Initial Temperature Research Articles

Experimental investigation of flow characteristics of a jet in low atmospheric pressure conditions on the Tibetan Plateau

The indoor humidity of heated buildings on the Tibetan Plateau can be as low as 5%RH. Indoor air humidification is very important to people's life and health. Due to the low atmospheric pressure on the plateau, the air physical parameters and wet component diffusion characteristics are different from those of standard atmospheric pressure. This paper investigates experimentally the effects of horizontal and vertical wet jets with various initial velocities, pipe diameters, ambient temperatures, and moisture temperatures on the indoor temperature and humidity field. It is shown that low atmospheric pressure will lead to an increase in relative humidity nearly the jet outlet, but the effective moisture delivery distance becomes shorter and the actual moisture load increases. When the same relative humidity is reached, the specific humidity under low atmospheric pressure is about 1.5–2.5 times as that under standard atmospheric pressure. The average relative humidity of jets produced by the ultrasonic humidification source is 10% higher than the evaporative humidification source during the same time. During the actual humidification process, it is necessary to consider the balance between the initial velocity of the jet and the humidification distance and select the jet tube diameter according to the humidification space area. Additionally, choosing a jet with a temperature slightly higher than the ambient temperature can avoid reducing the indoor temperature. This study should be helpful to the plateau humidification jet characteristics and parameter selection.

Using the vronskian to analyse the thermogram of a producing well

The functional dependence of thermograms in producing wells has been studied in order to determine the initial temperature distribution along the wellbore. Information about the initial thermal field makes it possible to ensure the reliability of solving the problem of determining the operating intervals in production wells. In this paper, we propose a method for isolating the linear dependence on the thermogram profile in the intervals of the absence of fluid movement (in the sump of a working and along the trunk of an idle well) by constructing a special function – the vronskian. In this paper, it is established that the use of the vronskian can be used to restore the geothermal distribution, as well as to obtain the value of the geothermal gradient and temperature in the analysis of the thermogram. To discuss the possibilities of the proposed method, three cases were used: a model and two thermograms in a real field study. The first option considered is a synthetic thermogram with a quasi-stationary mode of operation of the well. In the second and third cases, the results of thermometric studies in the well with a short-term inflow from the reservoir with the same and different lithological structure of the intervals in the sump are presented. The obtained algorithm can be used to isolate the intervals of linear dependence during express processing of registered thermograms in order to obtain quantitative parameters of the operation of the borehole-formation system.

Investigation of Rock Mechanical Properties under Liquid Nitrogen Environment

In order to promote sustainable energy development and reduce the impact of fossil fuels on the environment, it is crucial to strengthen the development and utilization of clean and renewable geothermal energy. Liquid nitrogen fracturing, as an emerging waterless fracturing technology, has outstanding advantages in rock fracturing effect and thermal exchange ability with hot dry rock and is more environmentally friendly. In order to evaluate the influence of liquid nitrogen on the mechanical properties, acoustic emission characteristics, and cross-sectional crack propagation characteristics of granite at different initial temperatures, this paper carried out three-point bending tests and acoustic emission detection on granite treated by high-temperature heating and liquid nitrogen cooling. Finally, based on the cross-sectional scanning test, the expansion characteristics of microcracks in granite were analyzed. The results show that the higher the initial temperature of granite, the stronger the cold impact of liquid nitrogen on granite, and the faster the rock’s mechanical performance declines. The acoustic emission ringing count is closely related to the development of microcracks in granite, and as the initial temperature of granite increases, the more ringing counts there are, indicating that the huge temperature difference induces more microcracks inside the rock. In addition, the cold impact of liquid nitrogen can effectively promote the fracturing of granite. After liquid nitrogen treatment, the fractal dimension of the granite cross-section increases, the shape of the cross-section becomes rough, and many micropores appear. This study can provide a scientific basis for the engineering application of liquid nitrogen fracturing technology.

