Pub Date : 2026-01-13DOI: 10.1016/j.ijrefrig.2026.01.015
Chaoqi Wei, Jiapeng Liu, Dongxiao Liu
This article presents a new adaptive neural network control method designed for thermoelectric refrigeration systems. This approach leverages the capabilities of neural networks to address the uncertain nonlinear dynamics within the system. A self-learning mechanism is developed to enable the online training of the neural network’s weights, as well as the center points and widths of the basis functions, resulting in improved control performance. Additionally, an adaptive law based on a projection algorithm is introduced to prevent potential parameter drift and singularities of the basis functions. The stability of the closed-loop system is analyzed using Lyapunov stability theory. To demonstrate the effectiveness of this proposed method, both simulation and experimental results are presented. Compared with traditional neural network control method, our control method reduces the maximum error by 29.4% and the set time by 39.3% in the experiment.
{"title":"Adaptive neural network temperature control for thermoelectric refrigeration systems using online self-learning mechanism","authors":"Chaoqi Wei, Jiapeng Liu, Dongxiao Liu","doi":"10.1016/j.ijrefrig.2026.01.015","DOIUrl":"10.1016/j.ijrefrig.2026.01.015","url":null,"abstract":"<div><div>This article presents a new adaptive neural network control method designed for thermoelectric refrigeration systems. This approach leverages the capabilities of neural networks to address the uncertain nonlinear dynamics within the system. A self-learning mechanism is developed to enable the online training of the neural network’s weights, as well as the center points and widths of the basis functions, resulting in improved control performance. Additionally, an adaptive law based on a projection algorithm is introduced to prevent potential parameter drift and singularities of the basis functions. The stability of the closed-loop system is analyzed using Lyapunov stability theory. To demonstrate the effectiveness of this proposed method, both simulation and experimental results are presented. Compared with traditional neural network control method, our control method reduces the maximum error by 29.4% and the set time by 39.3% in the experiment.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 379-390"},"PeriodicalIF":3.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023289","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 : 2026-01-13DOI: 10.1016/j.ijrefrig.2026.01.018
Edgardo J. Tabilo , Roberto Lemus-Mondaca , Juan I. Jaime , Nelson O. Moraga
This study develops a three-dimensional conjugate numerical model to predict the unsteady solidification of blueberry pulp in a container cooled by buoyancy-driven turbulent natural convection within a domestic freezer. The finite volume method, combined with the SIMPLERnP algorithm, simultaneously solves airflow turbulence, heat conduction, natural convection within the pulp, and the liquid-to-solid phase change. Results demonstrate that reducing food thickness and optimizing placement enhance heat transfer, shorten freezing time, and lower energy consumption. Specifically, thinner samples (aspect ratio 0.125) achieved a 200% increase in heat flux compared to the baseline, while dividing the food into two batches placed at the corners increased heat flux by 223%, reducing freezing time by nearly half. The average drip loss decreased from ∼17% in thicker samples to ∼15% in thinner ones, and the pectin content increased from 0.90 to 0.99 g/kg, indicating improved texture and quality. The model also captured differences in airflow, predicting counter-rotating vortices and boundary-layer thinning, which reinforced convection and accelerated cooling. It accurately reproduces freezing curves, isotherms, velocity fields, and Nusselt numbers, confirming its reliability. Overall, the model underscores the significant impact of food geometry and placement in the freezer on performance, offering a robust tool to optimize energy efficiency and product quality in frozen fruit pulps.
