Pub Date : 2024-09-24DOI: 10.1016/j.ijrefrig.2024.09.020
Antoine Metsue , Hakim Nesreddine , Yann Bartosiewicz , Sébastien Poncet
Optimal operation and design of ejectors are the subject of recent concerns, especially for the enhancement of refrigeration and heat pump cycles based on natural refrigerants like carbon dioxide. In this study, a thermodynamic analysis of an ejector-based refrigeration cycle is performed to determine both what operating pressures lead to the highest physically possible performance depending on the ambient conditions, and what are the main dimensions of the ejector leading to the best performance at a given ambient temperature. A state-of-the-art thermodynamic model for the prediction of the ejector performance is for the first time utilized to generate reliable operation and performance maps of the ejector cycle. Most notably, it is found that the optimal coefficient of performance is not necessarily found when the ejector operates at critical conditions but mostly when the device is under off-design regime, depending on the ejector internal efficiency and the hot side temperature. In addition, the analysis reveals that the performance of the cycle is not highly sensitive to the throat area ratio of the ejector given that the latter lies within an acceptable range. Those findings contribute to getting a better understanding of how the cycle benefits from the ejector and define design and control strategies for the cycle.
{"title":"Theoretical analysis of the optimal ejector operation and design within an ejector-based refrigeration system","authors":"Antoine Metsue , Hakim Nesreddine , Yann Bartosiewicz , Sébastien Poncet","doi":"10.1016/j.ijrefrig.2024.09.020","DOIUrl":"10.1016/j.ijrefrig.2024.09.020","url":null,"abstract":"<div><div>Optimal operation and design of ejectors are the subject of recent concerns, especially for the enhancement of refrigeration and heat pump cycles based on natural refrigerants like carbon dioxide. In this study, a thermodynamic analysis of an ejector-based refrigeration cycle is performed to determine both what operating pressures lead to the highest physically possible performance depending on the ambient conditions, and what are the main dimensions of the ejector leading to the best performance at a given ambient temperature. A state-of-the-art thermodynamic model for the prediction of the ejector performance is for the first time utilized to generate reliable operation and performance maps of the ejector cycle. Most notably, it is found that the optimal coefficient of performance is not necessarily found when the ejector operates at critical conditions but mostly when the device is under off-design regime, depending on the ejector internal efficiency and the hot side temperature. In addition, the analysis reveals that the performance of the cycle is not highly sensitive to the throat area ratio of the ejector given that the latter lies within an acceptable range. Those findings contribute to getting a better understanding of how the cycle benefits from the ejector and define design and control strategies for the cycle.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 334-344"},"PeriodicalIF":3.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-24DOI: 10.1016/j.ijrefrig.2024.09.023
Lanbo Lai , Xiaolin Wang , Gholamreza Kefayati , Eric Hu , Kim Choon Ng
Solid desiccant-assisted dew-point indirect evaporative cooling (SD-DPIEC) systems have gained considerable attention as a potential eco-friendly alternative to vapour-compression cooling systems in building cooling applications. However, one major drawback of these systems is their substantial water consumption during evaporative cooling. To tackle this issue, this study aims to improve the cooling efficiency and water utilisation of an SD-DPIEC system using response surface methodology (RSM). This research focuses on optimising four key parameters: supply air temperature, humidity ratio, water consumption rate and coefficient of performance (COP). The independent variables encompass the ambient temperature, relative humidity, regeneration temperature, and recirculation air ratio. Employing a multi-objective optimisation approach via the desirability function, the optimised SD-DPIEC system is subsequently tested in two prevalent weather patterns in Australia. The results demonstrated that the regression models derived from RSM exhibited commendable predictive capability, with the determination coefficient and Adequate Precision exceeding 0.97 and 40.46, respectively. The outcomes revealed that the system attained its optimal performance with a supply air temperature of 20.36 °C, humidity ratio of 12.56 g kg-1, a water consumption rate of 3.11 kg/hr, and COP of 2.03 under the ambient temperature of 33.79 °C, relative humidity of 68.48 %, regeneration temperature of 51.78 °C, and recirculation air ratio of 60 %. Based on the optimisation results, a case study was undertaken to evaluate the system's applicability in representative Australian climates. The results demonstrated that the system could uphold air conditions with the supply air temperature below 19 °C and humidity ratio below 11.51 g kg-1 under the studied Australian climates.
