An investigation of worn work roll materials used in the finishing stands of the hot strip mill for steel rolling

The surface failure characteristics of different work roll materials, i.e. High Speed Steel, High Chromium Iron and Indefinite Chill Iron, used in the finishing stands of a hot strip mill have been investigated using stereo microscopy, 3D optical profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the surface failure mechanisms of work rolls for hot rolling are very complex, involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation. Despite the differences in chemical composition and microstructure, the tribological response of the different work roll materials was found to be strongly dependent on the material microstructure and especially the presence and distribution of microstructural constituents, such as the different carbide phases and graphite (in the case of Indefinite Chill Iron). Cracking and chipping of the work roll surfaces, both having a negative impact on work roll wear, are strongly influenced by the presence of carbides, carbide networks and graphite in the work roll surface. Consequently, the amount of carbide forming elements as well as the manufacturing process must be controlled in order to obtain an optimised microstructure and a predictable wear rate.

Energy Efficiency through Thermal Energy Storage : Possibilities for the Swedish Building Stock

The need for heating and cooling in buildings constitutes a considerable part of the total energy use in a country and reducing this need is of outmost importance in order to reach national and international goals for reducing energy use and emissions. One important way of reaching these goals is to increase the proportion of renewable energy used for heating and cooling of buildings. Perhaps the largest obstacle with this is the often occurring mismatch between the availability of renewable energy and the need for heating or cooling, hindering this energy to be used directly. This is one of the problems that can be solved by using thermal energy storage (TES) in order to save the heat or cold from when it is available to when it is needed. This thesis is focusing on the combination of TES techniques and buildings to achieve increased energy efficiency for heating and cooling. Various techniques used for TES as well as the combination of TES in buildings have been investigated and summarized through an extensive literature review. A survey of the Swedish building stock was also performed in order to define building types common in Sweden. Within the scope of this thesis, the survey resulted in the selection of three building types, two single family houses and one office building, out of which the two residential buildings were used in a simulation case study of passive TES with increased thermal mass (both sensible and latent). The second case study presented in the thesis is an evaluation of an existing seasonal borehole storage of solar heat for a residential community. In this case, real measurement data was used in the evaluation and in comparisons with earlier evaluations. The literature reviews showed that using TES opens up potential for reduced energy demand and reduced peak heating and cooling loads as well as possibilities for an increased share of renewable energy to cover the energy demand. By using passive storage through increased thermal mass of a building it is also possible to reduce variations in the indoor temperature and especially reduce excess temperatures during warm periods, which could result in avoiding active cooling in a building that would otherwise need it. The analysis of the combination of TES and building types confirmed that TES has a significant potential for increased energy efficiency in buildings but also highlighted the fact that there is still much research required before some of the technologies can become commercially available. In the simulation case study it was concluded that only a small reduction in heating demand is possible with increased thermal mass, but that the time with indoor temperatures above 24 °C can be reduced by up to 20%. The case study of the borehole storage system showed that although the storage system worked as planned, heat losses in the rest of the system as well as some problems with the system operation resulted in a lower solar fraction than projected. The work presented within this thesis has shown that TES is already used successfully for many building applications (e.g. domestic hot water stores and water tanks for storing solar heat) but that there still is much potential in further use of TES. There are, however, barriers such as a need for more research for some storage technologies as well as storage materials, especially phase change material storage and thermochemical storage.