{"title":"Conjugate heat transfer model of non-Newtonian fruit pulp freezing by turbulent convective air flow in a refrigeration cabinet","authors":"Edgardo J. Tabilo , Roberto Lemus-Mondaca , Juan I. Jaime , Nelson O. Moraga","doi":"10.1016/j.ijrefrig.2026.01.018","DOIUrl":"10.1016/j.ijrefrig.2026.01.018","url":null,"abstract":"<div><div>This study develops a three-dimensional conjugate numerical model to predict the unsteady solidification of blueberry pulp in a container cooled by buoyancy-driven turbulent natural convection within a domestic freezer. The finite volume method, combined with the SIMPLERnP algorithm, simultaneously solves airflow turbulence, heat conduction, natural convection within the pulp, and the liquid-to-solid phase change. Results demonstrate that reducing food thickness and optimizing placement enhance heat transfer, shorten freezing time, and lower energy consumption. Specifically, thinner samples (aspect ratio 0.125) achieved a 200% increase in heat flux compared to the baseline, while dividing the food into two batches placed at the corners increased heat flux by 223%, reducing freezing time by nearly half. The average drip loss decreased from ∼17% in thicker samples to ∼15% in thinner ones, and the pectin content increased from 0.90 to 0.99 g/kg, indicating improved texture and quality. The model also captured differences in airflow, predicting counter-rotating vortices and boundary-layer thinning, which reinforced convection and accelerated cooling. It accurately reproduces freezing curves, isotherms, velocity fields, and Nusselt numbers, confirming its reliability. Overall, the model underscores the significant impact of food geometry and placement in the freezer on performance, offering a robust tool to optimize energy efficiency and product quality in frozen fruit pulps.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 350-363"},"PeriodicalIF":3.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979353","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 : 2026-01-13DOI: 10.1016/j.ijrefrig.2026.01.009
Hongmin Liu , Changlei Ke , Kongrong Li , Zhaozhang Hao , Jiansheng Zuo , Xiaohua Zhang , Nan Peng , Lianyou Xiong , Liqiang Liu
Improving the efficiency of hydrogen liquefaction cycles is essential for reducing costs and promoting clean hydrogen energy. As the core refrigeration component, the helium turbo-expander (HTE) experiences significant efficiency losses within the impeller passage. However, current design methodologies often involve complex manual iterations that can limit systematic 3D optimization. This paper explores a parametric approach for 3D impeller design based on cylindrical projection (Cylindrical Projection based Parametric Impeller Design). This method allows for the definition of blade profiles at the hub, mid span, and shroud sections using projection parameters (, ), facilitating smooth geometric transitions. To evaluate the approach, a final stage HTE impeller for a 5 TPD hydrogen liquefier was analyzed. Numerical simulations indicate that adjusting the flow path geometry using these parameters can lead to significant performance variations: Case C1 showed a calculated 16.58% reduction in helium mass flow at a constant refrigeration power of 30,551.4 W, while Case C2 yielded a predicted isentropic efficiency of 92.33% (a 2.81% absolute increase) with a 3.5% reduction in required inlet pressure. Flow field analysis using the vortex identification method suggests that these improvements are associated with the suppression of high loss vortex structures. Specifically, the concave blade profiles appear to mitigate transverse pressure differences, reducing the intensity of passage vortices. These results demonstrate that the parametric projection method offers a useful alternative for the geometric optimization of cryogenic turbo-expander impellers.
{"title":"Optimization and flow field analysis of a helium turbo-expander impeller for a 5 TPD hydrogen liquefier using a cylindrical projection based parametric approach","authors":"Hongmin Liu , Changlei Ke , Kongrong Li , Zhaozhang Hao , Jiansheng Zuo , Xiaohua Zhang , Nan Peng , Lianyou Xiong , Liqiang Liu","doi":"10.1016/j.ijrefrig.2026.01.009","DOIUrl":"10.1016/j.ijrefrig.2026.01.009","url":null,"abstract":"<div><div>Improving the efficiency of hydrogen liquefaction cycles is essential for reducing costs and promoting clean hydrogen energy. As the core refrigeration component, the helium turbo-expander (HTE) experiences significant efficiency losses within the impeller passage. However, current design methodologies often involve complex manual iterations that can limit systematic 3D optimization. This paper explores a parametric approach for 3D impeller design based on cylindrical projection (Cylindrical Projection based Parametric Impeller Design). This method allows for the definition of blade profiles at the hub, mid span, and shroud sections using projection parameters (<span><math><msub><mi>T</mi><mi>u</mi></msub></math></span>, <span><math><msub><mi>T</mi><mi>r</mi></msub></math></span>), facilitating smooth geometric transitions. To evaluate the approach, a final stage HTE impeller