•PCM and insulation component are used to improve thermal performance of Trombe wall.•Effects of design parameters of insulation component are studied using the validated model.•Design approach of ...heat preservation at night of a TW-PCM is proposed.•Thermal comfort is analyzed based on operative temperature and radiant temperature asymmetry.
A classical Trombe wall cannot satisfy the thermal comfort for the whole day due to the limited heat storage capacity and large heat loss at night. In present work, phase change materials and an external insulation component are used to improve thermal performance of a Trombe wall. The design approach of heat preservation at night is first obtained. An unsteady heat transfer model of a Trombe wall with phase change materials under heat preservation condition in the nighttime is established by MATLAB. The reliability of the mathematical model is validated by an experiment in Yuzhong (Gansu, China). With this model, the effects of the design parameters of the external insulation component on the thermal performance are analyzed. Finally, the indoor thermal comfort of a passive solar room is analyzed based on the experimental data. The results indicate that, it has a significant impact of the thermal conduction resistance of the insulation component and the thermal resistance of the closed air cavity. For closed air cavity, the internal surface emissivity of the insulation component plays an important role. The optimized additional thermal resistance for the external insulation component is 2 m2⋅°C⋅W−1, and the corresponding maximum thermal resistance of the closed air cavity is determined as about 0.5 m2⋅°C⋅W−1. Compared with no heat preservation at night, the operative temperature improves significantly, and the radiant temperature asymmetries of two massive walls are similar. The investigation can provide a design approach of heat preservation at night for a Trombe wall.
•Thermal conductivities of CNT-coated fiber-reinforced nanocomposites are analyzed.•Transverse thermal conductivity is enhanced by coating CNTs on the fiber surfaces.•Transverse thermal conductivity ...rises with increasing CNT content and length.•Considering CNT random orientation, waviness and interfacial effect is necessary.
The role of carbon nanotube (CNT) coating on the carbon fiber (CF) surfaces in the effective thermal conductivities of the unidirectional polymer hybrid nanocomposites is investigated by a newly presented multi-stage micromechanical method. The constructional feature of the hybrid nanocomposite is that randomly oriented CNTs grown on the CF surfaces. For simulating, a new version of the semi-empirical Halpin-Tsai (H-T) model is appropriately coupled with an analytical unit cell micromechanical model developed in the present research. The model captures the influences of the CNTs random dispersion, waviness, length, diameter, volume fraction and the CNT/polymer interfacial thermal resistance and also the CF cross-section shape parameters. The predicted results for the thermal conductivities of fibrous composites and polymer nanocomposites containing CNTs are verified with the available experimental data and a very good agreement is found. The results show that the longitudinal thermal conductivity of CF-reinforced hybrid nanocomposites is not affected by the CNTs coating. However, the nanocomposites transverse thermal conductivities are significantly enhanced over those of the conventional fibrous composites without the CNTs coating. An improvement in the nanocomposites transverse thermal conducting behavior can be observed with (i) increasing the CNTs volume fraction and length (ii) using straight CNTs and (iii) forming a perfect bonding interface.
•A misprint has been detected in a previously published paper.•The misprint has been corrected in the Corrigendum•Instead of the temperature differences, the logarithms of the temperature differences ...should be insert in eq. 1.
•The interfacial thermal resistance between epoxy and graphene edges is 7.13 ± 1.58 × 10–9 m2KW-1, which is essential to the overall thermal transport of epoxy/ graphene composites.•The active amino ...groups can reduce the interfacial thermal resistance between epoxy and graphene edges to 42% due to strong covalent bonds.•The amino groups have a great influence on the density distribution near the interface.•The effect of inactive amino groups on the interfacial thermal resistance depends on its coverage rate.
Epoxy/graphene nanocomposites have attracted significant attention in microelectronic devices due to the ultra-high thermal conductivity of graphene. However, the high interfacial thermal resistance between graphene and polymer hinders its application. In this paper, the effect of amino groups on the interfacial thermal resistance between epoxy and graphene edges is investigated by using molecular dynamic simulations. The density distribution and the phonon density of states near the interface are calculated to study the mechanism of interfacial heat transfer. The results show that the active amino group reduces the interfacial thermal resistance to 42%, while the effect of the inactive amino group on the interfacial thermal resistance depends on its coverage rate. The presence of the inactive amino group increases the interfacial gap width and leads to poor heat transfer. In a lower coverage rate, the epoxy fills the spacing between amino groups and half-wraps them. The phonon mismatch is reduced due to the increase of contact areas between graphene and epoxy. Therefore, the interfacial thermal resistance decreases with the decrease of the coverage rate. This work is of practical importance for the design of amino groups distribution on graphene edges in nanocomposites materials.
