Search

In this study, the welding thermal cycle, as well as the microstructural and mechanical properties of welded AA6061-T6 plates, were studied. The plates were prepared and bead-on-plate welded using gas metal arc welding (GMAW). Numerical simulations using SYSWELD® were performed to obtain the thermal distribution in the welded plates. The numerical heat source was calibrated using the temperatures obtained from the experimental work and the geometry of the melting pool. The mechanical properties were obtained through microhardness tests and were correlated with the welding thermal cycle. Moreover, the mechanical behavior and local deformation in the heat-affected zone (HAZ) were investigated using micro-flat tensile (MFT) tests with digital image correlation (DIC). The mechanical properties of the subzones in the HAZ were then correlated with the welding thermal cycle and with the microstructure of the HAZ. It was observed that the welding thermal cycle produced microstructural variations across the HAZ, which significantly affected the mechanical behavior of the HAZ subzones. The results revealed that MFT tests with the DIC technique are an excellent tool for studying the local mechanical behavior change in AA6061-T6 welded parts due to the welding heat. [ABSTRACT FROM AUTHOR]

The digital age provides greater possibilities for quantitative research on rural tourism. This article examines Jilin Province as a case and analyzes the interannual, monthly, and holiday characteristics of rural tourism heat using big data. Using A-level rural tourism operating units as research samples, a mathematical model is constructed to evaluate the rural tourism heat from 2016 to 2021. Through a trend surface analysis and kernel density analysis, the spatiotemporal differentiation characteristics are explored; additionally, the spatial evolution law of the rural tourism hot and cold pattern is analyzed using counties as units. The research results show the following: (1) As an important component of the Jilin tourism industry, temporally, rural tourism has an overall trend of increasing popularity, with clear seasonal and holiday distribution patterns. Simultaneously, the periodic sporadic occurrence of the COVID-19 epidemic caused an obvious vulnerability in rural tourism fever. (2) Spatially, the structure of rural tourism shows an evolutionary process of "single core → multi core" and a diffusion trend of "central → eastern" and "central → western". (3) Regarding the influencing factors, transportation conditions and resource endowments are dominant, and the impact of the economic development level is gradually weakening, while the impact of the ecological environment and industrial foundation is gradually increasing. [ABSTRACT FROM AUTHOR]

In the evolving realm of precision machinery, paramount importance is placed on the efficiency and performance of transmission systems. A central role is played by gears within these systems, with their thermal variations and distributions during operation critically influencing the stability and efficiency of the systems at large. Despite the theoretical support lent by traditional thermodynamic theories and empirical formulas, their prediction accuracy is found lacking, particularly in the face of complex operational environments and dynamic changes. To address this shortfall, this study introduces an advanced thermodynamic model, augmented by the application of a Temporal Convolutional Network (TCN). The integration of these methodologies facilitates a comprehensive thermal analysis and prediction specific to gear operation, aiming to provide enhanced accuracy and real-time thermal data support. This endeavor is vital for not only understanding but also optimizing the thermal behavior of gears in precision transmission systems, ultimately contributing to the advancement of the field. [ABSTRACT FROM AUTHOR]

Thermal analysis of high-temperature phase change materials (PCM) is conducted with the consideration of a 20% void and buoyancy-driven convection in a stainless-steel capsule. The effects of the thermal expansion and the volume expansion due to phase change on the energy storage and retrieval process are explored. The used water to fill the void between two different wax paraffin and stearic acid spheres is considered as a potential PCM for concentrated solar power. The charging/discharging process into and from the capsule wall is simulated under different boundary conditions for laminar and turbulent flows. Computational models are conducted by applying an enthalpy-porosity method and volume of fluid method to calculate the transport phenomena within the PCM capsule, including an internal air void. A simplified twodimensional model of the PCM contained within the spheres is constructed and thermal analyses are performed for the transition from solid to liquid states. Simulated charging process modes are compared with the theory. According to experiments, the temperature distributions from 40-60 mm without and with 60 mm with copper fin have different behavior. The paraffin takes less time than stearic acid for total transformation at a rate of 0.5. The size of the sphere increases over the amount of time and the phase of the sphere to complete changes as stearic acid expands more than paraffin during the transition. Inserting a rectangular fin, that is made from copper into the ball reduces the cycle time and increases output. [ABSTRACT FROM AUTHOR]

