Article
Thermodynamics
Giorgio Besagni, Nicolo Cristiani, Lorenzo Croci, Gael Raymond Guedon, Fabio Inzoli
Summary: This paper evaluates the performance of a CFD model for single-phase supersonic ejectors through comprehensive validation, considering a wide range of ejector designs, boundary conditions, and working fluids. Different modeling approaches, including mesh criteria, geometrical modeling, solvers, and turbulence models, are screened. The study shows that k-omega SST has the best agreement with experimental measurements, with an average entrainment ratio error of 14% and a maximum of 20% under on-design operating mode.
APPLIED THERMAL ENGINEERING
(2021)
Article
Thermodynamics
Muhammad Haider, Stefan Elbel
Summary: Recent studies have expanded the operational envelope of ejector by utilizing both pressure recovery and liquid recirculation mechanisms. A new ejector efficiency has been introduced and trends of existing and new ejector efficiencies are studied. A single curve, termed as ejector performance map, has been developed to represent the ejector performance with high prediction accuracy.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2021)
Article
Energy & Fuels
Kittiwoot Sutthivirode, Tongchana Thongtip
Summary: In this paper, the performance enhancement of a two-phase ejector installed in an ejector-expansion refrigeration system (EERS) is experimentally investigated and compared with a conventional vapour-compression refrigeration system (VCRS). The results show that the EERS performs better than the VCRS when the expansion pressure ratio is sufficiently large. Decreasing the cooling temperature can increase the system's performance and prolong the compressor's lifespan.
Article
Energy & Fuels
Kittiwoot Sutthivirode, Tongchana Thongtip
Summary: This paper experimentally investigates the performance enhancement of a two-phase ejector installed in a refrigeration system, comparing it with a conventional vapour-compression refrigeration system. Results show that the ejector-expansion refrigeration system (EERS) outperforms the vapor-compression refrigeration system (VCRS) when the expansion pressure ratio is sufficiently large, leading to improved system COP and compressor longevity.
Article
Thermodynamics
Yu Lu, Tao Bai, Jianlin Yu
Summary: In this study, the effect of geometric parameters on the performance of a two-phase ejector using R290 as the working fluid was experimentally investigated. Key geometric parameters including nozzle throat diameter, nozzle exit position, diameter and length of the mixing section were discussed. The experimental results showed that the pressure lift ratio of the ejector was sensitive to nozzle throat diameter and nozzle exit position. Empirical correlations for the efficiencies of R290 two-phase ejector components were also summarized.
INTERNATIONAL JOURNAL OF REFRIGERATION
(2023)
Article
Energy & Fuels
Knut Emil Ringstad, Krzysztof Banasiak, Asmund Ervik, Armin Hafner
Summary: This study proposes a novel nozzle design concept to enhance the performance of CO2 two-phase ejectors. Experimental tests and simulations were conducted to validate the model and investigate the effects of different ejector inlet designs. The results show that the swirl-bypass inlet can reduce the entrainment of the ejector and the axial position of the inlet plays a crucial role in performance. Several design improvements are proposed for future designs.
Article
Energy & Fuels
Wichean Singmai, Kasemsil Onthong, Tongchana Thongtip
Summary: This paper proposes an experimental study on the performance improvement of the ejector-expansion heat pump (EEHP), which is equipped with a two-phase ejector. The system performance of the EEHP is compared with that of a vapor-compression heat pump (VCHP), and the potential for improvement is determined and discussed. The results show that the EEHP always outperforms the VCHP in terms of heating rate and COP(HP), with an increase in COPHP by 5.7-11.6% depending on the working conditions. It is also observed that the EEHP exhibits lower compressor discharge temperature and pressure ratio, indicating better working characteristics and longer compressor lifetime compared to the VCHP.
Article
Thermodynamics
Michal Palacz, Jakub Bodys, Michal Haida, Jacek Smolka, Andrzej J. Nowak
Summary: The dynamic development of R744 refrigeration cycles in recent years has led to increasing interest in optimizing the performance of R744 ejectors. While there have been numerous computational studies on ejector performance, experimental studies on two-phase R744 flow are limited. This study focuses on visualizing the two-phase flow and mixing inside an R744 ejector designed for an industrial-scale refrigeration system. Experimental results show the variation of expansion angle and mixing angle under different operating conditions, providing insights for ejector design and optimization.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Pengtao Wang, Hongbin Ma, Jeremy Spitzenberger, Ahmad Abu-Heiba, Kashif Nawaz
Summary: A gas-fired air-to-water ejector heat pump for domestic hot water production was proposed and analyzed thermodynamically in this study. The use of binary fluids and active control of backpressure showed improvements in COP. The first-stage ejector plays a dominant role in system performance, and optimizing various parameters can enhance the EHP performance.
ENERGY CONVERSION AND MANAGEMENT
(2021)
Article
Thermodynamics
K. Ameur, Z. Aidoun
Summary: By simulating a CO2 transcritical heat pump cycle integrating a two-phase ejector, adjustments can be made to the ejector geometry based on operating conditions for improved overall efficiency.
ENERGY CONVERSION AND MANAGEMENT
(2021)
Article
Chemistry, Analytical
Matthew Mullen, Christopher Katilie, Greg E. Collins, Braden C. Giordano
Summary: The study investigated the transport efficiency of explosive vapors through tubing materials, finding that RDX vapors were significantly affected by tubing materials and dimensions, while 2,4-DNT and TNT vapors were less affected.
Article
Energy & Fuels
Yongseok Jeon, Dongchan Lee, Honghyun Cho
Summary: This study investigates the influence of the motive nozzle exit position (NXP) on the performance of a dual evaporator ejector cycle (DEEC) in a household refrigeration system. An artificial neural network (ANN) model is used to analyze the pressure lifting ratio and coefficient of performance (COP) of the DEEC under various operating and ejector geometry conditions. The optimal NXP is proposed to achieve maximum performance in the DEEC, resulting in a COP that is 2.3% and 8.4% higher than those of the conventional NXP and the baseline cycle, respectively.
Article
Physics, Multidisciplinary
Seher Karakuzu, Andy Tanjaroon Ly, Peizhi Mai, James Neuhaus, Thomas A. Maier, Steven Johnston
Summary: This study investigates stripe orders in the doped single-band Hubbard-Holstein model and finds that the lattice couples more strongly with the charge component of the stripes, leading to an enhancement or suppression of stripe correlations depending on model parameters. This has implications for our understanding of high-Tc cuprates.
COMMUNICATIONS PHYSICS
(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
Thermodynamics
Jia Yan, Liuyi Zeng, Yuetong Shu
Summary: This study investigated the effects of LVF on the performance of a two-stage ejector in a multi-evaporator refrigeration system using CFD simulation. The results showed that increasing the LVF of one inlet significantly increased the two-phase mass flow rate due to the increase in mixture density. Furthermore, improving the LVF of a two-phase inlet enhances the performance of both stages, while increasing the LVF of two inlets with the same proportion provides the best performance. Lastly, increasing the LVF of three inlets improves the efficiency of both stages.
APPLIED THERMAL ENGINEERING
(2023)
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)