Cooler Regime Research Articles

Effects of High Temperature and Cooling Regimes on Properties of Marble Powder-Based Cementitious Composites

The demand for cement is increasing every day worldwide. To meet this demand, natural resources are rapidly being depleted. The excessive consumption of natural resources encourages researchers to conduct studies on the use of waste materials instead of cement. Marble waste is one of the major natural wastes abundantly generated worldwide. It has been evaluated that there is a gap in the literature regarding a study comparing the effects of different cooling regimes on cementitious composites with a marble powder (MP) replacement that has been exposed to high temperatures. In this study, waste marble powder (MP) was used as a replacement for cement at percentages of 5%, 10%, 15%, 20%, and 25% by mass. The water-to-binder ratio was kept constant at 0.5 for all mixture groups. Subsequently, the prepared cementitious composites were exposed to high temperatures (300 °C, 600 °C, and 800 °C) and subjected to air- and water-cooling regimes. Within the scope of this study, unit weight (Uw), ultrasonic pulse velocity (UPV), flexural strength (ffs), compressive strength (fcs), and mass loss tests were conducted. Additionally, a microstructure analysis was carried out using scanning electron microscopy (SEM) to examine the effect of MP replacement and the cooling regime. When examining the results of the samples tested in the laboratory, it was observed that the mortar with 5% MP replacement exhibited better mechanical properties compared with the others. In general, it can be said that the mechanical properties of samples cooled in air after exposure to high temperatures were better than those of samples cooled in water. As a result of this study, it was determined that MP replacement could positively contribute to the resistance of cementitious composites to high temperatures. Additionally, the use of a significant amount of waste MP can lead to savings in cement usage and significant reductions in CO2 emissions.

Study of Decomposition of Supersaturated Solid Solution upon Quenching of Al–Mg–Si Alloy Sheets at Different Cooling Regimes

Study of Decomposition of Supersaturated Solid Solution upon Quenching of Al–Mg–Si Alloy Sheets at Different Cooling Regimes

Mechanical Properties of Cement Mortars Reinforced with Polypropylene Fibers Subjected to High Temperatures and Different Cooling Regimes

This study experimentally investigated the mechanical properties of cement mortars that were reinforced with polypropylene (PP) fibers after being exposed to high temperatures and cooled under different regimes. PP fibers were added in amounts of 2, 3 and 4 kg/m3, the residual strengths of the mortars exposed to various temperatures up to 500 °C and cooled under different regimes were determined. It was found that the addition of PP fiber at the level of 2 kg/m3 improves the residual flexural and compressive strengths up to 300 °C. The residual flexural strength was approximately 75%, which is 15% higher than that observed in the simple mortar, and the same happens with the residual compressive strength which was approximately 85%, which is 17% higher than that observed in the simple mortar, regardless of the types of cooling used on the specimens. It was determined by means of a statistical analysis that there are no significant differences in the mechanical properties of the mortar according to the cooling regimes used, after having been exposed to high temperatures. The correlation of the residual flexural and compressive strengths was achieved with a coefficient of determination, R2 = 0.82, and the relationships between the variables were considered acceptable regardless of the types of cooling used.

The influences of cooling regimes on fire resistance of ultra-high performance concrete under static-dynamic coupled loads

Cooling regimes have a significant effect on the mechanical properties of ultra-high performance concrete (UHPC) after exposure to elevated temperatures. Load-bearing structures are easily subjected to the coupling action of static and dynamic loads in the fire. This study investigated the dynamic behavior and failure characteristics of UHPC after exposure to heating-cooling treatments. The variations in the P-wave velocities, compressive strengths, elastic modulus and dynamic increase factor (DIF) of the specimens in terms of the different cooling regimes (natural cooling, water cooling) were analyzed. The experimental results indicated that as compared to natural cooling, water cooling caused significant losses in the P-wave velocities, quasi-static and dynamic compressive strength, and dynamic elastic modulus due to the thermal shock induced by water cooling. As the target temperature increased from 250 to above 500 °C, the difference of mechanical property losses varied from small to large, indicating that the thermal shock induced by water cooling caused insignificant damage to the specimen at 250 °C, whereas considerable damage was induced to the specimen above 500 °C. Water cooling enhanced the DIF values of the specimens below 500 °C, but reduced the DIF values at 750 °C. Axial static-pressure loading improved the mechanical properties of the specimen when UHPC was in the elastic phase, which could be attributed to the initial microcracks and pores closed and compacted by the axial static-pressure. However, when the axial static-pressure exceeded the elastic limit of UHPC, microcracks were prone to expansion under impact loads and the mechanical properties of the specimens deteriorated rapidly. Likewise, the failure pattern of the specimen under a given impact load was mainly determined by the heating temperature and cooling regime, whereas the axial static-pressure loading could only affect the fragment size.

