Hasil untuk "Heat"

E. Sparrow, R. Cess, E. Schmidt

M. Schlesinger, M. Ashburner, A. Tissières

V. Babrauskas, R. Peacock

V. Pecharsky, K. Gschneidner

Zengyuan Guo, Deyu Li, B. Wang

K. Boomsma, D. Poulikakos, F. Zwick

S.D. Sharma, K. Sagara

Sheng‐Qi Zhou, R. Ni

Y. Sui, C. Teo, P. Lee et al.

Francis Agyenim, P. Eames, M. Smyth

Jie Xiong, Degui Wang, Liping Xie et al.

The construction of mass concrete foundations for nuclear power plants faces significant challenges in controlling hydration heat and preventing early-age thermal cracking. This study develops an integrated framework combining high-fidelity thermal–mechanical simulation, real-time temperature monitoring, and construction process optimization to address these issues. Focusing on the VVER-1200 reactor raft foundation in the Xudapu NPP Phase II Project, an innovative center-to-periphery synchronous pouring method is proposed, departing from conventional inclined or layered pouring by strategically utilizing stage time lags to moderate the radial temperature gradient. Numerical simulations demonstrate that this method significantly reduces the peak temperature and thermal stress. Field validation shows that the maximum core-to-surface temperature difference is controlled within 19.8 °C, well below the critical threshold of 25 °C, and the peak concrete temperature remains at 66.7 °C, safely below the risk level for delayed ettringite formation (82–85 °C). The cracking risk coefficient K remains below 0.65, indicating a low probability of thermal cracking. Post-construction inspection confirms the absence of thermal cracks in the 5240 m³ monolithic pour. The proposed methodology offers a reliable, science-based approach for thermal crack mitigation and serves as a valuable reference for similar large-scale mass concrete structures in nuclear and other critical infrastructure projects.

E. Sjölander, S. Seifeddine

Doohyun Kim, Y. Kwon, Yonghyeon Cho et al.

Ulzie Rea, T. Mckrell, Lin-wen Hu et al.

S. Hajat, Tom Kosatky

Although rapid response capacity has been instituted in many cities following recent catastrophic heatwave events, the recognition that theoretically preventable heat-related deaths may occur throughout the summer has provoked much less response. This essay reviews published estimates of the general summertime temperature–mortality relationship characterised in different settings around the world. A random-effects meta-regression is applied to the estimates in relation to a number of standardised city-level characteristics of demography, economy and climate. Heat thresholds were generally higher in communities closer to the equator, suggesting some population adaptation. In almost half of the locations, the risk of mortality increased by between 1% and 3% per 1°C change in high temperature. Increasing population density, decreasing city gross domestic product and increasing percentage of people aged 65 or more were all independently associated with an increase in the heat slope. Improved care of older people, residential architecture and urban planning measures to reduce high temperatures in densely populated areas are likely to play a key role alongside targeted heat-health warning systems in reducing future heat burdens.

Utpal Jyoti Das, Deepjyoti Mali

The current study contains a steady laminar bioconvective magnetohydrodynamic (MHD) flow involving water (H2O)-based hybrid nanofluid composed of silver (Ag) and alumina oxide (Al2O3) as nanoparticles. This flow passes over a thin moving slender needle including gyrotactic motile microorganisms through a porous medium. The study examines how various physical characteristics, such as Cattaneo-Christov heat and mass flow, and viscous dissipation, affect the system's flow. Our objective is to find the impact of pertinent parameters on velocity, temperature, concentration, and microorganisms. This type of flow problem is important to control the heat and fluid flow phenomena around a needle which are applied to biotechnology (bioreactors, microbial fuel cells), biomedical engineering, microfluidics, and cooling systems. The reason for this investigation combines both scientific curiosity and practical applications. The controlling equations are simplified into nonlinear ordinary differential equations, solved numerically via MATLAB bvp4c tool, and their impact on temperature, velocity, microorganism, and concentration outline is graphically depicted, also, their impact on local microorganism's number, local Sherwood number, frictional drag coefficient, and local Nusselt number, are tabulated. This study's novelty is that it fills the gaps left by Kandasamy et al. [31]. This study demonstrates great agreement with Kandasamy et al. [31]. The study's findings indicate that improvement of thermal and concentration relaxation parameters declines fluid temperature and concentration respectively. Also, enhancement of bioconvection Lewis and Peclet numbers diminishes the microorganisms' profile. Again, when the Dufour and Soret numbers rise, then the temperature and concentration distribution also improve respectively. Furthermore, introducing 1 % of alumina oxide (Al2O3), and silver (Ag) nanoparticles into the base fluid increased frictional drag by 2.64 %, and 3.03 %, respectively, compared to water.

Guorui Xu, Yin Wang, Zhiqiang Li et al.

