Recently, the requirements for cold-chain logistics in air freight (CLAF) have appeared to grow steadily. However, such an issue has been discussed less in the relevant research. The main purpose of this research is to evaluate the CLAF's service quality. In this paper, a Perception-Expectation gap model based on the fuzzy Best-Worst Method (BWM) is proposed to evaluate the service quality of CLAF. A typical CLAF operator with its main shippers in Taiwan was then empirically investigated to validate the proposed model. The result shows that shippers are mostly concerned with the service qualities of Stable and multiple shipping spaces, Pricing reasonableness, and Perfect cargo delivery. Based on the results, theoretical and managerial implications are discussed. The results can provide practical information for air freight operators to make managerial policies to improve their cold-chain operational performances. Further, the proposed model can provide a theoretical reference regarding the service quality gap in practical applications.
{"title":"An assessment of service quality for cold-chain logistics in air freight: A Perception-Expectation gap model based on fuzzy Best-Worst Method","authors":"Show-Hui Huang , Jun-Wen Chen , Huynh Tan Nguyen , Wen-Kai Hsu","doi":"10.1016/j.ijrefrig.2024.11.028","DOIUrl":"10.1016/j.ijrefrig.2024.11.028","url":null,"abstract":"<div><div>Recently, the requirements for cold-chain logistics in air freight (CLAF) have appeared to grow steadily. However, such an issue has been discussed less in the relevant research. The main purpose of this research is to evaluate the CLAF's service quality. In this paper, a Perception-Expectation gap model based on the fuzzy Best-Worst Method (BWM) is proposed to evaluate the service quality of CLAF. A typical CLAF operator with its main shippers in Taiwan was then empirically investigated to validate the proposed model. The result shows that shippers are mostly concerned with the service qualities of <em>Stable and multiple shipping spaces, Pricing reasonableness</em>, and <em>Perfect cargo delivery</em>. Based on the results, theoretical and managerial implications are discussed. The results can provide practical information for air freight operators to make managerial policies to improve their cold-chain operational performances. Further, the proposed model can provide a theoretical reference regarding the service quality gap in practical applications.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 164-171"},"PeriodicalIF":3.5,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.ijrefrig.2024.11.026
Xinxin Liu , Shimai Guo , Yu Wang , Dingbiao Wang , Guanghui Wang , Hang Li
The scroll compressor is an essential part of the heat pump air conditioning system in electric vehicles, with its performance and efficiency having a significant impact on the vehicle's range. This paper employs a combination of experimental and numerical simulations (using the dynamic mesh method) to study the scroll compressor in electric vehicles, exploring the effects of rotational speed and pressure ratio on compressor performance. The results reveal a significantly uneven temperature distribution across the chambers, primarily due to tangential leakage, which results in elevated temperatures in the central areas of the chambers and reduced temperatures near the meshing points. As the rotational speed increases, both the mass flow rate and the isentropic efficiency of the scroll compressor rise, whereas the discharge temperature declines; notably, discharge temperature drops by an average of 1.6 % for 600 r·min-1 increase in rotational speed. For each unit increase in the pressure ratio, the discharge temperature increases by an average of 12.22 K, while the mass flow rate decreases by 7.95 %. The study also shows that the isentropic efficiency initially rises with increasing pressure ratio, reaching a maximum of 67.06 % before starting to decline. These findings provide valuable insights into the performance characteristics of scroll compressors and offer theoretical support for optimizing compressor efficiency in practical applications.
