Thermal Influence Research Articles

Investigation of the combustion process of activated fuel in an automotive diesel engine

BACKGROUND: Intensive development of the transport sphere and the extension of the fleet of tractors and cars, as well as the tightening of standards and requirements in the field of exhaust gas emissions have resulted in increased requirements for the combustion process. This problem can be solved by improving the working process in the engine by preheating the fuel to 300 C in the high pressure fuel supply system. Under external thermal influence, the conditions of mixture formation are improved, an increase in the rate of preflame reactions and a positive change in the dynamics of the combustion process are observed. When potential energy of hydrocarbon molecules increases in the activated complex system, energy is redistributed among active molecules. Along with this, the rate coefficient of a chemical reaction increases due to the concentration of foci of hydrocarbon molecules that have reached the energy barrier.
 The object of research is the process of diesel fuel combustion at preliminary external influence on it.
 AIMS: The aim is to study the combustion process of a motor-tractor diesel engine upon fuel activation. Development of a scheme of individual phases of the activated diesel fuel combustion of depending on the temperature at heating.
 METHODS: Theoretical study and analysis of the combustion process of thermally preprepared fuel for an automotive diesel engine. Theoretical determination of the dependence of the rate of formation and concentration of toxic components and dispersed particles on the rate constant of direct and reverse chemical reactions, as well as on the activation temperature of fuel at emission in exhaust gases.
 RESULTS: The actual coefficient of molecular change of the working mixture increases when diesel fuel is activated. The rate of formation of total nitrogen oxides and hydrocarbons increases by 1.79% and 3.66%. The proportion of unburned carbon in the combustion process on activated fuel varies within (24) %.
 CONCLUSIONS: Theoretically, a scheme for changing individual phases of the activated fuel combustion process by time and temperature has been developed. Fuel heating accelerates the pre-flame preparation in the liquid phase, shortens the duration of the rapid gorenje phase. The concentration of toxic indicators depends on the constant of the chemical reaction rate and the activation temperature of the fuel.

(Digital Presentation) Adsorption Characteristics of SiO2/Si, Nanocomposites of Multiwalled Carbon Nanotubes and Polyamide, Polyvinyl Chloride, Polyethylene, Porous Polystyrene

Kyiv national university, Kyiv-01601, Ukraineonanko@i.ua : In this work nondestructive method, which is allow to determine from internal friction difference ΔQ-1/Q-1 0 of elastic vibrations structure defects density Nd and the depth of broken layer hb, is offered for SiO2/Si wafer-plates. Outcomes of the evaluation of dynamic characteristics interstitial atoms, vacancy and O-complexes can be applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si wafer-plates. Introduction The leading factor of the elastic anisotropy forming is a crystallography orientation and the orientation of grains on the form with the orientation of miсrocracks, pores [1]. Acoustic emission (AE) allow to receive the additional information about the process of miсrocracks [2]. A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and elastic modulus E after laser radiation was developed. Experimental procedure The study of influence of structure defects on damping of vibrations in Si/SiO2 plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 470 000 nm, allows to estimate the degree of perfection of crystalline structure. Brief thermal influence is created by the powerful impulsive nanosecond neodymium laser resulted to local surface tissue fusion. After stopping of the laser radiation action of fusion solidification begun exactly from the surface, but the crater underbody is extended (molten) and created the additional squeezing mechanical tension σi, that „pull” the central part of crater surface in depth with the liquid crater fusion.The pressure dynamics Рi(t) is following: at the beginning of destruction Рi grows quickly, and on the completion of impulse action diminishes instantly on the value of the light pressure created by the laser. Then the diminishing pressure Рi becomes slower, for nanosecond times of laser influence the appearance of acoustic emission (AE) review is important in time range τ ≈ 0.2 nanosec [3,4]. Results and discussion Effects of AE after nanosecond neodymium and ruby laser irradiation in fluid SiO2 are investigated. The fusion depth as the result of relaxation of photothermal elastic strains Ϭi at the large time ∂T/∂t = (55±100).109 K/sec and spatial ∂T/∂x = (1±2).104 K/sm temperature gradients on the SiO2 surface was appraised Δh ≈ 10000 nm. The quantity of reflections N = τ/t ≈ 0.2 nsec/0.02 nsec = 10, approximately 10 times forward-back in specimen. There was a small value of IF background in SiO2 Qo -1 ≈ 2.10-6 to T ≈ 385 K. AE method was measured the group longitudinal wave velocity in fluid SiO2 by water solution of NaCl with the concentration ρ ≈ 38.125 g/l there was v║ = l/τ » 0.03032 m/10.7 mcsec » 2830 m/sec; shear wave velocity v┴ » 2300 m/sec. Oscilloscopegramma of impulses with transversal polarization, which are reflected in SiO2/Si wafer-plate is represented in Figure 1. Figure 1. Oscilloscopegramma of impulses with transversal polarization, which are reflected in SiO2/Si wafer-plate.Taking into account the value of density ρ ≈ 2.63.103 kg/m3, shear modulus G = ρ.v┴ 2 » 13.91 GPa and elastic modulus E = ρ.v║ 2 » 21.06 GPa were determined. Conclusions The value of internal friction background Q-1 0 after temperature, mechanical treatments describes the changes of the elastic stress σi fields in SiO2/Si wafer-plate after laser radiation.After laser radiation outcomes of the evaluation of dynamic characteristics interstitial atoms Sij, vacancy V and O-complexes can be applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si. Acknowledgements This work has been supported by Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv.

