Pub Date : 2026-02-01Epub Date: 2025-12-05DOI: 10.1016/j.ijrefrig.2025.12.004
Yu Tian, Guoyuan Ma
As an environmentally benign natural refrigerant, air has emerged as a promising alternative for sustainable refrigeration systems, where the expander-compressor performance represents the critical limiting factor. This paper proposes a coupled design method for compressors and expanders in air refrigeration cycles, featuring identical pressure ratios, flow similarity, and high-efficiency operation across all working conditions. The imperialist competitive algorithm was implemented with annual system efficiency as the objective function to optimize the turboexpander-compressor. Experimental validation confirms the accuracy of the one-dimensional loss model and computational fluid dynamics simulation, demonstrating the feasibility of the proposed methodology. Under summer conditions of Beijing (2023), the designed system achieves an average turboexpander-compressor system efficiency of 2.759. Results indicate that the ratio of pressure ratio between the compressor and expander remains within 0.9–1.05, satisfying the identical pressure ratio design requirement. The system maintains high efficiency even under peak cooling demand, effectively mitigating performance degradation in high-load scenarios.
{"title":"Coupled design and optimization of the turboexpander-compressor for full-range high efficiency in reverse brayton cycles","authors":"Yu Tian, Guoyuan Ma","doi":"10.1016/j.ijrefrig.2025.12.004","DOIUrl":"10.1016/j.ijrefrig.2025.12.004","url":null,"abstract":"<div><div>As an environmentally benign natural refrigerant, air has emerged as a promising alternative for sustainable refrigeration systems, where the expander-compressor performance represents the critical limiting factor. This paper proposes a coupled design method for compressors and expanders in air refrigeration cycles, featuring identical pressure ratios, flow similarity, and high-efficiency operation across all working conditions. The imperialist competitive algorithm was implemented with annual system efficiency as the objective function to optimize the turboexpander-compressor. Experimental validation confirms the accuracy of the one-dimensional loss model and computational fluid dynamics simulation, demonstrating the feasibility of the proposed methodology. Under summer conditions of Beijing (2023), the designed system achieves an average turboexpander-compressor system efficiency of 2.759. Results indicate that the ratio of pressure ratio between the compressor and expander remains within 0.9–1.05, satisfying the identical pressure ratio design requirement. The system maintains high efficiency even under peak cooling demand, effectively mitigating performance degradation in high-load scenarios.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 312-322"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733325","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 : 2026-02-01Epub Date: 2025-11-19DOI: 10.1016/j.ijrefrig.2025.11.016
Yixin Liu, Xiangji Yue, Zhijun Zhang, Jiawei Guo
The over-compression phenomenon in CO₂ scroll compressors, compared to those using conventional refrigerants, significantly impairs performance. To address this issue, a three-dimensional simulation model of a CO₂ scroll compressor incorporating pre-discharge valves was developed to mitigate the impact of the over-compression phenomenon on compressor performance. Simulation results indicate that, compared to scroll compressors without a pre-discharge valve (NPDV) structure, those with a pre-discharge valve (PDV) structure exhibits a reduction of 4.4 MPa in the maximum pressure and 25 K in the maximum temperature within the compression chamber. The range of the over-compression effect has been reduced from 251 - 425°to 373 - 425°, and the pre-compression phenomenon is improved. Additionally, the pre-discharge valve structure reduces the impact of the gas on the main discharge valve. It also decreases both the axial and radial clearance gas leakage velocities, with the average mass flow rate of axial clearance leakage reduced by 12 %. As a result of the pre-discharge valve structure, the inlet mass flow rate increases by 4.2 % and the volumetric efficiency improves by 3.2 %. Moreover, the discharge temperature, torque, and shaft power of the scroll compressor are reduced by 5 K, 1.39 N·m, and 99 W, respectively.