Gas-liquid contact evaporation of concentrate leachate from disk-tube reverse osmosis treatment in waste incineration plant

In order to utilize waste heat such as exhaust steam and hot air passing through air preheater in the waste incineration plant to heat air used for evaporating leachate concentrate (LC) by gas-liquid contact evaporation technology, hot air of 600 °C, 450 °C and 250 °C was used to evaporate LC in a laboratory-scale evaporator to obtain purified condensate used for supplying water for circulating cooling water system. The influence of pH, hot air temperature and evaporation rate on COD and NH3–N in condensate were investigated to identify the optimum operation of this technology. The results showed that COD concentration in condensate obviously decreased with increase in hot air temperature. Higher hot air temperature led to higher initial evaporation temperature, and evaporation rate of water was significantly greater than that of small molecular organic matter with lower boiling point than water with increasing hot air temperature. Reduction in contents of phenol, ketone and benzene was responsible for COD decreasing in condensate. COD in condensate decreased with increase in pH, as the amount of volatile organic matter such as fatty acids escaped from LC to condensate decreased. The pH had little influence on the DOM in condensate according to EEM spectra analysis. Evaporation rate had little influence on COD in the condensate water. NH3–N concentrations in condensate in all experimental groups were far away from the limit value (10 mg/L) in the water quality standard. Under the premise of meeting water quality standard, the lowest temperature (450 °C) of hot air was selected to save energy and use lower grade waste heat. Therefore, the optimum condition was 450 °C of hot air, pH = 7 of LC and CF = 10. At this condition, molecular weight of DOM in the condensate was smaller and humification degree and aromaticity of DOM were lower according to UV–visible absorption spectrum analysis.

Adsorption of hexavalent chromium from aqueous solution onto corn cobs – activated carbon

This study evaluated the performance of a new activated carbon (CCs-AC) produced from corn cobs by boric acid activation for the effective removal of hexavalent chromium, a heavy metal with high potential to pollute the environment, from wastewater. For this purpose, with the help of parameters such as solution pH, contact time, initial Cr(VI) concentration, CCs-AC dose, desorption and temperature, the removal of Cr(VI) ions from aqueous solution by adsorption on CCs-AC was investigated from equilibrium, kinetic and thermodynamic point of view. As a result of the experiments, it was determined that the optimum solution pH was 2.0, the contact time was 4 hours, and the desorption solution was 3.0 M NaOH. From the kinetic data, it was determined that the adsorption was compatible with the pseudo-second order kinetic model and the maximum Cr(VI) adsorption capacity (123.7 mg/g) obtained from the Langmuir isotherm model showed that CCs-AC was of competitive quality with the literature. From the thermodynamic data, the positive ΔH value indicates that the adsorption is endothermic and the value of 12.00 kj/mol indicates that the adsorption is rather chemically driven. The negative ΔG value indicates that the process proceeds spontaneously with an increase in temperature, while the ΔS value indicates an increase in the amount of unused energy.

Synthesis and Thio-Functionalization of Metal Organic Frameworks of Isonicotinate Ligands and their Application for Fluorescein Removal from Aqueous Solution

Mechanochemical syntheses of four (4) know metal organic frameworks (MOFs) were obtained by grinding stoichiometric amounts of metal salts [Zn (II) and Cu (II)] and corresponding carboxylate ligands [Fumaric and Isonicotinic acids] in a mortar with a pestle. Also, Solvent-based syntheses of MOFs were carried out with the reaction of metal salts and each carboxylate ligand by mixing in the presence of solvents. The compounds were characterized by the comparison of melting point, elemental analysis, FT-IR spectroscopy and XRPD results with those of the free ligands and literature. The analytical and spectroscopic data of the compounds prepared via the two different methods gave the expected product.
 The presence of coordinatively unsaturated metal centers in the synthesized MOFs provides an accessible way to selectively functionalize them through coordination bonds. In this work, thiol-functionalization of MOFs were described by choosing six well known MOFs in which three (3) are Zn-based while the other three (3) are Cu-based MOF, by a facile coordination based postsynthetic strategy. The obtained thiol-functionalized MOFs were characterized by powder X-ray diffraction, CHN and infrared spectroscopy. The analytical and spectroscopic data of the unmodified and modified compound were different.
 A series of [Cu (Ina)2] samples stoichiometrically decorated with thiol groups has been prepared through coordination bonding of coordinatively unsaturated metal centers with –SH group in thioglycolic acid. [Cu (Ina)2]. H2O and [Cu(Ina)2]-TH were investigated for the adsorptive removal of fluorescein from aqueous solution. The parameters that affect the dye sorption such as contact time, solution pH, initial fluorescein concentration and temperature, have been investigated and optimized conditions determined at PH of 7.8. Dubinin–Radushkevich Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of MOFs and experimental results showed that the removal efficiency decreases in the order of [Cu(Ina)2]-TH > [Cu(Ina)2].H2O both in adsorption rate and adsorption capacity. The Langmuir, Freundlich, Temkin and Dubinin Radushkevich models have been applied and the data correlate well with Dubinin Radushkevich model. The adsorption mechanism may be explained with a simple electrostatic interaction and π- π interaction. Finally, it can be suggested that modification of MOFs can be use to improve their adsorption capacity and rate, making them a better adsorbent to remove emerging dyes contaminants from waste water.