Electroplasticity mechanism study based on dislocation behavior of Al6061 in tensile process

The thermal and athermal influence of electric current on dislocation motion is the fundamental mechanism for the electroplastic effect in different metals. Due to the significant scale difference between dislocation evolution and macroscopic deformation, it is difficult to figure out how the electric current affects the dislocation motion and further leads to the macroscopic electroplastic behavior since several interweaving mobile and immobile dislocations are involved. As a macroscopic manifestation of the interaction between dislocations and interstitial atoms, the Portevin–Le Chatelier (PLC) effect provides a satisfying entry point for solving the above problems by connecting the microscopic dislocation mechanism to the macro-scale electroplastic effect in a straightforward manner. Experiments of Al6061 in the tensile process show that the introduction of current causes two opposite effects, i.e., an increase of the pinning strength and a reduction of the time for dislocations to escape from pinning. Further microscopic characterization reveals that the reasons for the above phenomena include two aspects: (1) Promotion of the dissolution of the precipitated phase and increases in the concentration of interstitial atoms in the system. (2) Promotion of the motion of dislocations and the activation of additional slip systems. Those changes are closely related to the thermal and athermal effects of the current. Based on the observation results in this paper, the contradictions in the existing literature can be well explained. • Study on the influence of electric current on dislocation behavior based on the Portevin-le Chatelier effect. • The influence of currents on dislocation motion has two competing mechanisms related to thermal and athermal effects. • The research results successfully explained the contradictions in the existing research.

Theoretical, experimental and numerical study on the influence of connectors on the thermal performance of precast concrete sandwich walls

The thermal performance of precast concrete sandwich walls is in direct relation to energy efficiency of prefabricated buildings. This paper presents the theoretical, experimental and numerical studies on the thermal performance of precast concrete sandwich walls. The equivalent heat transfer coefficient model was proposed by theoretical analysis, and verified by experimental and numerical study. Six specimens with three types of connectors were fabricated, tested and modeled. The theoretical, experimental and numerical results agreed well, the accuracy of the equivalent heat transfer coefficient model was verified. It revealed how the material and geometrical parameters of connectors influenced the thermal performance of walls. The results showed that as the thickness of insulation increased from 30 mm to 90 mm, the heat transfer coefficient decreased by about 56.8%, 58.8% and 59.9% for theoretical, experimental and numerical results respectively. Meanwhile, an increased spacing and decreased connector length led to a better thermal performance, which further indicated the necessity to research the impact on thermal performance caused by connectors. It was also found that the proposed model was more suitable for the walls with stainless steel connector in this paper, for the walls with low thermal conductivity of connector like GFRP connector, the equivalent heat transfer coefficient could be obtained based on a prediction model of thermal bridge influence area and revised by correction factor in further research.