{"title":"Optimisation of cooling performance and water consumption of a solid desiccant-assisted indirect evaporative cooling system using response surface methodology","authors":"Lanbo Lai , Xiaolin Wang , Gholamreza Kefayati , Eric Hu , Kim Choon Ng","doi":"10.1016/j.ijrefrig.2024.09.023","DOIUrl":"10.1016/j.ijrefrig.2024.09.023","url":null,"abstract":"<div><div>Solid desiccant-assisted dew-point indirect evaporative cooling (SD-DPIEC) systems have gained considerable attention as a potential eco-friendly alternative to vapour-compression cooling systems in building cooling applications. However, one major drawback of these systems is their substantial water consumption during evaporative cooling. To tackle this issue, this study aims to improve the cooling efficiency and water utilisation of an SD-DPIEC system using response surface methodology (RSM). This research focuses on optimising four key parameters: supply air temperature, humidity ratio, water consumption rate and coefficient of performance (COP). The independent variables encompass the ambient temperature, relative humidity, regeneration temperature, and recirculation air ratio. Employing a multi-objective optimisation approach via the desirability function, the optimised SD-DPIEC system is subsequently tested in two prevalent weather patterns in Australia. The results demonstrated that the regression models derived from RSM exhibited commendable predictive capability, with the determination coefficient <span><math><msup><mrow><mi>R</mi></mrow><mn>2</mn></msup></math></span> and Adequate Precision exceeding 0.97 and 40.46, respectively. The outcomes revealed that the system attained its optimal performance with a supply air temperature of 20.36 °C, humidity ratio of 12.56 g kg<sup>-1</sup>, a water consumption rate of 3.11 kg/hr, and COP of 2.03 under the ambient temperature of 33.79 °C, relative humidity of 68.48 %, regeneration temperature of 51.78 °C, and recirculation air ratio of 60 %. Based on the optimisation results, a case study was undertaken to evaluate the system's applicability in representative Australian climates. The results demonstrated that the system could uphold air conditions with the supply air temperature below 19 °C and humidity ratio below 11.51 g kg<sup>-1</sup> under the studied Australian climates.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 376-388"},"PeriodicalIF":3.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-23DOI: 10.1016/j.ijrefrig.2024.09.021
Atif Muzaffar , Ahmad Abbas , Lorenzo Cremaschi , Zahid Ayub
In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (R/do ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m−2 s−1, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and R/do ratio of the bend.
Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.
在制冷和空调系统的蒸发器和冷凝器中，各种直管通过 U 形弯管连接在一起。由于流动干扰和离心效应，这些 U 形弯管会产生较高的压降。准确预测这些弯管中的压降对于可靠的设计和运行至关重要。本研究调查了水平 U 形弯管中氨水在各种实验条件下的两相流压降。使用了三根公称外径在 22.2、15.9 和 9.5 毫米之间的管道，每根管道都有三个弯曲半径（R/do 比），水平配置的弯曲半径在 1.2 和 2.5 之间。试验在 +10 和 -15 °C 饱和温度下进行，质量通量在 10 和 50 kg m-2 s-1 之间变化，蒸汽质量在 0.1 和 0.9 之间变化。与小管子相比，大管子的压降随着质量通量的增加和弯曲率的减小而增大，而小管子的绝对值更高，在两个饱和温度下的整个蒸汽质量范围内的性能更稳定。在高饱和温度和高质量通量下，管子直径的影响较小，而弯曲曲率比则主要影响大直径管子的压降性能。只有当蒸汽质量低于 0.5 时，文献中的一种相关性才能很好地预测数据。对于更宽的质量范围，文献中的现有模型并不适合预测氨 U 形弯管的压降。
{"title":"Experimental study of two-phase pressure-drop in horizontal return bends with ammonia","authors":"Atif Muzaffar , Ahmad Abbas , Lorenzo Cremaschi , Zahid Ayub","doi":"10.1016/j.ijrefrig.2024.09.021","DOIUrl":"10.1016/j.ijrefrig.2024.09.021","url":null,"abstract":"<div><div>In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (<em>R/d<sub>o</sub></em> ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m<sup>−2</sup> s<sup>−1</sup>, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and <em>R/d<sub>o</sub></em> ratio of the bend.</div><div>Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 593-606"},"PeriodicalIF":3.5,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-20DOI: 10.1016/j.ijrefrig.2024.09.010
Jiacheng Ma , Donghun Kim , James E. Braun
