Search

At present, there is no method for predicting oil retention applicable to various working fluids. Oil retention characteristics in compressor suction lines are studied and a general method for predicting oil retention is established. The database of oil retention in suction lines is established according to experimental values in the public literature. After analyzing the influencing factors, a correlation of the volume ratio of oil retention in the database is fitted. According to the correlation and the state of working fluid at the inlet of suction line, the amount of oil retention can be predicted. In addition, oil retention of R32/PVE VG68 in suction lines is tested. A comparison of the experimental values and the prediction values indicate that for the flow of R32/PVE VG68 in suction lines, the calculation method can accurately show the variation trend of oil retention with various factors, and can accurately predict the amount of oil retention under different conditions.

The objective of this study is to establish generalized correlations for R32 flow boiling heat transfer and frictional pressure drop in channels with wide ranges of geometric and flow parameters. In this paper, two consolidated databases for heat transfer and frictional pressure drop were amassed from open literature, which involved R32 as working fluid. The heat transfer database consisted of 1 489 data points from 8 sources, with hydraulic diameters of 1—6.3 mm, while the pressure drop database included 496 data points from 8 sources, which covered hydraulic diameters of 0.643—6 mm. A new heat transfer coefficient correlation and a frictional pressure drop correlation were developed based on the prediction technique of dimensionless parameter analysis considering the governing force effect. Moreover, the existing correlations were also introduced to perform assessment. The validation results show that the existing correlations have poor results of mean absolute errors (MAE) and significantly high maximum absolute errors (MAX), but the new heat transfer coefficient correlation provides a superior prediction accuracy with a MAE of 14.59% and 90.85% of data within ±30% error bands. In addition, the new pressure drop correlation exhibits the best performance, which yields a MAE of 17.86%. The two new correlations have a broad application range and satisfactory prediction accuracy, which are applicable to analyze the heat transfer and pressure drop performance of heat exchangers with refrigerant R32.

The construction of 3D geological models based on geological maps is a subject worthy of study. The construction of geological interfaces is the key process of 3D geological modeling. It is hard to build the bottom interfaces of quaternary strata only using boundaries in large-scale geological maps. Moreover, it is impossible to construct bedrock geological interfaces through sparse occurrence data in large-scale geological maps. To address the above-mentioned two difficulties, we integrated two key algorithms into a new 3D modeling workflow. The buffer algorithm was used to construct virtual thickness contours of quaternary strata. The Inverse Distance Weighted (IDW) algorithm was applied to occurrence interpolation. Using a regional geological map of a city in southern China, the effectiveness of our workflow was verified. The complex spatial geometry of quaternary bottom interfaces was described in detail through boundaries buffer. The extension trends of bedrock geological interfaces were reasonably constraint by occurrence interpolation. The 3D geological model constructed by our workflow accords with the semantic relationship of tectonics. Through the model, the complex spatial structure of urban shallow strata can be displayed stereoscopically. It can provide auxiliary basis for decision-making of urban underground engineering.

Amino acid surfactants (AASs) based on environmentally friendly biomasses have the characteristics of renewable, easy biodegradation, antibacterial and low toxicity, and have been widely used in daily chemicals, pharmaceuticals, and other fields. This study concerned the use of octanal and amino acids as raw materials. In addition, seven types of amino acid‐based surfactants, through Collins reagents, Wittig‐Hornor reaction, and aza‐Micheal addition reaction, and amino acid head groups were connected with the alkyl chain by the CN bond. The structures were confirmed by infrared spectroscopy (FT‐IR) and nuclear magnetic resonance spectroscopy (1HNMR). Its surface activity and adsorption properties are evaluated. The physical properties of amino acid‐based surfactants were tested by surface tension and dynamic contact angle. The results demonstrated that histidine‐based amino acid surfactant (C8His) has the lowest critical micelle concentration (CMC) and surface tension at CMC (γCMC), 0.39 mmol L−1 and 28.79 mN L−1, respectively. Amino acid residues contribute to reducing the critical micelle concentration of surfactant. The interfacial adsorption of glycine‐based amino acid surfactant (C8Gly) significantly improved with the increase in temperature, so the surface tension decreased significantly. In addition, sodium chloride could effectively enhance the interfacial adsorption, and the gas–liquid interfacial tension and contact angle of AASs decrease. [ABSTRACT FROM AUTHOR]