{"title":"Simulation study of a CO2 scroll compressor with main and pre-discharge valves","authors":"Yixin Liu, Xiangji Yue, Zhijun Zhang, Jiawei Guo","doi":"10.1016/j.ijrefrig.2025.11.016","DOIUrl":"10.1016/j.ijrefrig.2025.11.016","url":null,"abstract":"<div><div>The over-compression phenomenon in CO₂ scroll compressors, compared to those using conventional refrigerants, significantly impairs performance. To address this issue, a three-dimensional simulation model of a CO₂ scroll compressor incorporating pre-discharge valves was developed to mitigate the impact of the over-compression phenomenon on compressor performance. Simulation results indicate that, compared to scroll compressors without a pre-discharge valve (NPDV) structure, those with a pre-discharge valve (PDV) structure exhibits a reduction of 4.4 MPa in the maximum pressure and 25 K in the maximum temperature within the compression chamber. The range of the over-compression effect has been reduced from 251 - 425°to 373 - 425°, and the pre-compression phenomenon is improved. Additionally, the pre-discharge valve structure reduces the impact of the gas on the main discharge valve. It also decreases both the axial and radial clearance gas leakage velocities, with the average mass flow rate of axial clearance leakage reduced by 12 %. As a result of the pre-discharge valve structure, the inlet mass flow rate increases by 4.2 % and the volumetric efficiency improves by 3.2 %. Moreover, the discharge temperature, torque, and shaft power of the scroll compressor are reduced by 5 K, 1.39 N·m, and 99 W, respectively.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 273-286"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733327","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 : 2026-02-01Epub Date: 2025-11-20DOI: 10.1016/j.ijrefrig.2025.11.020
Jiayuan Cao , Xiaofeng Xu , Liang Zhang , Yujuan Xia , Hanyi Liu , Yang Yang
Low-temperature refrigeration is indispensable for cryogenic applications like superconductivity and helium liquefaction, and its efficiency hinges on helium compression. This study is critical as it addresses the long-standing gap of rolling piston type rotary compressors (RPTRCs) in helium compression, a key advance for diversifying cryogenic compression technologies. Currently, helium compression relies mostly on scroll or screw compressors, limiting equipment miniaturization and cost-effectiveness; RPTRCs’ poor heat dissipation and high discharge temperatures have excluded them, hindering field progress. To address these challenges, we modified an RPTRC with oil-injection cooling, optimized exhaust, and an external heat exchanger, then built an experimental setup. The tests encompassed rotational speeds ranging from 50 to 100 rps, oil injection volumes between 3.5 to 4.5 L, and inlet water temperatures of 18–24 °C at flow rates of 1–3 L·min-1. The results demonstrated that the modified RPTRC maintained a discharge temperature below 100 °C; specifically at a speed of 100 rps, the exhaust pressure stabilized around 27.2 bar while achieving a volumetric efficiency increase of approximately 10.5 %. Notably, using an oil volume of 4.5 L reduced the exhaust temperature by 12.3 %, although it resulted in an increase in input power by 8.8 %. Furthermore, adjusting inlet water parameters enhanced volumetric efficiency by up to 5 % due to reductions in oil viscosity. This work first validates RPTRCs for helium two-phase compression, provides critical empirical data, and expands cryogenic compressor options, significantly advancing low-temperature refrigeration research and application.
{"title":"Performance investigation of a helium compression system driven by a revamped rolling piston type rotor compressor","authors":"Jiayuan Cao , Xiaofeng Xu , Liang Zhang , Yujuan Xia , Hanyi Liu , Yang Yang","doi":"10.1016/j.ijrefrig.2025.11.020","DOIUrl":"10.1016/j.ijrefrig.2025.11.020","url":null,"abstract":"<div><div>Low-temperature refrigeration is indispensable for cryogenic applications like superconductivity and helium liquefaction, and its efficiency hinges on helium compression. This study is critical as it addresses the long-standing gap of rolling piston type rotary compressors (RPTRCs) in helium compression, a key advance for diversifying cryogenic compression technologies. Currently, helium compression relies mostly on scroll or screw compressors, limiting equipment miniaturization and cost-effectiveness; RPTRCs’ poor heat dissipation and high discharge temperatures have excluded them, hindering field progress. To address these challenges, we modified an RPTRC with oil-injection cooling, optimized exhaust, and an external heat exchanger, then built an experimental setup. The tests encompassed rotational speeds ranging from 50 to 100 rps, oil injection volumes between 3.5 to 4.5 L, and inlet water temperatures of 18–24 °C at flow rates of 1–3 L·min<sup>-1</sup>. The results demonstrated that the modified RPTRC maintained a discharge temperature below 100 °C; specifically at a speed of 100 rps, the exhaust pressure stabilized around 27.2 bar while achieving a volumetric efficiency increase of approximately 10.5 %. Notably, using an oil volume of 4.5 L reduced the exhaust temperature by 12.3 %, although it resulted in an increase in input power by 8.8 %. Furthermore, adjusting inlet water parameters enhanced volumetric efficiency by up to 5 % due to reductions in oil viscosity. This work first validates RPTRCs for helium two-phase compression, provides critical empirical data, and expands cryogenic compressor options, significantly advancing low-temperature refrigeration research and application.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 102-113"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682297","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 : 2026-02-01Epub Date: 2025-11-26DOI: 10.1016/j.ijrefrig.2025.11.027
