Pub Date : 2025-02-16DOI: 10.1016/j.ijrefrig.2025.02.017
R. Kiefe, J.S. Amaral
A critical challenge for magnetic refrigeration is designing shape-optimized refrigerants. When applying a magnetic field to the refrigerant, its magnetocaloric effect (MCE) heterogeneity is directly related to the demagnetizing field (a geometric phenomenon). Striking a balance between the total mass/volume of refrigerant, and its effective performance at a given temperature and applied magnetic field is a complex non-linear magnetostatics problem. We present a tool for estimating both the spatially-resolved and effective MCE for any refrigerant design, via the 3D finite element method - Finite Element Magnetocaloric Effect (FEMCE). FEMCE allows the user to input complex refrigerant shapes, together with the thermophysical properties of the material, to estimate and optimize its refrigerant performance for a given temperature and applied magnetic field change. The tool can be readily employed for both the conventional and demagnetizing-field induced MCE.
{"title":"FEMCE – A 3D finite element simulation tool for magnetic refrigerants","authors":"R. Kiefe, J.S. Amaral","doi":"10.1016/j.ijrefrig.2025.02.017","DOIUrl":"10.1016/j.ijrefrig.2025.02.017","url":null,"abstract":"<div><div>A critical challenge for magnetic refrigeration is designing shape-optimized refrigerants. When applying a magnetic field to the refrigerant, its magnetocaloric effect (MCE) heterogeneity is directly related to the demagnetizing field (a geometric phenomenon). Striking a balance between the total mass/volume of refrigerant, and its effective performance at a given temperature and applied magnetic field is a complex non-linear magnetostatics problem. We present a tool for estimating both the spatially-resolved and effective MCE for any refrigerant design, via the 3D finite element method - Finite Element Magnetocaloric Effect (FEMCE). FEMCE allows the user to input complex refrigerant shapes, together with the thermophysical properties of the material, to estimate and optimize its refrigerant performance for a given temperature and applied magnetic field change. The tool can be readily employed for both the conventional and demagnetizing-field induced MCE.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 180-184"},"PeriodicalIF":3.5,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465428","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 : 2025-02-13DOI: 10.1016/j.ijrefrig.2025.02.012
Lingeng Zou , Ye Liu , Jianlin Yu
The traditional transcritical CO2 two-stage compression refrigeration cycle (TTRC) has a great advantage in supermarket refrigeration applications. Currently, however, the performance of the TTRC still has the potential to be improved. In this paper, an ejector-enhanced transcritical two-stage compression CO2 cycle is presented for supermarket refrigeration application. Based on the basic TTRC with a subcooler, a flash tank, an ejector and are introduced. On the one hand, part of the expansion work can be recovered by the ejector. Moreover, the subcooler is employed to increase the subcooling degree of refrigerant entering the expansion valve, which could increase the evaporator's cooling capacity. The cycle performances of the cycles are theoretically studied by energy, exergy and carbon footprint evaluation. Meanwhile, the intermediate pressures of the two cycles are also optimized. Under optimum intermediate pressure, the energy analyses show that the coefficient of performance is improved by 9.6–11.0% and the volume cooling capacity is enhanced by 14.5%-18.4% with the modified cycle. Moreover, the exergy analysis indicates that the expansion valves account for 27.1% of the exergy destruction of the basic cycle, while it is just 7.51% for the modified cycle. The carbon footprint analysis shows that the modified system with CO2 refrigerant could reduce carbon emissions by 17.95% compared to the conventional refrigerant R404A. It shows the feasibility of using CO2 to replace R404A refrigerant in commercial supermarket refrigeration, and has significant eco-friendly benefits.