Heat transfer performance of new efficient coaxial casing heat exchanger based on thermostatic thermal response test

Ground-source heat pump (GSHP) systems are helpful for reducing building-sector heating and cooling energy consumption. As the core part of the GSHP system, the underground heat exchanger has a large influence on the heat transfer performance (HTP) of the system. The ground temperature variation characteristics of a new efficient coaxial casing heat exchanger (ECCHE) for heat extraction or rejection were investigated. The study was based on dynamic analysis of linear thermostatics used in the thermal response test and the HTP of the ECCHE. The influences of drilled borehole depth, circulation flow rate, and exchanger structure were considered. Results show that the HTP of the ECCHE is 1.61 (1.46) times that of the doublet U-pipe heat exchangers during heat extraction (heat rejection), and the radius thermal influence distance of the ECCHE is > 10 m. The spiral ribs of the ECCHE extended the heat transfer time between the fluid and surrounding rock, and the heat transfer in the upper part of the borehole was greater than that near the deeper part, so it is easy to produce continuous heat or cold accumulation near the borehole tops. Higher thermal conductivity rock, such as gneiss, has shown a faster recovery rate of the ground temperature after heat extraction. This work provides a theoretical basis for the optimization of the design and installation of GSHPs equipped with ECCHEs.

Research on formability, microstructure and mechanical properties of selective laser melted Mg-Y-Sm-Zn-Zr magnesium alloy

Selective laser melting (SLM) refers to a laser additive manufacturing technology. It shows its advantages of high efficiency and is capable of processing arbitrary complex structural parts. However, the SLM of magnesium alloy is highly challenging and should be studied in depth due to the low melting and boiling point of magnesium alloy. In this study, selective laser melting (SLM) technology was used to manufacture the Mg-Y-Sm-Zn-Zr alloy. Microstructure characteristics and performance mechanism of the SLMed samples were investigated. As revealed by the results, samples characterized by relatively high densities and low surface roughness could be produced when the energy density was 83.3–166.7 J/mm 3 . The highest density of 97.8% could be obtained when the energy density was 125.7 J/mm 3 . The molten pool was found to consist of slender columnar grains at the edge and a small amount of equiaxed grains at the top, while the grains below the molten pool were coarsened under the action of the thermal influence. The role played by Y 2 O 3 in the solidification of SLM was characterized using the degree of lattice mismatch. Impacted by the high lattice mismatch between Y 2 O 3 and Mg, Y 2 O 3 could not serve as an effective heterogeneous nucleation particle. The highest comperssive performance was obtained at energy density of 125.7 J/mm 3 (YS = 304 ± 5 Mpa, UTS = 394 ± 5 Mpa). The main strengthening mechanism was fine-grain strengthening, followed by precipitation strengthening and the effect of solid solution strengthening was not obvious. This work provides a certain guiding significance for the follow-up research of SLMed rare earth magnesium alloy. • SLM process parameters of Mg-Y-Sm-Zn-Zr which can obtain ideal relative density and surface roughness were determined. • The influence of Y and Zr elements on the solidification behavior of SLMed Mg-Y-Sm-Zn-Zr was determined. • The orientation relationship between precipitated particles and the magnesium matrix was studied. • The improvement of the compressive properties of the SLMed sample was analyzed.