Chuang Pan , Jinlei Li , Runfa Zhou , Shuhong Li , Yanjun Li , Jun Wu , Gui Li
As the core component of the ammonia-water absorption refrigeration system (AARS), the falling film absorber plays a crucial role in enhancing the absorption process, which significantly impacts the improvement of the system's performance. In this paper, a novel absorber that combines ultrasonic oscillation and atomization to enhance the falling film absorption process of ammonia water is proposed. This innovative approach can simultaneously increase the mass transfer area and the driving force for mass transfer. Moreover, a theoretical model of this new absorber is established to analyze its absorption enhancement effect. The results demonstrate that the combined enhancement effect of oscillation and atomization on absorption is superior to that of atomization or oscillation alone. When the total power of the atomizer and oscillator for a single falling film tube is 2 W, the droplet diameter is 17 μm, and the atomization rate is 0.54, the maximum absorption effect is increased by 44.95 %. This study provides a new perspective for the structural optimization of absorbers and the effective improvement of the performance of AARS systems.
{"title":"Theoretical analysis of the enhancement effect of the combination of ultrasonic oscillation and atomization on the falling film absorption process of ammonia water and optimization of the combined parameters","authors":"Chuang Pan , Jinlei Li , Runfa Zhou , Shuhong Li , Yanjun Li , Jun Wu , Gui Li","doi":"10.1016/j.ijrefrig.2025.11.027","DOIUrl":"10.1016/j.ijrefrig.2025.11.027","url":null,"abstract":"<div><div>As the core component of the ammonia-water absorption refrigeration system (AARS), the falling film absorber plays a crucial role in enhancing the absorption process, which significantly impacts the improvement of the system's performance. In this paper, a novel absorber that combines ultrasonic oscillation and atomization to enhance the falling film absorption process of ammonia water is proposed. This innovative approach can simultaneously increase the mass transfer area and the driving force for mass transfer. Moreover, a theoretical model of this new absorber is established to analyze its absorption enhancement effect. The results demonstrate that the combined enhancement effect of oscillation and atomization on absorption is superior to that of atomization or oscillation alone. When the total power of the atomizer and oscillator for a single falling film tube is 2 W, the droplet diameter is 17 μm, and the atomization rate is 0.54, the maximum absorption effect is increased by 44.95 %. This study provides a new perspective for the structural optimization of absorbers and the effective improvement of the performance of AARS systems.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 74-92"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682238","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 : 2026-02-01Epub Date: 2025-11-15DOI: 10.1016/j.ijrefrig.2025.11.013
Shuaiyue Shao, Wei Wang, Zhengxing Zuo, Wenlong Liu, Hejia Wang
To meet the stringent requirements of rapid temperature changes in the polymerase chain reaction (PCR) process for digital microfluidic chips, this study investigates the transient heat transfer characteristics and optimization strategies of the PCR process based on thermoelectric cyclic-thermal regulation. Research has shown that transient cooling is more efficient than steady-state cooling, and the dimensionless optimal values ZHT and ZCT for thermoelectric materials under transient conditions have been derived. It was determined that the thermoelectric leg height providing high heating and cooling heat flux should be between 0.5∼ 0.7 mm, and it was also found that smaller H values lead to higher temperature control stability. When the equivalent heat capacity exceeds 8.5 J/K, it is capable of achieving at least 4.02 W/cm2 of cooling heat flux and 13.02 W/cm2 of heating heat flux, providing a basis for the miniaturization design of the heat sink. Through optimization of the heat dissipation structure, a thermal management system using PID control was implemented, achieving a heating rate of 8.78 °C/s and a cooling rate of 5.33 °C/s. Furthermore, the system supports an array of multiple temperature control units. This study offers design and optimization strategies for the thermal management system in microfluidic systems and provides theoretical support and experimental data for thermal cycling scenarios.