Effect of the Cooling Regime on the Mineralogy and Reactivity of Belite-Sulfoaluminate Clinkers

This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days.

Effect of Molybdenum and Cooling Regime on Microstructural Heterogeneity in Bainitic Steel Wires

Hot‐rolled wire is often further processed into complex components and therefore has to meet high demands on mechanical properties. Above all, during wire production, close control of the cooling parameters after hot rolling is required if strength and toughness must be set within narrow limits. Parameter studies are conducted in laboratory investigations to adjust bainitic microstructures, that consist of bainitic ferrite as the primary phase, whereas retained austenite films and martensite–austenite (M–A) constituents represent the secondary phase. Hot deformation trials with subsequent continuous cooling are conducted in a thermomechanical treatment simulator using two microalloyed steels with 0.25% C, 2% Mn, 0.03% Nb, and 0.03% Ti with or without Mo. The cooling parameters are set according to the process window of the cooling conveyor at the wire rod rolling mill. A microstructural analysis shows inhomogeneities in the appearance of the secondary phase depending on the cooling schedule. A quantitative analysis of the microstructural constituents indicates that the distribution function of the morphological characteristics of the M–A constituents corresponds to the mechanical properties. Therefore, cooling cycle and chemical composition are adjusted precisely to adjust the bainitic microstructure and achieve the desired mechanical properties.

Influence of Desert Sand and Cooling Regime on the Compressive Strength of High Strength Concrete after High Temperatures

An experimental investigation is conducted to analyze the influence of desert sand replacement ratio and cooling regime on the compressive strength of desert sand-based high strength concrete (DS-HSC). According to the design of experiment, six desert sand replacement ratios (0%, 20%, 40%, 60%, 80% and 100%) are employed to concrete mixture. DS-HSCs are subjected to two cooling regimes (air cooling and water cooling) and various temperatures (20°C, 400°C, 500°C, 600°C, 700°C and 850°C, respectively) in this paper. The results indicate that the compressive strength of DS-HSC with air cooling is higher than that with water cooling. Moreover, the highest compressive strength appears with the desert sand replacement ratio of 20%. The compressive strength of DS-HSC gradually decreases with the increase of desert sand replacement ratio when the desert sand replacement ratio is more than 20%.

Checking the Influence of Sudden and Gradual Cooling Regimes on Strength, Near Surface Characteristics and Modulus of Elasticity of Hybrid Fibre Reinforced Blended Concretes Subjected to Sustained Elevated Temperatures using Artificial Neural Networks

Prediction is made on strength, near surface characteristics, and modulus of elasticity of hybrid fibre reinforced blended concretes subjected to sustained elevated temperatures for 3 hours retention period using artificial neural networks (ANN). Temperature ranges from 100°C to 1000°C at an interval of 100°C and after that, specimens are subjected to two cooling regimes, that is, sudden and gradual. These specimens are subjected to tests for compressive strength, split tensile strength, water absorption, sorptivity, and modulus of elasticity. For building ANN models, available 440 experimental results produced with eight different mixture proportions are used. Two major artificial neural networks are used for prediction. One is for all the concrete combinations with sudden cooling [SCR] and other is with gradual cooling [GCR]. The data used in the multilayer feed forward neural network models (architecture, 8-15-1) is designed with eight input parameters covering temperature [T], cement [C], fly ash [FA], GGBFS [GGBFS] Silica Fume [SF], galvanized iron fibre [GIF] polypropylene fibre [PPF], and cooling regime [SCR or GCR]. These five tests are the outputs and they are predicted individually for both the cooling regimes. It shows that neural networks have high potential for predicting the results.

Dynamic evolution of damage by microcracking with heat dissipation

A new thermo-mechanical damage model is constructed in the present contribution using a two-scale approach. The model is deduced from microstructures with microcracks evolving dynamically in a nominally brittle material and for which the fracture energy dissipated at the moving tips is converted to heat. The use of an homogenization method based on asymptotic developments leads to a damage evolution law coupled with the macroscopic thermoelasticity system. The obtained model accounts for inertial effects, thermo-elastic coupling and heat dissipation effects due to damage propagation. The local effective response of the model is analyzed with special emphasis on thermal evolutions. Strain-rate and microstructural size effects are illustrated. Cooling and heating regimes associated to damage initiation and propagation are identified and analyzed for different values of the model parameters. Results of numerical simulations for a compact compression specimen test are presented and compared with the experimental data for temperature field measurements during rapid failure of PMMA samples. Good agreement is found between the model predictions and the measured thermal evolution.