for a 5 TPD hydrogen liquefier was analyzed. Numerical simulations indicate that adjusting the flow path geometry using these parameters can lead to significant performance variations: Case C1 showed a calculated 16.58% reduction in helium mass flow at a constant refrigeration power of 30,551.4 W, while Case C2 yielded a predicted isentropic efficiency of 92.33% (a 2.81% absolute increase) with a 3.5% reduction in required inlet pressure. Flow field analysis using the <span><math><mstyle><mi>Ω</mi></mstyle></math></span> vortex identification method suggests that these improvements are associated with the suppression of high loss vortex structures. Specifically, the concave blade profiles appear to mitigate transverse pressure differences, reducing the intensity of passage vortices. These results demonstrate that the parametric projection method offers a useful alternative for the geometric optimization of cryogenic turbo-expander impellers.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 336-349"},"PeriodicalIF":3.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979355","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 : 2026-01-11DOI: 10.1016/j.ijrefrig.2026.01.016
Ding Luo , Hengliang Zhang , Yi Qiu , Hao Chen , Yaohua Li , Junshuo Chen , Yangyong Liu , Xiaoye Sun , Guili Wang
Conventional two-stage thermoelectric coolers (TECs) generally employ identical continuous pulse current waveforms. In this study, we for the first time systematically investigate double-pulse current excitation with different waveform shapes under thermal shock. By analyzing the double-pulse waveform combinations, the amplitude and width of the second pulse, as well as the intervals between thermal shock and the first pulse (Δt1) and between double-pulses (Δt2), we reveal their governing effects on the transient subcooling performance of TECs, including the minimum cold end temperature (Tc,min), the maximum overshoot temperature (Tc,max), the cold-holding time (thold), and the recovery time (trec). The results show that the cold end waveform influences the transient response more strongly than the hot end, and triangular excitation effectively suppresses overshoot and accelerates recovery. Specifically, compared with the Square + Square case, the Triangle + Triangle case reduces Tc,max from 347.23 K to 325.31 K and shortens trec from 82.96 s to 75.47 s, while thold increases from 0.66 s to 0.84 s. Increasing the second pulse amplitude enhances cooling but intensifies Joule heating, and an excessively long second pulse width significantly degrades recovery. In addition, larger Δt2 promotes heat dissipation between pulses. For example, increasing Δt2 from 1 s to 3 s reduces Tc,max from 336.15 K to 316.05 K and shortens trec from 69.10 s to 63.50 s. These findings provide theoretical guidance for waveform design and parameter selection of two-stage TECs under thermal shock.
{"title":"Revealing dynamic characteristics of the two-stage thermoelectric cooler under double-pulse excitation","authors":"Ding Luo , Hengliang Zhang , Yi Qiu , Hao Chen , Yaohua Li , Junshuo Chen , Yangyong Liu , Xiaoye Sun , Guili Wang","doi":"10.1016/j.ijrefrig.2026.01.016","DOIUrl":"10.1016/j.ijrefrig.2026.01.016","url":null,"abstract":"<div><div>Conventional two-stage thermoelectric coolers (TECs) generally employ identical continuous pulse current waveforms. In this study, we for the first time systematically investigate double-pulse current excitation with different waveform shapes under thermal shock. By analyzing the double-pulse waveform combinations, the amplitude and width of the second pulse, as well as the intervals between thermal shock and the first pulse (Δ<em>t</em><sub>1</sub>) and between double-pulses (Δ<em>t</em><sub>2</sub>), we reveal their governing effects on the transient subcooling performance of TECs, including the minimum cold end temperature (<em>T</em><sub>c,min</sub>), the maximum overshoot temperature (<em>T</em><sub>c,max</sub>), the cold-holding time (<em>t</em><sub>hold</sub>), and the recovery time (<em>t</em><sub>rec</sub>). The results show that the cold end waveform influences the transient response more strongly than the hot end, and triangular excitation effectively suppresses overshoot and accelerates recovery. Specifically, compared with the Square + Square case, the Triangle + Triangle case reduces <em>T</em><sub>c,max</sub> from 347.23 K to 325.31 K and shortens <em>t</em><sub>rec</sub> from 82.96 s to 75.47 s, while <em>t</em><sub>hold</sub> increases from 0.66 s to 0.84 s. Increasing the second pulse amplitude enhances cooling but intensifies Joule heating, and an excessively long second pulse width significantly degrades recovery. In addition, larger Δ<em>t</em><sub>2</sub> promotes heat dissipation between pulses. For example, increasing Δ<em>t</em><sub>2</sub> from 1 s to 3 s reduces <em>T</em><sub>c,max</sub> from 336.15 K to 316.05 K and shortens <em>t</em><sub>rec</sub> from 69.10 s to 63.50 s. These findings provide theoretical guidance for waveform design and parameter selection of two-stage TECs under thermal shock.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 278-286"},"PeriodicalIF":3.8,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978886","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 : 2026-01-11DOI: 10.1016/j.ijrefrig.2026.01.010