{"title":"Research on optimization strategies for thermal management system of digital microfluidic chips based on thermoelectric cyclic-thermal regulators","authors":"Shuaiyue Shao, Wei Wang, Zhengxing Zuo, Wenlong Liu, Hejia Wang","doi":"10.1016/j.ijrefrig.2025.11.013","DOIUrl":"10.1016/j.ijrefrig.2025.11.013","url":null,"abstract":"<div><div>To meet the stringent requirements of rapid temperature changes in the polymerase chain reaction (PCR) process for digital microfluidic chips, this study investigates the transient heat transfer characteristics and optimization strategies of the PCR process based on thermoelectric cyclic-thermal regulation. Research has shown that transient cooling is more efficient than steady-state cooling, and the dimensionless optimal values Z<sub>H</sub>T and Z<sub>C</sub>T for thermoelectric materials under transient conditions have been derived. It was determined that the thermoelectric leg height providing high heating and cooling heat flux should be between 0.5∼ 0.7 mm, and it was also found that smaller H values lead to higher temperature control stability. When the equivalent heat capacity exceeds 8.5 J/K, it is capable of achieving at least 4.02 W/cm<sup>2</sup> of cooling heat flux and 13.02 W/cm<sup>2</sup> of heating heat flux, providing a basis for the miniaturization design of the heat sink. Through optimization of the heat dissipation structure, a thermal management system using PID control was implemented, achieving a heating rate of 8.78 °C/s and a cooling rate of 5.33 °C/s. Furthermore, the system supports an array of multiple temperature control units. This study offers design and optimization strategies for the thermal management system in microfluidic systems and provides theoretical support and experimental data for thermal cycling scenarios.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 1-13"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571213","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 : 2026-02-01Epub Date: 2025-11-10DOI: 10.1016/j.ijrefrig.2025.11.009
Liaoliang Jiang , Yulong Song , Ying Chen , Hongsheng Xie , Jiahang Ren , Xiang Yin , Feng Cao , Xuebo Pang , Gang Bai , Tao Yang , Min Sun
To effectively respond to the goals of carbon neutrality and the Kigali Amendment, it is crucial to address the issue of refrigerant substitution in railway heat pump air conditioning systems. This article focuses on studying the challenges related to thermal management logic control when using CO2 as the alternative refrigerant for heat pump air conditioning in high-speed rail vehicles. The study includes the development of a comprehensive model of the entire cabin and heat pump air conditioning system cycle using the AMESim simulation platform. An experimental platform was also constructed to conduct relevant verification experiments. The unique operational conditions and requirements of high-speed railways necessitate distinct CO2 heat pump air conditioning requirements compared to passenger cars. The rail vehicles, characterized by high thermal load and inertia, exhibit slow temperature response rates. Conventional thermal management techniques employed in passenger cars often lead to frequent start-stop cycles of the compressor during dynamic vehicle operations(start and stop once every 200 s). By implementing new thermal management strategies, the duration of compressor start-stop cycles was extended(start and stop once every 1200 s), the starting constant cooling capacity is 10 kW, and the constant starting COP is around 2.5, aligning better with real-world practical applications.
{"title":"The performance improvement and optimum control of the transcritical CO2 air conditioning and heat pump system used in the high-speed railway vehicles","authors":"Liaoliang Jiang , Yulong Song , Ying Chen , Hongsheng Xie , Jiahang Ren , Xiang Yin , Feng Cao , Xuebo Pang , Gang Bai , Tao Yang , Min Sun","doi":"10.1016/j.ijrefrig.2025.11.009","DOIUrl":"10.1016/j.ijrefrig.2025.11.009","url":null,"abstract":"<div><div>To effectively respond to the goals of carbon neutrality and the Kigali Amendment, it is crucial to address the issue of refrigerant substitution in railway heat pump air conditioning systems. This article focuses on studying the challenges related to thermal management logic control when using CO<sub>2</sub> as the alternative refrigerant for heat pump air conditioning in high-speed rail vehicles. The study includes the development of a comprehensive model of the entire cabin