{"title":"CFD-based unsteady simulation and performance analysis of scroll compressor","authors":"Xinxin Liu , Shimai Guo , Yu Wang , Dingbiao Wang , Guanghui Wang , Hang Li","doi":"10.1016/j.ijrefrig.2024.11.026","DOIUrl":"10.1016/j.ijrefrig.2024.11.026","url":null,"abstract":"<div><div>The scroll compressor is an essential part of the heat pump air conditioning system in electric vehicles, with its performance and efficiency having a significant impact on the vehicle's range. This paper employs a combination of experimental and numerical simulations (using the dynamic mesh method) to study the scroll compressor in electric vehicles, exploring the effects of rotational speed and pressure ratio on compressor performance. The results reveal a significantly uneven temperature distribution across the chambers, primarily due to tangential leakage, which results in elevated temperatures in the central areas of the chambers and reduced temperatures near the meshing points. As the rotational speed increases, both the mass flow rate and the isentropic efficiency of the scroll compressor rise, whereas the discharge temperature declines; notably, discharge temperature drops by an average of 1.6 % for 600 r·min<sup>-1</sup> increase in rotational speed. For each unit increase in the pressure ratio, the discharge temperature increases by an average of 12.22 K, while the mass flow rate decreases by 7.95 %. The study also shows that the isentropic efficiency initially rises with increasing pressure ratio, reaching a maximum of 67.06 % before starting to decline. These findings provide valuable insights into the performance characteristics of scroll compressors and offer theoretical support for optimizing compressor efficiency in practical applications.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 150-163"},"PeriodicalIF":3.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.ijrefrig.2024.11.025
Shi Shangguan , Lei Wang , Peijie Sun , Bin Wang , Bowen Liu , Yanzhong Li
In most practical occasion, frost is formed on cold surface which is cooled from the ambient temperature. Although the initial cooling stage may account for a small proportion in the whole frosting process, the effects of the initial cooling on frosting characteristics could not be overlooked. In this paper, a semi-empirical model of cryogenic frosting involving the initial cooling process under forced convection is established by employing frost properties correlations and heat and mass balance analysis. The frost thickness calculated by the proposed semi-empirical model showed good agreement with experimental data within a maximum error of 15 %. Within the constraints of correlation validity, this model is applicable to conditions where ambient temperatures range from 10 °C to 30 °C, air flow Reynolds numbers span from 7 × 104 to 1.5 × 105, air humidity varies between 3.5 g/kg and 18 g/kg, and initial cooling durations extend from 15 min to 40 min, and the final wall temperature is decreased to about 80K. The results indicate that frost thickness increases with rising ambient temperature, air humidity, and airflow velocity. Notably, higher rates of frost growth are observed during the initial cooling under conditions of elevated air humidity or increased airflow velocity. The trend in frost mass closely mirrors that of frost thickness, however, a more pronounced increase in frost mass occurs with increasing ambient temperature. Furthermore, extending the duration of initial cooling could accelerate the frost growth rate and cause a higher frost surface temperature.
{"title":"A semi-empirical model of frost formation on a cryogenic surface cooled from ambient temperature under forced convection condition","authors":"Shi Shangguan , Lei Wang , Peijie Sun , Bin Wang , Bowen Liu , Yanzhong Li","doi":"10.1016/j.ijrefrig.2024.11.025","DOIUrl":"10.1016/j.ijrefrig.2024.11.025","url":null,"abstract":"<div><div>In most practical occasion, frost is formed on cold surface which is cooled from the ambient temperature. Although the initial cooling stage may account for a small proportion in the whole frosting process, the effects of the initial cooling on frosting characteristics could not be overlooked. In this paper, a semi-empirical model of cryogenic frosting involving the initial cooling process under forced convection is established by employing frost properties correlations and heat and mass balance analysis. The frost thickness calculated by the proposed semi-empirical model showed good agreement with experimental data within a maximum error of 15 %. Within the constraints of correlation validity, this model is applicable to conditions where ambient temperatures range from 10 °C to 30 °C, air flow Reynolds numbers span from 7 × 10<sup>4</sup> to 1.5 × 10<sup>5</sup>, air humidity varies between 3.5 g/kg and 18 g/kg, and initial cooling durations extend from 15 min to 40 min, and the final wall temperature is decreased to about 80K. The results indicate that frost thickness increases with rising ambient temperature, air humidity, and airflow velocity. Notably, higher rates of frost growth are observed during the initial cooling under conditions of elevated air humidity or increased airflow velocity. The trend in frost mass closely mirrors that of frost thickness, however, a more pronounced increase in frost mass occurs with increasing ambient temperature. Furthermore, extending the duration of initial cooling could accelerate the frost growth rate and cause a higher frost surface temperature.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 124-134"},"PeriodicalIF":3.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.ijrefrig.2024.11.023
Tuany Gabriela Hoffmann , Manfred Linke , Ulrike Praeger , Akshay D. Sonawane , Felix Büchele , Daniel Alexandre Neuwald , Reiner Jedermann , Barbara Sturm , Pramod V. Mahajan