In this study, the welding thermal cycle, as well as the microstructural and mechanical properties of welded AA6061-T6 plates, were studied. The plates were prepared and bead-on-plate welded using gas metal arc welding (GMAW). Numerical simulations using SYSWELD® were performed to obtain the thermal distribution in the welded plates. The numerical heat source was calibrated using the temperatures obtained from the experimental work and the geometry of the melting pool. The mechanical properties were obtained through microhardness tests and were correlated with the welding thermal cycle. Moreover, the mechanical behavior and local deformation in the heat-affected zone (HAZ) were investigated using micro-flat tensile (MFT) tests with digital image correlation (DIC). The mechanical properties of the subzones in the HAZ were then correlated with the welding thermal cycle and with the microstructure of the HAZ. It was observed that the welding thermal cycle produced microstructural variations across the HAZ, which significantly affected the mechanical behavior of the HAZ subzones. The results revealed that MFT tests with the DIC technique are an excellent tool for studying the local mechanical behavior change in AA6061-T6 welded parts due to the welding heat.

The focus of this work is on developing a nonlinear grey model for the laminar flow regime of carrier fluid across the flat plate collector. The trust region reflective algorithm was used to solve the nonlinear laminar flow problem and handle the sparse matrix. The stream function, dimensionless velocity, gradients of velocity components, carrier fluid temperature, and the absorber plate temperature were estimated for a flat plate collector operated with and without a circular chimney. Similarly, the same technique was adopted to determine a model for heat transfer across the absorber plate. The numerically obtained solution was also compared with the parameters obtained through the instrumental measurement. The relative tolerance was kept at 10−5 for the white and grey box solutions. The developed model was noticed to have a smaller deviation than the conventional analytical model to predict the experimental values. The slip condition was observed for the proposed scheme. The uncertainty in the temperature measurement through the proposed model varies from ±0.53 to ±1.47 K. The minimum absolute percentage error (MAPE) lies in the domain of 0.52–1.67% for the nonlinear grey model, whereas the linear grey model for measuring absorber plate temperature has a percentage error of 0.0011–0.02%. [ABSTRACT FROM AUTHOR]

The fin-and-tube heat exchangers (FTHE) are extensively applied in HVAC (Heating Ventilation and Air Conditioning) system, power generation, process industries. The current study dedicates to develop an elliptical fin-and-tube heat exchanger filled with a novel X-VGs vortex generator (X-VGs), so as to improve the hydraulic and heat performance of FTHE. Two different placement schedules of vortex generator have been discussed firstly which are upper-flow (UF) and down-flow (DF)orientations. The effect of streamwise distance, transverse placement and main flow angel on air-side thermal hydraulic performance are investigated subsequently, the friction factor f , Colburn factor j , and performance evaluation criteria (PEC) j/f are analyzed separately corresponding to evaluate heat transfer effect, hydraulic characteristic and comprehensive performance. The results illustrate that increasement of streamwise distance and main flow angel would decrease the thermal hydraulic performance, while there is a nonlinear relationship between longitudinal placement and thermal hydraulic performance. The Genetic algorithm (GA) combined with radial basis function neuro network (RBFNN)prediction model is further employed to obtain the optimal layout of X-VGs, the best layout was obtained in streamwise space ratio at 1.995, longitudinal placement ratio 0.387 and main attack angel ratio 0.053, which achieved the increasement of 109.681% in PEC compared with baseline case. • Modeling of fin-and-tube heat exchanger with innovative X-VGs. • Placement parameter investigation of X-VGs. • Hydraulic and heat performance predicted model based on RBFNN. • Single-objective optimization on the basis of genetic algorithm. [ABSTRACT FROM AUTHOR]

