Influence of solder condition on effective thermal conductivity of two-directional random fibres: Pore-scale simulation

It is indicated that the solder joint of the metal fibrous materials is a critical factor impacting the heat conduction. To reveal the mechanism by which solder joint sizes, solder joint skips, solder flux materials, and filling media affect the thermal conductivity of fibres, pore-scale numerical simulation is employed to study the thermal transport in two-directional (2-D) random fibres. Satisfactory agreement with existing data validates the numerical model. The dimensionless effective thermal conductivity (ETC) of the porous fibres increases with the solder joint sizes. As the solder joint size (i.e., solder joint ratio) increases by 3.06%, the in-plane (ke-in) and out-of-plane (ke-out) dimensionless ETC increase by 9.0% and 437.2%, respectively. However, the solder joint skips will weaken the thermal conductivity of the fibres. For the same fibre, the ETC of the fibre increases as the thermal conductivity of solders increases. Further, when the dissimilarity in thermal conductivity between the filling medium and the fibre is reduced, the fibre is less affected by the solder joint skips. Finally, it should be supplemented that the in-plane and out-of-plane ETC (ke-in and ke-out) of the fibre without any solder joint are reduced by an average of 14.3% and 98.8%, respectively.Process and Energ

Performance Comparison between Data Centers with Different Airflow Management Technologies

Air cooling systems are widely used in current data centers owing to their low capital costs and high reliability. To satisfy the increasing rack power density, the optimal air-cooling technology and an economic analysis should be carefully discussed. Therefore, this study discusses four airflow management technologies: Case 1: raised floor and cold aisle containment supply/computer room air conditioning (CRAC) direct return; Case 2: CRAC direct supply/hot aisle containment (HAC) return; Case 3: overhead duct supply/CRAC direct return; and Case 4: overhead duct supply/HAC return. Using a validated model, the thermal and economic performances of each case were compared. Results showed that Case 4 exhibited the best thermal performance, followed by Cases 3, 2, and 1. Case 1 cannot satisfy the heat dissipation requirement when the rack power density is larger than 12.5 kW; whereas only Case 4 can be used when the power density is larger than 15 kW. Regarding location within China, owing to the high ambient temperature, Shenzhen showed the highest annual cost value and power usage effectiveness, followed by Shanghai, Xi’an, Beijing, and Harbin. Finally, Cases 3 and 4 are recommended for application when the rack power density is greater than 10 kW.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Process and Energ

Combustion Air Humidification for NOx Emissions Reduction in Gas Boiler: An Experimental Study

NOx emission reduction from gas boilers has become a key issue in improving air quality. Combustion air humidification technology is gradually being used to reduce NOx emissions. However, the NOx emission reduction effect of gas boilers at a higher combustion air humidity has been studied less. A flue gas with low NOx emissions and a waste heat recovery system using combustion air humidification technology are proposed in this study. In the ultra-low NOx mode, the effect of high combustion air humidity on NOx emission reduction and efficiency of the gas boiler were studied experimentally. In the waste heat recovery mode, the effects of the heat network backwater temperature on the NOx emission reduction and system efficiency were studied experimentally. Results showed that an increase in air humidity can significantly reduce the NOx concentration formed by combustion. The ultra-low NOx mode reduces NOx emissions from 130 mg/m3 to 23.3 mg/m3 and affects the boiler efficiency slightly. In the waste heat recovery mode, NOx emissions can be reduced to 39.9 mg/m3 when the backwater temperature of the heat network is 55 °C. This condition improves the efficiency to 93.8%. The analysis results provide suggestions for the selection of the operation modes.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Process and Energ

Design and assessments on a hybrid pin fin-metal foam structure towards enhancing melting heat transfer: An experimental study

Solar energy, as a kind of renewable energy, offers a large reserve to be harvested at a reasonably low cost for engineering applications. To decouple the temporal and spatial relevance of the continuous energy supply of solar energy, latent heat thermal energy storage can deal with this problem at different temperatures. Aiming to improve energy efficiency, a novel hybrid metal foam-pin fin structure is designed and assessed. Upon conducting measurements on a well-designed experimental bench, the phase change processes of paraffin that is filled in fins, metal foam, and a combination of both (hybrid structure) are evaluated. During the experiments, the transient melting interface is snapshotted and temperature development is documented under five different heat source temperatures of 61 °C, 63 °C, 65 °C, 68 °C, and 70 °C. In the foreground of the novel hybrid structure, each segment of the hybrid is also justified and discussed. Results indicate that the hybrid structure augments marked heat transfer. Compared to pure PCM, complete melting time decreases by 63.4% and simultaneously the temperature response rate increases by 143.9% as implementing the hybrid. Attempts to design hybrid structure find a solution to assess and operate thermal storage applications for solar engineering.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Process and Energ

