Search

We evaluate the heat transfer from radiant ceilings that have suspended acoustical panels present for noise reduction. An upward-directed ceiling fan is added to offset the reduction of heat exchange due to the acoustical panels. We systematically simulate the indoor thermal environment and the changes to heat transfer coefficients caused by the interaction between radiant ceiling panels, acoustical panels, and ceiling fan under four influencing factors: (1) coverage ratio of acoustical panels, (2) fan rotational speed, (3) radiation panel temperature and (4) room height. The simulation method is validated with experimental data. Numerical results show that the augmented air speed increases convective and total heat transfer for radiant panel. Simulated temperature non-uniformity, air and operative temperature in the occupied part of the room is reduced with increased fan speed, and with decreased acoustical panel coverage ratio. The PMV increased with increased acoustical panel coverage ratio and radiant surface temperature, and also with reduced fan speed. When using fans, the radiant surface temperature can be raised 2 ℃ while maintaining equivalent thermal comfort, allowing higher water supply temperatures. The radiation heat transfer coefficient of the bare ceiling is decreased 25% by adding 63% acoustical panel coverage. The total heat transfer coefficient of radiant ceiling increases with fan speed up to 106.2% over a no-fan base case, and decreases with increased acoustical panel coverage ratio. The study indicates that an upward-directed ceiling fan is a worthwhile method to enable raised radiant surface temperatures, save cooling energy, and reduce surface condensation risk.

Owing to the complexity of metros, the energy consumption characteristics of metro systems exhibit variability and the energy‐saving management of the systems encounters challenges. To encapsulate the essential characteristics of energy usage and to objectively assess the energy performance of metro systems, this study presents a generalized framework and applies it to a case study conducted in Tianjin. The study also employs correlation analysis to investigate the applicability of the indicators relevant to ridership. The results indicate that the monthly traction electricity consumption exhibits slight variation, while station electricity usage demonstrates substantial fluctuation with seasonal changes. For Tianjin Metro, the passenger factor hardly shows any effect on the electricity use of metro lines. The median value of traction electricity use is approximately 2.0 kWh/(car‐km) and that of the average annual station electricity use of underground lines ranges from 95 to 155 kWh/m2. The emission from the traction sector is 12.2 kgCO2/(vehicle‐km) and from the station sector is 118.6 kgCO2/m2. The study also identifies the energy‐intensive lines of the Tianjin Metro and compares the energy utilization among various global metro systems. The authors hope that this study can help shed light on the assessment of the energy status of metro systems and serve as a source of information for other City‐Metros to implement energy‐saving management. [ABSTRACT FROM AUTHOR]

Developing high-performance cathodic catalysts and exploiting new techniques to investigate the nanoscale process of the oxygen reduction reaction (ORR) are of significant importance for the wide application of microbial fuel cells (MFCs). Here, novel Fe-based clusters embedded in nitrogen doped activated carbon (Fe-clusters/NAC) catalysts were developed via a simple ball milling method. Abiotic electrochemical tests demonstrated that these Fe-clusters/NAC catalysts exhibited an enhanced ORR performance due to the formation of Fe-based clusters, and the exposure of abundant active sites including quaternary N, Fe–N and Fe-based clusters. More importantly, the Fe-clusters/NAC catalysts exhibited an even better ORR performance than Pt due to the existence of more active sites than Pt, which was confirmed by using a scanning electrochemical microscope. Acid etching treatment and density functional theory calculations further verified the superior ORR activity of Fe-based clusters. The power density of the Fe-clusters/NAC catalyst-based MFCs reached 2387 mW m−2, which is the highest value among the reported Fe–N–C catalysts under the same/similar experimental conditions over the last five years, at least 65% higher than that of AC and 50% higher than that of commercial Pt. [ABSTRACT FROM AUTHOR]