and heat pump air conditioning system cycle using the AMESim simulation platform. An experimental platform was also constructed to conduct relevant verification experiments. The unique operational conditions and requirements of high-speed railways necessitate distinct CO<sub>2</sub> heat pump air conditioning requirements compared to passenger cars. The rail vehicles, characterized by high thermal load and inertia, exhibit slow temperature response rates. Conventional thermal management techniques employed in passenger cars often lead to frequent start-stop cycles of the compressor during dynamic vehicle operations(start and stop once every 200 s). By implementing new thermal management strategies, the duration of compressor start-stop cycles was extended(start and stop once every 1200 s), the starting constant cooling capacity is 10 kW, and the constant starting COP is around 2.5, aligning better with real-world practical applications.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 49-60"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145616490","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 : 2026-02-01Epub Date: 2025-12-07DOI: 10.1016/j.ijrefrig.2025.12.007
Türkan Üçok Erkek , Mehmet Erkek , Mehmet Bora Aydın , Koray Gezer
Data center cooling accounts for a substantial fraction of facility energy consumption, with environmental pressures driving the transition from high-GWP refrigerants to sustainable alternatives. However, rigorous experimental comparisons of next-generation refrigerants under realistic operational conditions remain limited, and existing benchmarking protocols often fail to account for ambient variability across test conditions. This study addresses these gaps by conducting a comprehensive experimental evaluation of an in-rack air-conditioning unit, comparing the conventional refrigerant R410A with the low-GWP alternative R454B (GWP = 466) across 24 tests spanning varied server loads and thermal conditions. The methodology integrates a transparent steady-state detection algorithm for time-series measurement processing, normalized Energy Efficiency Ratio (EER) calculations at fixed reference conditions to enable equitable cross-test comparison, and sensitivity analyses quantifying the influence of ambient and evaporator-side temperatures on system performance. Cooling capacity, raw and normalized EER, facility-level Power Usage Effectiveness (PUE), and Total Equivalent Warming Impact (TEWI) were derived for each refrigerant. Results demonstrate that R454B exhibits load-dependent performance advantages: under high-load conditions (9 kW), R454B achieved 38 % higher EER (∼5.8 vs. ∼4.2) and superior cooling capacity (13 kW vs. 9.5 kW median) compared to R410A, with reduced operational variability. However, under supply-air matched baseline conditions (16–20 °C), both refrigerants exhibited equivalent performance, confirming that R454B's efficiency gains emerge primarily under elevated thermal stress and higher refrigerant flow rates. PUE analysis showed equivalent facility-level efficiency, enabling R454B as a direct drop-in replacement. TEWI analysis revealed that indirect emissions dominate climate impact (>90 %), establishing operational efficiency optimization as the primary environmental lever, with refrigerant selection providing secondary benefits through GWP reduction. These findings support the adoption of R454B in high-load data center environments, while the transparent methodological framework provides a reproducible benchmark for condition-aware refrigerant evaluation in mission-critical cooling systems.
数据中心冷却占设施能源消耗的很大一部分，环境压力推动了从高gwp制冷剂向可持续替代品的转变。然而，在实际操作条件下对下一代制冷剂进行严格的实验比较仍然有限，现有的基准测试协议往往无法考虑测试条件下的环境变化。本研究通过对机架式空调机组进行全面的实验评估，将常规制冷剂R410A与低GWP替代R454B （GWP = 466）进行了24次测试，涵盖了不同的服务器负载和热条件，从而解决了这些差距。该方法集成了用于时间序列测量处理的透明稳态检测算法，固定参考条件下的归一化能效比（EER）计算，以实现公平的交叉测试比较，以及量化环境温度和蒸发器侧温度对系统性能影响的敏感性分析。每种制冷剂的制冷量、原始和标准化EER、设施级功率使用效率（PUE）和总等效变暖影响（TEWI）均得到了推导。结果表明，R454B具有负载相关的性能优势：与R410A相比，在高负载条件下（9 kW）， R454B的EER比R410A高38% (~ 5.8 vs. ~ 4.2)，冷却能力更强（13 kW vs. 9.5 kW中值），同时降低了运行变异性。然而，在送风匹配的基线条件下（16-20°C），两种制冷剂表现出相同的性能，这证实了R454B的效率提高主要是在更高的热应力和更高的制冷剂流量下实现的。PUE分析显示，R454B具有相同的设施级效率，可以直接替代R454B。TEWI分析显示，间接排放主导了气候影响（> 90%），将运行效率优化作为主要的环境杠杆，制冷剂选择通过降低全球升温潜能值提供次要效益。这些发现支持在高负载数据中心环境中采用R454B，而透明的方法框架为关键任务冷却系统的状态感知制冷剂评估提供了可重复的基准。