Optimization of adaptive metal foam arrangement in a heat storage tank

The integration of phase change materials (PCMs) and metal foam has been widely concerned recently. To decrease non-uniformity of uniform metal foam-PCMs, adaptive metal foam arrangement strategy with increasing porosity from inside to outside has attracted widespread attention. This work conducted a symmetric simulation model of vertical thermal energy storage (TES) tube validated by experiments, for optimization of adaptive metal foam arrangement in basic design (0.94–0.94–0.94). It was followed by assessing the performance of gradient metal foam structures that included 27 cases with radial foam gradients of larger porosity on the outside and smaller porosity on the inside. Results demonstrated that a smaller difference between the inside and outside subregions resulted in better thermal performance when the same porosity of the intermediate subregion was used. More intense natural convection with stronger liquid paraffin vortex could be obtained by an adaptive arrangement. With the same average porosity, the faster phase change evolution, which was influenced by the maximum promotion of stronger natural convection, was achieved by using a larger intermediate porosity and a larger porosity difference between the inside and outside regions. The optimal strategy (0.87–0.94–0.97) could significantly shorten the melting duration as maximal as 17.15% compared with the original uniform (0.94–0.94–0.94), which contributed to efficient vertical metal foam TES systems, also as light and cost-effective as possible while also avoiding sacrificing thermal capacity.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Process and Energ

Transcription of Il17 and Il17f Is Controlled by Conserved Noncoding Sequence 2

T helper 17 (Th17) cells specifically transcribe the Il17 and Il17f genes, which are localized in the same chromosome region, but the underlying mechanism is unclear. Here, we report a cis element that we previously named conserved noncoding sequence 2 (CNS2) physically interacted with both Il17 and Il17f gene promoters and was sufficient for regulating their selective transcription in Th17 cells. Targeted deletion of CNS2 resulted in impaired retinoic acid-related orphan receptor gammat (ROR gamma t)-driven IL-17 expression in vitro. CNS2-deficient T cells also produced substantially decreased amounts of IL-17F. These cytokine defects were associated with defective chromatin remodeling in the Ild17-Il17f gene locus, possibly because of effects on CNS2-mediated recruitment of histone-modifying enzymes p300 and JmjC domain-containing protein 3 (JMJD3). CNS2-deficient animals were also shown to be resistant to experimental autoimmune encephalomyelitis (EAE). Our results thus suggest that CNS2 is sufficient and necessary for Il17 and optimal Il17f gene transcription in Th17 cells.T helper 17 (Th17) cells specifically transcribe the Il17 and Il17f genes, which are localized in the same chromosome region, but the underlying mechanism is unclear. Here, we report a cis element that we previously named conserved noncoding sequence 2 (CNS2) physically interacted with both Il17 and Il17f gene promoters and was sufficient for regulating their selective transcription in Th17 cells. Targeted deletion of CNS2 resulted in impaired retinoic acid-related orphan receptor gammat (ROR gamma t)-driven IL-17 expression in vitro. CNS2-deficient T cells also produced substantially decreased amounts of IL-17F. These cytokine defects were associated with defective chromatin remodeling in the Ild17-Il17f gene locus, possibly because of effects on CNS2-mediated recruitment of histone-modifying enzymes p300 and JmjC domain-containing protein 3 (JMJD3). CNS2-deficient animals were also shown to be resistant to experimental autoimmune encephalomyelitis (EAE). Our results thus suggest that CNS2 is sufficient and necessary for Il17 and optimal Il17f gene transcription in Th17 cells

Sindrome extrapiramidale e dermatite da ipocorticosurrenalismo. Case report

Due to rapid economic development and population growth, China is facing severe water problems that include sea-level rise and increasing salinization, floods, water pollution, water shortage, soil erosion and ecosystem deterioration, as well as biodiversity loss. In recent decades, China is progressively more concerned with its water issues that are now at the center of social and political attention. Having to overcome similar challenges, Germany has taken a leading role in the field of water sciences and technology. In particular, China can benefit from the lessons learnt in Germany concerning the rehabilitation of water resources in areas heavily affected by chemical industry and mining after the reunification in 1989. German-Chinese cooperation in water sciences started over 25 years ago and dealt with increasing challenges in the 21st century. Following the open space workshop during the Water Research Horizon Conference in Berlin 2014, this article provides a view of some of the challenges and potential opportunities of German-Chinese cooperation in water science and technology