{"title":"Thermodynamic and environment analysis of a modified transcritical CO2 refrigeration cycle integrated with ejector and subcooler","authors":"Lingeng Zou , Ye Liu , Jianlin Yu","doi":"10.1016/j.ijrefrig.2025.02.012","DOIUrl":"10.1016/j.ijrefrig.2025.02.012","url":null,"abstract":"<div><div>The traditional transcritical CO<sub>2</sub> two-stage compression refrigeration cycle (TTRC) has a great advantage in supermarket refrigeration applications. Currently, however, the performance of the TTRC still has the potential to be improved. In this paper, an ejector-enhanced transcritical two-stage compression CO<sub>2</sub> cycle is presented for supermarket refrigeration application. Based on the basic TTRC with a subcooler, a flash tank, an ejector and are introduced. On the one hand, part of the expansion work can be recovered by the ejector. Moreover, the subcooler is employed to increase the subcooling degree of refrigerant entering the expansion valve, which could increase the evaporator's cooling capacity. The cycle performances of the cycles are theoretically studied by energy, exergy and carbon footprint evaluation. Meanwhile, the intermediate pressures of the two cycles are also optimized. Under optimum intermediate pressure, the energy analyses show that the coefficient of performance is improved by 9.6–11.0% and the volume cooling capacity is enhanced by 14.5%-18.4% with the modified cycle. Moreover, the exergy analysis indicates that the expansion valves account for 27.1% of the exergy destruction of the basic cycle, while it is just 7.51% for the modified cycle. The carbon footprint analysis shows that the modified system with CO<sub>2</sub> refrigerant could reduce carbon emissions by 17.95% compared to the conventional refrigerant R404A. It shows the feasibility of using CO<sub>2</sub> to replace R404A refrigerant in commercial supermarket refrigeration, and has significant eco-friendly benefits.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 123-138"},"PeriodicalIF":3.5,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445710","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 : 2025-02-13DOI: 10.1016/j.ijrefrig.2025.02.015
Jieyu Li, Xingxiang Xie, Leyang Dai, Lijie Xu
With increasing global energy demand, improving the efficiency of refrigeration systems and reducing their environmental impact is crucial, especially since refrigeration often accounts for a significant portion of energy consumption. Traditional Proportional-Integral-Derivative (PID) control methods struggle with the complex, nonlinear nature of refrigeration systems, resulting in slow response times and limited optimization capabilities. While metaheuristic algorithms can perform global searches, they often lack the real-time fine-tuning necessary for optimal dynamic control. This study introduces Dynamic Synergy Optimization (DSO), a novel framework that integrates metaheuristic algorithms with PID control. Unlike conventional methods that only turn PID parameters using metaheuristics, DSO combines the global optimization power of metaheuristics with the real-time adjustment capabilities of PID, providing effective global search and local refinement. The PID controller ensures quick adaptation and system stability. Experimental results show that the Harris Hawks Optimization algorithm integrated with PID control outperforms standard PID control with a 63.3 % reduction in response time, a 69.2 % decrease in stabilization time, and a 19.65 % enhancement in energy efficiency. The DSO strategy significantly enhances the dynamic response and stability of refrigeration systems, reduces hysteresis, and accelerates the attainment of steady-state operation.