{"title":"Experimental performance characterization of R-454B and R-410A in data center server rack mount cooling unit: Energy efficiency and environmental impact assessment","authors":"Türkan Üçok Erkek , Mehmet Erkek , Mehmet Bora Aydın , Koray Gezer","doi":"10.1016/j.ijrefrig.2025.12.007","DOIUrl":"10.1016/j.ijrefrig.2025.12.007","url":null,"abstract":"<div><div>Data center cooling accounts for a substantial fraction of facility energy consumption, with environmental pressures driving the transition from high-GWP refrigerants to sustainable alternatives. However, rigorous experimental comparisons of next-generation refrigerants under realistic operational conditions remain limited, and existing benchmarking protocols often fail to account for ambient variability across test conditions. This study addresses these gaps by conducting a comprehensive experimental evaluation of an in-rack air-conditioning unit, comparing the conventional refrigerant R410A with the low-GWP alternative R454B (GWP = 466) across 24 tests spanning varied server loads and thermal conditions. The methodology integrates a transparent steady-state detection algorithm for time-series measurement processing, normalized Energy Efficiency Ratio (EER) calculations at fixed reference conditions to enable equitable cross-test comparison, and sensitivity analyses quantifying the influence of ambient and evaporator-side temperatures on system performance. Cooling capacity, raw and normalized EER, facility-level Power Usage Effectiveness (PUE), and Total Equivalent Warming Impact (TEWI) were derived for each refrigerant. Results demonstrate that R454B exhibits load-dependent performance advantages: under high-load conditions (9 kW), R454B achieved 38 % higher EER (∼5.8 vs. ∼4.2) and superior cooling capacity (13 kW vs. 9.5 kW median) compared to R410A, with reduced operational variability. However, under supply-air matched baseline conditions (16–20 °C), both refrigerants exhibited equivalent performance, confirming that R454B's efficiency gains emerge primarily under elevated thermal stress and higher refrigerant flow rates. PUE analysis showed equivalent facility-level efficiency, enabling R454B as a direct drop-in replacement. TEWI analysis revealed that indirect emissions dominate climate impact (>90 %), establishing operational efficiency optimization as the primary environmental lever, with refrigerant selection providing secondary benefits through GWP reduction. These findings support the adoption of R454B in high-load data center environments, while the transparent methodological framework provides a reproducible benchmark for condition-aware refrigerant evaluation in mission-critical cooling systems.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 469-481"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836495","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 : 2026-02-01Epub Date: 2025-11-17DOI: 10.1016/j.ijrefrig.2025.10.028
Jakub Bodys , Michal Palacz , Michal Haida , Francesco Fabris , Antonio Rossetti , Jacek Smolka
The design of small-scale CO2 ejectors with throat diameters below 1 mm for mobile CO2 refrigeration units is demanding particularly when prototypes are required in limited quantities for pilot deployment. In this study, a numerical analysis was performed to evaluate design constraints, focusing on six key dimensions of the motive nozzle and mixing section. Simulations were conducted at motive conditions of 86 bar and 35∘ C and two suction nozzle conditions representative of low-temperature (LT) and medium-temperature (MT) evaporator outlets. The optimized geometry achieved efficiencies of approximately 20 % at pressure lifts of 4-5 bar, fulfilling the cooling power requirements under rated conditions (ambient 30∘ C). Experimental tests on a dedicated lab-scale test rig validated the design and provided insight into manufacturing tolerances and general performance characteristics. Ejectors demonstrated mass entrainment ratios between 0.45 and 0.50 at the design point (86 bar, 35∘ C motive; -21∘ C LT and -10∘ C MT evaporation). Flow stability varied between configurations: the MT ejector exhibited higher stability, whereas the LT ejector–despite more fluctuation–achieved higher efficiency ( ∼ 26 %). Manufacturing quality was assessed using numerical sensitivity analysis, revealing that deviations in tolerance and surface roughness could lead to reductions of up to 9 % in motive and suction nozzle mass flow rates. These novel findings underscore the critical importance of precision machining for scaled-down CO2 ejector components and demonstrate the feasibility of integrating such systems into compact mobile refrigeration applications.