Phase change materials composite boards and mortars: Mixture design, physical, mechanical and thermal behavior

Energy dependence is currently a serious problem faced by the European Union. In recent years there has been an effort to increase the use of renewable energy sources, which will allow for a sustainable increase in the energy independence of different countries. On the other hand, given the rising energy costs seen in recent years and the low income of families, energy poverty is increasingly a reality throughout Europe, especially weakening the most economically disadvantaged families. Thus, there is a need to combat this reality using renewable energies combined with functional and more energy efficient construction materials. In this study, composite boards based in mortars activated with phase change materials were developed. Initially, it was developed a study in the main properties of the PCM mortars based in the mechanical behavior, microstructure observation and thermal influence. Subsequently, PCM composite boards were developed and tested for their main physical and mechanical properties, in order to assess their possibility of inclusion in the market. Based in the results it was possible to conclude that the PCM incorporation in mortars and boards alters its properties from the physical, mechanical and thermal point of view. Regarding to the mortars characterization, there was a decrease in the flexural and compressive strength higher than 27 % and 26 % with the incorporation of non-encapsulated PCM, respectively. It was also observed a decrease in the microporosity, due to the more compact microstructure. Regarding to the thermal behavior it was verify a decrease in the maximum temperature of 6 % in summer situation and 9 % in spring season. On the other hand, there was an increase in the minimum temperature of 3 % in spring season. In the boards characterization there was an increase in the microporosity, due to the increase higher than 48 % of total porosity and 3 % in the water absorption by immersion with the PCM incorporation and a decrease in the flexural strength higher than 15 %. However, it was possible to conclude that the production of manufacturing boards based in PCM mortars can be seen as possible solution to increase the energy efficiency of buildings and decrease the energy poverty in the society.

A geospatial assessment of bio-thermal influence around Çatalagzı power plant region

Combustion of coal in thermal power plants poses significant threat to surrounding ecology, by the release of harmful effluents. This study assesses the bio-thermal impact of emissions from Catalagzı Thermal Power Plant Region (CTPPR). A geospatial analytical framework has been modeled, utilizing satellite-based bio and thermal indicators. Average hazardous bio and thermal influence zones around CTPPR have been found to be 1465 m and 1380 m, respectively. Bio-influence zone extent depends upon a combination of meteorological factors, whereas, the bio-hazard severity depends mainly on atmospheric temperature. Thermal influence extent is inversely related to seasonal temperature, whereas corresponding severity depends upon local heat sinks as well. Collectively, hazardous bio-thermal influence in the surroundings of CTPPR shows spatial constancy over long term. The study concludes usefulness of satellite-based economical alternatives for monitoring area under stress around CTPPR for sustainable environmental management of ecological landscapes, needed to improve the human-environment nexus. Highlights Investigation of Thermal Power Plant (T P P) as source of environmental pollution Dynamic geospatial bio-monitoring of vegetation using satellite-based VIs is done Geospatial analysis reveals details of zones of hazardous bio-influence around T P Ps. Identified factors determining extent and severity of hazard by T P P emissions. Effectiveness of geospatial technology for ecological assessment is demonstrated

A MODEL OF WELDING THERMAL PROCESSES WITH A LIMITED NUMBER OF FICTITIOUS POINT SOURCES

Analytical methods of calculation of thermal processes at welding enable to estimate operatively the influence of welding modes on parameters of a temperature field and to predict structural changes in a zone of thermal influence. In the mid-twentieth century it was suggested to calculate the heat processes in welded products with parallel boundary planes by summing up the temperature fields of the main and infinite number of fictitious point sources using thereflection method. However, due to computational difficulties, this method could not be brought to a state of wide practical application. Furthermore, since the schematization of heated bodies is conditional, the choice of the body scheme (plate, flat layer, semi-infinite body) and therefore the thermal calculation model is performed intuitively based on the accumulated experience. This uncertainty inevitably leads to discrepancy between the calculated and actual parameters of the thermal welding process. The purpose of this work is to adapt a model of thermal processes with a limited number of fictitious fast moving point sources to the calculation of thermal welding processes. The proposed model, solvable in Mathcad software, contains the equations of temperature field and temperature rate of change with account of the number
 of fictitious heat sources involved in the calculation. This model allows a reasonable limitation of the number of fictitious heat sources for providing the required accuracy of calculations, since as the fictitious heat sources move away from the product and their influence on the product heating decreases. In most cases for practical calculations 2 pairs of fictitious sources are enough for welding of 2 cm thick steel products, of 0.5 cm thick products ‒ 5 pairs, of 0.2 cm thick products ‒ 12 pairs. Comparison of the calculated values of the proposed model with actual temperature field measurements and known effects of cooling rate in the plate, plane layer and semi-infinite body within the accepted limits have confirmed its adequacy. The presented comparative results demonstrate versatility of the proposed model with a limited number of fictitious fast moving point sources, which can be applied sufficiently and successfully for analysis of the thermal welding processes of real industrial products of arbitrary thickness without discriminating into plate, plane layer and semi-infinite body models.