Karakterisasi Termal Briket Ampas Tebu melalui Uji Termogravimetri


 
 
 
 Sugarcane bagasse has potential to be used as one of the renewable energy resources. The present work is dealt with thermal characterization of sugarcane bagasse briquettes through thermogravimetry method. The briquette samples are cylinder of 40 mm in diameter and 20 mm long. Both non-carbonized and carbonized briquettes are considered in this work. The samples comprise two different densities, i.e. 1.3 g/cm3 and 2.3 g/cm3. The samples are heated in an inert and non-isothermal atmosphere with heating rates of 5oC/min and 15oC/min. The TG curves exhibit three phases of thermal decomposition. The decomposition of the samples with higher heating rate and higher density shifts to higher temperature. The decomposition of the carbonized samples also shift to higher temperature, but to a lesser degree. The initial degradation temperature ranges from 186oC to 273oC, while the final degradation temperature ranges from 328oC to 432oC. The temperature at which the rate of decomposition is amximum ranges from 232oC to 303oC. At higher heating rate, the degradation rate shifts to lower temperatures
 
 
 

Low-temperature preparation of spherical nano α-Al2O3 particles by chelating the structure of anhydrous aluminium sols

α-Al2O3 exhibits excellent physical and chemical stabilities and thus has a wide range of applications in various fields, however the potential application are often called off because of the grains coarsening and vermiculite structures originated from the high-temperature calcination process. In this paper, the calcination temperature has been significantly reduced by selecting the chelating anhydrous aluminium sols as the precursor. It was found that when the chelating agent was malic acid and the addition amount was 0.06 mol, the chelated structure had the highest content of [AlO6] octahedra, which was more favourable for the low-temperature synthesis of α-Al2O3. Kinetic analysis showed that the activation energy for the conversion of γ-Al2O3 to α-Al2O3 in this work was 398.09 kJ mol−1, which has been reduced by nearly 100 kJ mol−1 and thus the complete conversion of γ-Al2O3 to α-Al2O3 was achieved by holding at 900 °C for 2 h. The obtained spherical α-Al2O3 nanoparticles, with a particle size of about 67.2 nm and a uniform morphology. After further extending the holding time to 30 h, the complete conversion of α-Al2O3 was achieved at 825 °C, while the initial nucleation temperature was lower than 760 °C.

Thermal stability analysis and mechanical performance of Mediterranean lignocellulosic fiber reinforced polypropylene sustainable composites

The utilization of the available agro waste to make sustainable materials was recently emphasized to develop better bio-products and sustainable socio-economic environment. This work investigates the effect of reinforcing polypropylene with lemon leaves (LL) and fig leaves (FL) on the overall mechanical performance of the prepared composites considering various reinforcement conditions. The investigations including determining the tensile strength, tensile modulus, elongations at break, flexural and impact properties as well as revealing the thermal characteristics of the fibers to expose their suitability for such bio-based composites. Thermal gravimetric analysis (TGA) and its derivative (DTG) were used to study the thermal stability of fiber composition during manufacturing. The surface morphology of the fibers as well as their polypropylene composites were analyzed using scanning electron microscopy (SEM). Results have revealed that LL positively affects both tensile strength and modulus. The 20 wt% of LL have enhanced the tensile modulus from 1229 MPa to 1321 MPa. However, FL had negative impact on the tensile properties regardless of weight %. FL and LL reduced the flexural strength and impact toughness of PP regardless of weight %. The tensile strength of the 30 wt% lemon leaves-PP composite reaches its highest value at 43.4 MPa. Furthermore, thermal analysis showed that the fibers did not decompose during the manufacturing process. The initial decomposition temperatures of LL and FL were 239 °C and 226 °C, respectively, exceeding the processing temperature of 170 °C. Furthermore, an in-depth comparison of the tensile strength of the studied FL/PP and LL/PP composites with other commonly used PP composites available in the literature was also performed here to demonstrate the potential of Mediterranean fibers and their suitability for green bio-composites.