Yicheng Zhu , Ceyi Wang , Zhewen Xiong , Aiguo Wei , Juan Huang , Fei Wang , Junming Li , Haishan Cao
Comprehensive analysis of the condenser-side thermal resistance in heat pump water heaters (HPWHs) offers valuable insights for improving system efficiency and reducing energy consumption. This study presents both experimental investigations on a prototype HPWH and a numerical analysis based on a thermal resistance network model. In the model, the total thermal resistance is decomposed into three components for separate calculation and analysis, namely the refrigerant-side condensation resistance, the thermal conduction resistance of the microchannels and the thermally conductive silicone grease as thermal interface materials, and the combined resistance of cylinder wall conduction and water-side convection. A quantitative analysis of each component was conducted, and the calculated total thermal resistance deviated by only 4.9 % from experimental measurements, demonstrating the accuracy of the proposed model. The results showed that the combined resistance of cylinder wall conduction and water-side convection contributed more than 60 % of the total resistance. Therefore, reducing the combined resistance should be a primary focus to enhance overall HPWH performance. This study establishes a quantitative basis for the optimization and design of next-generation, high-efficiency HPWH systems.
{"title":"Condenser-side thermal resistance in heat pump water heaters: Experimental investigation and quantitative decomposition","authors":"Yicheng Zhu , Ceyi Wang , Zhewen Xiong , Aiguo Wei , Juan Huang , Fei Wang , Junming Li , Haishan Cao","doi":"10.1016/j.ijrefrig.2026.01.010","DOIUrl":"10.1016/j.ijrefrig.2026.01.010","url":null,"abstract":"<div><div>Comprehensive analysis of the condenser-side thermal resistance in heat pump water heaters (HPWHs) offers valuable insights for improving system efficiency and reducing energy consumption. This study presents both experimental investigations on a prototype HPWH and a numerical analysis based on a thermal resistance network model. In the model, the total thermal resistance is decomposed into three components for separate calculation and analysis, namely the refrigerant-side condensation resistance, the thermal conduction resistance of the microchannels and the thermally conductive silicone grease as thermal interface materials, and the combined resistance of cylinder wall conduction and water-side convection. A quantitative analysis of each component was conducted, and the calculated total thermal resistance deviated by only 4.9 % from experimental measurements, demonstrating the accuracy of the proposed model. The results showed that the combined resistance of cylinder wall conduction and water-side convection contributed more than 60 % of the total resistance. Therefore, reducing the combined resistance should be a primary focus to enhance overall HPWH performance. This study establishes a quantitative basis for the optimization and design of next-generation, high-efficiency HPWH systems.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 315-325"},"PeriodicalIF":3.8,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978890","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 : 2026-01-10DOI: 10.1016/j.ijrefrig.2026.01.013
Baolin Guo , Lanfang Zheng , Xiaobin Li
To explore the combustion safety characteristics of environmentally friendly mixed refrigerants, this study systematically investigates the impact and mechanism of R1233zd(E) on the explosion behavior of R290 through a combination of experiments, spectral analysis, and density functional theory calculations. The results indicate that R1233zd(E) has a significant dual effect on the combustion process of R290: when the volume fraction ratio of R1233zd(E)/R290 is ≤ 0.2, it exhibits a slight promoting effect, with the pressure peak and maximum pressure rise rate increasing by 1.86% and 17.16%, respectively, the flame propagation speed increasing by 0.418 m/s, and the CH* peak time advancing by 8.33%. However, when the volume fraction exceeds 1.1, a significant inhibiting effect is observed. At a volume fraction of 1.6, the pressure peak and maximum pressure rise rate decrease by 56.08% and 82.97%, respectively, the time to reach the explosion pressure peak is extended by 155.54%, the flame propagation speed is only 17% of that of pure R290, and the peak times of OH* and H2O* are delayed by 446.15%. Furthermore, as the concentration of R1233zd(E) increases, the intensity peak times of key reactive radicals/molecules CH*, OH*, H2O* and O2* exhibit exponential growth, and when the volume fraction is ≤ 1.1, the transition process from CO to CO₂ is delayed. Simultaneously, theoretical calculations and flame-retardant radical spectra indicate that R1233zd(E) preferentially cleaves the CCl bond to generate chlorine radicals, which effectively capture reactive radicals, becoming the dominant factor in blocking chain reactions.
