Numeric modeling of a compact high temperature heat exchanger

The numeric investigations of a high temperature compact gas/gas heat exchanger are shown in this paper. The results of the numeric modelling and their analysis for two different simulation models with and without the regards of the development of the velocity field are presented in the article. The results have been obtained for two different geometries one of which is the two semi-channels model and second of which regards the heat transfer through the heat exchanger volume. The article presents the comparison of the model solutions with the evaluation of the received reliability results. The comparison between the simulations and experimental results are presented too. On the base of the second numeric model the two-dimensional simulation task with the regard of the inlet and outlet volume before and after the heat exchanger was developed. The influence of the change of the channel sizes on the hydraulic and thermal characteristics of the researched heat exchanger is shown. The solution of this two dimensional model confirms the inhomogeneous distribution of the hydraulic and thermal fields in the heat exchanger. The obtained results were analyzed with the conclusions and further investigations complete the represented results. “COMSOL-Multiphysics” was used for the numeric simulation

Numerical investigations of advanced volumetric reseiver materials

This paper presents the results of a numerical analysis of the mass transport and the heat flow through a volumetric solar receiver as a candidate component for a central receiver system for solar electricity generation. The receiver investigated was an extruded honeycomb structure made out of Silicon carbide. The objective of the study is to investigate the influence of slight geometric changes on to the overall performance of the receiver. The results are compared with those of an experimental study. Two numerical models have been developed. One makes use of the real geometry of the channel (single channel model), the other one considers the receiver to be “porous continuum”, which described with homogenized properties such as permeability and effective heat conductivity. The experimental parameters such as average solar heat flux and mass flow were taken into account in the models as boundary conditions. Various parameters such as the average air outlet temperatures, the temperature distributions and the solar-to-thermal efficiency were used for the comparison. The good correspondence between the experimental and numeric results of the both numeric investigations confirms the usefulness of the approach for further studies

High performance solar receiver-reactor for solar hydrogen generation

This paper reports on the numerical analysis of a volumetric solar receiver-reactor for hydrogen production, using the 2-step reduction–oxidation cycle. A detailed parametric sweep covering hundreds of various parameter combinations is performed for a large solar reactor, using a transient physical model. We generate performance maps which are currently cost prohibitive via experimental or high–fidelity simulation studies. The following performance metrics are evaluated: solar to fuel efficiency, hydrogen yield, conversion extent and specific hydrogen yield. We show that the relations between the different performance metrics are complex, leading to different optimal points depending on the metric pursued. The daily hydrogen yield for a single reactor varied between 0.89 kg for an absorber thickness of 30 mm, and up to 1.04 kg for a 60 mm thick receiver, with solar to fuel efficiency values of 3.84% and 3.81% respectively. For a case with 45 mm thick receiver, an intermediate hydrogen yield of 0.94 kg is calculated, while exhibiting the highest efficiency (4.05%). The efficiency can be further increased to 5.86% by using a simple heat recovery system, and reach an upper limit of 21.16% with a more sophisticated heat recovery method

Aluminium dross/ soda lime glass waste-derived high-quality glass foam

This work introduces for the first time the use of waste aluminium dross obtained from the aluminium industry as a foaming agent to produce sustainable foam glasses from soda-lime glass powders derived from the lapping machine. The resulting foam briquettes (8ⅹ8ⅹ8 cm3) have a crack-free, 3-D cellular structure with closed pores whose geometries varied between elliptical-, pentagonal-, and hexagonal-shaped constructions. These glass foams demonstrate a lightweight (≥0.28 g/cm3), high CCS (≤12 MPa), low thermal conductivity (0.11–0.21 W/m-K), and contain more than ∼ 85 vol.% gas bubbles enclosed between 15 vol.% impervious glass walls. These properties are in line with the requirements of the international standard for commercial glass foams, revealing their strong capability to be used in potential applications in sustainable buildings and energy efficiency in the industry