Development and calibration of first-principles dynamic models of vapor compression cycles (VCCs) is of critical importance for applications that include control design and fault detection and diagnostics. Nevertheless, the inherent complexity of models that are represented by large systems of differential–algebraic equations leads to significant challenges for model calibration processes that utilize classical gradient-based methods. Bayesian optimization (BO) is a sample-efficient and gradient-free approach using a probabilistic surrogate model and optimal search over a feasible parameter space. Despite the benefits of BO in reducing computational costs, challenges remain in dealing with a high-dimensional calibration task resulting from a large set of parameters that have significant impacts on system behavior and need to be calibrated simultaneously. This paper presents a reduced-dimension BO framework for calibrating transient VCCs models where the calibration space is projected to a low-dimensional subspace for accelerating convergence of the solution algorithm and consequently reducing the number of transient simulations. The proposed approach was demonstrated via two case studies associated with different VCC applications where 10 parameters were calibrated in each case using laboratory measurements. The reduced-dimension BO framework only required of the iterations associated with a standard BO method that deals with high-dimensional calibration parameters for converged solutions and yielded comparable accuracy. Furthermore, both calibrated models revealed significant accuracy improvements compared to uncalibrated models.
蒸汽压缩循环（VCC）第一原理动态模型的开发和校准对于控制设计、故障检测和诊断等应用至关重要。然而，由大型微分代数方程系统表示的模型固有的复杂性给利用经典梯度法进行模型校准的过程带来了巨大挑战。贝叶斯优化（BO）是一种样本效率高、无梯度的方法，它使用概率代理模型和在可行参数空间上的最优搜索。尽管贝叶斯优化法具有降低计算成本的优势，但在处理高维校准任务时仍面临挑战，因为大量参数会对系统行为产生重大影响，而且需要同时进行校准。本文提出了一种用于校准瞬态 VCC 模型的降维 BO 框架，将校准空间投影到低维子空间，以加速求解算法的收敛，从而减少瞬态模拟的次数。我们通过两个与不同 VCC 应用相关的案例研究对所提出的方法进行了演示，每个案例都使用实验室测量结果对 10 个参数进行了校准。缩小维度的 BO 框架所需的迭代次数仅为处理高维度校准参数的标准 BO 方法的 1/8，并获得了相当的精度。此外，与未经校准的模型相比，两种校准模型的精度都有显著提高。
{"title":"Reduced-dimension Bayesian optimization for model calibration of transient vapor compression cycles","authors":"Jiacheng Ma , Donghun Kim , James E. Braun","doi":"10.1016/j.ijrefrig.2024.09.010","DOIUrl":"10.1016/j.ijrefrig.2024.09.010","url":null,"abstract":"<div><div>Development and calibration of first-principles dynamic models of vapor compression cycles (VCCs) is of critical importance for applications that include control design and fault detection and diagnostics. Nevertheless, the inherent complexity of models that are represented by large systems of differential–algebraic equations leads to significant challenges for model calibration processes that utilize classical gradient-based methods. Bayesian optimization (BO) is a sample-efficient and gradient-free approach using a probabilistic surrogate model and optimal search over a feasible parameter space. Despite the benefits of BO in reducing computational costs, challenges remain in dealing with a high-dimensional calibration task resulting from a large set of parameters that have significant impacts on system behavior and need to be calibrated simultaneously. This paper presents a reduced-dimension BO framework for calibrating transient VCCs models where the calibration space is projected to a low-dimensional subspace for accelerating convergence of the solution algorithm and consequently reducing the number of transient simulations. The proposed approach was demonstrated via two case studies associated with different VCC applications where 10 parameters were calibrated in each case using laboratory measurements. The reduced-dimension BO framework only required <span><math><mrow><mn>1</mn><mo>/</mo><msup><mrow><mn>8</mn></mrow><mrow><mi>th</mi></mrow></msup></mrow></math></span> of the iterations associated with a standard BO method that deals with high-dimensional calibration parameters for converged solutions and yielded comparable accuracy. Furthermore, both calibrated models revealed significant accuracy improvements compared to uncalibrated models.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 246-258"},"PeriodicalIF":3.5,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.ijrefrig.2024.08.006
Zhichao Chen , Shaoshuai Liu , Xinquan Sha , Yunwei Shen , Wang Yin , Zheng Huang , Lei Ding , Zhenhua Jiang , Zhihua Gan , Yinong Wu
Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications.
