Time-temperature Profiles Research Articles

EVALUATION OF THE BOTTOM SURFACE WATER JET IMPINGEMENT COOLING RATE USING MODIFIED RUN-OUT TABLE

Evaluation of Temperature-Time Profiles by the Lumped Thermal Mass analysis method for bottom surface jet impingement cooling system was carried out. This was done by controlled accelerated cooling using a modified run-out table (ROT). The evaluation was with variant pipe diameters of 10mm - 40mm by a single water jet, having impingement gaps in the range of 55mm - 95mm and controlled sub-cooled to a range of 150oC – 110oC. The results revealed that the cooling rate was faster at an impingement gap of 95mm in all the pipe diameters. This was evident from the plot of temperature-time, with a gap of 95mm showing 1.93oC/s and 3.24oC/s at diameters of 10mm and 40mm respectively. This evidently revealed that at any given pipe diameter the cooling rate is higher at a higher impingement gap for bottom surface controlled cooling. This is also suggested by the calculated heat transfer coefficient that shows an increase with the increase in pipe diameter and impingement gap for an increase in cooling rate. Therefore, for bottom surface jet impingement cooling, a higher impingement gap for any pipe diameter will give a better cooling rate for the steel austempering process.

A comparative study of interface material through selective microwave hybrid heating for joining metal plates

The development of joints using microwave hybrid heating (MHH) received extensive attention over conventional heating due to its uniform heating, environment friendly characteristics. For effective microwave joining of bulk metals, joint region was targeted selectively naming it as selective microwave hybrid heating (SMHH). Microwave joining of stainless steel using Nickel as interface material is explored extensively through MHH; however no comparative study showing better interface material for microwave joining of Stainless steel is reported. In the present study, SS304-SS304 lap joint is simulated for two different interface materials that are nickel and Inconel-718 for an exposure time of 22 min. These joints were developed using pulverized charcoal as a susceptor material and at the power output of 700 W. Microwave hybrid heating has been simulated by implementing different assumptions and boundary conditions at better mesh quality. A time-temperature curve, resistive heating, electric field distribution, and temperature profile along different directions are those parameters that have been discussed to examine better interface material. From the results, it is observed that Inconel-718 shows better resistive heating when compared to nickel interface material, however electric field distribution remains similar for both interface materials. Further, the time-temperature profile revealed that the time taken for Inconel-718 interface material to reach fusion zone is lesser than Nickel interface material.

Thermal and structural behavior of cold-formed steel frame wall under fire condition

Light gauge Steel Frame (LSF) system, are extensively used in residential, commercial and industrial buildings. Its growing popularity in building construction industry is due to several advantages over other construction materials such as light weight, high strength and stiffness, uniform quality, ease of prefabrication and mass production, economy in transportation and handling. Fire safety of cold-formed steel structures has become more important since cold-formed thin-walled steel sections heat up quickly under fire condition (high section factor and high thermal conductivity) and present low fire resistance. LSF wall systems are used as primary load bearing structural members providing strength and stability in multi-story LSF buildings. Therefore a better understanding of the fire performance of LSF wall systems is required. The structural behavior of the LSF walls at high temperatures depends on the temperature distribution at the wall component and the mechanical property of cold-formed steel and other materials used in LSF walls at elevated temperatures. Also, the thermal performance of the LSF wall is influenced by its components, including the stud cross-section, stud size, sheathing, and insulation types and their thicknesses, and thermal properties of them. In this paper, a numerical study was undertaken using the finite element program ABAQUS. The structural finite element analysis were conducted under transient state condition using the time–temperature profiles of wall components obtained from the thermal analysis. The finite element thermal and structural models were first validated by comparing their results with the previous test results and then a parametric study was conducted with considering the effect of various parameters such as type of sheathing and its arrangement, stud web depth, stud flange width, and stud cross-section shape. The temperature distribution and time–temperature profile of the wall component and Fire-Resistance Rating (FRR) of the wall have been calculated. The results showed that sheathing is one of the most critical factors in fire resistance of walls and has a significant influence on the FRR of walls and increasing the stud depth affects the thermal and structural behavior of the LSF wall and leads to an increase in the FRR of the wall against fire. Also, increasing the stud flange width of LSF wall does not affect the thermal behavior and temperature distribution of the wall, but leads to an increase in the FRR of the wall against fire. The stud cross-section shape does not affect the temperature distribution in the cross-section but can affect the wall’s behavior under fire conditions.