Increasing corrosion and mechanical resistance destruction of welding cover capacities water towers

The paper considers standard methods for determining the corrosion and mechanical characteristics of pipes and their welded joints, steel shell structures for water supply to consumers. It was found that sharp fluctuations in the values of microhardness in the zone of thermal influence of the welded joint exceed the baseline values in the middle part of the weld and the base metal of the pipe. The obtained results can be used to test the performance of carbon steel steels designed for the construction of water towers of long service life in corrosive environments. Under the action of the temperature gradient on the outer surfaces of the walls of the water tank tensile stresses occur, and on the inner surfaces-compressive, which is a favorable factor that reduces the risk of corrosion. Temperature stresses that occur in the case of temperature inhomogeneity along the contour of the cylindrical tank are unfavorable. Stresses from the weight load are small and do not have a significant effect on the destruction of the steel tank, because they are compressive. The value of technological final stresses was determined experimentally by mechanical strain gauge according to the classical method, as well as with the help of electric strain gauges and ultrasonic method according to the method of E. O. Paton Electric Welding Institute (PWI). It has been experimentally established that the most dangerous final welding stresses in assembly seams, the value of which for the longitudinal stress component is close to or exceeds the yield strength , and for the transverse – close to the yield strength , while on steel plates VSt3 of the same thickness . It is likely that welding during installation in conditions of rigid compression of the metal causes an increased level of final stresses. The magnitude and sign of the final stresses significantly depends on the method of installation. Even during block installation, when the water tower is mounted from several pre-annealed blocks, the connection between the mounting ring seams in some areas of the base metal near these seams during fitting creates significant stresses (up to 17.6 kgf / mm2), in some areas – up to 6 kgf / mm2. When sheet assembly stresses can reach a level close to the yield strength.

EFFECT OF HEATING TEMPERATURE AND COOLING RATE ON THE FORMATION OF STRUCTURAL COMPONENTS IN STEELS

Formulation of the problem. One of the key areas of research into the mechanical properties of steels lies in developing methods of manufacturing steels with a grain structure and a high degree of carbides dispersion or other inclusions that will be located in the pearlite grain as a result of heat treatment. Changes in external factors such as temperature, pressure etc. are known to cause changes in the structural components of alloys and steels. The most usual way of fixing the high-temperature state for metal systems is through hardening, which is the removal of heat at high rateIt is known that microcomplexes formation is possible in melts at temperatures exceeding the liquidus temperature. There is much research of melts at temperatures above liquids for the presence of stable microcomplexes in binary alloys. However, there are no data on heat flow above the liquidus line for phase formation during crystallization and the structural components formation in steels. Purpose of research − investigation of chemical composition effect and heating temperature above the liquidus line and cooling rate on the structure formation in steels. Methods. Microstructural, micro X-ray spectral and X-ray phase analyses to determine the steel structural properties are used. Results. A new type of heat treatment including heating of the experimental steels with the alloy system (K + (Al + N + Ti)) and (K + (Al + + N) above the low-temperature line by 50...150 ºC is suggested and investigated. Subsequent cooling at rates of 102…105 ºС to fix the melt high-temperature state after experimental steels heating over the liquidus line by 50…150 ºС is performed. As a result of such processing the dispersed structure which is strengthened by dispersed inclusions is formed. The inclusions were < 0,1 μm in size and were evenly distributed in the grain volume and partially along the boundaries. The martensite formed by the steel rapid cooling had a finely differentiated and rail-like morphology. Scientific novelty. A new method of steel processing is proposed. Regularities of structural components formation in the heat treatment process including steels’ heating over the liquidus line by 150…170 ºС is determined. Practical significance. This method of thermal action influence allows to receive the homogeneous structure strengthened by dispersed inclusions. The method allows choosing the optimal modes of differentiated heat treatment to obtain the most homogeneous structural state and specified mechanical properties.

