Article
Thermodynamics
Francesco Fabris, Paolo Artuso, Sergio Marinetti, Silvia Minetto, Antonio Rossetti
Summary: This paper discusses the dynamic characterization of a novel CO2 system in a medium-size refrigerated truck for the refrigerated transport sector. The system utilizes a two-phase ejector and an auxiliary evaporator to improve performance, with the ability to switch between configurations during operation to maximize COP or refrigerating capacity. Simulation results show the system's performance during a delivery mission, as well as the potential counterproductivity of using both evaporators simultaneously.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Min-Qiang Zeng, Qiu-Yun Zheng, Xue-Lai Zhang, Fan-Yang Mo, Xin-Rong Zhang
Summary: A multi-target temperature ejector-expansion subcooler vapor-injection refrigeration cycle is proposed to improve the performance of natural fluid CO2 refrigeration cycles. A thermodynamics model is established to simulate the new cycle, and the results show that the new cycle has higher COP and exergy efficiency compared to traditional cycles, with more significant performance improvement under low temperature and high ambient temperature conditions.
Article
Thermodynamics
Ayan Sengupta, Mani Sankar Dasgupta
Summary: This paper presents a thermodynamic analysis of a novel dual-ejector transcritical CO2 refrigeration system for applications in warm climate. The proposed system is compared with various previously published CO2 systems and a multi-stage ejector system. The investigation reveals the significant effect of ambient temperature and gas-cooler pressure on the system performance. The COP of the proposed system is found to be significantly higher than the comparison systems. Exergy analysis is also carried out to understand the system response to different parameters. A detailed analysis of the ejector performance is presented, highlighting the importance of mixing chamber diameter.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2023)
Article
Thermodynamics
Jiarui Liu, Ye Liu, Jianlin Yu
Summary: This paper proposes a modified dual-ejector and dual-evaporator transcritical CO2 refrigeration cycle for supermarket application, which significantly reduces the compressor pressure ratio and improves energy efficiency and exergy efficiency. The performance comparison between the two cycles demonstrates the energy-saving potential of the modified cycle in supermarket refrigeration.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2021)
Article
Thermodynamics
Xiang Qin, Yuxiang Zhang, Dingbiao Wang, Jiaheng Chen
Summary: The paper proposes a novel compression/ ejection transcritical CO2 heat pump system that improves the performance of the compressor and utilizes multiple heat sources. Numerical analysis verifies the feasibility of the system and shows that it has high cooling efficiency and economic benefits under specific conditions.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Thermodynamics
Yafei Li, Jianqiang Deng
Summary: This study simulated flashing flow in the transcritical CO2 ejector using a novel non-equilibrium evaporation-cavitation CFD model, which was verified through experiments. The results revealed that mass transfer rates of cavitation and evaporation increased with nozzle diverging angles, while the dimensions of the mixing chamber and diffuser also affected the ejector performance.
Article
Energy & Fuels
Xi Liu, Kaihong Yu, Xinchen Wan, Minfeng Zheng, Xuelai Li
Summary: This paper evaluates the exergetic performance of the EJE + TES system through exergy analysis, demonstrating that increasing the efficiency of different components can reduce exergy destruction. The study suggests that improving the compressor should be a top priority for enhancing system performance.
Article
Thermodynamics
Tao Bai, Rongxuan Shi, Jianlin Yu
Summary: This paper proposes a modified parallel compression transcritical CO2 refrigeration cycle with an ejector and a sub-cooler to improve the cycle performance. The effects of different parameters on the cycle performance are analyzed, and the optimal values are obtained using particle swarm optimization. The results show significant improvements in COP and volumetric refrigeration capacity compared to the conventional cycle, with the utilization of ejector and sub-cooler playing important roles.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)
Article
Thermodynamics
Yuxiang Zhang, Xinli Wei, Xiang Qin
Summary: This paper experimentally investigates a novel compression/ejection transcritical CO2 heat pump system, showing that it outperforms the conventional system in heating capacity, outlet water temperature, and energy efficiency.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Thermodynamics
Riley B. Barta, Davide Ziviani, Eckhard A. Groll
Summary: The HVAC&R industry is in need of low-GWP solutions as the adverse effects of global warming become more apparent; alternative working fluids and high-efficiency systems are ways to mitigate negative environmental impacts; research is focused on investigating various CO2 cycles and a novel test stand has been developed for experimental comparison.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2021)
Article
Automation & Control Systems
Abdallah Alansaari, Igor Boiko, Sean Swei
Summary: A novel variable structure controller for satellite attitude control is investigated, which avoids the chattering problem by not leading to a sliding mode, making it practical for implementation. The controller formulation and stability analysis for a second order system are presented. The system with this nonlinear controller is homogeneous, resulting in similar responses at large and small deviations from equilibrium. A procedure for tuning homogeneous controllers for all initial conditions is proposed. Through numerical optimization using a detailed model of satellite attitude dynamics, actuator dynamics, and system delays, the proposed controller is found to have better transients and lower energy consumption compared to a conventional PID controller.