Predictive Microbial Modeling of Enterococcus faecium NRRL B-2354 Inactivation during Baking of a Multicomponent Low-Moisture Food

The use of baking ovens as a microbial kill step should be validated based on results of thermal inactivation models. Although traditional isothermal models may not be appropriate for these dynamic processes, they are being used by the food industry. Previous research indicates that the impact of additional process conditions, such as humidity, should be considered when validating thermal processes for the control of microbial hazards in low-moisture foods. In this study, the predictive performance of traditional and modified thermal inactivation kinetic models accounting for process humidity were assessed for predicting inactivation of Enterococcus faecium NRRL B-2354 in a multi-ingredient composite food during baking. Ingredients (milk powder, protein powder, peanut butter, and whole wheat flour) were individually inoculated to achieve ∼6 log CFU/g, equilibrated to a water activity of 0.25, and then mixed to form a cookie dough. An isothermal inactivation study was conducted for the dough to obtain traditional D- and z-values (n = 63). In a separate experiment, cookies were baked under four dynamic heating conditions: 135°C, high humidity; 135°C, low humidity; 150°C, high humidity; and 150°C, low humidity. Process humidity measurements; time-temperature profiles for the product core, surface, and bulk air; and microbial survivor ratios were collected for the four conditions at six residence times (n = 144). The traditional isothermal model had a high root mean square error (RMSE) of 856.51 log CFU/g, significantly overpredicting bacterial inactivation during the process. The modified model accounting for the dynamic time-temperature profile and process humidity data was a better predictor with an RMSE of 0.55 log CFU/g. These results indicate the importance of accounting for additional process parameters in baking inactivation models and that model performance can be improved by utilizing model parameters obtained directly from industrial-scale experimental data.

A Method for Characterising the Influence of Casting Parameters on the Metallurgical Bonding of Copper and Steel Bimetals.

Traditional casting technology offers two mayor drawbacks towards research activities. On the one hand, time and resources needed for every casting are rather high. The mould has to be able to withstand the high temperatures introduced by the melt and provide cooling for the cast part. Preparation and installation of measuring equipment therefore takes time. Additionally, due to the high mass of the mould when compared to the cast part, parameter variations are rather limited in their resulting effect on the temperature-time profile being one of the most prominent factors regarding cast quality. Especially when pouring by hand, variations in casting times and rates superimpose effects created intentionally. Therefore, a different process was advanced and evaluated, allowing to minimise some of the drawbacks mentioned before. The key idea is to drastically reduce casting size to the dimensions of one specimen and to apply a highly automated production route. As such, a mirror furnace was modified as to allow the processing of melt. Due to the specimens size, an adaption of mechanical testing equipment was performed and evaluated. As an example, copper-iron bimetal specimens were examined by light microscopy, micro hardness testing, nanoindentation as well as tensile and torsion testing. As the results were consistent, the newly introduced method can be applied successfully in casting research. This allows for highly reproducible results, reducing the uncertainty of temperature measurements of a specimen due to the distance between them. The possibility of separating influencing variables like maximum temperature and cooling rate allows an analysis of the casting process, which would require different moulds to do so in traditional casting methods. The next steps will be directed at a broader variety of metals processed and at a direct comparison between the new process route and traditional casting technology.

Sequentially coupled structural modelling of LSF floor-ceiling systems

Fire resistance levels provide a standardised measurement of building elements' fire resistance under structural, integrity and insulation criteria, and are usually obtained from standard full-scale fire tests. However, these tests consume excessive time and money and thus the use of validated advanced numerical models is preferred. This paper presents the details of a sequentially coupled structural modelling study of LSF floor-ceilings made of Lipped Channel beam (LCB) and rivet fastened Rectangular Hollow Flange Channel beam (RHFCB) section joists used in eight different floor-ceiling configurations, and its results. Ambient temperature structural finite element (FE) models of LCB and RHFCB joists were developed first and validated using experimental results. Full scale fire test results of LCB floor system were then used to validate a structural FE model developed and analysed using a sequentially coupled approach utilising the time-temperature profiles from the same fire test. Finally, using the validated sequentially coupled structural FE models, the effects of a range of influential parameters such as joist types and floor-ceiling configurations were investigated. The results of structural fire resistance/failure times versus load ratio showed that the new RHFCB joists gave only minor improvements, however, they provided superior load bearing capacities. Fire resistance improved significantly when more gypsum plasterboard layers were used. The use of thin steel sheathing also improved the failure times, and is recommended as the fire exposed layer due its ability prevent plasterboard fall-off. Finally, suitable critical mid-web temperatures are proposed for predicting the structural fire resistance times of LSF floor-ceiling systems.