Heat transfer in micropolar hybrid nanofluid flow past a vertical plate in the presence of thermal radiation and suction/injection effects

Hybrid nanofluid are considered as advanced nanofluid, as shown by their thermal properties and budding benefits that aid the drive of increasing the heat transfer rate. This article deals with the MHD natural convective flow of micropolar CuO-Ag/water hybrid nanofluid over a plate placed vertically in a porous medium with the involvement of the suction/injection at the surface of the plate, heat generation/absorption, Joule heating, viscous dissipation, and thermal radiation influence. The similarity transformations are used to translate the fundamental controlling PDEs to ODEs. After that, nonlinear ODEs are solved by means of the R − K − F 4–5th order method and shooting technique. The comparison between the behavior of solution profiles of temperature, micro-rotation and velocity distribution for suction and injection has been visualized graphically. The effect of different shape factors on the solution profiles is also discussed. The influence of the relevant flow parameters on the heat transfer and skin friction factor are also studied. The main observation is that the heat flow rate is higher with the injection effect than with the suction effect.

A Top-Oil Thermal Model for Power Transformers That Considers Weather Factors

The aim of this work is to develop a top-oil thermal model based on the thermal-electrical analogy and heat transfer principles that captures the thermal influence of prevailing winds and solar radiation which can be generally applied to large power transformers. The key improvements of the proposed thermal model are calculating the heat transfer coefficient of the radiator on the air side using the Nusselt number of combined forced and natural convection, and including the solar radiation as an addition heat source. The proposed model is validated with the operational measurements of 3 transformers that are comprised of a 120/240-MVA unit and two 90/180-MVA units. The results are also compared with the predictions based on the IEEE-Annex G model. The proposed model is more accurate over windy and summer periods as expected.

In Planta Nitrate Sensor Using a Photosensitive Epoxy Bioresin.

Nitrogen management through monitoring of crop nitrate status can improve agricultural productivity, profitability, and environmental performance. Current plant nitrate test methods require expensive instruments, time-intensive labor, and trained personnel. Frequent monitoring of in planta nitrate levels of the stalks in living plants can help to better understand the nitrogen cycle and the physiological responses to environmental variations. Although existing enzymatic electrochemical sensors provide high selectivity, they suffer from short shelf life, high cost, low-temperature storage requirement, and potential degradation over time. To overcome these issues, an artificial enzyme (vitamin B12 or VB12) and a two-dimensional material (graphene oxide or GO) are introduced into a conventional photoresist (SU8) to form a bioresin SU8-GO-VB12 that can be patterned with photolithography and laser-pyrolyzed into a carbon-based nanocomposite C-GO-VB12. The electrocatalytic activity of the cobalt factor in VB12, the surface enhancement properties of GO, and the porous feature of pyrolytic carbon are synergized through design to provide C-GO-VB12 with a superior ability to detect nitrate ions through redox reactions. In addition, laser writing-based selective pyrolysis allows applying thermal energy to target only SU8-GO-VB12 for selective pyrolysis of the bioresin into C-GO-VB12, thus reducing the total energy input and avoiding the thermal influence on the materials and structures in other areas of the substrate. The C-GO-VB12 nitrate sensor demonstrates a year-long shelf lifetime, high selectivity, and a wide dynamic range that enables a direct nitrate test for the extracted sap of maize stalk. For in situ monitoring of the nitrate level and dynamic changes in living maize plants, a microelectromechanical system-based needle sensor is formed with C-GO-VB12. The needle sensor allows direct insertion into the plant for in situ measurement of nitrate ions under different growth environments over time. The needle sensor represents a new method for monitoring in planta nitrate dynamics with no need for sample preparation, thus making a significant impact in plant sciences.