Discontinuous dynamic recrystallization behavior and texture evolution of large-size pure titanium flat ingot via electron beam cold hearth melting during short process direct hot rolling

Large-size pure titanium ingots melted by single electron beam cold hearth melting (EBCHM)) could be rolled into large-width and heavy-weight titanium strip coils using short process without forging. It is crucial to study the large-span refinement mechanism from highly coarse grains, whose sizes are in the order of ∼cm, to micronmeter. In this study, the recrystallization mechanism and texture evolution of pure titanium with a size of 1570 × 200 × > 8000 mm was investigated by multi-pass simulated rolling and experimental rolling. The results indicated the hot deformation can result in marked reduction in grain size of the as-cast grain, from 3 to 5 cm to 17–23 μm. The discontinuous dynamic recrystallization (DDRX) mechanism of a pure titanium ingot during direct multi-pass hot deformation causes the reconstruction of as-cast microstructure and refinement of hot rolling microstructure. Furthermore, DDRX occurred, during hot deformation, and was accompanied with weakening of deformation texture. Raising the initial hot deformation temperature results in a modification of the texture type of the {0001} crystal plane. The strength of the texture experiences a decrease initially and then eventually an increase. This alteration in strength is inversely related to the degree of dynamic recrystallization. Based on the simulated rolling experiment, the results of experimental rolling also found the coarse as-cast grains was broken and reconstructed. It has strength (average yield strength: 334 MPa, ultimate tensile strength: 371 MPa), ductility (total elongation: 30 %). Such a combination of mechanical properties makes the hot rolling plate a potential choice for sheet practical application.

Investigation of catalytic activation of peroxydisulfate on cu-doped mesoporous silica-based particles (Cu-BMS) for efficient degradation of methylene blue

The Cu-doped mesoporous silica-based particles (Cu-BMS) were prepared using an evaporation-induced self-assembly sol-gel procedure as a heterogeneous catalyst for the activation of peroxydisulfate (PDS). The formation of well-organized mesoporous structures with amorphous nature and high surface area of 286 m2/g was demonstrated. The catalytic activity of Cu-BMS in the degradation of Methylene Blue (MB) and the effects of operating parameters, including Cu-BMS dosage, initial PDS amount, initial MB concentration, temperature and initial pH, were investigated in details. The Cu-BMS demonstrated a remarkable catalytic activity (93.5% degradation efficiency within 60 min) and good stability.

A novel macromolecular phosphorus-nitrogen containing flame retardant for polycarbonate

In this paper, an innovative macromolecular phosphorus-nitrogen containing flame retardant (PDPSB) was successfully designed and synthesized to investigate its impact on the flame retardancy, burning behavior, thermal stability, mechanical properties of polycarbonate (PC) composites. Furthermore, an in-depth exploration of the potential flame-retardant mechanism was conducted. The combustion results indicated that PC-3 with 3 wt% PDPSB reached V-0 rating in UL-94 test and showed a high limiting oxygen index (LOI) of 33.0 %. Compared to pure PC, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of PC-3 were decreased by 37.9 %, 11.1 % and 4.9 %, respectively. It was noteworthy that the amount of char residue for PC-3 was raised from 7.4 % for pure PC to 15.8 % with increasing 113.5 %. The thermogravimetric analysis (TGA) results under N2 atmosphere revealed that PDPSB possessed preferable thermal stability with initial decomposition temperature (Tinitial) of 342.6 °C and higher char residue yield of 48.4 %. With increasing the amount of PDPSB, the maximum mass loss rate (Rpeak) was reduced and the char residue yield was increased for PC/PDPSB composites. In addition, the mechanical properties of PC/PDPSB composites were well maintained due to the good compatibility and dispersion between PDPSB and PC matrix. The tensile, flexural and izod impact strength of PC-3 were weakened by 4.3 %, 1.7 % and 16.8 % in comparison of pure PC, respectively. Based on the investigation into the flame-retardant mechanism of PDPSB, the excellent flame retardance of PC/PDPSB composites has been validated. In gaseous, the release of pyrolysis gases was suppressed and active radicals were captured by generated phosphorus free radicals. In condensed phase, the stable char residue with phosphorus and nitrogen elements acted as a barrier to hinder heat, flame and oxygen. This high-efficient single-component multifunctional additive presented a novel approach to the development of fire-resistant polymers with enhanced performance characteristics.