{"title":"Dynamic synergy optimization (DSO): An integrated approach of metaheuristic algorithms and PID control for real-time stability enhancement in refrigeration systems","authors":"Jieyu Li, Xingxiang Xie, Leyang Dai, Lijie Xu","doi":"10.1016/j.ijrefrig.2025.02.015","DOIUrl":"10.1016/j.ijrefrig.2025.02.015","url":null,"abstract":"<div><div>With increasing global energy demand, improving the efficiency of refrigeration systems and reducing their environmental impact is crucial, especially since refrigeration often accounts for a significant portion of energy consumption. Traditional Proportional-Integral-Derivative (PID) control methods struggle with the complex, nonlinear nature of refrigeration systems, resulting in slow response times and limited optimization capabilities. While metaheuristic algorithms can perform global searches, they often lack the real-time fine-tuning necessary for optimal dynamic control. This study introduces Dynamic Synergy Optimization (DSO), a novel framework that integrates metaheuristic algorithms with PID control. Unlike conventional methods that only turn PID parameters using metaheuristics, DSO combines the global optimization power of metaheuristics with the real-time adjustment capabilities of PID, providing effective global search and local refinement. The PID controller ensures quick adaptation and system stability. Experimental results show that the Harris Hawks Optimization algorithm integrated with PID control outperforms standard PID control with a 63.3 % reduction in response time, a 69.2 % decrease in stabilization time, and a 19.65 % enhancement in energy efficiency. The DSO strategy significantly enhances the dynamic response and stability of refrigeration systems, reduces hysteresis, and accelerates the attainment of steady-state operation.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 100-110"},"PeriodicalIF":3.5,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438189","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}
The solution of integrating large-scale high-temperature heat pump (HTHP) with data center not only reduces carbon emissions but also enhances energy efficiency, aligning with dual-carbon goals. However, pressure ratios and environmentally friendly refrigerants limit the conventional HTHPs. Therefore, this paper proposes an improved transcritical CO2 HTHP steam system (CO2-NC) with dual-pressure gas coolers and expander. Detailed thermodynamic analysis, exergy analysis, and economic analysis are conducted to evaluate the cycle performance. Compared to the conventional CO2 cycle, the COP of CO2-NC is improved by 32.7 %, and the pressure ratio is reduced by 13.22 %, with a 110 °C saturated steam supply. With the superior thermal matching performance of dual-pressure gas coolers, the irreversible loss of gas coolers in CO2-NC is diminished by 75.89 %. The total pressure ratio of CO2-NC is less than 1/4 of that in the conventional cycles with HFC/HFO refrigerants, providing an advantage in large-scale HTHPs with centrifugal compressors. Exergy analysis highlights that the expander in the CO2-NC decreases irreversible losses in the expansion process by 81.27 %. CO2-NC with the least variation in COP and pressure ratio shows excellent adaptability to data center heat sources, and CO2-NC exhibits the least variation with changes in saturated steam temperature. Furthermore, the optimum compressor discharge pressure for CO2 HTHPs is analyzed. Economic analysis highlights the advantages of CO2-NC in operation and refrigerant costs with the constraints of high initial capital costs. This study emphasizes the potential of combining transcritical CO2 HTHP to fulfill data center cooling and industrial heating needs.
{"title":"Research of CO2 high temperature heat pump for industrial steam generation with data center heat source","authors":"Junbin Chen, Cong Guo , Chunyu Feng, Xiao Qu, Sicong Tan, Yuyan Jiang","doi":"10.1016/j.ijrefrig.2025.02.014","DOIUrl":"10.1016/j.ijrefrig.2025.02.014","url":null,"abstract":"<div><div>The solution of integrating large-scale high-temperature heat pump (HTHP) with data center not only reduces carbon emissions but also enhances energy efficiency, aligning with dual-carbon goals. However, pressure ratios and environmentally friendly refrigerants limit the conventional HTHPs. Therefore, this paper proposes an improved transcritical CO<sub>2</sub> HTHP steam system (CO<sub>2</sub>-NC) with dual-pressure gas coolers and expander. Detailed thermodynamic analysis, exergy analysis, and economic analysis are conducted to evaluate the cycle performance. Compared to the conventional CO<sub>2</sub> cycle, the COP of CO<sub>2</sub>-NC is improved by 32.7 %, and the pressure ratio is reduced by 13.22 %, with a 110 °C saturated steam supply. With the superior thermal matching performance of dual-pressure gas coolers, the irreversible loss of gas coolers in CO<sub>2</sub>-NC is diminished by 75.89 %. The total pressure ratio of CO<sub>2</sub>-NC is less than 1/4 of that in the conventional cycles with HFC/HFO refrigerants, providing an advantage in large-scale HTHPs with centrifugal compressors. Exergy analysis highlights that the expander in the CO<sub>2</sub>-NC decreases irreversible losses in the expansion process by 81.27 %. CO<sub>2</sub>-NC with the least variation in COP and pressure ratio shows excellent adaptability to data center heat sources, and CO<sub>2</sub>-NC exhibits the least variation with changes in saturated steam temperature. Furthermore, the optimum compressor discharge pressure for CO<sub>2</sub> HTHPs is analyzed. Economic analysis highlights the advantages of CO<sub>2</sub>-NC in operation and refrigerant costs with the constraints of high initial capital costs. This study emphasizes the potential of combining transcritical CO<sub>2</sub> HTHP to fulfill data center cooling and industrial heating needs.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 185-200"},"PeriodicalIF":3.5,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464623","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 : 2025-02-12DOI: 10.1016/j.ijrefrig.2025.02.008