{"title":"Experimental and simulation analysis of the explosive behavior and free radical spectroscopic characteristics of R1233zd(E)/R290 mixed gas","authors":"Baolin Guo , Lanfang Zheng , Xiaobin Li","doi":"10.1016/j.ijrefrig.2026.01.013","DOIUrl":"10.1016/j.ijrefrig.2026.01.013","url":null,"abstract":"<div><div>To explore the combustion safety characteristics of environmentally friendly mixed refrigerants, this study systematically investigates the impact and mechanism of R1233zd(E) on the explosion behavior of R290 through a combination of experiments, spectral analysis, and density functional theory calculations. The results indicate that R1233zd(E) has a significant dual effect on the combustion process of R290: when the volume fraction ratio of R1233zd(E)/R290 is ≤ 0.2, it exhibits a slight promoting effect, with the pressure peak and maximum pressure rise rate increasing by 1.86% and 17.16%, respectively, the flame propagation speed increasing by 0.418 m/s, and the CH* peak time advancing by 8.33%. However, when the volume fraction exceeds 1.1, a significant inhibiting effect is observed. At a volume fraction of 1.6, the pressure peak and maximum pressure rise rate decrease by 56.08% and 82.97%, respectively, the time to reach the explosion pressure peak is extended by 155.54%, the flame propagation speed is only 17% of that of pure R290, and the peak times of OH* and H<sub>2</sub>O* are delayed by 446.15%. Furthermore, as the concentration of R1233zd(E) increases, the intensity peak times of key reactive radicals/molecules CH*, OH*, H<sub>2</sub>O* and O<sub>2</sub>* exhibit exponential growth, and when the volume fraction is ≤ 1.1, the transition process from CO to CO₂ is delayed. Simultaneously, theoretical calculations and flame-retardant radical spectra indicate that R1233zd(E) preferentially cleaves the C<img>Cl bond to generate chlorine radicals, which effectively capture reactive radicals, becoming the dominant factor in blocking chain reactions.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 306-314"},"PeriodicalIF":3.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978889","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 : 2026-01-10DOI: 10.1016/j.ijrefrig.2026.01.014
Xiuqin Zhang , Jian Lin , Xiaohang Chen
A direct ethanol fuel cell is the device to directly convert the chemical energy of the ethanol and oxygen into the electricity and heat. To improve the electrical power density and increase the energy conversion efficiency as much as possible, a three-heat-reservoir refrigeration cycle is coupled to the direct ethanol fuel cell, so that the waste heat of the fuel cell can be effectively utilized. The performances of the direct ethanol fuel cell and hybrid system are systemically assessed and compared.
The whole performance of the hybrid system is optimized. The maximum power densities of the hybrid system can attain, respectively, 0.20, 0.21, and 0.22 (Js-1cm-2), which are 1.41, 1.71, and 2.10 times those of the fuel cell, when the temperatures of the fuel cell are 328.15, 338.15, and 348.15 (K). The partial current densities, voltage output, and flow density of waste heat of the fuel cell, and coefficient of performance and cooling rate of the three-heat-reservoir cycle are determined at a given molar concentration of the inlet ethanol at the optimum power density, and consequently, the optimum selection criterion of the molar concentration of the inlet ethanol is obtained.