Functionalized magnetic chitosan-based adsorbent for efficient tetracycline removal: Deep investigation of adsorption behaviors and mechanisms

As removal performance of tetracyclines in traditional wastewater treatment plants cannot satisfy the increasingly strict discharge requirements, developing an efficient approach to overcome this problem is quite urgent. Herein, a novel functionalized magnetic chitosan-based adsorbent (Fe3O4@CAA) with core-shell structure and unique magnetic responsiveness was facilely prepared by ultrasound-initiated radical grafting copolymerization and cross-link reaction. The as-prepared Fe3O4@CAA was fully characterized with TEM, SEM, BET, FTIR, TGA, XRD, VSM, and served as an efficient adsorbent for tetracycline hydrochloride (TCH) removal. Adsorption behaviors of TCH by Fe3O4@CAA were deeply evaluated at different adsorption time, initial TCH concentration, reaction temperature, solution pH, and background pollutant concentration. Results showed that Fe3O4@CAA presented a more competitive adsorption capacity of 325.04 mg g−1 compared with Fe3O4@CS and other reported adsorbent, due to the introduction of more active adsorption sites by abundant functional groups, including amino groups, hydroxyl groups, and sulfonic acid groups. After saturated adsorption, TCH loaded Fe3O4@CAA was easily collected by magnetic separation, and recycled after acid pickling. Fe3O4@CAA was successfully reused in five adsorption-desorption cycles, without obvious adsorption capacity loss. In binary pollutant systems, inorganic cations and Pb(II) restrained TCH adsorption by competitive effect, while proper amount of Cu(II) promoted TCH adsorption by bridge effect. FTIR and XPS analyses revealed that the adsorption mechanism of TCH by Fe3O4@CAA mainly included electrostatic interaction and hydrogen bonding, and Cu(II) could play a “mediator” role to form a strong Cu(II)-TCH complex to enhance TCH removal performance. This study provides an effective strategy for the design of magnetic chitosan-based adsorbents and valuable guidance for the removal of tetracyclines from wastewater.

Performance and carcass characteristics of cattle with different castration practices

The aim of this research was to evaluate the performance and carcass characteristics of immunocastrated cattle, in comparison to castrated and non-castrated cattle supplemented on pasture. 36 bovines were used, distributed in a completely randomized design, in 3 treatments: non-castrated animals (ANC), animals castrated late by the surgical method (ACC) and immunocastrated animals (AIC), with 12 replicates each. Immunocastration was performed following the protocol of two doses of the immunocastrating vaccine, with an interval of 60 days, promoting a castrated effect of 120 days. The animals were kept on mixed pasture in an extensive rearing system using rotational grazing, they received mineral supplement in the first 3 months and specific feed for the fattening season in the subsequent 3 months, according to the property’s standards. The total experimental period was 180 days. Data were hidden from the normality test, analysis of variance and mean comparisons were performed using the Tukey test, except for the variable degree of finishing, which was maintained at the chi-square test, at 5%. Average daily weight and total weight gains, hot and cold carcass weights and hot and cold carcass yield did not show statistical differences (P>0.05) for animals submitted to different treatments. However, the cooling loss was lower in immunocastrated animals (P<0.05), followed by surgically castrated and non-castrated animals. Immunocastrated and surgically castrated animals showed better carcass finishing (P<0.05) than non-castrated animals. The initial temperature of the carcass was lower (P<0.05) in the immunocastrated group, while for the final temperature no statistical differences (P>0.05) were verified for the animals submitted to different treatments. Final carcass pH was higher (P<0.05) in immunocastrated than in surgically castrated animals, but did not differ (P>0.05) from non-castrated animals. Immunocastrated animals, in a grazing system receiving supplementation, showed similar gains in weight and carcass weight in relation to non-castrated and surgically castrated animals, however, with lower losses to carcass cooling.