The article investigates the thermal behaviour of a solar collector retrofitted with a natural draught unit. The objective of this work is to draw a comparative line between a system that is equipped with a circular vertical channel and the conventional one. The effectiveness of the solar heating system and how to further improve the prevailing system are examined in this study. The flat plate solar collector was used to assess the dynamics of the system. The Hottel–Whillier–Bliss equation was used to obtain the useful heat gain rate. The instantaneous collector efficiency was reduced by 22.84%. The net heat loss encountered with natural draught was augmented by 10.89%. The net pressure drop along the length of the collector was increased when a solar collector related to the circular chimney. The stagnant temperature of the collector with the natural draught was decreased by 3.20%. The heat loss to the surrounding was computed to be 33.94% of the net energy received by a solar collector connected with the circular stack. The Fanning friction factor for airflow was reduced in the system equipped with natural draught. The static pressure was marginally dropped at the inlet, whereas it was steeply increased at the outlet of the solar collector. The static pressure would be the same for both systems at collector length l = 0.84 m. The inference can be deducted from the comparative analysis that the air stream flow behind the collector plate and could provide better prospects for a collector unit equipped with natural draught at the exhaust end of the solar dryer.

The temperature control system is one of the most important subsystems of the strapdown airborne gravimeter. Because the quartz flexible accelerometer based on springy support technology is the core sensor in the strapdown airborne gravimeter and the magnet steel in the electromagnetic force equilibrium circuits of the quartz flexible accelerometer is greatly affected by temperature, in order to guarantee the temperature control precision and minimize the effect of temperature on the gravimeter, the SGA-WZ temperature control system adopts a three-level control method. Based on the design experience of the SGA-WZ-01, the SGA-WZ-02 temperature control system came out with a further optimized design. In 1st level temperature control, thermoelectric cooler is used to conquer temperature change caused by hot weather. The experiments show that the optimized stability of 1st level temperature control is about 0.1 °C and the max cool down capability is about 10 °C. The temperature field is analyzed in the 2nd and 3rd level temperature control using the finite element analysis software ANSYS. The 2nd and 3rd level temperature control optimization scheme is based on the foundation of heat analysis. The experimental results show that static accuracy of SGA-WZ-02 reaches 0.21 mGal/24 h, with internal accuracy being 0.743 mGal/4.8 km and external accuracy being 0.37 mGal/4.8 km compared with the result of the GT-2A, whose internal precision is superior to 1 mGal/4.8 km and all of them are better than those in SGA-WZ-01.

In this paper, the overall and zonal thermal balances of the blast-furnace smelting were analyzed. Under the current blast furnace smelting conditions, the specific consumption of coke is determined by the development of the heat transfer processes occurring in the lower zone of the furnace. In this case, the heat losses found by using the heat balance of the lower zone of the furnace sufficiently reflect such technological factors as specific coke consumption and silicon content in cast iron. It was shown that the existing methods of analytical calculation of the heat losses occurring during smelting of cast iron in blast furnaces do not adequately reflect the actual melting process. It was established that the analysis of the heat balance of the lower stage of heat transfer enables determining the heat losses in this zone of the furnace and estimating the correction factors when the blast furnace smelting conditions change. The control of heat losses is necessary for estimating the condition of the blast furnace masonry, rational gas distribution, and also, for adjustment of coke consumption. [ABSTRACT FROM AUTHOR]

The ventilation in the ship engine rooms is an essential issue concerning finest performance of engines and diesel generators as well as electric motors. The present study has aimed at the analysis of temperature distribution inside the ship main engine room. In the same way, attempts have been made to identify those points with considerable thermal concentration in main engine room space, so that proper ventilation systems could be engineered and utilized and favorable thermal conditions could be realized. The CFD approach has been utilized in order to analyze impact of the designed ventilation system on the temperature distribution pattern. The Inlet layout and area have been analyzed under a variety of scenarios in order to decrease the average temperature and eliminate the heat concentrations in various points of the engine room. The temperature distribution and location and area of ventilation air inlet have been studied in different modes resulted in temperature distribution pattern, heat concentration outline and average volumetric temperature level in each mode. The results indicated that considerable circulating air volume is required compared to those levels suggested by common practices, calculations and standards in order to eliminate the heat concentration. [ABSTRACT FROM AUTHOR]