Abnormal Brain Iron Metabolism in Irp2 Deficient Mice Is Associated with Mild Neurological and Behavioral Impairments

Iron Regulatory Protein 2 (Irp2, Ireb2) is a central regulator of cellular iron homeostasis in vertebrates. Two global knockout mouse models have been generated to explore the role of Irp2 in regulating iron metabolism. While both mouse models show that loss of Irp2 results in microcytic anemia and altered body iron distribution, discrepant results have drawn into question the role of Irp2 in regulating brain iron metabolism. One model shows that aged Irp2 deficient mice develop adult-onset progressive neurodegeneration that is associated with axonal degeneration and loss of Purkinje cells in the central nervous system. These mice show iron deposition in white matter tracts and oligodendrocyte soma throughout the brain. A contrasting model of global Irp2 deficiency shows no overt or pathological signs of neurodegeneration or brain iron accumulation, and display only mild motor coordination and balance deficits when challenged by specific tests. Explanations for conflicting findings in the severity of the clinical phenotype, brain iron accumulation and neuronal degeneration remain unclear. Here, we describe an additional mouse model of global Irp2 deficiency. Our aged Irp2−/− mice show marked iron deposition in white matter and in oligodendrocytes while iron content is significantly reduced in neurons. Ferritin and transferrin receptor 1 (TfR1, Tfrc), expression are increased and decreased, respectively, in the brain from Irp2−/− mice. These mice show impairments in locomotion, exploration, motor coordination/balance and nociception when assessed by neurological and behavioral tests, but lack overt signs of neurodegenerative disease. Ultrastructural studies of specific brain regions show no evidence of neurodegeneration. Our data suggest that Irp2 deficiency dysregulates brain iron metabolism causing cellular dysfunction that ultimately leads to mild neurological, behavioral and nociceptive impairments

Evolution of Neuronal and Endothelial Transcriptomes in Primates

The study of gene expression evolution in vertebrates has hitherto focused on the analysis of transcriptomes in tissues of different species. However, because a tissue is made up of different cell types, and cell types differ with respect to their transcriptomes, the analysis of tissues offers a composite picture of transcriptome evolution. The isolation of individual cells from tissue sections opens up the opportunity to study gene expression evolution at the cell type level. We have stained neurons and endothelial cells in human brains by antibodies against cell type-specific marker proteins, isolated the cells using laser capture microdissection, and identified genes preferentially expressed in the two cell types. We analyze these two classes of genes with respect to their expression in 62 different human tissues, with respect to their expression in 44 human “postmortem” brains from different developmental stages and with respect to between-species brain expression differences. We find that genes preferentially expressed in neurons differ less across tissues and developmental stages than genes preferentially expressed in endothelial cells. We also observe less expression differences within primate species for neuronal transcriptomes. In stark contrast, we see more gene expression differences between humans, chimpanzees, and rhesus macaques relative to within-species differences in genes expressed preferentially in neurons than in genes expressed in endothelial cells. This suggests that neuronal and endothelial transcriptomes evolve at different rates within brain tissue

Clinical relevance of molecular characteristics in Burkitt lymphoma differs according to age

While survival has improved for Burkitt lymphoma patients, potential differences in outcome between pediatric and adult patients remain unclear. In both age groups, survival remains poor at relapse. Therefore, we conducted a comparative study in a large pediatric cohort, including 191 cases and 97 samples from adults. While TP53 and CCND3 mutation frequencies are not age related, samples from pediatric patients showed a higher frequency of mutations in ID3, DDX3X, ARID1A and SMARCA4, while several genes such as BCL2 and YY1AP1 are almost exclusively mutated in adult patients. An unbiased analysis reveals a transition of the mutational profile between 25 and 40 years of age. Survival analysis in the pediatric cohort confirms that TP53 mutations are significantly associated with higher incidence of relapse (25 ± 4% versus 6 ± 2%, p-value 0.0002). This identifies a promising molecular marker for relapse incidence in pediatric BL which will be used in future clinical trials