Paweł Jakończuk, Kamil Śmierciew, Adam Dudar, Jerzy Gagan, Dariusz Butrymowicz
The performance of two-phase ejectors critically depends on the efficiency of motive nozzles, which govern the critical mass flow rate and overall system operation. However, accurately predicting nozzle performance under two-phase flow conditions remains challenging due to the complex interplay of thermodynamic and flow dynamics. This study addresses this issue by evaluating the performance coefficient of motive nozzles for three refrigerants: CO2, R600a, and R1234ze(E). Beyond ejector applications, understanding two-phase flow dynamics is essential for optimizing other key components, such as control valves and safety valves, which operate under similar conditions. Experiments conducted on a versatile test bench revealed significant differences in nozzle performance among the refrigerants. The performance coefficient ranged from 0.85 to 1.35 for CO2, 0.90 to 1.15 for R600a, and 0.92 to 1.22 for R1234ze(E). The Henry-Fauske model, used to predict critical mass flow, demonstrated an average deviation of 30 % for CO2, while deviations were much lower for R600a (9 %) and R1234ze(E) (4 %). The results highlight the sensitivity of the performance coefficient to the refrigerant thermodynamic properties, with CO2 exhibiting the most complex flow behavior due to its lower critical temperature and higher compressibility. This study provides quantitative insights into the performance of motive nozzles under two-phase flow and validates the applicability of simplified models for predicting critical flow rates. The findings contribute to optimizing ejector and valve design, emphasizing the need for further validation with additional refrigerants to enhance model universality.
{"title":"Experimental assessment of two-phase nozzle performance for low-GWP refrigerants","authors":"Paweł Jakończuk, Kamil Śmierciew, Adam Dudar, Jerzy Gagan, Dariusz Butrymowicz","doi":"10.1016/j.ijrefrig.2025.02.008","DOIUrl":"10.1016/j.ijrefrig.2025.02.008","url":null,"abstract":"<div><div>The performance of two-phase ejectors critically depends on the efficiency of motive nozzles, which govern the critical mass flow rate and overall system operation. However, accurately predicting nozzle performance under two-phase flow conditions remains challenging due to the complex interplay of thermodynamic and flow dynamics. This study addresses this issue by evaluating the performance coefficient of motive nozzles for three refrigerants: CO<sub>2</sub>, R600a, and R1234ze(E). Beyond ejector applications, understanding two-phase flow dynamics is essential for optimizing other key components, such as control valves and safety valves, which operate under similar conditions. Experiments conducted on a versatile test bench revealed significant differences in nozzle performance among the refrigerants. The performance coefficient ranged from 0.85 to 1.35 for CO<sub>2</sub>, 0.90 to 1.15 for R600a, and 0.92 to 1.22 for R1234ze(E). The Henry-Fauske model, used to predict critical mass flow, demonstrated an average deviation of 30 % for CO<sub>2</sub>, while deviations were much lower for R600a (9 %) and R1234ze(E) (4 %). The results highlight the sensitivity of the performance coefficient to the refrigerant thermodynamic properties, with CO<sub>2</sub> exhibiting the most complex flow behavior due to its lower critical temperature and higher compressibility. This study provides quantitative insights into the performance of motive nozzles under two-phase flow and validates the applicability of simplified models for predicting critical flow rates. The findings contribute to optimizing ejector and valve design, emphasizing the need for further validation with additional refrigerants to enhance model universality.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 111-122"},"PeriodicalIF":3.5,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445764","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 : 2025-02-12DOI: 10.1016/j.ijrefrig.2025.02.011
Zhen Tong , Peng Wang , Zekun Han , Wencheng Wang
Currently, most two-phase thermosyphon loop (TPTL) systems used in data centers feature a multi-evaporator design. The flow rate of the working fluid through each evaporator is one of the crucial factors affecting the cooling effect of the TPTL. Therefore, this paper conducts a comparative study on the flow distribution patterns of gravity- and pump-driven multi-evaporator TPTLs. The impacts of flow resistance and load distribution on each branch's flow distribution of working fluid are analyzed. It was found that the flow distributions of both gravity- and pump-driven TPTLs were influenced by load distribution. Under non-uniform load conditions, the flow rate tended to skew towards evaporators with higher loads. Additionally, the flow distribution of the gravity-driven TPTL was highly affected by individual branch flow resistance, which was markedly different from the pump-driven TPTL. Under uniform load conditions, the flow rate of the pump-driven TPTL was generally evenly distributed among the evaporators.
