Comparison of Two-Phase Porosity Models for High Capacity Random Packing

High capacity random packing is used in absorption applications where a large throughput of gas is required while simultaneously maintaining as low a pressure loss as possible. Utilising computational fluid dynamics to capture the internal flow patterns and transients when designing packed bed towers can be advantageous in respect to expected performance and cost optimisation. However, capturing the direct interaction between gas, liquid and packing is not computationally feasible and therefore the packed bed is modelled as a porous media. In this work four different porosity model are calibrated with idealised equations to data for the high capacity packing IMTP or I-Ring. The different models are evaluated based on their ability to predict pressure loss and liquid holdup in the packed bed. An Eulerian two-phase model with a porous zone representing the packed bed is setup in a cylindrical tower. The CFD results are compared to the predictions of the best performing porosity model. It was found that the best performing model had an absolute mean error of 6.7% when calibrated with the idealised equations. This error increased to 10.5% when the porosity model was implemented into the CFD model

Modelling of hot air chamber designs of a continuous flow grain dryer

The pressure loss, flow distribution and temperature distribution of a number of designs of the hot air chamber in a continuous flow grain dryer, were investigated using CFD. The flow in the dryer was considered as steady state, compressible and turbulent. It is essential that the grain is uniformly dried as uneven drying can result in damage to the end-product during storage. The original commercial design was modified with new guide vanes at the inlets to reduce the pressure loss and to ensure a uniform flow to the line burner in the hot air chamber. The new guide vane design resulted in a 10% reduction in pressure loss and a γ-value of 0.804. Various design changes of the hot air chamber were analysed in terms of pressure loss and temperature distribution with the aim of a temperature variation of ±5 K at the outlet ducts. An obstruction design was analysed, which improved mixing and gave a temperature distribution within the limits. However, the pressure loss was six times larger than the original design with new guide vanes. Finally, The static mixer design resulted in a 23% reduction in the pressure loss, but had a mean absolute deviation of 22.9 K. Keywords: CFD, Fluid flow, Temperature distribution, Uniformity index, Continuous flow dryer, Grid convergence inde

Social isolation and all-cause mortality: a population-based cohort study in Denmark.

Social isolation is associated with increased mortality. Meta-analytic results, however, indicate heterogeneity in effect sizes. We aimed to provide new evidence to the association between social isolation and mortality by conducting a population-based cohort study. We reconstructed the Berkman and Syme's social network index (SNI), which combines four components of social networks (partnership, interaction with family/friends, religious activities, and membership in organizations/clubs) into an index, ranging from 0/1 (most socially isolated) to 4 (least socially isolated). We estimated cumulative mortality and adjusted mortality rate ratios (MRR) associated with SNI. We adjusted for potential important confounders, including psychiatric and somatic status, lifestyle, and socioeconomic status. Cumulative 7-year mortality in men was 11% for SNI 0/1 and 5.4% for SNI 4 and in women 9.6% for SNI 0/1 and 3.9% for SNI 4. Adjusted MRRs comparing SNI 0/1 with SNI 4 were 1.7 (95% CI: 1.1-2.6) among men and 1.6 (95% CI: 0.83-2.9) among women. Having no partner was associated with an adjusted MRR of 1.5 (95% CI: 1.2-2.1) for men and 1.7 (95% CI: 1.2-2.4) for women. In conclusion, social isolation was associated with 60-70% increased mortality. Having no partner was associated with highest MRR