In the last twenty-five years in the chemical process industry an important point of interest has been, how to minimize total costs, i.e. capital and operating costs expressed as annual charges.Pinch method is thermodynamically oriented method for the synthesis of heat exchanger networks with extended to combined heat and power system, separation schemes, integrated distillation columns and general process design. There have been two schools of the heat exchanger network synthesis. One relies on thermodynamic principles where the designer manually or interactively if software is available, synthesizes the network.The heat exchanger network of a nitric acid plant has been studied and it was found that it is possible to reduce requirements for cooling water and medium pressure steam. In order to enable these savings, three heat exchangers should be replaced with new ones. Energy consumption insteam power system increases slightly. However, the final result is a reduction of energy costs and a payback time of 14.5 months.The other approach relies on mathematical methods like linear and nonlinear programming. In this work thermodynamically oriented method is presented for the synthesis of heat exchanger network.

A hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed based on the mass and energy balance of the hydrogen, liquid, and the wall of the compression chamber at each time step and positional node with various compression ratios, to calculate the temperature distribution of the system. The amount of heat extracted from hydrogen, directly at the interface and through the walls, is investigated and compared with the adiabatic case. The results show that depending on heat transfer correlation, the hydrogen temperature reduces slightly between 0.2% and 0.4% compared to the adiabatic case, at 500 bar, due to the large wall resistance and small contact area at the interface. Moreover, the results of the sensitivity analysis illustrates that increasing the total heat transfer coefficients at the interface and the wall, together with compression time, play key roles in reducing the hydrogen temperature. Increasing the total heat transfer coefficient at the interface (10,000 times) or at the wall (200 times), leads to 22% or 33% reduction of hydrogen, compared to the adiabatic case, at 500 bar, during 3.5 s compression, respectively. [ABSTRACT FROM AUTHOR]

PVDF membranes, after surface modification by CF 4 plasma, have demonstrated surperhydrophobic surface characteristics and up to 30% flux enhancement in direct contact membrane distillation (MD). The heat transport in the MD process was modeled to assess the membrane distillation coefficients ( B m ). The experimentally determined B m showed up to 50% deviation from the modeled values for CF 4 modified PVDF membranes. An effective evaporation factor, as a function of surface porosity and surface water contact angle, was proposed to correlate surface wettability contribution to the MD flux. This factor was fitted by comparing the experimentally determined flux with modeled one. It was found that the factor, which is positively related to surface water contact angle and surface porosity, varied with the membrane wettability and can rationally explain the deviation between observed and theoretical fluxes. In addition, CF 4 plasma modification could increase the membrane׳s evaporation efficiency from 54.3% for the virgin membrane up to 63.4% for surface modified membranes because of the increase of the effective evaporation area factor. The introduction of the factor provides a means to evaluate the membrane surface hydrophobicity to the MD flux and necessitate the development of super even ultra-hydrophobic membranes. [ABSTRACT FROM AUTHOR]

In the present article, we have investigated the effects of heat transfer on peristaltic flow of carbon nanoparticles in a curved channel. Governing equations for flow and heat transfer are derived by analysing the effects of curvature of the curved channel and taking inboard the long wavelength and small Reynolds number assumptions. Exact solution is obtained for the stream function, which is used to find the velocity of the fluid flow in the curved channel. Effects of curvature parameter and Grashof number on the velocity and pressure gradient are analysed. The effect of heat transfer through the curved channel is also studied. [ABSTRACT FROM AUTHOR]

The transient thermal response of a newly developed ventilated brake disc cored with a porous medium (wire-woven bulk diamond) is compared with those of a solid brake disc and a conventionally ventilated brake disc with pin fins. The best-performing brake disc vis-à-vis the operating temperature is dependent on the duration of braking: for a short braking event, T(solid) < T(pin-finned) < T(porous); however, for extended braking T(porous) < T(pin-finned) < T(solid). These experimental results are explained in terms of the governing thermophysical parameters using a classical first-order unsteady-state differential equation. The initial rate of increase in the brake disc temperature is dominated by the thermal capacity term; hence, for a short braking event, solid discs with a large thermal capacity operate at a low temperature. However, for extended braking, ventilated discs run cooler and reach lower steady-state temperatures than solid rotors do owing to the increased convective surface area and the forced convection in the ventilated channels. With the wire-woven bulk diamond core which allows a slightly lighter disc than the conventional pin-finned disc, a substantially lower steady-state temperature can be achieved, resulting from promoted flow mixing by three-dimensional wire-woven bulk diamond ligaments which enhance convection. [ABSTRACT FROM AUTHOR]