{"title":"Numerical and experimental assessment of the CO2 ejector for a small-scale refrigeration system for mobile/automotive applications","authors":"Jakub Bodys , Michal Palacz , Michal Haida , Francesco Fabris , Antonio Rossetti , Jacek Smolka","doi":"10.1016/j.ijrefrig.2025.10.028","DOIUrl":"10.1016/j.ijrefrig.2025.10.028","url":null,"abstract":"<div><div>The design of small-scale CO<sub>2</sub> ejectors with throat diameters below 1 mm for mobile CO<sub>2</sub> refrigeration units is demanding particularly when prototypes are required in limited quantities for pilot deployment. In this study, a numerical analysis was performed to evaluate design constraints, focusing on six key dimensions of the motive nozzle and mixing section. Simulations were conducted at motive conditions of 86 bar and 35<sup>∘</sup> C and two suction nozzle conditions representative of low-temperature (LT) and medium-temperature (MT) evaporator outlets. The optimized geometry achieved efficiencies of approximately 20 % at pressure lifts of 4-5 bar, fulfilling the cooling power requirements under rated conditions (ambient 30<sup>∘</sup> C). Experimental tests on a dedicated lab-scale test rig validated the design and provided insight into manufacturing tolerances and general performance characteristics. Ejectors demonstrated mass entrainment ratios between 0.45 and 0.50 at the design point (86 bar, 35<sup>∘</sup> C motive; -21<sup>∘</sup> C LT and -10<sup>∘</sup> C MT evaporation). Flow stability varied between configurations: the MT ejector exhibited higher stability, whereas the LT ejector–despite more fluctuation–achieved higher efficiency ( ∼ 26 %). Manufacturing quality was assessed using numerical sensitivity analysis, revealing that deviations in tolerance and surface roughness could lead to reductions of up to 9 % in motive and suction nozzle mass flow rates. These novel findings underscore the critical importance of precision machining for scaled-down CO<sub>2</sub> ejector components and demonstrate the feasibility of integrating such systems into compact mobile refrigeration applications.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 93-101"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682237","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 : 2026-02-01Epub Date: 2025-12-01DOI: 10.1016/j.ijrefrig.2025.11.032
N.U. Qadir , H. Bahaidarah
None of the adsorption equilibrium models for both conventional and non-conventional adsorbent materials reported so far in literature represent a close-to-exact correlation with the equilibrium isotherm measured via experimentation. This not only affects the accuracy of performance simulation of adsorption refrigeration system negatively but also the subsequent assessment of feasibility of the system in commercial applications. A dual pressure-temperature interpolation model resulting in a close-to-exact degree of correlation with experimentally acquired equilibrium isotherm greater than all the previously reported models has been proposed which is applicable to both conventional and non-conventional adsorbent materials. Based on the proposed experimentally validated model, the numerical performance prediction of an integrated absorption-adsorption refrigeration system with a hydrostable Metal Organic Framework, MIL-101(Cr), as adsorbent and water as refrigerant has been presented. In addition, a completely novel model to accurately predict the transient dynamics of mass recovery cycle has further been developed. Results demonstrate that the refrigeration system based on the proposed adsorption equilibrium model for the silica-gel/water pair is characterized by a coefficient of performance numerically predicted to be 152 % and 115 % greater than the corresponding system based on the MIL-101(Cr)/water pair in the stand-alone and integrated configurations respectively. The outcome of the study suggests that MOFs can turn out to be outstanding potential adsorbents for adsorption refrigeration systems provided the intrinsic deficiency of lower thermal conductivity can be resolved without compromising their inherent water uptake.
