The front cover artwork is provided by Prof. Faze Wang's group at the Southeast University. The built-in electric field created by the semiconductor heterostructure confines the proton transport on the surface layer of the nanocomposite core-shell heterostructure imparting faster ion transport and lower activation energy. Read the full text of the Research Article at 10.1002/cphc.202200170.
Enhanced geothermal system (EGS) is the primary means during Dry Hot Rock development. It is necessary to build an underground heat exchange area during its construction, and the temperature of underground rock will change significantly, thus, the mechanical properties of those rocks underground will be affected. In order to judge whether the mechanical properties under temperature are related to the crystal structure of granite, we firstly used the crystalline rock heterogeneity coefficient H to describe the crystal structure of granite. Then, the discrete element software was used to construct the GBM equivalent crystalline model and the thermal temperature field coupling model. Finally, the temperature effect test was carried out to explore the law of heterogeneity coefficient H and damage and fracture development. The results show that: 1) the variation of granite heterogeneity coefficient H and temperature will lead to the decline of mechanical properties of rock samples. 2) At the same temperature, the damage value D increases with the increase of the H value. This phenomenon is more apparent when the temperature is greater than 400°C. 3) The microcracks caused by temperature change are mainly tensile. The H value increases the number of microcracks in the crystal. 4) The damage phenomenon caused by temperature change will be affected by heterogeneity. When the temperature is high, the crystal will denature, and the stress concentration caused by heterogeneity is easier to be reflected.
With the development of society, the energy crisis has become increasingly prominent, which greatly affects the sustainable development of the economy of various countries. Industrial energy consumption accounts for more than 70% of China’s total energy consumption, of which more than 50% is converted to industrial waste heat, and recyclable waste heat resources account for about 60% of the total waste heat resources, while China’s current utilization rate of industrial waste heat only reaches about 30%. The development of renewable energy and recovery of low-grade waste heat in industry is the key to solve the problem. As a type of volumetric expander with full flow expansion, the screw expander is extensively applied in the industrial waste heat recovery and geothermal energy generation industry because of its effective utilization of low enthalpy energy. Improving the performance of the screw expander as the core, the paper concludes and summarizes the research status of the leakage, rotor geometry, sealing and lubrication, processing and manufacturing, which can affect the performance of the screw expander. In addition, it also introduces the application status and potential utilization of screw expander.
Erosion is a failure phenomenon which caused by relative motion between the surface of a fluid and material, it often results in the failure of the device, affects the normal operation of equipment. This paper describes the design of a erosion experimental device combined with the characteristics of the existing types of erosion experimental advantages, disadvantages and metal material erosion experiment. The device consists of a plurality of tank, pump, spray tanks, cam nozzle, pipeline and so on. It can control to the impact velocity, impact angle.
It is essential to investigate person-to-person contaminant transport in mechanically ventilated spaces to improve air distribution design and reduce the infection risk from airborne infectious diseases. This article provides a systematic study of the effects of ventilation mode, ventilation rate, and person-to-person distance on person-to-person contaminant transport. This study first collected available cases of person-to-person contaminant transport from the literature to create a database. Then this investigation identified the limitations of the existing data and added a number of cases to complete the database. The additional cases were generated by using a Reynolds-averaged Navier-Stokes (RANS)-Eulerian model that was validated by experimental data from an occupied office with under-floor air-distribution (UFAD) systems. The database shows that the overall performance of displacement ventilation and the UFAD systems was better than that of mixing ventilation. A higher ventilation rate was beneficial in reducing person-to-person contaminant transport to some extent. Person-to-person contaminant exposure increased rapidly with a decrease in person-to-person distance when the distance was smaller than 1.1 m. Generally speaking, person-to-person distance is an important parameter when compared with ventilation mode and ventilation rate.
The requirements of laboratory facilities differ dramatically from those of other buildings. As we expand our biocontainment needs to Biosafety Levels (BSL) -2, -3, and -4, a clear need exists for an air quality and thermal comfort initiative targeting these facilities. The thermal comfort of occupants in laboratories can be controlled by the choice of ventilation strategy. Added benefits are the realization of a significant energy savings and improved indoor air quality. This study employs an advanced numerical simulation and empirical validation to assess the performance of active chilled beams in a general laboratory layout having some equipment intensive areas. The study examines the removal effectiveness of gases and airborne particles in such a system. Chilled beam performance is also compared to a ceiling diffuser system with and without cooling panels. The results of this study show that chilled beams improve thermal comfort and can be operated at reduced Air Changes per Hour (ACH) while maintaining a comfortable environment in occupied zones expressed as the Predicted Percentage Dissatisfied (PPD). To obtain a similar level of thermal comfort, a higher ACH is required in a ceiling diffuser system with cooling panels and bench exhausts. The chilled beam system also improves the removal effectiveness of gases or airborne particles because of the inherent better mixing in the room compared with the use of ceiling diffusers. In the cases studied, chilled beams have an insignificant effect on the fume hood containment. As satisfactory thermal comfort and air quality was achieved at a lower flow rate when compared with an all-air ceiling diffuser system, a savings of around 22% is estimated in annual energy costs for cooling and ventilating a typical lab in the Washington, DC area. The methodology and results of this study may be applied to further research for other laboratory types, or climatic conditions than those proposed in this study.
A ventilation jet diffuser is characterized by parameters such as diffuser effec tive area, diffuser dimension, diffuser position, air supply direction, flow rate, and air temperature. This paper studies the influence of the parameters of a jet diffuser on the airflow pattern, indoor air quality, and draft risk in an office with a jet diffuser on the rear wall near the ceiling. The presentation of furni ture and occupants in the office is included in the numerical simulation. The structure of a jet diffuser used in practice is complicated. Therefore, a simpli fied method is introduced to simulate the diffuser. The method is compared with the experimental data. The agreement between the simulations and the measurements is reasonably good. The distributions of the air velocity, tem perature, contaminant concentration, and percentage dissatisfied people due to draft risk with different parameters of the diffuser are numerically pre dicted by the k-ε model of turbulence. The effect of turbulence intensity is taken into account in the computation of draft risk. It has been found that the angle between the jet and the ceiling should be in the range from 20 to 60°C. The effective flow area has a strong impact on the indoor airflow pattern since it significantly affects the throw projection. The diffuser width has a larger influence on indoor air diffusion than the diffuser height. The distance between the inlet and ceiling has a remarkable influence on the total air move ment near the ceiling, but has a minor impact on the air diffusion in the occu pied zone. Air velocity distribution is sensitive to ventilation rate and supply air temperature. To achieve the same length of throw projection, the Reynolds number should be the same if the corresponding Archimedes number is close to each of them.
A numerical model has been developed to investigate the contaminant removal and air freshness in a ventilated two-zone enclosure. The average contaminants and the distributions of air age in each zone under variable positions of door, supply and exhaust are compared. The correlation between the average contaminants and each of the main parameters, such as door location, supply and exhaust positions etc., are presented, and the average air ages in both zones are illustrated against door position. It is found that the average air age in the upstream zone is less affected by the door position than that in the downstream zone, and that the door position near the side-walls seems to give better air circulation. It is also concluded that the supply and door positions affect the concentration in the upstream zone significantly, while the exhaust location does not seem to influence the average concentration in either the upstream or the downstream zone.
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