Exploring the microwave non‐thermal effects on the fatty acid composition of Atlantic salmon ( Salmo salar ) during pasteurization using the same time–temperature profiles method

The non-thermal effects of microwave fields on the fatty acid composition of pasteurized Atlantic salmon were investigated using the same time–temperature profiles method. Two pasteurization processes with same time–temperature profiles were designed using a microwave processing system and a water bath. Then, the fatty acid composition of the processed salmon fillets was analyzed using the gas chromatography/mass spectrometry (GC/MS) method. Results showed that the time–temperature profiles during microwave and water bath processing were well suited. With same time–temperature profiles, the fatty acid compositions of salmon fillets processed by microwave and water bath were obviously different. Furthermore, microwave process brought better fatty acid quality in terms of higher values of n-3 PUFA proportion, PUFA:SFA ratio, and lower n-6 PUFA proportion. This demonstrated that microwave fields did have non-thermal effects on the fatty acid composition of salmon with 3.5 min 8 kW microwave radiation and a final temperature of 90℃. Practical applications Microwave processing could provide volumetric heating for solid foods to improve product quality by achieving high-temperature short time process. The microbial safety of microwave thermal processing has been approved by the Food and Drug Administration of United States. Its industrial application is being accelerated. However, besides thermal effects, there also exists non-thermal effects during microwave processing due to the interaction between alternating electromagnetic waves and food molecules. Thus, the influence of microwave non-thermal effects on nutritional quality and chemical safety of foods are attracting great concerns both for consumers and researchers. It is essential to provide theoretical data concerning microwave non-thermal effects to sustain its industrial application. This study investigated the influence of microwave non-thermal effects on fatty acids composition of salmon fillets using same time–temperature profiles method. The results provide important information for quality evaluation of microwave processed foods, which promotes the application of microwave processing in food industry.

Formation of acrylamide in biscuits during baking under different heat transfer conditions

The effects of heat-transfer modes on acrylamide (AA), AA precursors, and the main quality characteristics of biscuits were investigated. Biscuits were baked in ventilated mode (V), with forced air convection, and static mode (S), based only on conduction, at 175 °C for 18, 20, 22, 24, 26 min. Both heat-transfer types promoted an increase in AA levels during baking. However, in the V mode the heat was distributed more evenly compared to the S one, causing a faster rise of temperature, as showed by recorded time-temperature profiles. As a consequence, the V biscuits reached higher AA levels compared to those baked under S conditions at 20 and 22 min. Both samples baked at 20 and 22 min in S mode were acceptable based on the results of quality parameters. Nevertheless, under the formulation and baking conditions applied, all samples showed AA levels below the reference value of Commission Regulation (EU) 2017/2158.

Effects of insulation materials and their location on the fire resistance of LSF walls

Lightweight walls incorporate insulation materials to compensate for their low thermal mass and to improve thermal performance. This helps in increasing the energy performance of the buildings. Since insulation materials are sensible heat storage materials, there is an increment in the room temperature. Phase Change Materials (PCMs) are used in lightweight walls due to their high thermal storage capacity and the resulting enhanced thermal comfort levels. However, the performance of the PCM incorporated building products/insulations in fire has not been investigated yet. This research has investigated the fire resistance of Light gauge steel framed (LSF) walls with PCM incorporated cellulose insulation through small-scale fire tests. It has also investigated the effects of using different insulation materials and their location on the fire resistance of LSF walls. Important results of this research are presented in this paper in the form of time-temperature profiles for cavity and externally insulated LSF wall configurations with and without PCM incorporated cellulose insulation. Findings reveal that externally insulated LSF walls have higher fire resistance levels than cavity insulated LSF walls based on insulation failure criterion. Importantly, adding PCM to cellulose insulation improves the fire resistance of both cavity and externally insulated LSF walls. PCM incorporated cellulose insulation can be used externally in LSF walls to enhance their fire and energy performance. However, the fire behaviour of Vacuum Insulation Panel (VIP) incorporated LSF wall is completely different to other wall systems.