{"title":"Flow distribution characteristics of gravity- and pump-driven CO2 two-phase thermosyphon loops with three evaporators","authors":"Zhen Tong , Peng Wang , Zekun Han , Wencheng Wang","doi":"10.1016/j.ijrefrig.2025.02.011","DOIUrl":"10.1016/j.ijrefrig.2025.02.011","url":null,"abstract":"<div><div>Currently, most two-phase the<em>r</em>mosyphon loop (TPTL) systems used in data centers feature a multi-evaporator design. The flow rate of the working fluid through each evaporator is one of the crucial factors affecting the cooling effect of the TPTL. Therefore, this paper conducts a comparative study on the flow distribution patterns of gravity- and pump-driven multi-evaporator TPTLs. The impacts of flow resistance and load distribution on each branch's flow distribution of working fluid are analyzed. It was found that the flow distributions of both gravity- and pump-driven TPTLs were influenced by load distribution. Under non-uniform load conditions, the flow rate tended to skew towards evaporators with higher loads. Additionally, the flow distribution of the gravity-driven TPTL was highly affected by individual branch flow resistance, which was markedly different from the pump-driven TPTL. Under uniform load conditions, the flow rate of the pump-driven TPTL was generally evenly distributed among the evaporators.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 76-87"},"PeriodicalIF":3.5,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438190","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 : 2025-02-12DOI: 10.1016/j.ijrefrig.2025.02.010
Renan Luis Fragelli , Vicente Luiz Scalon , Luiz Eduardo de Angelo Sanchez
Alternatives to cutting fluids have been extensively researched in machining. While they provide lubrication and cooling for tools, they pose health risks, cause environmental damage, and increase manufacturing costs. Considering that many researchers worldwide have been focusing their efforts on new applications for nanofluids, the objective is to evaluate the application of nanorefrigerants alongside the Electrohydrodynamic Effect (EHD) in a similar device to an internally cooled toolholder in order to reduce or eliminate cutting fluids. R141b/Al2O3 nanorefrigerants with three different concentrations were prepared and subsequently characterized. A heating chamber similar to a toolholder was developed to circulate nanofluids, apply the EHD effect, and evaluate its efficacy in reducing cutting tool temperature. The nanorefrigerants remained stable for up to 48 h; their viscosities increased by 44–64%, depending on concentration. The thermal conductivity of the nanorefrigerant with the lowest concentration increased by 44%. The EHD effect showed positive results in all analyzed conditions, with an increase in the heat transfer coefficient (h) of up to 19%. However, higher nanoparticle concentrations resulted in a smaller increase in the h values. Based on the heat transfer coefficient, the internal cooling system proved viable for reducing or eliminating cutting fluids. The combination of nanorefrigerants and EHD Effect can enhance the internal cooling method, extending tool life.