Plasticity Behavior of the Steel Depending on the Cooling Regimes in the Case of a Non-Conventional Treatments

Plasticity of the steel -as an important property of the material -has the role to show the capability of the steel to support plastic deformation necessary to obtain pieces for industry. Plasticity can be influenced by cooling regimes from higher temperatures in the cases of non-conventional treatments. An important factor is the cooling speed of the steel from higher temperatures during non-conventional treatment applied after lamination of the material. To modify the speed of the cooling, the medium of the cooling has been changed. The samples of the steel have been cooled in normal condition, in metallic box and using a jet of cold air. The evolution of the plasticity was studied taking in consideration the evolution of some characteristics. This paper might be considered as a review of the researches from the last years.

Influence of Sudden and Gradual Cooling Regimes on Strength, Near Surface Characteristics and Modulus of Elasticity of Polypropylene Fibre Reinforced Ternary Blended Concretes Subjected to Sustained Elevated Temperatures

It is necessary to study the effect of sudden and gradual cooling regimes on M30 grade blended concrete when subjected to sustained elevated temperatures for three hours. The temperatures considered for the study are 30 o C (RT), 100 o C, 200 o C, 300 o C, 400 o C, 500 o C, 600 o C, 700 o C, 800 o C, 900 o C, and 1000 o C. There is a comparison between conventional concrete and two ternary blended concretes (cement, fly ash, GGBFS and Cement, fly ash, silica fume) along with the inclusion of polypropylene fibre in each. After temperature test and cooling, concrete specimen was subjected to several strength and durability tests. As a result, all the specimens tested for gradual cooling regime shows better results than those tested for sudden cooling. Ternary blended concrete produced with cement, fly ash, silica fume along with polypropylene fibre combination shows better resistance against all temperatures compared to other two concretes.

Effect of cooling regime on phase transformation and chromium enrichment in stainless-steel slag

ABSTRACT Cooling regime of stainless-steel slag has a great influence on the migration rule of chromium. Effect of cooling rate on chromium distribution in CaO–SiO2–MgO–Al2O3–Fe x O–Cr2O3 system has been studied by FactSage, XRD and SEM-EDS in this paper. Results showed that the main phases in stainless-steel slag are spinel, bredigite, wustite, lime and periclase. Chromium was enriched in the stable phases. With the decrease in cooling rate, the size of chromium-rich phase increased relatively while chromium content in spinel phase reduced. Rapid cooling was favourable to the chromium enrichment in spinel phase in high basicity (high than 2.0) stainless-steel slag.

Low resolution spectroscopic investigation of Am stars using Automated method

The automated method of full spectrum fitting gives reliable estimates of stellar atmospheric parameters (Teff, log g and [Fe/H]) for late A, F, G, and early K type stars. Recently, the technique was further improved in the cooler regime and the validity range was extended up to a spectral type of M6 - M7 (Teff 2900 K). The present study aims to explore the application of this method on the low-resolution spectra of Am stars, a class of chemically peculiar stars, to examine its robustness for these objects. We use ULySS with the Medium-resolution INT Library of Empirical Spectra (MILES) V2 spectral interpolator for parameter determination. The determined Teff and log g values are found to be in good agreement with those obtained from high-resolution spectroscopy.

Behavioural and Well Being Comparison of Broiler Chicks in the Different Cooling Regime during Hot-Dry and Hot-Humid Months of summer

Behavioural and Well Being Comparison of Broiler Chicks in the Different Cooling Regime during Hot-Dry and Hot-Humid Months of summer

Application of the Quasi-Regular Cooling Regime Method to Experimental Determination of the Thermophysical Parameters of Textile Materials

We have experimentally established that the surface temperature of vertically positioned flat samples, made from textile materials and previously uniformly heated to temperatures in the range 60°-80°C, under natural convection conditions varies with time according to a single law defined by two constants m and μ, respectively having the meaning of cooling rate and the change in cooling rate. The parameters m and μ of the cooling curve depend on the geometric and thermophysical characteristics of the test materials. We give a theoretical explanation for the time dependence of the cooling curve, based on solution of the nonlinear thermal conductivity problem. Based on the constructed theory, we find the correlation between the parameters of the cooling curve and the thermophysical characteristics of textile material. We propose an analytical method for using the values of the constants of the cooling curve to determine the thermophysical constants of textile materials. We show that the overall accuracy in the determination of the thermophysical constants of materials from the cooling curve is mainly limited by the measurements of the geometric characteristics of the samples, and is within 5% of the values of the thermophysical constants. We have conducted experimental studies to determine the thermal conductivity coefficient for needlepunched nonwoven fiber material as a function of the thermophysical parameters of its constituent components. The studies allowed us to find a quantitative correlation between the composition of the nonwoven material and its thermal insulation properties.