JOURNAL OF THE FRANKLIN INSTITUTE-ENGINEERING AND APPLIED MATHEMATICS
(2023)
Article
Chemistry, Physical
Gautam, Satyabrata Sahoo
Summary: A detailed evaluation of modified transcritical CO2 adsorption refrigeration systems integrated with an ejector and thermoelectric sub-cooler was conducted using simplified thermodynamic models. It was found that the use of an ejector and thermoelectric sub-cooler can enhance system performance.
JOURNAL OF SUPERCRITICAL FLUIDS
(2022)
Article
Energy & Fuels
Vinay Kumar Yadav, Jahar Sarkar
Summary: The study proposes and compares various ejector refrigeration-based dedicated subcooling methods in the CO2 refrigeration system. Cycle 4 is found to have the highest performance and efficiency at optimum operating conditions, but with operational restrictions, while cycles without an internal heat exchanger have less environmental pollution. In terms of cost-effectiveness, Cycle 4 is the best choice.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2021)
Article
Thermodynamics
Marco Azzolin, Gianluca Cattelan, Simone Dugaria, Silvia Minetto, Livio Calabrese, Davide Del Col
Summary: In Europe, CO2 transcritical booster systems have become a trusted solution in commercial refrigeration, but face challenges in warm climates. Providing all thermal needs with one single unit is an interesting possibility. System performance is greatly influenced by high gas cooler discharge temperature in summer and heat recovery control strategy. To improve system performance in warm climates, simulations have shown that vapor ejectors and evaporative gas coolers can reduce electrical power consumption, while overfed evaporators increase performance independently from external temperature. Adopting overfed evaporators, ejectors, and evaporative gas coolers can significantly increase the COP.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Qiang Zhang, Zewei Luo, Yongjie Zhao, Suniaikin Pavel
Summary: The novel combined system consisting of transcritical CO2 Rankine cycle and ejector refrigeration cycle can be adjusted for heating, cooling, and power according to shipboard demands. Performance analysis and comparison show that this system is more efficient in specific operation modes.
ENERGY CONVERSION AND MANAGEMENT
(2021)
Review
Thermodynamics
Shuling Guo, Ankuo Zhang
Summary: Low-temperature biopreservation is commonly used for medication storage to prolong their shelf life. However, cryo-injury can occur during cryopreservation, making it crucial to find a way to achieve long-term biopreservation without causing harm. The optimal storage temperature for different biomaterials should be investigated to improve storage efficiency. This review discusses the mechanisms of cryo-injury and biopreservation, as well as the reasons for storing biological tissues at various temperature zones. It provides valuable insights for the development of biostorage technology.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
M. Mohsin Tanveer, Craig R. Bradshaw, Joe Orosz, Greg Kemp
Summary: This study investigates the optimal geometric parameters for a spool compressor using simulation models, and the results indicate that a eccentricity ratio of 0.75 and L/D ratios between 1-1.5 can maximize the volumetric and isentropic efficiencies.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
Kongkuai Ying, Zhenhua Jiang, Wenting Wu, Jinjian Chu, Shaoshuai Liu, Yinong Wu
Summary: The Stirling/pulse tube cryocooler (SPC) is a highly efficient and long-lasting cryocooler for space applications. It has the ability to adjust the inter-stage refrigeration capacity dynamically by controlling the Stirling displacer in the first stage. This paper proposes an SPC with a second-stage active phase shifter (APS) that can control the phase difference at the second-stage hot end in real time. The experimental results show that the SPC with the APS can provide refrigeration capacity at different temperatures, with a minimum temperature of 13.5K.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
Ligeng Li, Hua Tian, Kai Liu, Yibo Wu, Xuan Wang, Xingyu Liang, Gequn Shu
Summary: This study focuses on improving the performance of carbon dioxide refrigeration systems by introducing a multi-ejector design with three controllable ejectors. Experimental analysis shows that the system's performance can be significantly improved by adopting an optimum pressure control strategy under different operating conditions.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
Joseph Al Khoury, Rabih Al Haddad, Ghiwa Shakrina, Christelle Bou Malham, Haytham Sayah, Chakib Bouallou, Maroun Nemer
Summary: This study investigates two implementation methods for calculating refrigerant thermodynamic properties and compares their performance. The results show that the implicit fitting method significantly speeds up simulation time and offers greater flexibility for modeling complex energy systems.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
Mariella Mateo-Villanueva, Rodolfo Echarri
Summary: This article details three models of different complexity levels for predicting the cold production of a solar cooling device and compares their advantages and disadvantages. The results show that the transient model underestimates the cold generation, while the equilibrium model and universal model overestimate it. The transient model is a useful tool for analyzing the impact of different variables in a solar adsorption refrigeration system, while the simpler models can be used for preliminary design and feasibility studies.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)
Article
Thermodynamics
Amin M. Elsafi, Majid Bahrami
Summary: The novel spherical micro-absorbers offer high sorption capacity and surface-to-volume ratios, solving issues such as solution carryover and corrosion associated with conventional absorbers.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2024)