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Tunnel construction often relies on drilling and blasting. High dust pollution is one of the primary problems of drilling and blasting construction. The level of secondary blown dust pollution caused by ventilation matches that of dust pollution caused by drilling construction. In this study, a critical flow model and blown dust rate model for deposited dust were established via force analysis, which was validated against the test data. The research results showed that the characteristic airflow velocity for blowing dust particles with a 100 μm diameter reached approximately 0.42 m/s for tunnel diameter is 10 m, and the ventilation Re values under smooth and rough conditions were 2.3 × 105 and 1.4 × 105, respectively. Furthermore, when ventilation Re reached 4 × 105, the blown dust pollution rate caused by ventilation under smooth conditions was approximately 1.8 × 10−2 kg/s. If dust particle size is more or less the critical dust particle size, the characteristic airflow velocity was increased. Moreover, the optimal velocity at which the deposited dust does not flow or move during tunnel construction was related to the tunnel size and roughness. For the smooth tunnel with a diameter of 10 m, the optimal ventilation velocity was 3.5 m/s. When the tunnel roughness was increased from 0.005 to 0.5 m, the optimal ventilation velocity decreased from 3.3 to 1.6 m/s. The deposited dust critical flow model and blown dust pollution rate model established in this study provide a sound theoretical basis for selecting the optimal velocity of tunnel ventilation and recognizing the risks of secondary blown dust pollution due to ventilation. [Display omitted] • Critical flow threshold of deposited dust increases with the dust particle size increase. • The blown dust pollution rate increases with the increase of ventilation Re. • The optimal velocity without resulting blown dust pollution is related only to tunnel size. [ABSTRACT FROM AUTHOR]

The resistance of local piping components in HVAC systems significantly contributes to building energy consumption. Therefore, this study proposes a method combining orthogonal experiment design (OED) and simple comparison design (SCD) to optimize the position and angle of the double guide vanes in the elbow, resulting in a low-resistance modified elbow with double guide vanes. The resistance performance and secondary flow intensity of the traditional and modified elbow with double guide vanes are analyzed by full-scale experiments and numerical simulations. The effectiveness of the modified elbow with double guide vanes in reducing resistance is verified for different inlet Reynolds numbers, nominal diameters, and curvature ratios. The results show that the modified elbow has a good resistance reduction effect, and the resistance reduction rate is 11.4%–29.4% when the Re number ranges from 0.1 × 105 to 8.0 × 105. Under different nominal diameters (DN25-DN200) and curvature ratios (0.8–2.0), the resistance reduction rate of the modified elbow was 0%–38.1%. For long elbows with a curvature ratio greater than 2.0, resistance reduction by inserting double guide vanes is not recommended. The insertion of double guide vanes can inhibit the development of secondary flow in the elbow, cutting the double-vortex core with high vortex intensity into a four-vortex core with low vortex intensity, thus decreasing the secondary flow intensity and mechanical energy consumption. This study provides new optimization methods and perspectives for the low-resistance and standardized design of piping components in HVAC systems. • Elbow with double guide vanes is optimized based on OED and SCD methods. • The resistance and secondary flow of the modified elbow with double GVs are analyzed. • The addition of double GVs achieves a maximum resistance reduction of 38.1%. • Double GVs can reduce flow nonuniformity and secondary flow intensity. [ABSTRACT FROM AUTHOR]

The energy loss and resistance effect of traditional local components widely used in HVAC systems in buildings are severe. To improve the significant energy loss effect, a method to reduce resistance and energy loss by inserting guide vanes in a confluent T-junction is proposed through full-scale experiments and numerical simulations, and the flow characteristics and energy loss distribution of the T-junction are analysed through the swirl intensity of the secondary flow and the entropy production principle. The energy loss reduction rates (ELRRs) of T-junctions are compared under different diameter ratios, branch angles, and flow ratios. The results show that the total energy loss coefficient of the T-junction with curved guide vanes is significantly smaller than that of the traditional T-junction. The maximum ELRR is 43.5% when the diameter ratio is 0.8 and the flow ratio is 0.2. The insertion of a guide vane cuts the large vortex into multiple small vortices, thereby weakening the entropy production and swirl intensity of the downstream secondary flow. Under different Reynolds numbers, the effect of the guide vane on reducing the resistance and energy loss of the T-junction is verified by full-scale experiments, and the experimental results are in excellent agreement with the simulation results. This study provides data support and a reference for the standardized and design of low-energy loss T-junctions in HVAC systems for the energy-saving operation of buildings. • A low-energy loss T-junction with a guide vane is investigated by experiments and numerical simulations. • The guide vane can cut the large vortex into multiple vortices with smaller swirl intensities. • Inserting guide vanes at suitable locations in the T-junction reduces entropy production. • T-junctions with guide vanes can reduce the energy loss coefficient by up to 43.5%. [ABSTRACT FROM AUTHOR]