Continuous Monitoring of the Thermoregulatory Response in Endurance Horses and Trotter Horses During Field Exercise: Baselining for Future Hot Weather Studies.

Establishing proper policies regarding the recognition and prevention of equine heat stress becomes increasingly important, especially in the face of global warming. To assist this, a detailed view of the variability of equine thermoregulation during field exercise and recovery is essential. 13 endurance horses and 12 trotter horses were equipped with continuous monitoring devices [gastrointestinal (GI) pill, heartrate (HR) monitor, and global positioning system] and monitored under cool weather conditions during four endurance rides over a total of 80 km (40 km loops) and intense trotter track-based exercise over 1,540 m. Recordings included GI temperature (Tc), speed, HR and pre- and post-exercise blood values. A temperature time profile curve of Tc was constructed, and a net area under the curve was calculated using the trapezoidal method. Metabolic heat production and oxygen cost of transport were also calculated in endurance horses. Maximum Tc was compared using an independent samples t-test. Endurance horses (mean speed 14.1 ± 1.7 km h–1) reached mean maximum Tc (39.0 ± 0.4°C; 2 × 40 km in 8 horses) during exercise at 75% of completion of Tc exercise and Tc returned to baseline within 60 min into recovery. However, the mean Tc was still 38.8 ± 0.4°C at a HR of 60 bpm which currently governs “fit to continue” competition decisions. Trotters (40.0 ± 2.9 km h–1) reached a comparable mean max Tc (38.8 ± 0.5°C; 12 horses) always during recovery. In 30% of trotters, Tc was still >39°C at the end of recovery (40 ± 32 min). The study shows that horses are individuals and thermoregulation monitoring should reflect this, no matter what type of exercise is performed. Caution is advised when using HR cut-off values to monitor thermal welfare in horses since we have demonstrated how Tc can peak quite some time after finishing exercise. These findings have implications for training and management of performance horses to safeguard equine welfare and to maximize performance.

Study the synergism of microwave thermal and non-thermal effects on microbial inactivation and fatty acid quality of salmon fillet during pasteurization process

Microwave processing is a combined treatment of thermal and non-thermal effects on microorganisms and food ingredients. There may exist synergism between these two types of effects. The objective of this study was to explore the synergism of microwave thermal (i.e. temperature) and non-thermal effects on microbial inactivation and on fatty acids quality of pasteurized salmon fillets. Water bath processes with same time-temperature profiles and same microbial inactivation intensity were designed as control. Results showed that the microwave non-thermal effect on microbial inactivation was significantly (P < 0.05) enhanced by increasing temperatures. Compared with the microbial inactivation of thermal effect, the inactivation efficiency of microwave non-thermal effect increased from 22.18% to 35.25% while final temperatures of samples increased from 84 °C to 100 °C. Furthermore, with the same microbial inactivation intensity of 7.5-log CFU/g, microwave process retained better fatty acids quality in consideration of significantly higher (P < 0.05) PUFAs (especially for ARA, EPA and DHA) than those with water bath treatments. These results demonstrated that high temperatures could bring significant enhancement on microwave non-thermal effect, and microwave processing could provide better bacteria control and meanwhile retain higher product quality due to the synergism of microwave thermal and non-thermal effects.

Redox Proteomic Analysis Reveals Microwave-Induced Oxidation Modifications of Myofibrillar Proteins from Silver Carp (Hypophthalmichthys molitrix).

