Effect of the weather conditions on natural convection in storage silo

摘要

In this paper, unsteady natural convection problem in vertical open ended, and porous cylinder has been investigated numerically to simulate the transient heat mass convection in the grain storage in silos. A varying temperature profile is imposed on the lateral wall of the enclosure. Time-dependent boundary temperature is presented as sinusoidal function which can approximate real weather conditions. In the case of constant temperature a map diagram (Ra, A, N, Ak) of the two observed flow types, with and without fluid recirculation, was obtained. In order to approve that heat transfers are dependents of reversal flow and control parameters, the phase diagrams connecting heat transfer (Nu) to the recirculation flow rate (Qr) was proposed. The observed relative difference between sinusoidal and constant wall temperature increases with increasing Rayleigh number (Ra), dimensionless temperature amplitudes (XA) and it is particularly sensitive to the values of buoyancy ratio (N).