Innovation of Poly(Lactic Acid)/Carbon Black Composite as an Environment-Friendly Antistatic Packaging

Antistatic packaging mainly functions to protect an electronic device from damage caused by the electronic discharge. However, antistatic packaging is typically made with a polymer that's hard to decompose naturally, this can badly affect Indonesian environments considering Indonesian produce a lot of plastic waste. Therefore, environmentally friendly antistatic packaging could potentially alleviate several plastic wastes generated. Antistatic packaging made of Conductive Polymer Composite (CPC) with Poly Lactic Acid as its matrics have a biodegradable characteristic, biocompatibility, resistance to thermal and chemical influence. And the use of Carbon Black as its filler can increase the electrical conductivity of CPC. CB is synthesis by burning coconut shells and activation with H 2 SO 4 . The synthesis of CPC samples was carried out by 2 methods; melt blending using an extruder and solvent blending using chloroform solvent and stirring with a magnetic stirrer at 650 rpm at 60°C. The filler composition was varied, namely 0, 0.5, 0.1, 1.5% by weight of PLA for blending melt and 0, 1.5% by weight of PLA for blending solvent. The thermal properties of the sample were tested by DSC, it was found that the Melting Temperature of the sample was not much different from that of pure PLA with a difference of 0.4-2.2°C. With the FTIR test, it is known that the solvent has completely disappeared from the sample, and the conductivity test shows a increase in conductivity along with the addition of filler from 9,505x10 -12 S/cm to 5,752x10 -7 S/cm and 9,872x10 -12 S/cm to 1,034x10 -6 S/cm for melt and solvent method.

The Effect of Laser Ablation Pulse Width and Feed Speed on Necrosis and Surface Damage of Cortical Bone

Bone cutting is of importance in orthopaedic surgery but is also challenging due to its nature of brittleness—where severe mechanical and thermal damages can be introduced easily in conventional machining. Laser machining is a new technology that can allow for complex cut geometries whilst minimising surface defects i.e., smearing, which occur in mechanical methods. However, comparative studies on the influence of lasers with different pulse characteristics on necrotic damage and surface integrity have not been reported yet. This paper for the first time investigates the effects of laser type on the necrotic damage and surface integrity in fresh bovine cortical bone after ex-situ laser machining. Three lasers of different pulse widths, i.e., picosecond, nanosecond and continuous wave lasers have been investigated with different feed speeds tested to study the machining efficiency. The cutting temperature, and geometrical outputs have been measured to investigate the thermal influence on the cooling behaviour of the bone samples while high-speed imaging was used to compare the material removal mechanisms between a pulsed and continuous wave laser. Furthermore, an in-depth histological analysis of the subsurface has revealed that the nanosecond laser caused the largest necrotic depth, owing to the high pulse frequency limiting the dissipation of heat. It has also been observed that surface cracks positioned perpendicular to the trench direction were produced after machining by the picosecond laser, indicative of the photomechanical effect induced by plasma explosions. Therefore, the choice of laser type (i.e., in terms of its pulse width and frequency) needs to be critically considered for appropriate application during laser osteotomy with minimum damage and improved healing.