To provide an insight into the oxidation behavior of cysteines in myofibrillar proteins (MPs) during microwave heating (MW), a quantitative redox proteomic analysis based on the isobaric iodoacetyl tandem mass tag technology was applied in this study. MPs from silver carp muscles were subjected to MW and water bath heating (WB) with the same time-temperature profiles to eliminate the thermal differences caused by an uneven energy input. Altogether, 422 proteins were found to be differentially expressed after thermal treatments as compared to that with no heat treatment. However, MW triggered a larger number of proteins and cysteine sites for oxidation. Myosin heavy chain, myosin-binding protein C, nebulin, α-actinin-3-like, and titin were found to be highly susceptible to oxidation under microwave irradiation. Notably, MW caused such modifications at cysteine site 9 in the head of myosin, revealing the enhancement mechanism of MP gelation by excess cysteine cross-linking during microwave processing. Furthermore, Gene Ontology and functional enrichment analyses suggested that the two thermal treatments resulted in some differences in ion binding, muscle cell development, and protein-containing complex assembly. Overall, this study is the first to report the redox proteomic changes caused by MW and WB treatments, thus providing a further understanding of the microwave-induced oxidative modifications of MPs.

Fire resistance of 3D printed concrete composite wall panels exposed to various fire scenarios

PurposeFire safety of a building is becoming a prominent consideration due to the recent fire accidents and the consequences in terms of loss of life and property damage. ISO 834 standard fire test regulation and simulation cannot be applied to assess the fire performance of 3D printed concrete (3DPC) walls as the real fire time-temperature curves could be more severe, compared to standard fire curve, in terms of the maximum temperature and the time to reach that maximum temperature. Therefore, this paper aims to describe an investigation on the fire performance of 3DPC composite wall panels subjected to different fire scenarios.Design/methodology/approachThe fire performance of 3DPC wall was traced through developing an appropriate heat transfer numerical model. The validity of the developed numerical model was confirmed by comparing the time-temperature profiles with available fire test results of 3DPC walls. A detailed parametric study of 140 numerical models were, subsequently, conducted covering different 3DPC wall configurations (i.e. solid, cavity and rockwool infilled cavity), five varying densities and consideration of four fire curves (i.e. standard, hydrocarbon fire, rapid and prolong).Findings3DPC walls and Rockwool infilled cavity walls showed superior fire performance. Furthermore, the study indicates that the thermal responses of 3DPC walls exposed to rapid-fire is crucial compared to other fire scenarios.Research limitations/implicationsTo investigate the thermal behaviour, ABAQUS allows performing uncoupled and coupled thermal analysis. Coupled analysis is typically used to investigate combined mechanical-thermal behaviour. Since, considered 3DPC wall configurations are non-load bearing, uncouple heat transfer analysis was performed. Time-temperature variations can be obtained to study the thermal response of 3DPC walls.Originality/valueAt present, there is limited study to analyse the behaviour of 3DPC composite wall panels in real fire scenarios. Hence, this paper presents an investigation on the fire performance of 3DPC composite wall panels subjected to different fire scenarios. This research is the first attempt to extensively study the fire performance of non-load bearing 3DPC walls.

Experimental and numerical modelling of solid and hollow biomass pellets high-temperature rapid oxy-steam combustion: The effect of integrated CO2/H2O concentration

Oxy-steam combustion behaviour of rice straw (RS) pellets was studied at high temperatures experimentally in a new plasma combustion system and numerically using an upgraded one-dimensional unsteady-state single particle combustion model with a new homogeneous devolatilization volatile combustion and heterogeneous char oxidation sub-models under different O2/H2O/CO2/N2 gas compositions. Experimental results showed that the temperature gradient profiles for both the surface and center decreased significantly when the steam was added to the gas mixture at 20 and 40%. At 30% H2O, the heat consumption of the gasification reaction decreased which resulted in a higher particle temperature and a higher char oxidation reaction rate. Combustion characteristics for heating, ignition, devolatization, and combustion stages were obtained and confirmed through the time of recorded pictures by high-speed camera. The obtained experimental results were validated through fitting the measured values of surface and center temperature-time profiles, ignition time, final pellet diameter, and time for the maximum amount of released volatiles, under different H2O and CO2 concentrations, with those predicted from the model solution. Also, the mass of the released volatiles and pellet diameter history were predicted from the model solution. Results of the model solution proved the reality and credibility of the measured and calculated experimental findings.