{"title":"A sustainable cooling solution for machining: Internally cooled toolholder enhanced by nanorefrigerants and electrohydrodynamic effect","authors":"Renan Luis Fragelli , Vicente Luiz Scalon , Luiz Eduardo de Angelo Sanchez","doi":"10.1016/j.ijrefrig.2025.02.010","DOIUrl":"10.1016/j.ijrefrig.2025.02.010","url":null,"abstract":"<div><div>Alternatives to cutting fluids have been extensively researched in machining. While they provide lubrication and cooling for tools, they pose health risks, cause environmental damage, and increase manufacturing costs. Considering that many researchers worldwide have been focusing their efforts on new applications for nanofluids, the objective is to evaluate the application of nanorefrigerants alongside the Electrohydrodynamic Effect (EHD) in a similar device to an internally cooled toolholder in order to reduce or eliminate cutting fluids. R141b/Al<sub>2</sub>O<sub>3</sub> nanorefrigerants with three different concentrations were prepared and subsequently characterized. A heating chamber similar to a toolholder was developed to circulate nanofluids, apply the EHD effect, and evaluate its efficacy in reducing cutting tool temperature. The nanorefrigerants remained stable for up to 48 h; their viscosities increased by 44–64%, depending on concentration. The thermal conductivity of the nanorefrigerant with the lowest concentration increased by 44%. The EHD effect showed positive results in all analyzed conditions, with an increase in the heat transfer coefficient (h) of up to 19%. However, higher nanoparticle concentrations resulted in a smaller increase in the h values. Based on the heat transfer coefficient, the internal cooling system proved viable for reducing or eliminating cutting fluids. The combination of nanorefrigerants and EHD Effect can enhance the internal cooling method, extending tool life.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 88-99"},"PeriodicalIF":3.5,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438188","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 : 2025-02-11DOI: 10.1016/j.ijrefrig.2025.02.007
Joel Boeng , Joaquim Manoel Gonçalves
In recent years, the application of heat storage materials (HSMs), particularly phase change materials (PCMs), in heat exchangers and/or refrigerated compartments of household refrigerators has increased substantially. This growth has been primarily driven by the implementation of stringent energy efficiency enhancement policies. The present study first provides a theoretical analysis of the impact of integrating HSMs into refrigerated compartments and heat exchangers of a refrigerator. Specifically, it elucidates the mechanism by which an HSM decreases the difference between condensing and evaporating temperatures and examines the behavior of this attenuation as a function of the compressor run-time ratio and the heat transfer coefficients involved. Subsequently, the study experimentally investigates the effects of incorporating HSMs into natural-draft condensers of household refrigerators. Four distinct types of HSMs were attached to a natural-draft wire-and-tube condenser of an A++ European single-compartment refrigerator. The performance of the refrigerator, with and without HSMs, was assessed through standardized energy consumption tests conducted under varying system operating conditions. Energy savings of up to 7.4 % were achieved by attaching 700 g of a copolymer compound to the condenser. The findings reveal that optimal system performance is associated with specific compressor on-time and off-time periods, which are influenced by the condenser size, HSM attachment method, and material thermal capacity. Furthermore, energy savings were observed to be more pronounced at lower compressor run-time ratios and shorter compressor on-time intervals. These observations suggest that the application of HSMs in natural-draft condensers is not recommended for systems equipped with variable-speed compressors.