Based on the contributions of carbon nanostructures and their composited species, great advances in electromagnetic wave interference shielding have been achieved. In this article, recent progress in ...electromagnetic wave shielding enabled by the synergism of carbon nanostructures and their corresponding composites is discussed encompassing the factors of microstructural defects, filler concentration, filler alignment, filler inherent conductivity and the surrounding temperature. Carbon nanostructures and their composites would energize the advanced electromagnetic wave shielding because of their light weight, high corrosion resistance, excellent thermal, mechanical, and electrical properties, broad absorption frequency bandwidth and cost-effectiveness. In this context of identifying suitable carbon composites that can enhance electromagnetic wave absorption. This review provides updated electromagnetic wave shielding knowledge of carbon nanostructures and their composites as well as their prospects and challenges.
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The transient dual interface method (TDIM), proposed by the JEDEC 51-14 standard <xref ref-type="bibr" rid="ref1">1 , determines the junction-to-case thermal resistance of power electronics with the ...separate point of two transient thermal impedance curves under different contact conditions. However, the influence of the junction temperature is not considered and this underestimates the actual value with earlier separation point. This phenomenon is presented first with experimental results at different junction temperatures. Electro-thermal finite element simulations and simulation with semiconductor physical behavior in the devices simulations are performed to explain the root reason. After that, the improved TDIM with the junction temperature compensation is proposed to improve the accuracy. The experimental results show that the improved TDIM improves the accuracy of about 9.5% for 600-V discrete IGBT devices.
The double-side cooling (DSC) packaging becomes more and more popular with the great demands of high power and fast speed, especially for silicon carbide metal oxide semiconductor field effect ...transistors. Measurements and modeling of thermal resistance are critical for thermal management of DSC module. However, the thermal resistance of DSC module is still unclear due to the asymmetric dual thermal paths. In this article, a clear understanding of thermal resistance of DSC module measured by transient dual-interface method (TDIM) is explained. The thermal impedance of DSC module is analyzed through time- and frequency-domain response of the DSC thermal model. The cooling conditions in TDIM have no influence on the measured thermal resistance of DSC module. The measured thermal resistance from junction to top case (or bottom case) is half of the actual value. The important conclusions are verified by transient simulations and experiments. Based on the results, a new definition of thermal resistance of DSC module is proposed for exact evaluation of thermal resistance and reliability.
•Performances of retrofitted educational building is investigated.•Thermal resistance, moisture-related risks and IEQ are investigated.•Thermal resistance could be estimated under winter ...period.•Overall safe behavior is observed despite some mold growth risks.•Hygrothermal comfort is achieved in the classroom.
This paper deals with the performance of a high school building renovated with prefabricated ventilated façade elements through a field experimental study under oceanic climate. Temperature, relative humidity and heat flux were measured at different points of the renovated façade, while temperature, relative humidity and CO2 concentration were monitored within a classroom. The performance of the renovated building is discussed based on the analysis of two years of measurement data. The experimental results show that the measured in situ thermal resistance of prefabricated ventilated façade elements could be evaluated reliably only under winter period and that it is higher than the design one. Secondly, we note that the application of exterior thermal insulation does not lead to major moisture related pathology on retrofitted building envelope. Only small mold growth risks may exist close to hygroscopic material in relation with solar radiation. Last, we observe that hygrothermal comfort is achieved most of the teaching time, whereas CO2 concentration exceed critical threshold levels every day.
This study investigates the interfacial thermal resistance effect, primarily associated with the bottom-gate stack, in self-aligned top-gate amorphous indium gallium zinc oxide (a-IGZO) thin-film ...transistors (TFTs). We analyze self-heating and heat transfer characteristics across three different a-IGZO TFT configurations: single-gate, dual-gate type 1, and dual-gate type 2. Temperature maps, corresponding to various bias conditions, are acquired using infrared thermal microscopy. The extracted values of thermal resistance reveal a significant disparity between single- and dual-gate configurations. This suggests that the bottom-gate stack in a-IGZO TFTs, including the interfaces, notably impedes heat dissipation. These findings offer crucial insights into the power dissipation aspects of TFT technology, highlighting the importance of interfacial design for thermal management in advanced electronic devices.
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•Detailed analysis of thermal resistance in self-aligned top-gate a-IGZO TFTs.•Significant disparities in thermal resistance between single-gate and dual-gate configurations.•Interfacial defects and roughness in DG structures increase thermal resistance.•Infrared thermal microscopy used to acquire temperature maps under different bias conditions.•Insights guide the design and improvement of thermal management in TFT technology.
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