Impact of the oxide scale on spray cooling intensity

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Heat treatment of steel is attended by oxide scales growth with various physical properties. The most common and most dominant impact of the oxide scale layers is on the surface quality and mechanical properties of steel. This paper is focused on study of influence of the oxide scale on cooling intensity. Spray cooling is a typical technique used in heat treatment and other metallurgical processes where controlled temperature regimes are required. Cooling intensity is primarily affected by spray parameters as pressure and coolant impingement density. It is not frequently reported but even thin layers of oxides can significantly modify the cooling intensity. This effect is dominant in the cooling of steel surfaces at high surface temperatures. Study of the influence of the oxide scale layers on cooling intensity was carried out by experimental measurements and numerical analysis. Experimental measurements compare the cooling of scale-free surfaces and oxidized surfaces. Experimental investigations show a difference in the cooling intensity. Numerical analyses were prepared to simulate cooling of the samples with different oxide scale layers and different thermal conductivity of scales. Even a scale layer of several microns can significantly modify the cooling intensity. A low thermal conductivity of the oxides can make the cooling more intensive. The paper provides experimental evidence of this fact and numerical study of the oxide scale layer thickness and thermal conductivity on the influence on the spray cooling with boiling. The Leidenfrost phenomenon and change in surface temperature provides key to the explanation why the hot surface covered by the oxides is sometimes cooled more intensively than the clean surface.cf201

Experimental study of hydraulic descaling

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Experimental work was concentrated on the study of descaling in relation to heat transfer and the quality of removing scale from the surface. Three types of measurements were implemented. The first one is a measurement of impact pressure distribution on spraying surface. The second is a measurement of temperature drop when a product is passing under the nozzle. The third type is a study of the surface quality where a defined layer of oxides is sprayed and its remaining thickness is evaluated. The heat transfer test is evaluated by inverse task and the results are prepared in a form of boundary conditions suitable for using in a numerical model.cs201

Heat treatment of long products

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.An in-line heat treatment of rolled materials is becoming frequently used by hot rolling plants. This method achieves the required material structure without the necessity of reheating. This paper describes a design procedure of cooling sections for obtaining the demanded structure and mechanical properties. Experimental stands, applied for the cooling study of steel samples, were built at the Brno University of Technology. The first experimental stand enables to simulate a variety of cooling regimes and evaluate the final structure of the tested samples which are instrumented by set of thermocouples indicating the temperature history of the tested material. The second experimental stand is a tool for the design of the cooling sections which can ensure obtaining demanded heat treatment procedure and demanded final structure. The heat transfer coefficient history at the surface is gained as an output of the inverse task. Mathematical model and its implementation into the software tool for computer simulation of heat treatment processes (quenching and tempering) of steel is presented. Heat transfer boundary conditions obtained from test on experimental stand are used for calculation of cooling curves followed by prediction of microstructure after austenite transformation and final mechanical properties as hardness, tensile strength and yield stress. The software QTSteel used for computer simulation of heat treatment of long products has been developed by ITA Ltd. Verification and practical examples of metallurgical predictions for long products, especially tubes and bars, are presented."This work is an output of research and scientific activities of this project LO1202 with financial support from the MEYS under the programme NPU I"am201

Regulation of Kainate Receptor Subunit mRNA by Stress and Corticosteroids in the Rat Hippocampus