在液氦温度下工作的焦耳-汤姆逊（JT）低温冷却器具有寿命长、振动小和电磁干扰小等优点，已被用于太空。然而，在一定的质量限制下，其冷却能力和热力学效率仍需进一步提高，这是 JT 低温冷却器在太空高效应用的必要改进。因此，本研究对在液氦温度下工作的 JT 低温冷却器进行了优化设计。在对斯特林低温冷却器、脉冲管低温冷却器和 JT 压缩机进行改进的基础上，所开发的 JT 低温冷却器在 4.18 K 时可提供 0.36 W 的冷却能力，而总输入功率和总质量（不含低温恒温器）分别为 1157 W 和 26.8 kg。与文献研究相比，可以发现所开发的 JT 低温冷却器适用于空间应用。
{"title":"Essential improvement of the JT cryocooler working at liquid helium temperature for space: Efficient and lightweight","authors":"Zhichao Chen , Shaoshuai Liu , Xinquan Sha , Yunwei Shen , Wang Yin , Zheng Huang , Lei Ding , Zhenhua Jiang , Zhihua Gan , Yinong Wu","doi":"10.1016/j.ijrefrig.2024.08.006","DOIUrl":"10.1016/j.ijrefrig.2024.08.006","url":null,"abstract":"<div><p>Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications.</p></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 89-94"},"PeriodicalIF":3.5,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142239276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.1016/j.ijrefrig.2024.09.008
Yansong Hu, Zhao Yang, Zhaoning Hou, Yanfeng Zhao
The escalating threat of global warming has highlighted the imperative to address the greenhouse effect. R513A is recognized as a viable substitute for R134a, providing a lower global warming potential (GWP) while preserving similar thermodynamic properties. However, refrigerant leakage is one of the common faults in heat pump equipment. For industrial heat pumps, refrigerant leakage can make the system less stable and affect normal industrial production, while long-term leakage can also affect the carbon emissions of the industry. When substituting refrigerants, it is crucial to consider not only their distinct properties under typical operating conditions but also the stability and environmental impact of the alternative refrigerant in cases of leakage. This paper focuses on experimentally evaluating the impact of using R513A to replace R134a on the performance of refrigeration systems under the condition of rapid refrigerant leakage. Then the life cycle climate performance evaluation (LCCP) theory is used to assist experimental results in evaluating the carbon footprints of R513A and R134a systems at different annual leakage rates. The results show that R513A has better stability than R134a when responding to rapid refrigerant leakage. This paper determines the changes in annual electricity consumption and indirect emissions under several annual leakage rates and finds that the impact of leakage on indirect emissions is also not negligible. During the utilization phase of the equipment, when leakage was taken into account, the carbon emissions of the R134a system were higher.