Abstract: The comprehensive analysis about heat-generating processes is presented in Er:tellutire glass. The heat fraction of each process and total heat fraction during pumping are investigated. The results show that upconversion is an important heat-generation process and heat problem is serious especially at high Er3+ doping level. The influence of pump power on heat fraction is also discussed. Based on the heat analysis, the optimized doping concentration range of Erbium ions is about 0.5mol% to 1.0mol%. [ABSTRACT FROM AUTHOR]

Abstract: To develop ZrCo hydride beds for the SDS and the LTS of the ITER, detailed design of the internal structural arrangement and the vessel of the SDS and LTS beds (Korea initial reference design) were implemented by using the ASME VIII, Division 1 pressure vessel design code. In order to validate this initial reference of the ZrCo hydride beds, the following heat analyses were performed: (i) heating performance of a ZrCo hydride packed bed during delivery operation, (ii) cooling performance (decay heat removal, etc.) to reduce the ZrCo hydride temperature during storage operation, (iii) thermal shielding performance for reduction of outer vessel surface temperature. The present paper provides the results of these heat analyses and discusses the effects of the endothermic and exothermic reactions (ZrCo+1/2T2 ↔ZrCoT+80.5kJ/mol (T2)), and that of cooling by using He gas. [Copyright &y& Elsevier]

Objective. Recently, the temporal interference stimulation (TIS) technique for focal noninvasive deep brain stimulation (DBS) was reported. However, subsequent computational modeling studies on the human brain have shown that while TIS achieves higher focality of electric fields than state-of-the-art methods, further work is needed to improve the stimulation strength. Here, we investigate the idea of EMvelop stimulation, a minimally invasive DBS setup using temporally interfering gigahertz (GHz) electromagnetic (EM) waves. At GHz frequencies, we can create antenna arrays at the scale of a few centimeters or less that can be endocranially implanted to enable longitudinal stimulation and circumvent signal attenuation due to the scalp and skull. Furthermore, owing to the small wavelength of GHz EM waves, we can optimize both amplitudes and phases of the EM waves to achieve high intensity and focal stimulation at targeted regions within the safety limit for exposure to EM waves. Approach. We develop a simulation framework investigating the propagation of GHz EM waves generated by line current antenna elements and the corresponding heat generated in the brain tissue. We propose two optimization flows to identify antenna current amplitudes and phases for either maximal intensity or maximal focality transmission of the interfering electric fields with EM waves safety constraint. Main results. A representative result of our study is that with two endocranially implanted arrays of size4.2 cm×4.7 cmeach, we can achieve an intensity of 12 V m -1 with a focality of3.6 cmat a target deep in the brain tissue. Significance. In this proof-of-principle study, we show that the idea of EMvelop stimulation merits further investigation as it can be a minimally invasive way of stimulating deep brain targets and offers benefits not shared by prior methodologies of electrical or magnetic stimulation., (Creative Commons Attribution license.)

The article investigates the thermal behaviour of a solar collector retrofitted with a natural draught unit. The objective of this work is to draw a comparative line between a system that is equipped with a circular vertical channel and the conventional one. The effectiveness of the solar heating system and how to further improve the prevailing system are examined in this study. The flat plate solar collector was used to assess the dynamics of the system. The Hottel–Whillier–Bliss equation was used to obtain the useful heat gain rate. The instantaneous collector efficiency was reduced by 22.84%. The net heat loss encountered with natural draught was augmented by 10.89%. The net pressure drop along the length of the collector was increased when a solar collector related to the circular chimney. The stagnant temperature of the collector with the natural draught was decreased by 3.20%. The heat loss to the surrounding was computed to be 33.94% of the net energy received by a solar collector connected with the circular stack. The Fanning friction factor for airflow was reduced in the system equipped with natural draught. The static pressure was marginally dropped at the inlet, whereas it was steeply increased at the outlet of the solar collector. The static pressure would be the same for both systems at collector length l = 0.84 m. The inference can be deducted from the comparative analysis that the air stream flow behind the collector plate and could provide better prospects for a collector unit equipped with natural draught at the exhaust end of the solar dryer. [ABSTRACT FROM AUTHOR]