The fluid and temperature distributions of the large air-cooled Synchronous Condenser (SC) are very complex, thereby the interaction of the stator and rotor airflows is often neglected in the previous study of the temperature field. In order to calculate the precise temperature rise of the SC under different operating conditions, this paper studies the effect of the temperature variation at the rotor airflow outlet on the stator temperature distribution. The loss, fluid and temperature distributions of a 300-MVar air-cooled SC are calculated based on the electromagnetic, fluid and heat transfer models. The temperature variation at the rotor airflow outlet along with the operating condition is revealed, and its effect on the stator temperature rise is analyzed. Further, it is studied that the variation laws of the stator and rotor maximum temperatures along with the air volume allocation, and the optimal air volume allocation is determined. The results can provide the reference for the accurate temperature calculation and the optimization design of the cooling systems for the large air-cooled SCs.

Margarita Velandia, Carlos Trejo-Pech, David Butler et al.

Alley cropping is an agroforestry practice that involves the planting of trees or shrubs alongside herbaceous crops within the same production system. Potential benefits of alley cropping include crop diversification, enhanced productivity of annual crops, reduced soil erosion, improved pollinators and wildlife habitat, decreased incidence of pests and diseases, carbon sequestration, and reduced nitrogen leaching. Despite these potential benefits, the adoption of alley cropping remains low. In Tennessee, specifically, only about 2% of the farms have used agroforestry practices, including alley cropping. We surveyed Tennessee fruit and vegetable farmers to assess their willingness to adopt alley cropping and the differences in characteristics of those willing and not willing to use this production practice. In general, those respondents who are willing to adopt alley cropping are more familiar with this production system and are facing or have faced production challenges that could be alleviated by adopting this production practice, such as low organic matter and crop heat stress. Our results also suggest that the type of trees or shrubs incorporated in this system and adequate payment for adoption that covers investment and maintenance costs could affect Tennessee fruit and vegetable farmers’ willingness to use this system.

Muzher Saleem, Ghada A. Khouqeer, Fazal Haq et al.

Ternary hybrid nanofluids (THNFs) are advanced thermal fluids that consist of three different types of nanoparticles dispersed in a base fluid. THNFs offer significant advantages in enhanced heat transfer, stability, and customizable properties. Their ability to improve efficiency and reduce energy consumption makes them a valuable option for various industrial and technological applications. The present study addresses the heat transfer performance of magnetohydrodynamic micropolar THNF (TiO2+Al2O3+Ag/blood) and hybrid nanofluid (HNF) (TiO2+Al2O3/blood) flow by vertically stretching cylinder. THNF fluid is developed by suspending the rigid nanoparticles of titanium dioxide (TiO2), aluminum oxide (Al2O3), and silver (Ag) into blood-based micropolar fluid. Phenomenon of thermal stratification is considered at the boundary of the cylinder. Physical aspects of Darcy Forchheimer, magnetic field, and surface porosity are considered in the momentum equation. Energy transport relation is formulated under the influences of heat source, Lorentz force, and internal friction forces. The dimensional flow model is altered into non-dimensional one by implementing the transformations. Non-dimensional mathematical model representing the physical phenomenon is solved through NDSolve function of Mathematica. Behavior of micropolar THNF and HNF velocity and thermal field versus influential variables are investigated. The results are discussed and compared in relation to HNF and THNF. Additionally, variations in Nusselt number, couple stress, and skin friction factors are examined. Heat transfer performance of THNF and HNF are compared via graphs. A reduction of 4 % in the skin friction coefficient of THNF compared to HNF is noticed. The THNF exhibits a higher average percentage heat transfer rate than HNF through variables curvature, Eckert number, Prandtl number, heat source, and thermal stratification, with values of 146, 135, 142, 139, 138, 150, and 140, respectively.

Shasha Huo, Bo Sun

While Moore's Law has approached its physical limits lately, the high integration and miniaturisation of electronics have also brought another thermal failure obstacle. Previous studies on single-phase flow demanded significant pump power to achieve higher CHF, but this approach risked exceeding the chip's mechanical limits and complicating packaging. The elevated junction temperature (above 175 C) of third-generation semiconductors makes them ideal for two-phase water cooling which utilizes the huge latent heat during boiling of water to minimize the flow rate and maximize the COP. In this work, we designed an embedded hierarchical microchannel heat sink for heat transfer by deionised water two-phase cooling. We observed an unprecedented Critical Heat Flux (CHF) of 1682W cm-2 with COP up to 23615 at flow rate of 3.0 ml s-1, which means Only 70 mW of power is needed to take away the heat on the 1682 W per square centimetre chip, corresponding to a 3-fold increase compared to single-phase microchannels with same flowrate. At a high flow rate of 10 ml s-1, we even achieved a remarkable heat flux of 2500 W cm-2. This technology is anticipated to overcome the bottleneck in electronic thermal management.