The continuous development of hydropower necessitates the extensive design and construction of hydropower stations. As an underground large space building, it is difficult for the air in the hydropower station to directly exchange with the external environment. Scientifically reasonable air supply modes are indispensable for ensuring a uniform air distribution with low energy consumption. In this study, numerical simulations were carried out to analyse the air distributions and thermal environments under three air supply modes: roof air supply (RAS), sidewall air supply (SAS), and attached air supply (AAS). A set of evaluation indices, namely, the air velocity, air temperature, nonuniformity coefficient, and energy efficiency coefficient, were adopted to assess the ventilation performance of these three modes. Moreover, an orthogonal experiment was conducted to optimize the ventilation performance with four factors (air outlet height, air outlet width, air supply velocity, and heat source intensity) in the AAS mode. The average temperatures among the RAS, SAS, and AAS were 26.1 °C, 26.4 °C, and 26.0 °C, respectively. The results indicated that the attached air supply (AAS) mode is recommended for generator hall applications due to its lower nonuniformity coefficient and higher energy efficiency coefficient. Based on the range analysis and variance analysis, the air outlet height exhibited significant effects on the air distribution and ventilation performance. This research provides design references for the innovative design of air supply systems in large space buildings. • An innovative attached air supply mode was conducted in hydropower stations. • The dimensionless velocity and the temperature distribution of attached air supply mode were acquired. • Air-outlet height had a significant effect on the attached ventilation performance. [ABSTRACT FROM AUTHOR]

A sonodynamic therapy-based therapeutic nanoplatform capable of continuous CO 2 bubbling-enhanced inertial cavitation has been constructed to, induce robust immune responses associated with more infiltrations of activated effector T lymphocytes and alleviated ISM including M2-like macrophage polarizations into M1-like counterparts and anti-tumor cytokine secretions, which synergistically magnify SDT and ICD against primary and distant tumors. • Novel approach (continuous CO2 bubbling-enabled ultrasound-triggered inertial cavitation) for maximally augmenting ROS production. • Deep insights into ROS for enhancing SDT, activating ICD-associated immune responses, mitigating ISM and inhibiting immune escape. • High generality of continuous inertial cavitation as a promising method to guide the rational design of other ROS-based nanoplatforms. Intratumoral immunosuppressive microenvironment (ISM) remains the dominant limitation to disable oncological immunotherapy such as immunogenic cell death (ICD). To resolve the immune escape, a sonodynamic therapy (SDT)-based nanoplatform featuring continuous CO 2 bubbling has been engineered to enforce continuous ultrasound-triggered inertial cavitation (UIC) for augmenting ROS production. Systematic in vitro and in vivo results demonstrate that the continuous UIC expedites massive production of reactive oxygen species (ROS), consequently enabling multiple enhancements of SDT under only one administration. More significantly, the highly-accumulative ROS arising from continuous UIC have been demonstrated to induce robust ICD that is typically represented by more antigen exposure and presentation, augmented DCs maturation and more activated effector CD8+ T cells infiltration in vitro & in vivo. Concurrently, the most ISM alleviation via releasing more pro-inflammatory cytokines and facilitating pro-tumorigenic M2-like macrophage polarization into anti-tumorigenic M1-like counterparts is accompanied, enabling immune escape blockade. Contributed by the significant ISM alleviation and massive ROS production for enhancing SDT and ICD, such SDT-based composite nanoplatforms harvest the most substantially enhanced inhibitory consequences against primary and metastatic tumors, which, thus, provide a profound attribute for T cell-based immunotherapy against tumor. [ABSTRACT FROM AUTHOR]