Thermal energy storage in Swedish single family houses : a case study

In a Nordic climate, space heating (SH) and domestic hot water (DHW) used in buildings constitute a considerable part of the total energy use in the country. For 2010, energy used for SH and DHW amounted to almost 90 TWh in Sweden which corresponds to 60 % of the energy used in the residential and service sector, or almost 24 % of the total final energy use for the country. Storing heat and cold with the use of thermal energy storage (TES) can be one way of increasing the energy efficiency of a building by opening up possibilities for alternative sources of heat or cold through a reduced mismatch between supply and demand. Thermal energy storage without the use of specific control systems are said to be passive and different applications using passive TES have been shown to increase energy efficiency and/or reduce power peaks of systems supplying the heating and cooling needs of buildings, as well as having an effect on the indoor climate. Results are however not consistent between studies and focus tend to be on the reduction of cooling energy or cooling power peaks. In this paper, passive TES introduced through an increased thermal mass in the building envelope to two single family houses with different insulation standard is investigated with building energy simulations. A Nordic climate is used and the focus of this study is both on the reduction of space heating demand and space heating power, as well as on reduction of excess temperatures in residential single family houses without active cooling systems. Care is taken to keep the building envelope characteristics other than the thermal mass equal for all cases so that any observations made can be derived to the change in thermal mass. Results show that increasing the sensible thermal mass in a single family house can reduce the heating demand only slightly (1-4 %) and reduce excess temperatures (temperatures above 24 degrees C) by up to 20 %. Adding a layer of PCM (phase change materials) to the light building construction can give similar reduction in heating demand and excess temperatures, however the phase change temperature is important for the results.

Evaluation of a high temperature solar thermal seasonal borehole storage

A solar thermal system with seasonal borehole storage for heating of a residential area in Anneberg, Sweden, approximately 10 km north of Stockholm, has been in operation since late 2002. Originally, the project was part of the EU THERMIE project “Large-scale Solar Heating Systems for Housing Developments” (REB/0061/97) and was the first solar heating plant in Europe with borehole storage in rock not utilizing a heat pump. Earlier evaluations of the system show lower performance than the preliminary simulation study, with residents complaining of a high use of electricity for domestic hot water (DHW) preparation and auxiliary heating. One explanation mentioned in the earlier evaluations is that the borehole storage had not yet reached “steady state” temperatures at the time of evaluation. Many years have passed since then and this paper presents results from a new evaluation. The main aim of this work is to evaluate the current performance of the system based on several key figures, as well as on system function based on available measurement data. The analysis show that though the borehole storage now has reached a quasi-steady state and operates as intended, the auxiliary electricity consumption is much higher than the original design values largely due to high losses in the distribution network, higher heat loads as well as lower solar gains.

Economic Evaluation of a Solar Charged Thermal Energy Store for Space Heating

A thermal energy store corrects the misalignment of heating demand in the winter relative to solar thermal energy gathered in the summer. This thesis reviews the viability of a solar charged hot water tank thermal energy store for a school at latitude 56.25N, longitude -120.85W

Estudo ergonômico sobre o calor

O calor, no ambiente onde o ser humano vive ou trabalha, atribui-se a: -fatores físicos: relação entre temperatura, radiação, umidade e movimento do ar; fatores humanos: o ser humano atua como fonte de energia através de seu metabolismo e atividade física. o calor caracterizado por um determinado meio ambiente é o resultado da atuação de diferentes variáveis, tais como: sistema de construção, situação geográfica do ambiente físico, climatização artificial, etc.; idade, sexo, capacidade física, estado de aclimatação, vestuário, tipo, carga e regime de trabalho, etc. A partir do momento em que o indivíduo for introduzido num determinado meio ambiente térmico, todos estes fatores vão influenciar a transmissão de calor entre ele e o ambiente. Na pretensão de haver equilíbrio térmico no meio ambiente quente, constata-se a necessidade de providenciar medidas de proteção a nível do sujeito e do ambiente, para que prevaleçam situações ambientais "confortáveis", ou pelo menos, "tolerantes". Desse modo, através da: definição das condições térmicas tolerantes e de conforto, parte-se para projetar meios ambientes de trabalho, que tornem praticáveis um isolamento térmico do calor exterior, assim como a perda de calor de dentro para fora. Atuando-se sobre variáveis individuais e ambientais estaremos incidindo diretamente sobre os meios de transmissão, procurando-se diminuir a quantidade de calor que o organismo produz e/ou recebe e aumentar a possibilidade de dissipá-lo.

