Developing a nanoscale secondary thermal conduction network within carbon fiber performs is a challenging yet effective method to substantially enhance the thermal conductivity of C/C composites. In this study, a strategy for creating a three-dimensional (3D) SiC nanowires (SiCNWs) thermal conductivity network in carbon felts (CFs) was implemented using vacuum thermal evaporation technology to fabricate SiCNWs modified C/C composites (SiCNW-C/C). The growth mechanism of SiC nanowires within CFs and their impact on the microstructure and thermal conductivity of the C/C composite were thoroughly investigated. The findings indicate that a SiC nanowires thermal conduction network can be successfully established within carbon felts without catalysts by initiating nucleation sites and managing reaction pressure. An appropriate reaction pressure is crucial not only for the uniform growth of SiC nanowires but also as a key factor in modulating the content and microstructure of the SiC nanowires. SiC nanowires prepared at 150 Pa exhibit minimal structural defects and are evenly distributed throughout the carbon felts, markedly enhancing the thermal response rate of the felts. The thermal conductivity of these SiCNW-modified C/C composites, both parallel and perpendicular to the carbon fibers, increased to 173 W/m center dot K and 112 W/m center dot K, respectively, approximately tripling that of the pure C/C composite. The exceptional thermal management capabilities of SiCNW-C/C were empirically validated through simulated operational chips and finite element simulation. This work presents an effective approach for producing C/C composite with high thermal conductivity particularly through the thickness, offering promising applications in the thermal management of advanced electronics.

Mg-3(Sb, Bi)(2)-based materials possess excellent room-temperature thermoelectric performance, while poor interfacial behaviors occur when connected with metal electrodes due to the strong chemical activity and volatility of Mg element. In this study, a high efficiency of 7.1% under a temperature difference of 230 K is achieved in n-Mg-3(Sb, Bi)(2)/p-Bi2Te3 thermoelectric module. When changing the interfacial layer from Fe powder to Fe foil, it effectively prevents a significant diffusion of both Mg and Bi elements from the material matrix to the interfacial layer, resulting in an extremely low contact resistivity approximate to 3.4 mu Omega cm(2) that is almost one order lower than of that of Fe powder/Mg-3(Sb, Bi)(2) junction approximate to 30 mu Omega cm(2). Particularly, a thin diffusion layer with a width of approximate to 2 mu m is initially observed in the unannealed Fe foil/Mg-3(Sb, Bi)(2) junction. Even after thermal aging at 573 K for 28 days, the diffusion-layer width is basically unchanged and its corresponding contact resistivity maintained as low as approximate to 5.8 mu Omega cm(2). Overall, this work provides deep insights into interfacial design and paves the way for high-performance and sustainable low-grade waste heat recovery.

As a highly potential environmental-friendly medium-temperature thermoelectric material, pure SnTe exhibits relatively poor performance due to its intrinsic high carrier concentration and large energy offset between the two valence bands. In the present work, dilute Sc/Y doping is innovatively adopted to synergistically decrease carrier concentration and achieve strong band convergence. The Hall measurement results indicate that 3 % Y doping realizes the lowest carrier concentration of 2.6 x 1019 cm-3 in SnTe. Sc and Y have similar effects in promoting band convergence, with their effects second only to toxic Hg elements at the same doping concentration. The effective decoupling of electrical and thermal transport parameters results in a high average ZT of 0.453 for Sn0.975Sc0.025Te sample, which is 103 % higher than that of pure SnTe. In addition, with Li2Te alloying to regulate carrier concentration, high-performance temperature range could be adjusted, which is more conducive to dealing with different temperature scenarios. The role of Sc/Y doping disclosed in this work pro-vides more options for further improving the performance of SnTe-based materials.

In dropwise condensation, the heat transfer performance is determined by the heat transfer through a single droplet and the droplet size distribution on the cooled condensing surface. The conduction resistance inside a droplet is an important part of all heat transfer resistances, and it also affects the size distribution of small droplets further, such as in the popular population balance model. The heat transfer of a single droplet can be measured by the Nusselt number (Nu), and internal conduction resistance can be measured by the dimensionless shape factor (f). Previous studies have shown that Nu and f are functions of droplet contact angle (theta) and Biot number (Bi). Based on this, some fitting correlations of Nu or f in a certain range of Bi and. are established. However, previous results show unreasonable values when Bi is very large or very small, the effective ranges of these fitting correlations are not broad enough, and the fitting accuracy is not gratifying enough. In this paper, the heat transfer characteristics of condensing droplets are investigated by a CFD method which is validated by comparing the simulation results and theoretical solution for hemisphere droplets. By adopting this method, f and Nu are obtained for droplets with 10 degrees <= theta <= 170 degrees and 10(-3) <= Bi <= 10(4). Considering the relationship between current numerical results and the model of Kim and Kim (2011), an improved general fitting correlation covering all 374 simulation cases is proposed, and the root mean square (RMS) errors of f and Nu are 3.6% and 2.6%, respectively. (c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In this paper, the condensation heat transfer characteristics of light tubes and spiral tube tubes are studied by numerical analysis. The condensation characteristics of vertical spiral tube containing non-condensing gas vapor were explored, and the distribution of steam velocity, pressure and temperature near the wall of the heat transfer tube was analyzed. The enhanced heat transfer method of non-condensing gas vapor was obtained, which provided a theoretical basis for the enhanced heat transfer of steam condensation. The results show that the spiral tube can increase the heat exchange performance. The spiral can effectively reduce the thickness of the liquid film, which can impressively enhance the heat transfer performance.