{"title":"Performance assessment and parametric optimum selection of the hybrid system consisting of a direct ethanol fuel cell and three-heat-reservoir cycle","authors":"Xiuqin Zhang , Jian Lin , Xiaohang Chen","doi":"10.1016/j.ijrefrig.2026.01.014","DOIUrl":"10.1016/j.ijrefrig.2026.01.014","url":null,"abstract":"<div><div>A direct ethanol fuel cell is the device to directly convert the chemical energy of the ethanol and oxygen into the electricity and heat. To improve the electrical power density and increase the energy conversion efficiency as much as possible, a three-heat-reservoir refrigeration cycle is coupled to the direct ethanol fuel cell, so that the waste heat of the fuel cell can be effectively utilized. The performances of the direct ethanol fuel cell and hybrid system are systemically assessed and compared.</div><div>The whole performance of the hybrid system is optimized. The maximum power densities of the hybrid system can attain, respectively, 0.20, 0.21, and 0.22 (Js<sup>-1</sup>cm<sup>-2</sup>), which are 1.41, 1.71, and 2.10 times those of the fuel cell, when the temperatures of the fuel cell are 328.15, 338.15, and 348.15 (K). The partial current densities, voltage output, and flow density of waste heat of the fuel cell, and coefficient of performance and cooling rate of the three-heat-reservoir cycle are determined at a given molar concentration of the inlet ethanol at the optimum power density, and consequently, the optimum selection criterion of the molar concentration of the inlet ethanol is obtained.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 391-401"},"PeriodicalIF":3.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023185","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}
Refrigerants are essential working fluids in refrigeration systems, and small amounts of lubricating oil are entrained during circulation. Therefore, investigating the thermodynamic properties of refrigerant/lubricant mixtures is critical. In this study, molecular models of isobutane (R600a) with three linear pentaerythritol esters (PECs), including pentaerythritol tetrabutyrate (PEC4), pentaerythritol tetrahexanoate (PEC6), and pentaerythritol tetraoctanoate (PEC8), were constructed, and thermodynamic properties of R600a/PECs mixtures were computed using the COSMO-RS model, with molecular geometries optimized via density functional theory. Results indicate that the electrostatic potential of R600a is uniformly distributed across its molecular surface, whereas negative electrostatic regions appear near oxygen atoms in PECs. The solubility of R600a in the three PECs follows the order PEC8 > PEC6 > PEC4. In mixtures of R600a with the three PECs, the activity coefficients, Henry’s constants, excess Gibbs free energies, and excess enthalpies follow the trend PEC4 > PEC6 > PEC8, whereas the excess entropy follows PEC8 > PEC6 > PEC4. Pressure–enthalpy–quality diagrams of R600a/PECs mixtures were further studied, and the critical vapor quality (), enthalpy ratio () and non-evaporated refrigerant quantity (NEQ) were analyzed. The , , and NEQ are influenced by the type of lubricant and its circulation fraction, lower refrigerant solubility and smaller lubricant circulation fractions lead to higher , closer to 1, and reduced NEQ. This study provides a comprehensive comparison of R600a/PECs mixtures, and the results provide guidance for optimizing refrigerant/lubricant formulations and offer a reliable theoretical basis for the selection and matching of refrigerants and lubricants.