Investigation of processes in spark gap during contact butt welding of railway rails

Modern equipment for contact butt welding of railway rails has a huge number of technological parameters (input factors) that affect the quality of the resulting welded joint. These parameters do not allow the optimal welding modes to be fully selected. The study of the processes occurring in the spark gap (formation of microcontacts, increase or decrease in their cross-sectional area, explosion of the resulting microcontacts) will make it possible to determine the amount and uniformity of the invested heat during rail welding. The acquired knowledge will reduce the number of influencing factors on quality of the welded joint. Using a large amount of statistical data, the authors have investigated the processes occurring in the spark gap during contact butt welding of railway rails of R65 type of DT350 category on K1000 rail welding machine. When studying the influence of movable plate movement of the welding machine during reflow on the strength of welding current, it was determined that there is no dependence between these values. The random nature of distribution of the welding current values is assumed, changing as a result of the processes of formation, existence and explosion of a large number of tiny electrical contacts. Based on the analysis of frequency distribution, it is certain that distribution of the spark gap resistance does not correspond to the normal distribution law. As the sample increases, the deviation from it increases; visually the histogram describes the gamma distribution. With the help of the gamma distribution law, the welding current forces during contact butt welding were modeled by reflow. The research results are planned to be used to simulate thermal processes and formation of the structure of weld metal and the zones of thermal influence of railway rails welded joint.

A comparative numerical study of shell and multi-tube heat exchanger performance with different baffles configurations

This study presents a numerical modeling of a shell and tube heat exchanger to analyze six various baffle configurations for increasing the thermal parameters performance and hydraulic parameters performance. The baffle configurations include conventional single segmental (CSS), staggered single segmental (SSS), Flower segmental (FS), hybrid segmental (HS), circular ring baffle (CR), and circular ring with holes (CRH) baffles. Flow of water field characteristics, pressure loss, and heat transfer performance, including effectiveness (ε) and the heat transfer coefficient (h) are studied with a variation of Reloads numbers from 10500 to 38500 to analyze the best performance. The effectiveness and the heat transfer coefficient increase with increasing the Reynolds numbers. The HS configuration results are the largest shell side pressure loss while HS and CR thermal influence on heat exchanger performance augmentation is found to be more significant compared to other configurations for all test cases. Compared to the CSS and SSS baffle configurations, the dead spaces and the recirculation zones are disappearing in both FS and HS configurations where the RCH is superior in overcoming the dead zones completely. The maximum values of the effectiveness and heat transfer coefficient of STHX are achieved in the case of CRH type with enhancement about 166% and 142% respectively, compared to CSS baffle. The CRH accomplished less friction losses than hybrid and ring baffles where the shell side pressure drop for HS was the highest value. The heat transfer coefficients per pressure loss of the RCH are about 138% higher than that of other configurations.

Methods for Solving Multiphase Fluid Flow Problem under Thermal Influence on the Reservoir through Horizontal Wells

Methods for Solving Multiphase Fluid Flow Problem under Thermal Influence on the Reservoir through Horizontal Wells

Soil Thermal Response to Temperature Cycles and End Boundary Conditions of Energy Piles

This paper explores the influence of building cover and pile toe boundary conditions on ground temperature distributions surrounding energy piles. Experimental and numerical studies were conducted on two isolated cast-in-place energy piles installed in dense unsaturated sand, one exposed to the atmosphere at the ground surface (diameter=0.6 m and length=16.1 m) and the other installed under a six-story building (diameter=0.6 m and length=10 m). Investigations were conducted for monotonic heating and daily cyclic temperature changes of the piles ranging between 10°C and 35°C. The changes in ground temperature decreased as radial distance increased from the edge of both piles. Cyclic temperatures in both piles induced lower ground temperature changes and decreased the radial thermal influence zone compared with monotonic heating. However, the radial thermal zone in cyclic operating mode can be influenced by different ratios of heating to cooling times and hence should be selected carefully to avoid unexpected ground temperature changes. Atmospheric effects were observed up to a depth of 2 m for the energy pile exposed to the atmosphere. The insulation provided by the building footprint slightly decreased the impacts of ground-atmosphere interaction on the soil temperature distribution with depth near the surface compared to the energy pile exposed to the atmosphere. The ground temperature variations were dominant along the length of the heat exchanger loops for both piles. However, they were negligible near the pile toe below the heat exchanger loops for both piles.