Developing high activity, low-cost and long durability catalysts for oxygen reduction reaction is of great significance for the practical application of microbial fuel cells. The full exposure of active sites in catalysts can enhance catalytic activity dramatically. Here, novel Fe-N-doped graphene is successfully synthesized via a one-step in situ ball milling method. Pristine graphite, ball milling graphene, N-doped graphene and Fe-N-doped graphene are applied in air cathodes, and enhanced performance is observed in microbial fuel cells with graphene-based catalysts. Particularly, Fe-N-doped graphene achieves the highest oxygen reduction reaction activity, with a maximum power density of 1380±20 mW/m2 in microbial fuel cells and a current density of 23.8 A/m2 at −0.16 V in electrochemical tests, which are comparable to commercial Pt and 390% and 640% of those of pristine graphite. An investigation of the material characteristics reveals that the superior performance of Fe-N-doped graphene results from the full exposure of Fe2O3 nanoparticles, pyrrolic N, pyridinic N and excellent Fe-N-G active sites on the graphene matrix. This work not only suggests the strategy of maximally exposing active sites to optimize the potential of catalysts but also provides promising catalysts for the use of microbial fuel cells in sustainable energy generation. [ABSTRACT FROM AUTHOR]

A dynamic mathematical model for simulating the coupled heat and moisture transfer within multilayer wall was proposed. The model was validated by comparing with representative benchmark tests. According to the mould germination conditions, a predictive evaluation method of mould germination risk in building wall was developed, which is based on transient distributions of temperature and relative humidity and their duration. Taking the red brick wall as example, the influence of relative humidity and temperature of indoor air on mould germination risk in wall was analyzed. And corresponding study was carried out for the major cities in Guangdong province. The results show that relative humidity of indoor air mainly influences the mould germination risk in the inner side of the wall. Relative humidity increase results in a rapid increase of the mould germination risk. The temperature of indoor air influences both the inner side and outer side of the wall. Temperature increase leads to increase of the mould germination risk in the inner side, but decrease in the outer side of the wall. Solar radiation has a great effect on mould germination risk, and less solar radiation results in a greater mould germination risk. In order to reduce the mould germination risk, different measure should be taken for different city and for different position in building wall. [ABSTRACT FROM AUTHOR]

Correction for 'Iron-based clusters embedded in nitrogen doped activated carbon catalysts with superior cathodic activity in microbial fuel cells' by Xiaoyuan Zhang et al., J. Mater. Chem. A, 2020, DOI: 10.1039/C9TA10797E. [ABSTRACT FROM AUTHOR]

Mn/Ce/Ti and Mn/Ce/Nb/Ti catalysts were synthesized using a precipitation method and their catalytic activities for NO selective reduction with NH 3 at low temperatures were evaluated. Nb doping not only improved the activity of the catalyst over a wide temperature range but also restricted the generation of NO 2 and N 2 O. The Mn/Ce/Nb/Ti catalyst displayed 100% NO conversion from 150 to 250 °C and >90% N 2 selectivity below 250 °C. The specific surface area of the catalyst was increased and its surface acidity was strengthened after Nb doping. Moreover, Nb doping increased the NO oxidation ability and lowered the NH 3 oxidation activity of the catalyst. All the above factors contributed to enhancing the overall NH 3 -SCR performance of the Mn/Ce/Nb/Ti catalyst compared with that of the Mn/Ce/Ti one. The long-term stability and resistance to H 2 O and SO 2 of the Mn/Ce/Nb/Ti catalyst were also evaluated. [ABSTRACT FROM AUTHOR]

Solar-driven interfacial evaporation aiming at producing clean water without conventional energy consumption, has attracted worldwide research interest. Nevertheless, complex preparation processes and costly absorber materials might be the challenges for the practical application of this technology. Herein, a ceramic fiber was preferably selected as the supporting matrix, and a composite of activated carbon and carbon black was used as the photothermal material. Different evaporation system configurations containing the as-synthesized solar absorber were constructed and compared. It was found that, due to an improved heat insulation and water transportation, the one-dimensional configuration exhibited a maximum evaporation rate of 1.70 kg m−2 h−1 and the highest solar-to-vapor energy conversion efficiency of 91.8% under one sun. Furthermore, material cost and preparation complexity were also incorporated to assess the comprehensive performance of this solar absorber. The ceramic fiber-based activated carbon‑carbon black composite (CF-ACB) solar absorber proposed in this contribution, featuring cost-effectiveness, easiness-to-manufacture and great evaporation performance, illuminated its application potential of future solar desalination to provide clean water for people who live in remote and less developed areas with limited and insufficient access to fresh water. Unlabelled Image • Ceramic fiber-based activated carbon‑carbon black composite facilitated evaporation. • One-dimensional configuration maximized the solar evaporation performance. • Great cyclic stability and purification performance were achieved in desalination. • Extremely low cost and high easiness-to-manufacture made this absorber stand out. [ABSTRACT FROM AUTHOR]