Modeling average gas–solid heat transfer using particle-resolved direct numerical simulation

Abstract

Particle-resolved direct numerical simulation Average fluid temperature equation Two-fluid model Fixed assembly of particles Nusselt number correlation for gas-solid flow a b s t r a c tThe purpose of this work is to develop gas-solid heat transfer models using Particle-resolved Direct Numerical Simulations (PR-DNS). Gas-solid heat transfer in steady flow through a homogeneous fixed assembly of monodisperse spherical particles is simulated using the Particle-resolved Uncontaminated-fluid Reconcilable Immersed Boundary Method (PUReIBM). PR-DNS results are obtained over a range of mean slip Reynolds number (1-100) and solid volume fraction (0.1-0.5). Fluid heating is important in gas-solid heat transfer, especially in dense low-speed flows, and the PUReIBM formulation accounts for this through a heat ratio which appears in the thermal self-similarity boundary condition that ensures thermally fully-developed flow. The average volumetric interphase heat transfer rate (average gas-solid heat transfer) that appears in the average fluid temperature evolution equation is quantified and modeled using PR-DNS results. The Nusselt number corresponding to average gas-solid heat transfer is obtained from PR-DNS data, and compared with Gunn's Nusselt number correlation (Gunn, 1978). A new Nusselt number correlation is proposed that fits the PR-DNS data more closely and also captures the Reynolds number dependence more accurately. It is shown that the use of Nusselt number correlations based on the average bulk fluid temperature in the standard two-fluid model for gas-solid heat transfer is inconsistent, and results in up to 35% error in prediction of the average gas-solid heat transfer. Using PR-DNS data, a consistent two-fluid model is proposed that improves the predicted average gas-solid heat transfer.

Momentum, heat and mass transfer simulations of bounded dense mono-dispersed gas-particle systems

“…The comparison shows that our methodology is fully capable of reproducing the results of Deen et al [33] and Sun et al [32], which are given in terms of an average, and not particle-based, Nusselt number. Discrepancies are observed for (i) high values of Nu (which are, however, outside the range of validity of correlation denoted as Nu DS ), and (ii) for ρ = 2 (see Figure 10a).…”

“…The use of an immersed boundary approach allows to solve the governing equations in a global domain Ω with simple shape (which can be efficiently meshed using a simple Cartesian grid) rather than the highly complex fluid domain Ω f . This is why immersed boundary methods are frequently used in the field of suspension flows, even in case particles are arrested (see, for example in [8] or [32,33,34,35,36,37]). The HFD-IB approach ensures that no errors arise due to highly skewed cells and, most important, it eliminates the effort to build a body-fitted mesh.…”

“…This temperature is different from the temperature available in a PU-EL simulation. A correction was proposed by Sun et al [32] that modifies the above correlation to be consistent with PU-EL:…”

Verification of Heat and Mass Transfer Closures in Industrial Scale Packed Bed Reactor Simulations

“…The models to define intraparticle diffusion [35,38] are given in Equations (3)- (5), while the [18,21,42,43] versus porosity value inside the particle. The comparison is made to Nusselt number from the ideal external heat transfer case without inside particle mesh.…”

CFD Analysis of Gas-Particle Heat Transfer in Gas-Phase Olefin Polymerizations

“…The detailed analysis of the particle proximity effects is beyond the scope of the present work and requires the use of stochastic procedures, because of the fast dynamics of suspended particle arrangements and broad size distributions of suspended polymer particles. [39][40][41][42][43][44][45][46][47][48][49] Previous studies analyzed effects of particle clustering in polymerization media using CFD, [ 10,[24][25][26][27] using some fi xed particle confi gurations to represent the system, which does not seem appropriate for analysis of suspended particles in the pneumatic section of the MZCR reactor. In general, these studies showed that particle clustering can lead to worse heat transfer conditions and to particle temperature rise.…”