Kainate receptors are a class of ionotropic glutamate receptors that have a role in the modulation of glutamate release and synaptic plasticity in the hippocampal formation. Previous studies have implicated corticosteroids in the regulation of these receptors and recent clinical work has shown that polymorphisms in kainate receptor subunit genes are associated with susceptibility to major depression and response to anti-depressant treatment. In the present study we sought to examine the effects of chronic stress and corticosteroid treatments upon the expression of the mRNA of kainate receptor subunits GluR5-7 and KA1-2. Our results show that, after 7 days, adrenalectomy results in increased expression of hippocampal KA1, GluR6 and GluR7 mRNAs, an effect which is reversed by treatment with corticosterone in the case of KA1 and GluR7 and by aldosterone treatment in the case of GluR6. 21 days of chronic restraint stress (CRS) elevated the expression of the KA1 subunit, but had no effect on the expression of the other subunits. Similarly, 21 days of treatment with a moderate dose of corticosterone also increased KA1 mRNA in the dentate gyrus, whereas a high corticosterone dose has no effect. Our results suggest an interaction between hippocampal kainate receptor composition and the hypothalamic-pituitary-adrenal (HPA) axis and show a selective chronic stress induced modulation of the KA1 subunit in the dentate gyrus and CA3 that has implications for stress-induced adaptive structural plasticity

Mitochondrial Fragmentation Is Involved in Methamphetamine-Induced Cell Death in Rat Hippocampal Neural Progenitor Cells

Methamphetamine (METH) induces neurodegeneration through damage and apoptosis of dopaminergic nerve terminals and striatal cells, presumably via cross-talk between the endoplasmic reticulum and mitochondria-dependent death cascades. However, the effects of METH on neural progenitor cells (NPC), an important reservoir for replacing neurons and glia during development and injury, remain elusive. Using a rat hippocampal NPC (rhNPC) culture, we characterized the METH-induced mitochondrial fragmentation, apoptosis, and its related signaling mechanism through immunocytochemistry, flow cytometry, and Western blotting. We observed that METH induced rhNPC mitochondrial fragmentation, apoptosis, and inhibited cell proliferation. The mitochondrial fission protein dynamin-related protein 1 (Drp1) and reactive oxygen species (ROS), but not calcium (Ca2+) influx, were involved in the regulation of METH-induced mitochondrial fragmentation. Furthermore, our results indicated that dysregulation of ROS contributed to the oligomerization and translocation of Drp1, resulting in mitochondrial fragmentation in rhNPC. Taken together, our data demonstrate that METH-mediated ROS generation results in the dysregulation of Drp1, which leads to mitochondrial fragmentation and subsequent apoptosis in rhNPC. This provides a potential mechanism for METH-related neurodegenerative disorders, and also provides insight into therapeutic strategies for the neurodegenerative effects of METH

High pressure spray cooling of a moving surface

A novel technique is described for investigating spray cooling of moving hot surfaces. An experimental investigation is described for vertically downwards water sprays impinging on a horizontal steel annulus of 250 mm diameter with a surface temperature up to 600 °C, and rotating at up to 120 rpm, giving a tangential velocity of 1.35 ms–1. The central homogeneous zones of sprays from full-cone atomizers are used at pressures up to 2.07 MPa and the ranges of impacting spray parameters are 0.98 to 12.5 kg m–2 s–1 for mass flux, 49–230 µm for volume median drop diameter, and 9.8–32.3 ms–1 for impinging velocity (Yule, A. J., Sharief, R. A., and Nasr, G. G., 2000, "The Performance Characteristics of Solid Cone Spray Pressure Swirl Atomizers," Ann. Tokyo Astron. Obs., 10(6), pp. 627–646). Time histories of the steel temperature, at positions within the annulus, are presented and analyzed to deduce the transient cooling as the instrumented section of the annulus was swept repeatedly under the spray. Discussion is provided on the physical processes occurring on the basis of the observations. Correlation equations derived to find relationships of surface heat flux with the spray and surface parameters provide further insight into these processes. The results confirm results for static surfaces, that droplet size is a relatively weak parameter, while droplet momentum flux and surface velocity are important. As the surface velocity is increased, peak heat transfer rate at the surface reduces, and its position moves downstream with respect to the spray centerline

Teaching Plyometric Training to Children

The main purpose of this article is to provide practical teaching guidelines and examples of plyometric exercises for children to promote active and healthy lifestyles as well as the development of athletic achievement