat transfer coefficient at side wall of a fully turbulent agitated vessel h was estimated from the universal expression of the tangential velocity at boundary layer edge, and it was shown that the estimated value of the heat transfer coefficient coincided well with the experimental one. Besides this, from the relation of the power consumption per unit volume P_v to the average shear stress at side wall of an agitated vessel τ_w, it was derived that the variable (h/ρc_pv_θ)Pr^2/3 containing the heat transfer coefficient h was proportional to the characteristic turbulent velocity (P_vν/ρ)^1/4, where the value of the proportional constant {(f³Re_G)^1/4/1.48m} calculated from the universal expression of the tangential velocity at side wall of an agitated vessel was almost constant at 1.5 for wide ranges of both impeller similarity parameter X and generalized Reynolds number Re_G. The value 1.5 was nearly equal to 0.13 the proportional constant of the correlation proposed by Calderbank and MooYoung. From the discussion of the local value of momentum flux at vessel wall, it was shown that the heat transfer coefficient at baffled agitated vessel was correlated with the same correlation form as that at non-baffled agitated vessel, though the proportional constant was slightly smaller than that for a non-baffled vessel.