Solution-Processed Multistacked Tin-Doped Indium Oxide Nanoparticle Conductors for Cost-Effective Thin Film Heaters

Tin-doped indium oxide (ITO) nanoparticle (NP) films were fabricated as a cost-effective and highly transparent electrode for high-performance thin film heaters (TFHs), using a solution coating process on glass substrate. The electrical and optical properties of the ITO NP films depended on the number of spin coatings and post-annealing with various conditions (temperature, time, and ambient gas). The optimized three layer ITO NP films annealed at 600 °C under ambient N2 showed a low sheet resistance of 14 Ω/sq and a high optical transmittance of 88% in the visible wavelength region of (400–800) nm. Cross-sectional TEM images showed the ITO nanoparticles to be evenly dispersed in the thin film with good crystallinity and well-defined elliptical shape in the range of 10 to 25 nm. X-ray diffraction analysis confirmed that heat treatment increased the size of the ITO NPs. The KPFM result exhibited that as the heat treatment duration increased, the surface roughness of the ITO NP films reduced. X-ray photoelectron spectroscopy surface analysis showed a relatively higher area ratio of oxygen vacancies and a more stable Sn state in the chemical states of the O 1s and Sn 3d5/2 spectra than those of typical ITO films deposited by a magnetron sputtering after heat treatment. Due to the thermal stability and uniformity of the ITO NP film, ITO NP-based TFHs showed a stable time–temperature profile and uniform IR imagery. Therefore, solution-processed ITO NPs films can be applied to a promising low-cost transparent electrode in the next-generation smart window for buildings and automobiles.

Spatio-temporal temperature fields generated coronally with bulk-fill resin composites: A thermography study

ObjectiveThis study aimed to investigate the effects of (i) a high-irradiance (3s) light-curing protocol versus (ii) two standard-irradiance (10s) protocols on 2D temperature maps during intra-dental photo-irradiation within a molar cavity restored with either Ultra-Rapid Photo-Polymerized Bulk Fill (URPBF) composites or a pre-heated thermo-viscous bulk-fill composite, compared to a standard bulk-fill resin-based-composite (RBC). The specific objectives included visual assessment of the temperature maps and quantitative assessment of several temperature/time plots at four different locations. MethodsA caries-free lower first molar cavity served as a natural tooth mold. Resin composites were placed without intermediary adhesive. Two URPBF composites (PFill; PFlow) and one pre-heated thermo-viscous bulk-fill composite (Viscalor: VC) were compared to a contemporary bulk-fill composite (One Bulk Fill: OBF). Two LED-LCU devices were used: Bluephase PowerCure (PC) and Elipar S10 (S10), with three light-irradiation protocols (PC-3s, PC-10s and S10-10s). 2D temperature maps over the entire coronal area were recorded for 120 s during and after irradiation using a thermal imaging camera. Changes at four different levels were selected from the data sets: (0, 2 and 4 mm from the cavity top and at 1 mm below the dentin cavity floor). The maximum temperature attained (Tmax), the mean temperature rise (ΔT), the time (s) to reach maximum temperature and the integrated areas (°C s) under the temperature/time (T/t) plots were identified. Data were analysed via three-way ANOVA, One-way ANOVA, independent t-tests and Tukey post-hoc tests (p < 0.05). ResultsAll RBCs showed qualitatively similar temperature-time profiles. PFlow reached Tmax in the shortest time. PC-3s (3000 mW/cm2) generated comparable ΔT to S10-10s, except with PFill, where ΔT was greater. Despite the same irradiance (1200 mW/cm2), Elipar S10 led to higher Tmax and ΔT compared to PC-10s. The highest Tmax and ΔT were observed at the 2 mm level, and the lowest were at 1 mm depth into the underlying dentin. SignificanceCoronal 2D temperature maps showed rises largely confined within the bulk-fill RBC materials, with maxima at 2 mm rather than 4 mm depth indicating some extent of thermal insulation for the underlying dentin and pulp. RBCs polymerized via different irradiation protocols showed similar temperature changes. With the PC-3s protocol – also with pre-heated VC – minimal temperature rises at 1 mm within dentin suggest their clinical safety when sufficient remaining dentin thickness is present.