{"title":"Theoretical and experimental analysis of heat storage material integration in household refrigerators","authors":"Joel Boeng , Joaquim Manoel Gonçalves","doi":"10.1016/j.ijrefrig.2025.02.007","DOIUrl":"10.1016/j.ijrefrig.2025.02.007","url":null,"abstract":"<div><div>In recent years, the application of heat storage materials (HSMs), particularly phase change materials (PCMs), in heat exchangers and/or refrigerated compartments of household refrigerators has increased substantially. This growth has been primarily driven by the implementation of stringent energy efficiency enhancement policies. The present study first provides a theoretical analysis of the impact of integrating HSMs into refrigerated compartments and heat exchangers of a refrigerator. Specifically, it elucidates the mechanism by which an HSM decreases the difference between condensing and evaporating temperatures and examines the behavior of this attenuation as a function of the compressor run-time ratio and the heat transfer coefficients involved. Subsequently, the study experimentally investigates the effects of incorporating HSMs into natural-draft condensers of household refrigerators. Four distinct types of HSMs were attached to a natural-draft wire-and-tube condenser of an <em>A</em>++ European single-compartment refrigerator. The performance of the refrigerator, with and without HSMs, was assessed through standardized energy consumption tests conducted under varying system operating conditions. Energy savings of up to 7.4 % were achieved by attaching 700 g of a copolymer compound to the condenser. The findings reveal that optimal system performance is associated with specific compressor on-time and off-time periods, which are influenced by the condenser size, HSM attachment method, and material thermal capacity. Furthermore, energy savings were observed to be more pronounced at lower compressor run-time ratios and shorter compressor on-time intervals. These observations suggest that the application of HSMs in natural-draft condensers is not recommended for systems equipped with variable-speed compressors.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 153-166"},"PeriodicalIF":3.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454257","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 : 2025-02-08DOI: 10.1016/j.ijrefrig.2025.01.036
Alireza Zendehboudi
Transcritical CO2 heat pumps are commonly used for tap water heating in buildings; however, their performance is often limited in space heating applications. Low-GWP CO2-based mixtures can enhance subcritical operation and reduce irreversibility during transcritical processes. Promoting this technology requires a comprehensive understanding of its thermo-economic performance; yet, there is a lack of relevant studies. This paper develops thermodynamic models using energy, exergy, and exergoeconomic analyses to evaluate the performance of four CO2-binary mixtures (CO2/R41, CO2/R1234yf, CO2/R290, and CO2/R1270) in space heating heat pumps. These mixtures are compared against pure CO2 in two cycle configurations: with and without an internal heat exchanger (IHX). The evaluation is conducted in accordance with the EN 14511–2 standard across various heating temperatures. Results indicate that the CO2/R41 blend achieves significant COP improvements, exceeding pure CO2 by up to 17.1% at 30/35 ° and 8.3% at 47/55 °. CO2-based mixtures also significantly lower optimal discharge pressures, with reductions ranging from 24.4% for CO2/R41 to 52.9% for CO2/R1270. The inclusion of an IHX has a notable effect on COP, particularly for CO2/R41, where performance improves when the CO2 mass fraction exceeds 70% at lower temperatures. Exergy analysis demonstrates that the CO2/R41 mixture achieves the highest exergy efficiency up to and including a CO2 mass fraction of 80%, outperforming pure CO2 by up to 16.3%. Furthermore, CO2/R41 exhibits 16.3%–19.8% lower total exergy destruction cost rates compared to pure CO2, with significant cost reductions in the throttling valve (25.5%–42.5%). These findings highlight the potential of CO2/R41 as a highly effective and economically viable option for space heating heat pumps, offering superior performance and reduced operational costs compared to pure CO2 and other mixtures.