The preservation of apples in cold storage relies deeply on understanding the thermal dynamics governing their environment. Within packaging, apples engage in complex thermal interactions, between themselves and the environment, affecting convective and conductive heat transfer pathways. Challenges escalate in industrial cold storage facilities, manifesting as temperature stratification and non-uniform cooling. Nonetheless, a comprehensive understanding of heat transfer dynamics is vital for optimizing cold storage equipment design and enhancing cooling system operation efficacy. Building upon previous studies validating the use of Peltier elements for detecting and quantifying heat flux in individual apples, this research extends its application to industrial cold rooms. By strategically selecting locations within the apple bin and the storage cold room and comparing changes in total heat content obtained by a conventional method and comparing with the Peltier element for its validation. Results of the convective heat transfer coefficient in an upper-layer bin were in the range of 2.7-5.9 Wm-2 K-1 while in a bin at door level were 5.0-7.0 Wm-2 K-1. The higher values found in the position near the door can be correlated to the faster air speed experienced between the apples in this position. By applying these values in the transient heat transfer model to predict the fruit core temperature during the cooling process, a relatable prediction was found, with apple temperature difference <0.9 °C between predicted by the Peltier element and experimental cooling curves. This study can aid understanding of thermal dynamics in cold storage environments, and support future development for more efficient and sustainable cold storage practices.
{"title":"Heat transfer in large bins during the apples cool-down process","authors":"Tuany Gabriela Hoffmann , Manfred Linke , Ulrike Praeger , Akshay D. Sonawane , Felix Büchele , Daniel Alexandre Neuwald , Reiner Jedermann , Barbara Sturm , Pramod V. Mahajan","doi":"10.1016/j.ijrefrig.2024.11.023","DOIUrl":"10.1016/j.ijrefrig.2024.11.023","url":null,"abstract":"<div><div>The preservation of apples in cold storage relies deeply on understanding the thermal dynamics governing their environment. Within packaging, apples engage in complex thermal interactions, between themselves and the environment, affecting convective and conductive heat transfer pathways. Challenges escalate in industrial cold storage facilities, manifesting as temperature stratification and non-uniform cooling. Nonetheless, a comprehensive understanding of heat transfer dynamics is vital for optimizing cold storage equipment design and enhancing cooling system operation efficacy. Building upon previous studies validating the use of Peltier elements for detecting and quantifying heat flux in individual apples, this research extends its application to industrial cold rooms. By strategically selecting locations within the apple bin and the storage cold room and comparing changes in total heat content obtained by a conventional method and comparing with the Peltier element for its validation. Results of the convective heat transfer coefficient in an upper-layer bin were in the range of 2.7-5.9 Wm<sup>-2</sup> K<sup>-1</sup> while in a bin at door level were 5.0-7.0 Wm<sup>-2</sup> K<sup>-1</sup>. The higher values found in the position near the door can be correlated to the faster air speed experienced between the apples in this position. By applying these values in the transient heat transfer model to predict the fruit core temperature during the cooling process, a relatable prediction was found, with apple temperature difference <0.9 °C between predicted by the Peltier element and experimental cooling curves. This study can aid understanding of thermal dynamics in cold storage environments, and support future development for more efficient and sustainable cold storage practices.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 60-69"},"PeriodicalIF":3.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.ijrefrig.2024.11.022
Hira Yuksel Sarıoğlu, Safiye Nur Dirim
In this study, the effects of household refrigerator freezing (control group), ultrasound-assisted freezing at different power levels (40 %, 70 %, and 100 %) and metal plate assisted freezing on the quality characteristics of beef samples were investigated. While the freezing time decreased for the fillet samples with ultrasound-assisted freezing (40 % and 70 %, respectively) and for all samples with metal plate assisted freezing, the weight loss and cooking loss values generally decreased compared to control samples. The total color values of the ultrasound-assisted frozen samples were higher than those of the control samples, while the metal plate assisted frozen samples were lower than those of the control samples. The TBARS values were found to be lower in both methods compared to control samples. The hardness values of control samples were generally lower than the samples subjected to both methods after or before cooking. The protein denaturation temperatures of the metal plate-assisted frozen samples were generally higher than others. As a result, ultrasound and metal plate assisted freezing processes preserved the quality characteristics of beef and had significant effects on several quality characteristics of beef. The application of ultrasound at 40 % provides a significant advantage in terms of quality characteristics. The effects of conduction heat transfer with metal plate-assisted freezing processes also provides the positive impact on the freezing of beef samples. Thus, the use of innovative technologies during the freezing of food in household refrigerators were evaluated within the study which brings new idea to integrate them in the production of household refrigerators.
