No abstract

Owing to the airflow field within airtight machines, oil mist particles escape with the airflow from the machine shell gaps and are emitted externally to the post-environmental area, causing air pollution and threatening workers’ health. The existing local exhaust system is ineffective in capturing oil mist particles. This study proposes a gas–oil separation device that can “in-situ control” the oil mist particles in situ and weaken their outgoing emission and that uses numerical simulations to compare and analyse the emission characteristics of oil mist particles, before and after the addition of the separation device at different exhaust air volumes and particle emission speeds, and to design the structural parameters of the device to improve the separation efficiency of oil mist particles. The structural parameters of the proposed device are designed to improve the separation efficiency of oil mist particles. Studies have shown that for every 200 m3/h increase in exhaust air volume, the capture efficiency increases by around 3%, and the particle concentration at the gap in the machine loading door decreases from 9.4 × 10−7 kg/m3 to 7.7 × 10−7 kg/m3. The overall escape rate of oil mist particles is in the range of 10–13% after the addition of a pressure relief device. Numerical simulations are performed to analyse the effects of inlet airflow velocity, folding plate spacing, and folding plate angle on the separation efficiency of oil mist particles. Results show that an increase in the inlet velocity of the airflow increases the particle separation efficiency. The most suitable structural parameters for the separation device and the machine are as follows: 60° angle of the folding plate and 30 mm distance between plates, where the separation efficiency is above 80%, and the average separation efficiency is about 86%. The results of this study can be used as a reference for the study of the emission of oil mist particles from enclosed mechanical cutting machines.

R290 as a refrigerant has significant advantages of low cost, high energy efficiency, and more environmental protection, but the leakage will form a hazardous area inside the indoor unit and the room where the concentration exceeds the lower flammable limit of propane. In this paper, we focus on the gas-liquid two-phase leakage of R-290 indoor air conditioner at the evaporator, and use Computational Fluid Dynamics (CFD) method to numerically simulate the refrigerant leakage dispersion at three air conditioning supply volumes of 178.2 m3/h, 342 m3/h and 576 m3/h, and analyze the indoor velocity distribution and concentration distribution. The results show that the trajectory of the refrigerant jet changes under different air supply volumes, and the simulation results show that the spatial extent of the combustion explosion limit is mainly distributed at the air conditioning leak and the air conditioning outlet. Vortices were formed in the local area above the propane leakage port and then spread.

In industrial sites, the movement and contact behaviors of workers are random, but their frequency and statistical characteristics can be determined. Particularly in machining workshops, metalworking fluids (MWFs) cause liquid oil contamination on the processed workpieces, and the contamination spreads to the entire workshop given the random contact of workers or the handling of workpieces. This study proposes a contact transmission model based on the Markov chain to quantify oil contamination transfer. First, the transfer efficiency between the glove and the workpiece, which is regarded as a key model parameter in this research, was determined through experiments. The model was used to characterize and predict the spread of oil contamination across different regions, including production and assembly areas. Specifically, the oil contamination concentrations on workbench surfaces in seven locations of a machining workshop in Shanghai GKN HUAYU Driveline Systems Co., Ltd. (SDS) were measured on-site. Findings showed that the model could feasibly depict the transfer process of oil contamination across different surfaces. Then, the variation law of oil contamination concentration on the workbench surfaces over time was analyzed, the oil contamination distribution map of the entire workshop plane was drawn, and the effectiveness of two cleaning measures to reduce oil contamination concentrations was compared. The proposed contact transmission model offers a basis for identifying highly polluted surfaces in machining workshops and controlling the spread of liquid oil contamination.

Evaluation on the carbon emissions of large public buildings and carbon reduction measures are very important to help reach carbon peak demand and carbon neutral. The purpose of this study is to conduct energy audits and energy-saving assessments on large public and commercial buildings to find out the impact of various behavioural activities related to buildings on carbon emissions and energy consumption, and to explore the carbon reduction potential of buildings. In China, the energy structure based on fossil fuels will not change in a short term, and energy consumption will inevitably increase with economic development; however, the energy efficiency is the main factor that affects the building carbon emissions. And changing energy efficiency will reduce emissions by 9.29%, while improving the energy structure will reduce emissions by only 0.46%; it is the key work to slow down greenhouse gas emissions in buildings that is reducing power consumption of electrical equipment, especially the air-conditioning system, which can result in 49.72% energy saving after reforming.