{"title":"Study on the impacts of refrigerant leakage on the performance and environmental benefits of heat pumps using R513A as replacement of R134a","authors":"Yansong Hu, Zhao Yang, Zhaoning Hou, Yanfeng Zhao","doi":"10.1016/j.ijrefrig.2024.09.008","DOIUrl":"10.1016/j.ijrefrig.2024.09.008","url":null,"abstract":"<div><div>The escalating threat of global warming has highlighted the imperative to address the greenhouse effect. R513A is recognized as a viable substitute for R134a, providing a lower global warming potential (GWP) while preserving similar thermodynamic properties. However, refrigerant leakage is one of the common faults in heat pump equipment. For industrial heat pumps, refrigerant leakage can make the system less stable and affect normal industrial production, while long-term leakage can also affect the carbon emissions of the industry. When substituting refrigerants, it is crucial to consider not only their distinct properties under typical operating conditions but also the stability and environmental impact of the alternative refrigerant in cases of leakage. This paper focuses on experimentally evaluating the impact of using R513A to replace R134a on the performance of refrigeration systems under the condition of rapid refrigerant leakage. Then the life cycle climate performance evaluation (LCCP) theory is used to assist experimental results in evaluating the carbon footprints of R513A and R134a systems at different annual leakage rates. The results show that R513A has better stability than R134a when responding to rapid refrigerant leakage. This paper determines the changes in annual electricity consumption and indirect emissions under several annual leakage rates and finds that the impact of leakage on indirect emissions is also not negligible. During the utilization phase of the equipment, when leakage was taken into account, the carbon emissions of the R134a system were higher.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 399-410"},"PeriodicalIF":3.5,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1016/j.ijrefrig.2024.09.018
Peiqi Liu , Haitao Wang , Yang Yu , Yiming Zhao , Zewu Wang , Haigui Fan , Dapeng Hu
The gas wave oscillation tube (GWOT) transfers energy directly between gases of varying pressures using non-constant motion waves, and its low rotational speed operation offers a broader application potential in two-phase refrigeration compared to turbomachinery. The GWOTs achieve a high performance by optimizing the relationship between tube length, deflection displacement, rotational speed, and incident excitation wave (S1) velocity. However, under the liquid-carrying conditions, the optimizing matching relationship of the GWOTs deviates, leading to a decline in performance, so it is necessary to explore the matching relationship of the high performance of the GWOTs under the liquid-carrying conditions. This study focuses on "spoon" GWOTs, analyzing the impact of rotational speed, liquid-carrying capacity, and deflection displacement on their refrigeration performance under a fixed tube length through experimental analysis. It is found that the refrigeration efficiency at the design parameters of the GWOTs decreases by a maximum of about 25 % with the increase in the amount of liquid-carrying capacity within the study area of this paper, while the refrigeration efficiency can be improved by a maximum of about 8 % by varying the rotational speed. The findings provide valuable insights for enhancing the liquid-carrying performance of the GWOTs and promoting the application expansion of GWOTs in the field of gas-liquid two-phase.
{"title":"Experimental study on the matching relationship of gas wave oscillation tube under liquid-carrying condition","authors":"Peiqi Liu , Haitao Wang , Yang Yu , Yiming Zhao , Zewu Wang , Haigui Fan , Dapeng Hu","doi":"10.1016/j.ijrefrig.2024.09.018","DOIUrl":"10.1016/j.ijrefrig.2024.09.018","url":null,"abstract":"<div><div>The gas wave oscillation tube (GWOT) transfers energy directly between gases of varying pressures using non-constant motion waves, and its low rotational speed operation offers a broader application potential in two-phase refrigeration compared to turbomachinery. The GWOTs achieve a high performance by optimizing the relationship between tube length, deflection displacement, rotational speed, and incident excitation wave (S1) velocity. However, under the liquid-carrying conditions, the optimizing matching relationship of the GWOTs deviates, leading to a decline in performance, so it is necessary to explore the matching relationship