{"title":"The effect of ultrasound-assisted freezing, metal plate assisted freezing and conventional freezing on the quality characteristics of beef samples","authors":"Hira Yuksel Sarıoğlu, Safiye Nur Dirim","doi":"10.1016/j.ijrefrig.2024.11.022","DOIUrl":"10.1016/j.ijrefrig.2024.11.022","url":null,"abstract":"<div><div>In this study, the effects of household refrigerator freezing (control group), ultrasound-assisted freezing at different power levels (40 %, 70 %, and 100 %) and metal plate assisted freezing on the quality characteristics of beef samples were investigated. While the freezing time decreased for the fillet samples with ultrasound-assisted freezing (40 % and 70 %, respectively) and for all samples with metal plate assisted freezing, the weight loss and cooking loss values generally decreased compared to control samples. The total color values of the ultrasound-assisted frozen samples were higher than those of the control samples, while the metal plate assisted frozen samples were lower than those of the control samples. The TBARS values were found to be lower in both methods compared to control samples. The hardness values of control samples were generally lower than the samples subjected to both methods after or before cooking. The protein denaturation temperatures of the metal plate-assisted frozen samples were generally higher than others. As a result, ultrasound and metal plate assisted freezing processes preserved the quality characteristics of beef and had significant effects on several quality characteristics of beef. The application of ultrasound at 40 % provides a significant advantage in terms of quality characteristics. The effects of conduction heat transfer with metal plate-assisted freezing processes also provides the positive impact on the freezing of beef samples. Thus, the use of innovative technologies during the freezing of food in household refrigerators were evaluated within the study which brings new idea to integrate them in the production of household refrigerators.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 135-149"},"PeriodicalIF":3.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745535","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}
NH3/CO2 cascade refrigeration systems have a wide application prospect in the field of refrigeration, and using efficient centrifugal compressors is an important research direction. Considering the complex regulation process under various operating conditions, using centrifugal compressors for the low-temperature stage first is a feasible solution. In this paper, a mathematical model of a CO2 centrifugal compressor with gas bearing is established, and its performance is obtained through simulation. The CO2 centrifugal compressor shows good performance, and the maximum isentropic efficiency is about 84.5%. The refrigerating capacity, cooling motor mass flow rate, exergy efficiency, and isentropic efficiency of compressor decrease with the intermediate temperature, but the maximum COP of 1.46 is obtained. As the condensing temperature increases, the isentropic efficiency of the CO2 compressor increases, but the maximum COP, exergy efficiency, cooling motor mass flow rate, and refrigeration capacity decrease. The higher COP and intermediate temperature, larger refrigeration capacity and mass flow rate for motor cooling are shown for the larger evaporating temperature, but the low exergy efficiency, isentropic efficiency of CO2 compressor are obtained.
