Numerical study of turbulent heat transfer in 3D pin-fin channels: Validation of a quick procedure to estimate mean values in quasi-periodic flows

Pin-fin heat exchangers are widely used and there is an increasing interest in the design of compact units. This work investigated the prediction of the heat transfer rate in pin-fin channel flows using numerical simulation, considering pins of cylindrical geometry in aligned and staggered arrangements. The simulations were performed using the Reynolds-averaged Navier–Stokes equations together with the shear stress transport turbulence model. The main purpose of this work was to develop and validate a quick numerical procedure to evaluate the heat transfer rate in pin-fin channel flows using their quasi-steady behavior. The procedure was validated by comparing the mean Nusselt number results with time-averaged Nusselt numbers obtained from transient simulations. It was also shown that these values are in good agreement with available experimental data. This procedure could determine the overall mean Nusselt number up to 25 times faster. The importance of the quasi-steady flow behavior on the heat transfer was also quantified.     

The influence of shock-type vibrations on the absorption of mechanical energy in the hand and arm

In recent years there has been a discussion as to whether shock-type vibration from hand tools has stronger effects on the hand-arm system in comparison with non-impulsive vibration. The purpose of the investigation is to compare the influence of these two types of vibration on the absorption of mechanical energy in the human hand and on the grip and feed forces applied by the subjects.

The energy absorption has been measured by use of a specially designed laboratory handle. The grip and feed forces applied by the subject to the handle were measured simultaneously. In the study two different frequency weighted acceleration levels were used.

The outcome showed that the vibration exposure levels made a significant contribution to the vibration absorption as well as to the strength of the grip and feed forces. Moreover, it was found that the hand forces decrease while the absorption of energy increases during the experiment. Furthermore, the influence of shock-type exposure gave a significantly higher hand forces and absorption of energy compared with the non-impulsive exposure. It was, therefore, concluded that the vibration response characteristics of the hand and arm differ, depending upon whether the exposure is of shock or non-impulsive type.

Relevance to industry

The paper discusses the dynamic response of the hand and arm during exposure to shock and non-impulsive vibration. Whenever possible, a tool that requires low grip and feed forces should be used as well as tools that not generate shock-type excitation. This can be helpful in choosing the proper tool for the job.     

Inhibition of Carbonic Anhydrase IX Suppresses Breast Cancer Cell Motility at the Single-Cell Level

Protein Carbonic Anhydrase IX (CA IX), which is expressed in various hypoxic solid tumors in order to maintain proper pH, is also related to cancer cell adhesion, invasion, and metastasis processes. Here, we investigated whether CA IX inhibition by a highly CA IX selective agent benzenesulfonamide VD11-4-2 triggers changes in individual cell motility. We seeded breast cancer cells on an extracellular matrix-coated glass-bottomed dish and in a microfluidic device with a gradient flow of epidermal growth factor (EGF), tracked individual cell movement, calculated their migration speeds, and/or followed movement direction. Our results showed that the inhibitor VD11-4-2 decreased the speed of CA IX positive breast cancer cells by 20–26% while not affecting non-cancerous cell migration. The inhibitor suppressed the cell migration velocity increment and hindered cells from reaching their maximum speed. VD11-4-2 also reduced CA IX, expressing cell movement towards the growth factor as a chemoattractant. Such a single cell-based migration assay enabled the comprehensive investigation of the cell motility and revealed that VD11-4-2 shows the ability to suppress breast cancer cell migration at a lower concentration than previously tested CA IX inhibitors.     

The influence of stirring method on hydrogen removal during ladle treatment

A mathematical model based on fundamental transport equations for vacuum degassing in an Asea‐SKF ladle furnace was developed earlier and predicted hydrogen values from the model were found to agree well with experimental measurements from plant trials. In the present study, the mathematical model was used to predict the hydrogen removal for four different stirring methods: 1–2) combined gas and induction stirring with the inductive stirrer working upwards or downwards and 3–4) gas stirring with two different locations for two porous plugs. Plant data was used as input to the calculations. The hydrogen calculation was validated by simulation of an actual heat and comparison with measured data. After 44 minutes of stirring the predicted and measured hydrogen contents were 1.6 and 1.8 ppm, respectively. This agreement was considered satisfactory and the model was then used to study the effect of different stirring methods on hydrogen refining. A change in the stirring method was found to affect the hydrogen refining. Combined gas and induction stirring using downward stirring was found to result in the lowest final hydrogen content in the steel as it rendered the most favourable kinetic conditions for hydrogen refining.     

Modelling of the Steel/Slag Interface in a Continuous Casting Tundish

It is very important to understand the underlying physical phenomena at the steel/slag interface in a continuous casting tundish in order to control reoxidation and deoxidation phenomena that can occur. Aiming to investigate probable sources of exogenous inclusions originating from the covering slag, an existing mathematical model of the tundish was augmented to include key physical parameters needed for the prediction of the physical behaviour of steel/slag mixing phenomena. Results showed a recirculation flow in the inlet region to be responsible for both the entrainment of steel drops into the slag and slag fragments into the steel. The highest concentration of slag in the steel was found to be in the area behind the inlet where slag fragment sizes are smaller due to a high degree of turbulent energy dissipation. Likewise, higher concentrations of steel in the slag, consisting of smaller steel droplets, were only found in the inlet region and along the walls. The results indicate that only small slag fragments of approximately 10‐50 microns from the covering slag reach the outlet.     

Scaling laws in network models: porous medium property prediction during morphological evolution

A 3-D network model was used to represent a porous medium and the macroscopic properties of the network (like permeability) were simulated by Monte Carlo method. It was shown that these macroscopic properties can be related to network parameters (throat-size distribution parameters, network size and connectivity) through power law correlations, as can be inferred from percolation theory. In this way, macroscopic properties evaluation during the morphological evolution of a 3-D network requires less computational effort, which facilitates the incorporation of this model into oil flow simulators.     

Nonaplex real-time PCR detection of Listeria monocytogenes, Campylobacter, Salmonella and enteropathogene E. coli after universal enrichment in food samples

A universal cultivation media for Listeria monocytogenes, Salmonella and enteropathogenic Escherichia coli in conjunction with a highly efficient nonaplex PCR for the determination of L. monocytogenes, Campylobacter, Salmonella and enteropathogenic E. coli was developed and compared to classical microbiological assays. The achieved detection limit was at 2 colony-forming units per g for all analytes. The method allows screening of food samples within 24 h and is partly automatable. A ring trial showed that it can be easily established in other laboratories showing its robustness. The presented method yields results similar to the classical ISO methods based on cultivation.