Effect of adiabatic ground on thermofluidic behavior and cooling time analysis from a hollow tube

Efforts are made to elucidate natural convection around a tube placed on/close to the adiabatic ground in a stagnant ambient air within laminar regime. Thermofluidic characterization is carried out by employing important governing input quantities, such as Rayleigh number gap and aspect ratio The heat loss rate from the inner surface drops abruptly when the tube is placed on the ground. The growth rate of heat loss rate with is relatively more abrupt at higher value of for a constant Nusselt number on outer wall is found to increase monotonically as grows continually for a constant and whereas an opposite trend is anticipated for Nusselt number on inner wall The reduction gradient of with is considerably lower at lower value of in comparison to higher Again, two distinguished zones are identified (Zone A and B), namely, (i) zone A, where the effect of ground on the thermofluidic behvaiour around the tube is observed, and (ii) zone B suggests no effect of ground. Furthermore, cooling time estimation is performed by considering the initial temperature of the cylinder as the wall temperature at time 0 s. The required cooling time reduces considerably with the rise of for a particular and Lastly, a new correlation for Nusselt number has been anticipated. It shows quite satisfactory agreement within ±6% of the computational data.

Changes in boiling regime and heat transfer effectiveness during water droplet collision with a superheated wall

We experimentally investigated changes in boiling regime and heat transfer effectiveness when single droplets collided with superheated substrates at various initial temperatures. Saturated water droplets colliding at constant speeds were studied over a range of initial substrate temperatures that spanned all boiling regimes from nucleate through transition to film boiling. Space- and time-resolved infrared thermometry and convectional shadowgraph imaging were used to precisely derive local heat transfer distributions and detect characteristic boiling regimes. The results confirmed the existence of the typical regions of a boiling curve: nucleate, transition, and film. The transition boiling regime could be subdivided into three sub-regimes—bubbly, oscillating, and fingering—during which the heat transfer effectiveness (THE) varied in a non-linear manner, exhibiting local minima and maxima. To facilitate interpretation of non-linear variations in HTE during transition boiling, the basic physical parameters of local heat flux, contact area, and residence time were quantitatively measured using obtained thermometry images. In the transition boiling regime, HTE first rapidly decreased during bubbly boiling principally because of a substantial decrease in the droplet residence time. And THE increased during oscillating boiling because of contact area expansion and increased heat flux. Finally, THE decreased during fingering boiling due to substantial reduction in the area fraction of liquid contact. When liquid-solid contact was completely prohibited, stable film boiling was stable. Thus, the dynamic Leidenfrost temperature point could be detected based on heat transfer characteristics, rather than collision dynamics.

Temperature dependence of energy dissipation during nanoscale wear of AISI 304L stainless steel

In the sliding process, mechanical work is widely considered to be dissipated in the form of heat. The dissipation of frictional energy, especially in scenarios involving material wear at various initial temperatures, needs further exploration. This work aims to evaluate energy dissipation during sliding wear of AISI 304L stainless steel at different initial temperatures through a combination of theoretical and experimental approaches. Molecular dynamics (MD) simulation reveals that the mechanical work decreases with the initial temperature due to the thermal softening effect. The mechanical work is converted into total energy (including internal energy and strain energy) and frictional heat. A peak value is observed on the frictional heat-initial temperature curve due to the trade-off between mechanical work and the change in total energy. When the workpiece temperature exceeds a critical temperature, the dynamic recovery dominates, and the strain energy decreases due to the reduction in dislocations and twinning. The dynamic evolution of dislocations is further experimentally verified by measuring the hardness of AISI 304L stainless steel with different scratching times. The present work contributes to a deeper understanding of energy dissipation in the wear process and lays a theoretical foundation for optimizing energy utilization in tribological systems.