NH3/CO2 级联制冷系统在制冷领域具有广泛的应用前景，而使用高效离心压缩机是一个重要的研究方向。考虑到各种工况下复杂的调节过程，首先在低温阶段使用离心压缩机是一种可行的解决方案。本文建立了带气体轴承的二氧化碳离心压缩机的数学模型，并通过仿真获得了其性能。二氧化碳离心压缩机性能良好，最大等熵效率约为 84.5%。压缩机的制冷量、冷却电机质量流量、放能效率和等熵效率随中间温度的升高而降低，但获得了 1.46 的最大 COP。随着冷凝温度的升高，二氧化碳压缩机的等熵效率升高，但最大 COP、放能效率、冷却电机质量流量和制冷量均降低。蒸发温度越高，COP 和中间温度越高，制冷量和电机冷却质量流量越大，但 CO2 压缩机的放能效率和等熵效率越低。
{"title":"Performance analysis of NH3/CO2 cascade refrigeration system using CO2 centrifugal compressor with gas bearing","authors":"Zilong Wang, Yuqing Zuo, Yuandong Li, Guangbin Liu, Qichao Yang, Yuanyang Zhao, Liansheng Li","doi":"10.1016/j.ijrefrig.2024.11.020","DOIUrl":"10.1016/j.ijrefrig.2024.11.020","url":null,"abstract":"<div><div>NH<sub>3</sub>/CO<sub>2</sub> cascade refrigeration systems have a wide application prospect in the field of refrigeration, and using efficient centrifugal compressors is an important research direction. Considering the complex regulation process under various operating conditions, using centrifugal compressors for the low-temperature stage first is a feasible solution. In this paper, a mathematical model of a CO<sub>2</sub> centrifugal compressor with gas bearing is established, and its performance is obtained through simulation. The CO<sub>2</sub> centrifugal compressor shows good performance, and the maximum isentropic efficiency is about 84.5%. The refrigerating capacity, cooling motor mass flow rate, exergy efficiency, and isentropic efficiency of compressor decrease with the intermediate temperature, but the maximum COP of 1.46 is obtained. As the condensing temperature increases, the isentropic efficiency of the CO<sub>2</sub> compressor increases, but the maximum COP, exergy efficiency, cooling motor mass flow rate, and refrigeration capacity decrease. The higher COP and intermediate temperature, larger refrigeration capacity and mass flow rate for motor cooling are shown for the larger evaporating temperature, but the low exergy efficiency, isentropic efficiency of CO<sub>2</sub> compressor are obtained.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 44-59"},"PeriodicalIF":3.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.ijrefrig.2024.11.014
Junrui Nie, Guoyuan Ma, Lei Wang
The CO2 transcritical distributed compression cycle proposal provides a novel approach for refrigerant cooling in traditional transcritical cycles. This paper employed an exhaustive search method to derive the correlation formula for the optimal intermediate pressure. From the perspectives of thermodynamic performance and economics, a comparative analysis was conducted between the cycle established under the optimal intermediate pressure obtained in this study, the cycle based on equal compression ratios in traditional two-stage compression cycles, and the cycle established using the optimal secondary compression ratio method based on low-pressure stage discharge pressure mentioned in previous literature study. The research results indicate that the system's COP calculated using the obtained optimal intermediate pressure correlation method can be improved by up to 7.26% and 5.32%, respectively, compared to the traditional and literature-based methods. The exergy loss with the optimal intermediate pressure method is less than with the other two methods. The entransy dissipation rate of the system obtained using the optimal intermediate pressure correlation method is 24.61% and 50.14% lower than that of the traditional and literature-based methods, respectively. The investment cost of the main components using the optimal intermediate pressure correlation method is about 5% higher than that of the traditional method and about 1% higher than that of the optimal pressure ratio method. However, the total annual cost rate of the system is the lowest. The research enriches and improves the theory of the CO₂ transcritical distributed compression cycle, thereby facilitating the advancement of practical applications based on this cycle theory.