Rotating thermoelectric device in periodic steady state

We propose a novel rotating thermoelectric device operating in periodic steady state, whether it is possible to achieve better energy conversion performance for rotating device comparing to conventional stationary steady state. The rotating thermoelectric (TE) cooling device consisting of the single TE conductor is described. It operates in two periodical steady state modes: the switching periodical mode (P-mode) when hot and cold ends of the TE conductor are periodically instantly reversed and the continuous sinusoidal mode (S-mode) when the temperature of TE conductor edges varies continuously according to a sine wave. Cooling and power generation regimes of rotating (TE) device in the periodic steady state was studied analytically. The efficiency and the cooling temperature of rotating TE device was found to depend not only on the dimensionless TE figure of merit, but also upon an additional dimensionless parameter comprising of the rotation period, the size and the thermal diffusivity of the TE conductor. The proposed analytical method can be generalized to even more complex rotating cooling modes and allows us to solve the optimization problem for cooling TE device parameters. The S-mode was shown to demonstrate deeper cooling at certain times.

Effect of High Temperature and Cooling Regimes on Residual Properties and Spalling of HPFRCC

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Effect of different cooling regimes on the mechanical properties of cementitious composites subjected to high temperatures.

The influence of different cooling regimes (quenching in water and cooling in air) on the residual mechanical properties of engineered cementitious composite (ECC) subjected to high temperature up to 800°C was discussed in this paper. The ECC specimens are exposed to 100, 200, 400, 600, and 800°C with the unheated specimens for reference. Different cooling regimens had a significant influence on the mechanical properties of postfire ECC specimens. The microstructural characterization was examined before and after exposure to fire deterioration by using scanning electron microscopy (SEM). Results from the microtest well explained the mechanical properties variation of postfire specimens.

Reduction in Slab Surface Corner Crack Damage due to Development of Rational Secondary Cooling Regimes

The effect of heating condition for continuously-cast slabs of different cross section on the probability of corner crack formation is analyzed. Versions are considered for correction of cooling water and air flow rates in secondary cooling zone (SCZ) sprayers with the aim of optimizing the thermal profile of continuously-cast billets poured from crack-resistant steels. SCZ operating regimes are developed for the Azovstal Metallurgical Combine CBCM-6 making it possible to reduce the overall level of slab surface cleaning by 30%.

'Candidatus Liberibacter asiaticus' Titers in Citrus and Acquisition Rates by Diaphorina citri Are Decreased by Higher Temperature.

'Candidatus Liberibacter asiaticus' is the most prevalent Liberibacter sp. associated with huanglongbing (HLB) in Brazil. Within São Paulo state (SP), HLB has spread more rapidly to and reached higher incidence in regions with relatively mild (cooler) summer temperatures. This suggests that climate can influence disease spread and severity. 'Ca. L. asiaticus' titers on soft, immature leaves from infected 'Valencia' sweet orange plants exposed to different temperature regimes and adult Diaphorina citri fed for 48 h on these plants for 'Ca. L. asiaticus' acquisition were determined by quantitative polymerase chain reaction in two experiments. The first experiment included plants with three levels of infection, three incubation periods (IPs), and air temperatures favorable (14.6 to 28°C) and unfavorable (24 to 38°C) to 'Ca. L. asiaticus'. The second included plants with severe late-stage infections, 10 IPs (based on 3-day intervals over 27 days), and three air temperature regimes (12 to 24, 18 to 30, and 24 to 38°C). Overall, 'Ca. L. asiaticus' titers and the percentages of 'Ca. L. asiaticus'-positive psyllids were lower in plants maintained at the warmer temperature regime (24 to 38°C) than in plants maintained in the cooler regimes. The results suggest that the lower incidence and slower spread of 'Ca. L. asiaticus' to warmer regions of SP are related to the influence of ambient temperatures on titers of 'Ca. L. asiaticus' in leaves.