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15 results on '"Ji, Hongzeng"'

8. Review of Recent Advances in Transcritical CO 2 Heat Pump and Refrigeration Cycles and Their Development in the Vehicle Field.

Author

Ji, Hongzeng, Pei, Jinchen, Cai, Jingyang, Ding, Chen, Guo, Fen, and Wang, Yichun

Subjects
*HEAT pumps, *CARBON dioxide, *GLOBAL warming, *CARBON emissions
Abstract

Refrigerant substitution is an urgent need in the context of reducing carbon emissions and slowing global warming. CO2 is now being proposed as a promising solution based on its excellent properties and system performance, especially in low-temperature environments. This paper presents an overview of recent advances in system configuration and operation characteristics to improve the performance of transcritical CO2 heat pump and refrigeration systems. The paper first introduces the basic research background, system cycle, and thermodynamic characteristics. Secondly, CO2 cycle improvements with single modifications and modification combinations are reviewed. Then, some important operation characteristics and control methods are discussed. Additionally, the paper provides a detailed description of the development of transcritical CO2 heat pump and refrigeration systems in the vehicle field. At the end of this review, conclusions and opportunities for future work in this field are presented. [ABSTRACT FROM AUTHOR]

Published
2023
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11. Research on the air-side thermal hydraulic performance of louvered fin and flat tube heat exchangers under low-pressure environment

Author

Xinglei He, Revaz Kavtaradze, Rui Wan, Wang Yichun, and Ji Hongzeng

Subjects
Materials science, 020209 energy, Mechanical engineering, 02 engineering and technology, Thermal hydraulics, 020303 mechanical engineering & transports, 0203 mechanical engineering, Control and Systems Engineering, Heat exchanger, 0202 electrical engineering, electronic engineering, information engineering, Water cooling, Electrical and Electronic Engineering, Louver, Instrumentation, Overheating (electricity)
Abstract

In order to solve the problem of overheating of the engine and cooling system of the vehicle in the plateau low-pressure environment, it is necessary to study air-side thermal-hydraulic performance...

Published
2019

14. Research on the air-side thermal hydraulic performance of louvered fin and flat tube heat exchangers under low-pressure environment.

Author

Wan, Rui, Wang, Yichun, Kavtaradze, Revaz, Ji, Hongzeng, and He, Xinglei

Subjects
HEAT exchangers, HEAT transfer coefficient, WIND tunnel testing, PRESSURE gages, HEAT transfer, TUBES
Abstract

In order to solve the problem of overheating of the engine and cooling system of the vehicle in the plateau low-pressure environment, it is necessary to study air-side thermal-hydraulic performance of the vehicle cooling system heat exchanger under low-pressure environment. In this paper, the experimental study on the louvered fin and flat tube heat exchanger of the vehicle is carried out on the low-pressure wind tunnel test bench. The results show that at a gauge pressure of −44 kPa, the air-side convective heat transfer coefficient is reduced by 33.5%~23.3% compared with 0 kPa; the Colburn j-factor is increased by 36.8% on average; the f factor is increased by 51.2% on average. Based on this, numerical simulations are carried out to study the heat transfer and flow characteristics of louvered fins with different structural parameters under low-pressure environment. The empirical correlations of Colburn j-factor and Friction factor f are fitted by multiple linear regression. In the range of gauge pressure from 0 kPa to −44 kPa, the average deviation of the correlation calculation result of Colburn j-factor is 3.4%, and the average deviation of the correlation calculation result of f factor is 5.5%. The research results can provide a basis for the design of louvered fin heat exchangers utilized in the plateau environment. [ABSTRACT FROM AUTHOR]

Published
2020
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15. Dual Dynamic Cross-Linked Epoxy Vitrimers Used for Strong, Detachable, and Reworkable Adhesives

Author

Huang, Xiaoyu, Ding, Chen, Wang, Yichun, Zhang, Songmao, Duan, Xiuhui, and Ji, Hongzeng

Abstract

Novel reprocessable thermosetting adhesives (RTAs), which combine high adhesive strength, reusability, disassembly, and recyclability features, have attracted increasing attention. However, developing RTAs with a rapidly adhesive rate while ensuring high adhesive strength and self-healing ability is still a significant challenge. Here, we prepared a novel vitrimer called DAx–DTSAy, which can be used as an RTA. First, by adjusting the ratio of rigid and flexible segments, maximum tensile strength reached 35.92 MPa. Second, the combined effect of dynamic hydroxyl ester bonds and dynamic disulfide bonds resulted in a rapid stress relaxation behavior, with a complete relaxation time 13.6 times shorter than a vitrimer only cross-linked with hydroxy ester bonds. This feature endowed its good self-healing and reprocessing capabilities. After self-healing at 180 °C, the maximum healing rate of mechanical properties was 91.8%. After three reprocesses, the maximum recovery rate of tensile strength was 120.2%. Furthermore, the combination of rigid and flexible segments and the synergistic effect of dual dynamic covalent bonds made DAx–DTSAycapable of use as a high-performance RTA. The lap shear strength of a DAx–DTSAyfilm on stainless steel reached 18.18 MPa after 15 min, with a recovery rate of 91.9% after 5 rebonding cycles. Additionally, DAx–DTSAycan be disassembled in chemical agents and exhibited better insulation properties compared to traditional epoxy resins. DAx–DTSAycan be employed as a novel high-performance adhesive in applications such as electronic devices and transportation, contributing to the development of thermosetting adhesives toward recyclability and sustainability.

Published
2024
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