of the high performance of the GWOTs under the liquid-carrying conditions. This study focuses on \"spoon\" GWOTs, analyzing the impact of rotational speed, liquid-carrying capacity, and deflection displacement on their refrigeration performance under a fixed tube length through experimental analysis. It is found that the refrigeration efficiency at the design parameters of the GWOTs decreases by a maximum of about 25 % with the increase in the amount of liquid-carrying capacity within the study area of this paper, while the refrigeration efficiency can be improved by a maximum of about 8 % by varying the rotational speed. The findings provide valuable insights for enhancing the liquid-carrying performance of the GWOTs and promoting the application expansion of GWOTs in the field of gas-liquid two-phase.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 318-325"},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1016/j.ijrefrig.2024.09.016
Yifeng Hu, Samuel Fortunato Yana Motta, Cheng-Min Yang
To mitigate global warming, the world is transitioning to refrigerants with low global warming potential (GWP). Supporting this shift requires a model that can accurately predict the heat transfer and pressure drop of new refrigerants, crucial for designing efficient heat exchangers. Existing models, however, are largely based on currently deployed refrigerants and primarily developed for unexpanded micro-fin tubes with spiral angles of 6° to 30°. Their applicability to new refrigerants, especially in expanded micro-fin tubes, is uncertain. This study assesses the performance of four well-known condensation models for six emerging refrigerants—R-32, R-454B, R-454C, R-455A, R-1234yf, and R-1234ze(E)—against experimental data. Initially, the Han and Lee (2005) model shows the best prediction accuracy with a mean absolute deviation (MAD) of 22.1 %. To enhance the accuracy of heat transfer models for new refrigerants and geometries with large temperature glides, two approaches are proposed. The first approach applies a simple correction factor, reducing the MAD of the Cavallini et al. (2009) model from 68.2 % to 15.4 %. The second approach uses the variable metric method for minimization, fitting new constants to the data. This optimization results in the Kedzierski and Goncalves (1997) model achieving the highest accuracy, with a MAD of 13.1 %. For pressure drop models, the Cavallini et al. (1997) model is the most accurate with a MAD of 6.4 %, followed by the Haraguchi et al. (1993) model with a MAD of 9.4 %. Due to its simplicity, the Haraguchi et al. (1993) model is a practical option for predicting frictional pressure drop.
{"title":"Evaluation and development of flow condensation correlations using the data from low GWP refrigerants in an axial micro-fin aluminum tube","authors":"Yifeng Hu, Samuel Fortunato Yana Motta, Cheng-Min Yang","doi":"10.1016/j.ijrefrig.2024.09.016","DOIUrl":"10.1016/j.ijrefrig.2024.09.016","url":null,"abstract":"<div><div>To mitigate global warming, the world is transitioning to refrigerants with low global warming potential (GWP). Supporting this shift requires a model that can accurately predict the heat transfer and pressure drop of new refrigerants, crucial for designing efficient heat exchangers. Existing models, however, are largely based on currently deployed refrigerants and primarily developed for unexpanded micro-fin tubes with spiral angles of 6° to 30°. Their applicability to new refrigerants, especially in expanded micro-fin tubes, is uncertain. This study assesses the performance of four well-known condensation models for six emerging refrigerants—R-32, R-454B, R-454C, R-455A, R-1234yf, and R-1234ze(E)—against experimental data. Initially, the Han and Lee (2005) model shows the best prediction accuracy with a mean absolute deviation (MAD) of 22.1 %. To enhance the accuracy of heat transfer models for new refrigerants and geometries with large temperature glides, two approaches are proposed. The first approach applies a simple correction factor, reducing the MAD of the Cavallini et al. (2009) model from 68.2 % to 15.4 %. The second approach uses the variable metric method for minimization, fitting new constants to the data. This optimization results in the Kedzierski and Goncalves (1997) model achieving the highest accuracy, with a MAD of 13.1 %. For pressure drop models, the Cavallini et al. (1997) model is the most accurate with a MAD of 6.4 %, followed by the Haraguchi et al. (1993) model with a MAD of 9.4 %. Due to its simplicity, the Haraguchi et al. (1993) model is a practical option for predicting frictional pressure drop.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 454-468"},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1016/j.ijrefrig.2024.09.019