[Display omitted] • An open-source tool (BovHEAT) to process data from an activity monitoring system (Heatime, SCR) was developed. • BovHEAT was faster and more accurate compared to manual data extraction. • Executables are available and tested for Windows, Linux and macOS. This application note introduces the software called Bovine Heat Detection and Analysis Tool (BovHEAT), a validated and open-source analysis tool to process automated activity monitoring (AAM) data for estrus detection. We used activity data collected from a neck-attached accelerometer (Heatime, SCR Engineers Ltd., Netanya, Israel) that is widely adopted in the dairy industry. Developed with the Python programming language, BovHEAT offers fully automatic and scalable processing for estrus detection with additional functionality for handling missing values and a plausibility check for timing of events. Processed output is provided in an Excel file with result tables in the long and wide format. Additionally, a PDF file containing activity change line graphs is generated. For validation, we compared the accuracy and time of three different methods to process AAM data: 1) manual data evaluation (MAN), 2) Excel tool (EXCEL), and 3) BovHEAT. Two different datasets from 8 farms (1 farm in Canada; 7 farms in Germany) were used. Validation was performed independently by three investigators. In total, activity data from 60 cows representing a maximum number of 600 observations (50 days with 12 observations per day) per cow were used. Manual data evaluation was less accurate due to transcription errors, with 13 of 60 cows having at least one error. More specifically, 16 out of 110 estrus events were recorded incorrectly. The time to process AAM data and transfer the results into a standardized results table for 10 cows was 41.0 (range 28–53) minutes, 30.7 (18–48) minutes, and 11.7 (4–16) minutes for MAN, EXCEL and BovHEAT , respectively. Without the standardized results table, a fully automated run with BovHEAT processing the complete dataset of 5,477 cows, which consisted of 361 XLS and XLSX files, took 172 s. The results from this study indicate that BovHEAT speeds up processing, requires less user interaction and provides additional features. Our aim is to accelerate future research with AAM data and facilitate reproducibility via our validated analysis tool. Since BovHEAT is open-source and MIT-licensed, it allows customization to support different sensors and manufacturers. The BovHEAT tool can be evaluated, downloaded and contributed to on GitHub (https://github.com/bovheat/bovheat , https://doi.org/10.5281/zenodo.3890126). [ABSTRACT FROM AUTHOR]

• ESC behaviors at various temperatures are investigated experimentally. • ESC-induced heat generation and its impacts on electrical behaviors is modeled. • Distribution and anisotropy diffusion of ESC-caused heat generation is delineated. • An electro-thermal coupling model is proposed for batteries under ESCs. • Effectiveness of the proposed model is verified by experimental data. External short circuit (ESC) fault, which can cause large current and high temperature, is one of the main reasons for battery failure. Its analysis and diagnosis remains a challenging task due to complex electro-thermal characteristics of batteries under ESCs. In this paper, ESC experiments at various temperatures are conducted to investigate the impact of temperature on battery electro-thermal behaviors. Based on the analysis of the experimental data, heat generation inside a battery caused by ESC-induced high current and side reactions is modeled. The heat distribution and diffusion are also modeled by considering battery's internal jellyroll structure. The combination of the heat generation, distribution and diffusion models forms a novel electro-thermal coupling model, which is used to predict the complex thermal and electrical properties of a battery under ESCs. The presented model is simulated and verified by the test data. The maximum root mean square error of ESC current prediction is less than 1.73A and the maximum errors of the internal temperatures and the surface temperatures are only 1.771% and 3.915%, respectively. These results verify the effectivceness of the presented model. It is expected that the presented model is useful for safety analysis, temperature prediction and fault diagnosis applications of the lithium-ion batteries under ESC. [ABSTRACT FROM AUTHOR]