Análise da indução de fluxo de ar por convecção livre em chaminé solar

Experiments were performed to study the effect of surface properties of a vertical channel heated by a source of thermal radiation to induce air flow through convection. Two channels (solar chimney prototype) were built with glass plates, forming a structure of truncated pyramidal geometry. We considered two surface finishes: transparent and opaque. Each stack was mounted on a base of thermal energy absorber with a central opening for passage of air, and subjected to heating by a radiant source comprises a bank of incandescent bulbs and were performed field tests. Thermocouples were fixed on the bases and on the walls of chimneys and then connected to a data acquisition system in computer. The air flow within the chimney, the speed and temperature were measured using a hot wire anemometer. Five experiments were performed for each stack in which convective flows were recorded with values ranging from 17 m³ / h and 22 m³ / h and air flow velocities ranging from 0.38 m / s and 0.56 m / s for the laboratory tests and air velocities between 0.6 m/s and 1.1m/s and convective airflows between 650 m³/h and 1150 m³/h for the field tests. The test data were compared to those obtained by semi-empirical equations, which are valid for air flow induced into channels and simulated data from 1st Thermodynamics equation. It was found that the chimney with transparent walls induced more intense convective flows than the chimney with matte finish. Based on the results obtained can be proposed for the implementation of prototype to exhaust fumes, mists, gases, vapors, mists and dusts in industrial environments, to help promote ventilation and air renewal in built environments and for drying materials, fruits and seeds

Thermal characterization of solid lipid nanoparticles containing praziquantel

Solid lipid nanoparticles (SLNs), loaded and unloaded with praziquantel (PRZ-load SLN and PRZ-unload SLN) were prepared by two different procedures: (a) oil-in-water hot microemulsion method, obtaining at 70 degrees C an optically transparent blend composed of surfactant, co-surfactant, and water; and (b) oil-in-water microemulsion method, dissolving the lipid in an immiscible organic solvent, emulsified in water containing surfactants and co-surfactant, and then evaporated under reduced pressure at 50 degrees C. The mean diameter, polydispersity index (PdI), and zeta potential were 187 to 665 nm, 0.300 to 0.655, and -25 to -28 mV respectively, depending on the preparation method. The components, binary mixture, SLNs loaded and unloaded with PRZ, and physical mixture were evaluated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The non-isothermal isoconversional Flynn-Wall-Ozawa method was used to determine the kinetic parameters associated with the thermal decomposition of the samples. The experimental data indicated a linear relationship between the apparent activation energy E and the pre-exponential factor A, also called the kinetic compensation effect (KCE), allowing us to determine the stability with respect to the preparation method. Loading with PRZ increased the thermal stability of the SLNs.

Refrigerator COP with thermal storage

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Electricity, hot water and cold water production from biomass. Energetic and economical analysis of the compact system of cogeneration run with woodgas from a small downdraft gasifier

Wood gasification technologies to convert the biomass into fuel gas stand out. on the other hand, producing electrical energy from stationary engine is widely spread, and its application in rural communities where the electrical network doesn't exist is very required. The recovery of exhaust gases (engine) is a possibility that makes the system attractive when compared with the same components used to obtain individual heat such as electric power. This paper presents an energetic alternative to adapt a fixed bed gasifier with a compact cogeneration system in order to cover electrical and thermal demands in a rural area and showing an energy solution for small social communities using renewable fuels. Therefore, an energetic and economical analysis from a cogeneration system producing electric energy, hot and cold water, using wooden gas as fuel from a small-sized gasifier was calculated. The energy balance that includes the energy efficiency (electric generation as well as hot and cold water system; performance coefficient and the heat exchanger, among other items), was calculated. Considering the annual interest rates and the amortization periods, the costs of production of electrical energy, hot and cold water were calculated, taking into account the investment, the operation and the maintenance cost of the equipments. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