{"title":"Thermo-economic evaluation of low-GWP CO2-based zeotropic mixtures in space heating heat pumps with and without internal heat exchanger","authors":"Alireza Zendehboudi","doi":"10.1016/j.ijrefrig.2025.01.036","DOIUrl":"10.1016/j.ijrefrig.2025.01.036","url":null,"abstract":"<div><div>Transcritical CO<sub>2</sub> heat pumps are commonly used for tap water heating in buildings; however, their performance is often limited in space heating applications. Low-GWP CO<sub>2</sub>-based mixtures can enhance subcritical operation and reduce irreversibility during transcritical processes. Promoting this technology requires a comprehensive understanding of its thermo-economic performance; yet, there is a lack of relevant studies. This paper develops thermodynamic models using energy, exergy, and exergoeconomic analyses to evaluate the performance of four CO<sub>2</sub>-binary mixtures (CO<sub>2</sub>/R41, CO<sub>2</sub>/R1234yf, CO<sub>2</sub>/R290, and CO<sub>2</sub>/R1270) in space heating heat pumps. These mixtures are compared against pure CO<sub>2</sub> in two cycle configurations: with and without an internal heat exchanger (IHX). The evaluation is conducted in accordance with the EN 14511–2 standard across various heating temperatures. Results indicate that the CO<sub>2</sub>/R41 blend achieves significant COP improvements, exceeding pure CO<sub>2</sub> by up to 17.1% at 30/35 °<span><math><mi>C</mi></math></span> and 8.3% at 47/55 °<span><math><mi>C</mi></math></span>. CO<sub>2</sub>-based mixtures also significantly lower optimal discharge pressures, with reductions ranging from 24.4% for CO<sub>2</sub>/R41 to 52.9% for CO<sub>2</sub>/R1270. The inclusion of an IHX has a notable effect on COP, particularly for CO<sub>2</sub>/R41, where performance improves when the CO<sub>2</sub> mass fraction exceeds 70% at lower temperatures. Exergy analysis demonstrates that the CO<sub>2</sub>/R41 mixture achieves the highest exergy efficiency up to and including a CO<sub>2</sub> mass fraction of 80%, outperforming pure CO<sub>2</sub> by up to 16.3%. Furthermore, CO<sub>2</sub>/R41 exhibits 16.3%–19.8% lower total exergy destruction cost rates compared to pure CO<sub>2</sub>, with significant cost reductions in the throttling valve (25.5%–42.5%). These findings highlight the potential of CO<sub>2</sub>/R41 as a highly effective and economically viable option for space heating heat pumps, offering superior performance and reduced operational costs compared to pure CO<sub>2</sub> and other mixtures.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"173 ","pages":"Pages 1-17"},"PeriodicalIF":3.5,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394994","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 : 2025-02-07DOI: 10.1016/j.ijrefrig.2025.02.005
Xiaofei Wen , Tianyou Zhou , Chao Chen , Hongxing Li , Feng Zhou , Yunde Liu
By re-liquefying the evaporated gas in the BOG reliquefaction process, operational expenses are minimized, simultaneously advancing environmental sustainability and improving resource usage. Most current reliquefaction processes untilize a single precooling cycle, with limited research on multi-stage precooling configurations. This paper proposes a dual precooling cycle that utilizes propane and BOG itself as precooling agents, and reliquefies BOG using a nitrogen inverse Brayton cycle. The design focuses minimizing specific energy consumption (SEC) through simulation and optimization. Optimization results indicate that the BOG reliquefaction process achieves an SEC of 1.017 kWh/kgLNG and an exergy efficiency of 27.29 % respectively. More than 20 % improvement in SEC compared to other single precooling processes. Cost analyses show that the dual precooled BOG liquefaction process is economically sound. Ultimately, through an analysis of the system based on BOG components and temperature variations, the system was able to operate stably.
{"title":"Dual precooling enhanced nitrogen-expanded BOG reliquefaction process for LNG-fueled ships","authors":"Xiaofei Wen , Tianyou Zhou , Chao Chen , Hongxing Li , Feng Zhou , Yunde Liu","doi":"10.1016/j.ijrefrig.2025.02.005","DOIUrl":"10.1016/j.ijrefrig.2025.02.005","url":null,"abstract":"<div><div>By re-liquefying the evaporated gas in the BOG reliquefaction process, operational expenses are minimized, simultaneously advancing environmental sustainability and improving resource usage. Most current reliquefaction processes untilize a single precooling cycle, with limited research on multi-stage precooling configurations. This paper proposes a dual precooling cycle that utilizes propane and BOG itself as precooling agents, and reliquefies BOG using a nitrogen inverse Brayton cycle. The design focuses minimizing specific energy consumption (SEC) through simulation and optimization. Optimization results indicate that the BOG reliquefaction process achieves an SEC of 1.017 kWh/kg<sub>LNG</sub> and an exergy efficiency of 27.29 % respectively. More than 20 % improvement in SEC compared to other single precooling processes. Cost analyses show that the dual precooled BOG liquefaction process is economically sound. Ultimately, through an analysis of the system based on BOG components and temperature variations, the system was able to operate stably.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"172 ","pages":"Pages 284-294"},"PeriodicalIF":3.5,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394762","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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