{"title":"A novel dual pressure-temperature interpolation model for mathematically exact adsorption equilibrium for performance simulation of integrated absorption-adsorption refrigeration system using the MIL-101(Cr)/water pair","authors":"N.U. Qadir , H. Bahaidarah","doi":"10.1016/j.ijrefrig.2025.11.032","DOIUrl":"10.1016/j.ijrefrig.2025.11.032","url":null,"abstract":"<div><div>None of the adsorption equilibrium models for both conventional and non-conventional adsorbent materials reported so far in literature represent a close-to-exact correlation with the equilibrium isotherm measured <em>via</em> experimentation. This not only affects the accuracy of performance simulation of adsorption refrigeration system negatively but also the subsequent assessment of feasibility of the system in commercial applications. A dual pressure-temperature interpolation model resulting in a close-to-exact degree of correlation with experimentally acquired equilibrium isotherm greater than all the previously reported models has been proposed which is applicable to both conventional and non-conventional adsorbent materials. Based on the proposed experimentally validated model, the numerical performance prediction of an integrated absorption-adsorption refrigeration system with a hydrostable Metal Organic Framework, MIL-101(Cr), as adsorbent and water as refrigerant has been presented. In addition, a completely novel model to accurately predict the transient dynamics of mass recovery cycle has further been developed. Results demonstrate that the refrigeration system based on the proposed adsorption equilibrium model for the silica-gel/water pair is characterized by a coefficient of performance numerically predicted to be 152 % and 115 % greater than the corresponding system based on the MIL-101(Cr)/water pair in the stand-alone and integrated configurations respectively. The outcome of the study suggests that MOFs can turn out to be outstanding potential adsorbents for adsorption refrigeration systems provided the intrinsic deficiency of lower thermal conductivity can be resolved without compromising their inherent water uptake.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 230-252"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682353","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 : 2026-02-01Epub Date: 2025-12-01DOI: 10.1016/j.ijrefrig.2025.11.031
Ying Tan, Xiayao Peng, Yuanyuan Duan, Zhen Yang, Qiang Song
Trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) and trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), along with their mixtures, represent a new generation of low-global-warming-potential working fluids with significant promise. This study aimed to measure the gaseous speed of sound using Cylindrical Fixed-Path Interferometry. The core component, the cylindrical resonator, had its length and radius precisely calibrated using argon. Combining the calibrated dimensions with the measured resonance frequency, we determined the speed of sound of R1234ze(E) in the temperature range of 313.15 K∼363.15 K and the pressure range of 50 kPa∼1030 kPa with a relative extended uncertainty (k = 2) of 0.029 %. Our comparison with the available speed of sound data revealed that the multiparameter equation of state for R1234ze(E) exhibits a systematic positive bias in the pressure range of 0∼1000 kPa for speed of sound calculation. From the measured speed of sound of R1234ze(E), we calculated its ideal-gas heat capacity and acoustic second virial coefficients. These coefficients were subsequently regressed to obtain molecular parameters for the hard-core square-well molecular potential model, enabling the derivation of the density second virial coefficients. Furthermore, the speed of sound of R1234ze(E)+R1336mzz(E) binary mixture was measured in the temperature range of 313.15 K∼363.15 K and the pressure range of 59 kPa∼800 kPa with a relative extended uncertainty (k = 2) of 0.064 %. By integrating the mixture speed of sound with the pure component properties, we determined the acoustic second virial coefficients of R1234ze(E)+R1336mzz(E). These results provide essential data support for developing a specialized thermodynamic model for the mixture.
{"title":"Measurement of gaseous speed of sound for R1234ze(E) and R1234ze(E)+R1336mzz(E) binary mixture using a cylindrical resonator","authors":"Ying Tan, Xiayao Peng, Yuanyuan Duan, Zhen Yang, Qiang Song","doi":"10.1016/j.ijrefrig.2025.11.031","DOIUrl":"10.1016/j.ijrefrig.2025.11.031","url":null,"abstract":"<div><div><em>Trans</em>-1,3,3,3-tetrafluoropropene (R1234ze(E)) and <em>trans</em>-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), along with their mixtures, represent a new generation of low-global-warming-potential working fluids with significant promise. This study aimed to measure the gaseous speed of sound using Cylindrical Fixed-Path Interferometry. The core component, the cylindrical resonator, had its length and radius precisely calibrated using argon. Combining the calibrated dimensions with the measured resonance frequency, we determined the speed of sound of R1234ze(E) in the temperature range of 313.15 K∼363.15 K and the pressure range of 50 kPa∼1030 kPa with a relative extended uncertainty (<em>k</em> = 2) of 0.029 %. Our comparison with the available speed of sound data revealed that the multiparameter equation of state for R1234ze(E) exhibits a systematic positive bias in the pressure range of 0∼1000 kPa for speed of sound calculation. From the measured speed of sound of R1234ze(E), we calculated its ideal-gas heat capacity and acoustic second virial coefficients. These coefficients were subsequently regressed to obtain molecular parameters for the hard-core square-well molecular potential model, enabling the derivation of the density second virial coefficients. Furthermore, the speed of sound of R1234ze(E)+R1336mzz(E) binary mixture was measured in the temperature range of 313.15 K∼363.15 K and the pressure range of 59 kPa∼800 kPa with a relative extended uncertainty (<em>k</em> = 2) of 0.064 %. By integrating the mixture speed of sound with the pure component properties, we determined the acoustic second virial coefficients of R1234ze(E)+R1336mzz(E). These results provide essential data support for developing a specialized thermodynamic model for the mixture.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"182 ","pages":"Pages 217-229"},"PeriodicalIF":3.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682354","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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