{"title":"Study on the thermodynamic properties and evaporation performance of isobutane/linear pentaerythritol ester mixtures","authors":"Shuping Zhang, Zhao Yang, Hongxia He, Zhaoning Hou, Yanfeng Zhao, Lei Gao","doi":"10.1016/j.ijrefrig.2026.01.012","DOIUrl":"10.1016/j.ijrefrig.2026.01.012","url":null,"abstract":"<div><div>Refrigerants are essential working fluids in refrigeration systems, and small amounts of lubricating oil are entrained during circulation. Therefore, investigating the thermodynamic properties of refrigerant/lubricant mixtures is critical. In this study, molecular models of isobutane (R600a) with three linear pentaerythritol esters (PECs), including pentaerythritol tetrabutyrate (PEC4), pentaerythritol tetrahexanoate (PEC6), and pentaerythritol tetraoctanoate (PEC8), were constructed, and thermodynamic properties of R600a/PECs mixtures were computed using the COSMO-RS model, with molecular geometries optimized via density functional theory. Results indicate that the electrostatic potential of R600a is uniformly distributed across its molecular surface, whereas negative electrostatic regions appear near oxygen atoms in PECs. The solubility of R600a in the three PECs follows the order PEC8 > PEC6 > PEC4. In mixtures of R600a with the three PECs, the activity coefficients, Henry’s constants, excess Gibbs free energies, and excess enthalpies follow the trend PEC4 > PEC6 > PEC8, whereas the excess entropy follows PEC8 > PEC6 > PEC4. Pressure–enthalpy–quality diagrams of R600a/PECs mixtures were further studied, and the critical vapor quality (<span><math><msub><mi>X</mi><mrow><mi>c</mi><mi>r</mi></mrow></msub></math></span>), enthalpy ratio (<span><math><msub><mi>R</mi><mi>h</mi></msub></math></span>) and non-evaporated refrigerant quantity (NEQ) were analyzed. The <span><math><msub><mi>X</mi><mrow><mi>c</mi><mi>r</mi></mrow></msub></math></span>, <span><math><msub><mi>R</mi><mi>h</mi></msub></math></span>, and NEQ are influenced by the type of lubricant and its circulation fraction, lower refrigerant solubility and smaller lubricant circulation fractions lead to higher <span><math><msub><mi>X</mi><mrow><mi>c</mi><mi>r</mi></mrow></msub></math></span>, <span><math><msub><mi>R</mi><mi>h</mi></msub></math></span> closer to 1, and reduced NEQ. This study provides a comprehensive comparison of R600a/PECs mixtures, and the results provide guidance for optimizing refrigerant/lubricant formulations and offer a reliable theoretical basis for the selection and matching of refrigerants and lubricants.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"184 ","pages":"Pages 1-13"},"PeriodicalIF":3.8,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146037201","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 : 2026-01-08DOI: 10.1016/j.ijrefrig.2026.01.011
Vinay Pratap Singh Negi, Chennu Ranganayakulu
The environmental control system (ECS) of an aircraft manages pressure and temperature to establish a comfortable environment for passengers and crew, while ensuring efficient functioning of electronic equipment using a bleed/bleedless air cycle system (ACS). However, the adoption of ACS is limited by its low coefficient of performance (COP). Interest in low global warming potential (GWP) refrigerants for vapor compression refrigeration systems (VCRS) has increased, driven by regulations such as the Kigali Amendment to the Montreal Protocol and EU Regulation 517/2014, which promote environmental sustainability. This study incorporated both simulation and experimental approaches to evaluate the performance of the proposed VCRS-based ECS using the low-GWP refrigerant R1234yf. The experimental validation confirmed the precision of the VCRS-based ECS numerical simulation, showing that the variations in the cooling capacity and evaporator air-side temperature were ±15% and ±2%, respectively. The proposed VCRS-based ECS achieved a system cooling capacity of 30.27 kW and COP of 1.01 with the low-GWP refrigerant R1234yf during cruising. Independently, the VCRS cycle attained a COP of 12.58 at specific saturation pressures and temperatures in the evaporator and condenser. The study concluded that R1234yf demonstrated performance characteristics similar to those of R134a and had low GWP and total equivalent warming impact (TEWI), making it a suitable alternative to R134a in ECSs.