Mate attenuates DNA damage and carcinogenesis induced by diethylnitrosamine and thermal injury in rat esophagus

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural and thermal characterization of dioctadecyldimethylammonium bromide dispersions by spin labels

Dioctadecyldimethylammonium bromide (DODAB) dispersions obtained by simply mixing the amphiphile in water, and by bath-sonication, were investigated by electron spin resonance (ESR) of stearic acids and their methyl ester derivatives, labeled at the 5th and 16th carbons of the acyl chain. The ESR spectra indicate that the non-sonicated dispersions are formed mainly by one population of DODAB vesicles, either in the gel (T < T-m) or in the liquid-crystalline (T > T-m) state. Around T-m there is a co-existence of the two phases, with a thermal hysteresis of about 3.2 degreesC. In sonicated DODAB dispersions, spin labels indicate two different environments even for temperatures far below T-m: one similar to that obtained with non-sonicated samples, a gel phase, and another one in the liquid-crystalline state. The fluid phase domain present below T-m could correspond to either the periphery of bilayer fragments, reported to be present in sonicated DODAB dispersions, or to high curvature vesicles. (C) 2001 Elsevier B.V. Ireland Ltd. All rights reserved.

Cr3C2-NiCr and WC-Ni thermal spray coatings as alternatives to hard chromium for erosion-corrosion resistance

Cr3C2-NiCr and WC-Ni coatings are widely used for wear applications at high and room temperature, respectively. Due to the high corrosion resistance of NiCr binder, Cr3C2-NiCr coatings are also used in corrosive environments. The application of WC-Ni coatings in corrosive media is 14 not recommended due to the poor corrosion resistance of the (pure Ni) metallic matrix. It is well known that the addition of Cr to the metallic binder improves the corrosion properties. Erosion-corrosion performance of thermal spray coatings is widely influenced by ceramic phase composition, the size of ceramic particles and also the composition of the metallic binder. In the present work, two types of HVOF thermal spray coatings (Cr3C2-NiCr and WC-Ni) obtained with different spray conditions were studied and compared with conventional micro-cracked hard chromium coatings. Both as-sprayed and polished samples were tested under two erosion-corrosion conditions with different erosivity. Tungsten carbide coatings showed better performance under the most erosive condition, while chromium carbide coatings were superior under less erosive conditions. Some of the tungsten carbide coatings and hard chromium showed similar erosion-corrosion behaviour under more and less erosive conditions. The erosion-corrosion and electrochemical results showed that surface polishing improved the erosion-corrosion properties of the thermally sprayed coatings. The corrosion behaviour of the different coatings has been compared using Electrochemical Impedance Spectroscopy (EIS) and polarization curves. Total material loss due to erosion-corrosion was determined by weight loss measurements. An estimation of the corrosion contribution to the total weight loss was also given. (c) 2007 Elsevier B.V. All rights reserved.

Image analysis for assessing broiler breeder behavior response to thermal environment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal degradation of geomembranes after exposure to heat

HDPE and PVC geomembranes are sensitive to changes in their properties when in contact with high temperatures. The effects of hot temperature on polymeric geomembranes are assessed by the ASTM D794 and ASTM D5721.This paper brings an analysis of degradation of the Poly Vinyl Chloride (PVC) and High Density Poly Ethylene (HDPE) geomembranes when exposed to conventional and air oven after specific periods.. Mechanical and physical properties were evaluated. OIT tests were also performanced to evaluate the level of oxidation degradation occurred on the HDPE geomembranes. Geomembranes of two thicknesses were tested: 1.0, 2.0 nun (PVC) and 0.8, 2.5 mm, (HDPE). The results obtained show, for example, that after the last period of exposure, the PVC geomembranes (1.0, 2.0 mm) were more rigid and stiffer than fresh samples. The HDPE geomembranes, on the other hand, when exposed to heat presented increases in deformation. OIT tests showed efficient to detect some level of degradation on the HDPE geomembranes.