Huanmin Li, Qiuyue Huang, Jianlin Yu
In the application scope of large-scale supermarkets, the practicality of transcritical CO2 refrigeration device has been confirmed to be quite satisfying. A modified two-stage transcritical CO2 refrigeration cycle with an ejector and a subcooler (MTC) is proposed in this paper. In the modified cycle, the ejector recovers expansion works and reduces irreversible losses in the throttling process. The subcooler provides subcooling degree for the CO2 entering the low-temperature (LT) evaporator, thus increasing the refrigeration capacity and improving the COP of the modified cycle. Thermodynamic analysis has shown that the exergy efficiency and COP of MTC under given operating condition has been enhanced by 13.7 % and 14.2 % compared to BTC. The discharge temperature at the outlet of high-pressure compressor in MTC is decreased by 8.3℃. Under typical operating condition, the optimal discharge pressure of MTC is 9.07 MPa, which is lower than that of BTC. The correlation to calculate optimal discharge pressure for single-stage CO2 refrigeration cycle is also suitable for MTC under given operating conditions. The MTC has also shown better performance under variable operating conditions. For MTC, when the temperature at the outlet of gas cooler increases from 35 – 45℃, the COP and are enhanced by 14.1 % - 16.1 % and 12.8 % - 14.2 % compared to BTC, respectively. When gas cooler outlet pressure decreases from 11.0 to 7.5 MPa, the COP and are enhanced by 14.0 % - 22.8 % and 13.4 % - 18.7 %. As the evaporating temperature at the cold side of subcooler increases from -25 to -15℃, the COP and increase from 1.82 to 1.98 and 27.4 % to 29.7 %. With the ratio of refrigeration capacity () between medium-temperature evaporator and low-temperature evaporator varies from 0.7 to 1.2, the COP and are improved by 10.7 % - 16.3 % and 10.7 % - 15.4 % compared to BTC. There is the maximum exergy loss at gas cooler in the MTC, whereas that of BTC is located in the expansion valve before LT evaporator. The economic analysis shows the cost per unit of exergy of MTC is decreased by 11.5 % under typical operation condition. According to simulation results, the modified cycle has better performance in severe working conditions such as high gas cooler outlet temperature and low gas cooler outlet pressure in the given range of working conditions compared to BTC.
{"title":"Thermodynamic analysis of a modified two-stage transcritical CO2 refrigeration cycle with an ejector and a subcooler","authors":"Huanmin Li, Qiuyue Huang, Jianlin Yu","doi":"10.1016/j.ijrefrig.2024.09.019","DOIUrl":"10.1016/j.ijrefrig.2024.09.019","url":null,"abstract":"<div><div>In the application scope of large-scale supermarkets, the practicality of transcritical CO<sub>2</sub> refrigeration device has been confirmed to be quite satisfying. A modified two-stage transcritical CO<sub>2</sub> refrigeration cycle with an ejector and a subcooler (MTC) is proposed in this paper. In the modified cycle, the ejector recovers expansion works and reduces irreversible losses in the throttling process. The subcooler provides subcooling degree for the CO<sub>2</sub> entering the low-temperature (LT) evaporator, thus increasing the refrigeration capacity and improving the COP of the modified cycle. Thermodynamic analysis has shown that the exergy efficiency <span><math><mrow><mo>(</mo><msub><mi>η</mi><mrow><mi>e</mi><mi>x</mi></mrow></msub><mo>)</mo></mrow></math></span> and COP of MTC under given operating condition has been enhanced by 13.7 % and 14.2 % compared to BTC. The discharge temperature at the outlet of high-pressure compressor in MTC is decreased by 8.3℃. Under typical operating condition, the optimal discharge pressure of MTC is 9.07 MPa, which is lower than that of BTC. The correlation to calculate optimal discharge pressure for single-stage CO<sub>2</sub> refrigeration cycle is also suitable for MTC under given operating conditions. The MTC has also shown better performance under variable operating conditions. For MTC, when the temperature at the outlet of gas cooler increases from 35 – 45℃, the COP and <span><math><msub><mi>η</mi><mrow><mi>e</mi><mi>x</mi></mrow></msub></math></span> are enhanced by 14.1 % - 16.1 % and 12.8 % - 14.2 % compared to BTC, respectively. When gas cooler outlet pressure decreases from 11.0 to 7.5 MPa, the COP and <span><math><msub><mi>η</mi><mrow><mi>e</mi><mi>x</mi></mrow></msub></math></span> are enhanced by 14.0 % - 22.8 % and 13.4 % - 18.7 %. As the evaporating temperature at the cold side of subcooler increases from -25 to -15℃, the COP and <span><math><msub><mi>η</mi><mrow><mi>e</mi><mi>x</mi></mrow></msub></math></span> increase from 1.82 to 1.98 and 27.4 % to 29.7 %. With the ratio of refrigeration capacity (<span><math><msub><mi>R</mi><mrow><mi>e</mi><mi>c</mi></mrow></msub></math></span>) between medium-temperature evaporator and low-temperature evaporator varies from 0.7 to 1.2, the COP and <span><math><msub><mi>η</mi><mrow><mi>e</mi><mi>x</mi></mrow></msub></math></span> are improved by 10.7 % - 16.3 % and 10.7 % - 15.4 % compared to BTC. There is the maximum exergy loss at gas cooler in the MTC, whereas that of BTC is located in the expansion valve before LT evaporator. The economic analysis shows the cost per unit of exergy of MTC is decreased by 11.5 % under typical operation condition. According to simulation results, the modified cycle has better performance in severe working conditions such as high gas cooler outlet temperature and low gas cooler outlet pressure in the given range of working conditions compared to BTC.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 492-505"},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-18DOI: 10.1016/j.ijrefrig.2024.09.017
Feng Zhou , Ruimin Wang , Guoyuan Ma
The low-carbon transformation of data centers is of great significance to achieve the goals of carbon peaking and carbon neutrality. This study compared and analyzed the overall situation of data centers in China. Based on China's CO2 emission and intensity targets in key years, the four variables of energy efficiency improvement rate, nonfossil energy consumption proportion, negative emission technology intensity, and waste energy utilization rate were introduced, and a net zero emission path model of data centers was established. Using scenario analysis to predict the total CO2 emissions and emission intensity from 2021 to 2060, three emission reduction path scenarios were obtained. Results showed that the energy consumption of data centers increased gradually, the carbon emissions first increased and then decreased, and the power usage effectiveness (PUE) of the data centers decreased gradually. The carbon peak time of the three scenarios is 2030, and the time for carbon neutrality is 2055, 2053, and 2051 in three scenarios. The data center industry should further improve the energy efficiency utilization rate, increase the proportion of nonfossil energy consumption, strengthen the technological innovation of carbon capture and storage, enhance the level of carbon sink, and optimize the utilization rate of waste energy.
{"title":"Carbon emission scenario analysis of data centers in China under the carbon neutrality target","authors":"Feng Zhou , Ruimin Wang , Guoyuan Ma","doi":"10.1016/j.ijrefrig.2024.09.017","DOIUrl":"10.1016/j.ijrefrig.2024.09.017","url":null,"abstract":"<div><div>The low-carbon transformation of data centers is of great significance to achieve the goals of carbon peaking and carbon neutrality. This study compared and analyzed the overall situation of data centers in China. Based on China's CO<sub>2</sub> emission and intensity targets in key years, the four variables of energy efficiency improvement rate, nonfossil energy consumption proportion, negative emission technology intensity, and waste energy utilization rate were introduced, and a net zero emission path model of data centers was established. Using scenario analysis to predict the total CO<sub>2</sub> emissions and emission intensity from 2021 to 2060, three emission reduction path scenarios were obtained. Results showed that the energy consumption of data centers increased gradually, the carbon emissions first increased and then decreased, and the power usage effectiveness (PUE) of the data centers decreased gradually. The carbon peak time of the three scenarios is 2030, and the time for carbon neutrality is 2055, 2053, and 2051 in three scenarios. The data center industry should further improve the energy efficiency utilization rate, increase the proportion of nonfossil energy consumption, strengthen the technological innovation of carbon capture and storage, enhance the level of carbon sink, and optimize the utilization rate of waste energy.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"168 ","pages":"Pages 648-661"},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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