{"title":"A novel vapor compression based electrically-driven environmental control system (ECS) for a civil aircraft using low-GWP refrigerant R1234yf","authors":"Vinay Pratap Singh Negi, Chennu Ranganayakulu","doi":"10.1016/j.ijrefrig.2026.01.011","DOIUrl":"10.1016/j.ijrefrig.2026.01.011","url":null,"abstract":"<div><div>The environmental control system (ECS) of an aircraft manages pressure and temperature to establish a comfortable environment for passengers and crew, while ensuring efficient functioning of electronic equipment using a bleed/bleedless air cycle system (ACS). However, the adoption of ACS is limited by its low coefficient of performance (COP). Interest in low global warming potential (GWP) refrigerants for vapor compression refrigeration systems (VCRS) has increased, driven by regulations such as the Kigali Amendment to the Montreal Protocol and EU Regulation 517/2014, which promote environmental sustainability. This study incorporated both simulation and experimental approaches to evaluate the performance of the proposed VCRS-based ECS using the low-GWP refrigerant R1234yf. The experimental validation confirmed the precision of the VCRS-based ECS numerical simulation, showing that the variations in the cooling capacity and evaporator air-side temperature were ±15% and ±2%, respectively. The proposed VCRS-based ECS achieved a system cooling capacity of 30.27 kW and COP of 1.01 with the low-GWP refrigerant R1234yf during cruising. Independently, the VCRS cycle attained a COP of 12.58 at specific saturation pressures and temperatures in the evaporator and condenser. The study concluded that R1234yf demonstrated performance characteristics similar to those of R134a and had low GWP and total equivalent warming impact (TEWI), making it a suitable alternative to R134a in ECSs.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 364-378"},"PeriodicalIF":3.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979354","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 : 2026-01-08DOI: 10.1016/j.ijrefrig.2026.01.008
Antonio Rossetti, Francesco Fabris, Sergio Marinetti, Silvia Minetto
The global road transport refrigeration fleet serving the food supply chain is estimated at approximately 5.7 million vehicles. This sector is experiencing continuous growth, driven by evolving consumer habits such as the rise in e-commerce and the increasing incidence of short-distance deliveries. Sectoral emissions were estimated at approximately 50 Mt CO₂eq in 2021, with the majority attributable to diesel-powered traction systems. Approximately 20 % of these emissions originate from the energy consumption of refrigeration units. At the same time, the entire road transport sector is under increasing pressure to meet stringent environmental targets. Moreover, working fluids used in vapor compression cycles are undergoing regulatory scrutiny, with a primary focus on reducing greenhouse gas (GHG) emissions, while growing attention is being paid to other potential environmental and human health impacts. This study investigates high technology-readiness-level (TRL) solutions aimed at reducing the overall environmental footprint of road transport refrigeration. The solutions considered include improved thermal insulation of refrigerated boxes, the adoption of natural refrigerants, advanced control strategies under partial load conditions, vehicle electrification, and the integration of renewable energy sources. The potential effects of implementing these technologies across the European refrigerated fleet are numerically assessed in terms of primary energy consumption, carbon-equivalent emissions, and pollutant emissions. Results indicate that the adoption of these technologies could yield reductions of up to 28 % in annual primary energy consumption, up to 72 % in CO₂-equivalent emissions, and over 90 % in emissions of other air pollutants.
{"title":"The EU road refrigerated transport: current GHG footprint of transport refrigeration unit and projected impact of sustainable technologies","authors":"Antonio Rossetti, Francesco Fabris, Sergio Marinetti, Silvia Minetto","doi":"10.1016/j.ijrefrig.2026.01.008","DOIUrl":"10.1016/j.ijrefrig.2026.01.008","url":null,"abstract":"<div><div>The global road transport refrigeration fleet serving the food supply chain is estimated at approximately 5.7 million vehicles. This sector is experiencing continuous growth, driven by evolving consumer habits such as the rise in e-commerce and the increasing incidence of short-distance deliveries. Sectoral emissions were estimated at approximately 50 Mt CO₂eq in 2021, with the majority attributable to diesel-powered traction systems. Approximately 20 % of these emissions originate from the energy consumption of refrigeration units. At the same time, the entire road transport sector is under increasing pressure to meet stringent environmental targets. Moreover, working fluids used in vapor compression cycles are undergoing regulatory scrutiny, with a primary focus on reducing greenhouse gas (GHG) emissions, while growing attention is being paid to other potential environmental and human health impacts. This study investigates high technology-readiness-level (TRL) solutions aimed at reducing the overall environmental footprint of road transport refrigeration. The solutions considered include improved thermal insulation of refrigerated boxes, the adoption of natural refrigerants, advanced control strategies under partial load conditions, vehicle electrification, and the integration of renewable energy sources. The potential effects of implementing these technologies across the European refrigerated fleet are numerically assessed in terms of primary energy consumption, carbon-equivalent emissions, and pollutant emissions. Results indicate that the adoption of these technologies could yield reductions of up to 28 % in annual primary energy consumption, up to 72 % in CO₂-equivalent emissions, and over 90 % in emissions of other air pollutants.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"183 ","pages":"Pages 294-305"},"PeriodicalIF":3.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979356","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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