A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation

Methanol (CH3OH) is an attractive alternative fuel that can reduce net carbon release and decrease pollutant emissions. In this study, methanol and n-dodecane spray flames were investigated using Large-Eddy Simulation (LES) and direct coupling with finite-rate chemistry. The selected ambient conditions are relevant to engines and were previously unreported for numerical methanol spray studies, i.e. high pressure (60 bar) and temperature (900 – 1200 K) with high injection pressure (1500 bar). The Engine Combustion Network (ECN) Spray A case was used to validate the n-dodecane spray flame. For methanol, a modified ECN Spray A condition was used with a high initial ambient temperature (1100 K-1200 K) to ensure fast enough ignition relevant to engine time scales. The performed homogeneous reactor (0D) simulations revealed a new phenomenon of a two-stage ignition process for methanol, confirmed by the 3D LES at high pressure, high temperature, and lean conditions. The present numerical results also show that: 1) there is a strong ambient temperature sensitivity for methanol ignition delay time (IDT) with a five-fold decrease in IDT (IDT1100K/IDT1200K=5) and a factor of 2.6 decrease in the flame lift-off length (FLOL1100K/FLOL1200K=2.6) as the ambient temperature is increased from 1100 K to 1200 K, 2) methanol spray ignition takes place at a very lean mixture (ϕMR≈0.2) consistent with the 0D predicted most reactive mixture fraction (ZMR), 3) on average, methanol sprays are significantly leaner than n-dodecane sprays at quasi-steady-state (ϕmeoh,ave≈0.2 vs ϕndod,ave≈0.7), implying very low soot emissions, and 4) the methanol spray flames could have similar temperatures as the n-dodecane sprays depending on the initial conditions, thus a similar level of NOx emissions.

MODELING OF TEMPERATURE GRADIENTS DURING THE INTERACTION OF LASER RADIATION WITH BIOLOGICAL TISSUE

Modeling thermal gradients in biological tissues, when interacting with laser radiation, helps to understand how heat flows are distributed in the body and reflect heating zones. The main aspects of the simulation include the parameters of the laser source, such as the wavelength and power, the initial temperature conditions of the tissues, as well as the use of special numerical methods that help to optimally solve the heat conduction equations and visualize the obtained results. Temperature distribution in tissues plays an important role in determining the effectiveness and safety of laser treatment. This allows you to choose effective parameters of laser radiation and irradiation modes to achieve the desired result without negative consequences for the patient. However, it is important to consider that the actual behavior of tissues in response to laser radiation may be more complex due to the physiological characteristics of each person.Therefore, all models and calculations must take into account this feature and diversity and take into account safety regulations. Laser treatment should be carried out under the supervision of qualified specialists, in particular doctors who have relevant knowledge and experience in the field of medicine. This approach helps ensure the safety and effectiveness of laser procedures for patients. Modeling the distribution of tissue thermal gradients when interacting with laser radiation plays an important role in the development of modern medicine and scientific research and provides efficiency compared to the obtained experimental data. It helps to improve the understanding of thermal processes in biological tissues and to ensure the safety of patients receiving laser treatment. In this work, experiments were conducted on the effect of laser irradiation on biological tissue, as well as modeling of changes in temperature gradients during the effect of laser irradiation on biological tissue, using various models of heat and mass transfer, using the Matlab software environment. As a result of the modeling in this work, the patterns of changes in temperature gradients were obtained, which were compared with the experimentally obtained data, the errors of Pennes models and finite element methods, finite differences were analyzed, and conclusions were drawn.

A cost-effective over-temperature alarm system for cold chain delivery

Managing over-temperature alarms in cold chain logistics (CCL) is crucial for temperature monitoring systems. However, existing research in this area primarily focuses on improving identification accuracy while overlooking the associated cost implications. This study addresses this gap by proposing a cost-effective over-temperature alarm system using an artificial neural network (ANN) model that integrates multi-source data (MSD). This article demonstrates that utilizing ANN and MSD leads to significantly improved recognition accuracy compared to using single-source data while keeping the cost increase to a minimum. The paper found recognition accuracy to be 97.4% with three feature values and 98.6% with six feature values. Sensitivity analyses reveal that factors such as the initial food temperature, cumulative open time, data acquisition interval, and algorithm significantly impact the recognition accuracy of the over-temperature alarm system. The location of sensors, however, has a slight effect. Furthermore, the choice of the number of feature values and the granularity of the data influences the cost of temperature management and recognition accuracy. This study provides valuable insights into the factors influencing recognition accuracy, aiding in designing cost-effective over-temperature alarm systems for food supply chain management.