The set Up of an Experimental Testing Rig to Measure Time and Space Temperature Profiles in Laser Sintering of Polymeric Powders

Selective Laser Sintering (SLS) is the most common type of Additive Manufacturing (AM) process using granular materials which has the potential to revolutionize the manufacturing industry. However, in the layer-wise build-up of the three-dimensional specimen, the complex laser-material interactions and the poor selection of associated process parameters can give rise to an increase to a number of defects of the artifacts. In fact, the temperature distribution along the surface and in depth at the laser spot, which are strongly affected by the thermal conductivity of the powder bed, do affect the hatch distance and the thickness of the powder layer, as well as on the quality of the final artifact. In this study, a laser sintering experimental set-up, equipped with an Infra-red thermographic camera and a K-type thermocouple, is built to measure the temperature distribution at the surface and 1mm below the surface in a special Polyamide 12 (PA12) powder bed. A one-watt stationary diode laser is used as heat source on samples characterized by various particle size distributions (PSD). Using the set-up, an accurate in-situ thermal characterization of the powder bed along with heat distribution study can be performed. Preliminary tests were conducted and the pixelwise temperature profile along the surface and temperature at the depth of 1mm below the surface of the powder bed has been reported. On the basis of the results, it is possible to provide good estimates of the global energy balances on the system, which are essential in evaluating the energy required to optimize the sintering and melting process of the polymeric powders.

Influence of the production route on the phase formation, microstructure and wear behaviour of the high-entropy alloy AlCoCrFeNiTi0.5

Different manufacturing approaches have been investigated regarding their suitability to process high-entropy alloys (HEAs). However, comprehensive investigations on the influence of the production route on the microstructure, phase formation and properties have not been conducted yet. For the current study the alloy AlCoCrFeNiTi0.5 is considered. Previous investigations have proven the formation of phases with predominantly body centred cubic structure for this alloy. Castings are produced by arc-melting. Feedstock material for coating deposition and powder metallurgical processing is produced by inert gas atomisation. For the processing high-velocity-oxygen-fuel (HVOF) thermal spraying and spark plasma sintering (SPS) are applied. Due to the significantly differing process conditions and temperature-time profiles, differences of microstructure, phase formation and resulting properties can be observed. Wear investigations under various conditions have been conducted. Especially under sliding and reciprocating wear conditions the structural defects formed for the thermally sprayed coating cause a reduction of wear resistance. The formation of structural defects could be avoided by SPS. However, the additional tetragonal phase causes a reduction of the wear resistance. The current study contributes to a better understanding of the interaction between process, microstructure and properties.

Experimental analysis of the flight design effect on the temperature distribution in rotary kilns

An experimental parameter study in an indirectly heated rotary drum (L = 1.76 m, D = 0.5 m) with L-shaped flights was conducted. The influence of the flight design parameters as the flight length ratio (0.375–2.0) and the number of flights (6–18) on the temperature-time profile and the temperature drop are analyzed. Therefore, the rotary drum is filled with glass beads as reference material and heated in batch operation while contact heat transfer is the main heat transfer mechanism. After reaching an upper temperature of 330 °C, the system is cooled by forced convection as ambient air is sucked through the drum. Type k-thermocouples in three axial and six radial positions are used to measure the time evolution of the temperature. The thermocouples are mounted to a flight, such that they rotate with the drum and also capture the circumferential temperature distribution.

Fire tests and thermal analyses of LSF walls insulated with silica aerogel fibreglass blanket

Load-bearing light gauge steel framed (LSF) wall is one of the main structural elements in cold-formed steel (CFS) buildings. When cavity insulation is used to enhance the energy performance of LSF walls, their structural adequacy based fire resistance levels (FRL) decrease considerably. Hence, new insulation materials and/or different wall configurations are considered. This research study investigated the use of silica aerogel fibreglass blanket as external insulation to enhance the FRL of LSF walls. Three fire tests were conducted to determine the time-temperature profiles of different wall components and the FRL of aerogel blanket insulated LSF walls. Suitable finite element (FE) models were then developed, validated and used to further optimise the LSF wall configuration. This study shows that silica aerogel fibreglass blanket, when used as a form of external insulation, enhances the fire resistance by delaying the stud temperature development by about 20 min and reducing the stud flange temperature difference by up to 200 °C when compared with cavity insulated LSF walls. However, the aerogel blanket accelerates the temperature development of fire protective gypsum boards, which leads to an early failure of these boards. This paper presents the details of the fire tests, finite element study and their findings.