{"title":"Optimal Intermediate Pressure Investigation in a CO₂ Transcritical Distributed Compression Refrigeration Cycle","authors":"Junrui Nie, Guoyuan Ma, Lei Wang","doi":"10.1016/j.ijrefrig.2024.11.014","DOIUrl":"10.1016/j.ijrefrig.2024.11.014","url":null,"abstract":"<div><div>The CO<sub>2</sub> transcritical distributed compression cycle proposal provides a novel approach for refrigerant cooling in traditional transcritical cycles. This paper employed an exhaustive search method to derive the correlation formula for the optimal intermediate pressure. From the perspectives of thermodynamic performance and economics, a comparative analysis was conducted between the cycle established under the optimal intermediate pressure obtained in this study, the cycle based on equal compression ratios in traditional two-stage compression cycles, and the cycle established using the optimal secondary compression ratio method based on low-pressure stage discharge pressure mentioned in previous literature study. The research results indicate that the system's COP calculated using the obtained optimal intermediate pressure correlation method can be improved by up to 7.26% and 5.32%, respectively, compared to the traditional and literature-based methods. The exergy loss with the optimal intermediate pressure method is less than with the other two methods. The entransy dissipation rate of the system obtained using the optimal intermediate pressure correlation method is 24.61% and 50.14% lower than that of the traditional and literature-based methods, respectively. The investment cost of the main components using the optimal intermediate pressure correlation method is about 5% higher than that of the traditional method and about 1% higher than that of the optimal pressure ratio method. However, the total annual cost rate of the system is the lowest. The research enriches and improves the theory of the CO₂ transcritical distributed compression cycle, thereby facilitating the advancement of practical applications based on this cycle theory.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"169 ","pages":"Pages 405-417"},"PeriodicalIF":3.5,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142706616","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 energy consumption of variable refrigerant flow (VRF) systems can be reduced by adopting the variable evaporation temperature and constant superheat degree (VECS) control strategy instead of constant evaporation temperature and constant superheat degree (CECS) control strategy. However, the constant superheat degree control strategy may weaken the adjustment ability of cooling capacity of indoor units, and result in obvious room temperature fluctuations. In order to decrease room temperature fluctuations and reduce energy consumption simultaneously, a cooperative control strategy of variable evaporation temperature and variable superheat degree (VEVS) is proposed, i.e. one indoor unit is chosen to be controlled by variable evaporation temperature and the rest of the indoor units are controlled by variable superheat degrees. In this control strategy, the target value of evaporation temperature is the lowest value among the upper limits of the evaporation temperatures of all indoor units, and the target values of the superheat degrees of indoor units are predicted according to the cooling demands of rooms. Comparative experiments on room temperature fluctuation and energy consumption among the control strategies of CECS, VECS and VEVS are done. It is shown that both the control strategies of VECS and VEVS achieve smaller room temperature fluctuation and lower energy consumption than those of CECS; compared with the VECS control strategy, the average room temperature fluctuation of the VEVS control strategy is decreased from 1.1 °C to 0.5 °C due to variable superheat degree, and the energy consumption of the VEVS control strategy is reduced by 4.4 %.
{"title":"Cooperative control strategy of variable evaporation temperature and variable superheat degree for a VRF system to improve temperature stability in multiple rooms","authors":"Haomin Cao , Dawei Zhuang , Guoliang Ding , Shunquan Li , Zhigang Huang , Yanpo Shao , Hao Zhang , Dongyu Chen","doi":"10.1016/j.ijrefrig.2024.11.017","DOIUrl":"10.1016/j.ijrefrig.2024.11.017","url":null,"abstract":"<div><div>The energy consumption of variable refrigerant flow (VRF) systems can be reduced by adopting the variable evaporation temperature and constant superheat degree (VECS) control strategy instead of constant evaporation temperature and constant superheat degree (CECS) control strategy. However, the constant superheat degree control strategy may weaken the adjustment ability of cooling capacity of indoor units, and result in obvious room temperature fluctuations. In order to decrease room temperature fluctuations and reduce energy consumption simultaneously, a cooperative control strategy of variable evaporation temperature and variable superheat degree (VEVS) is proposed, i.e. one indoor unit is chosen to be controlled by variable evaporation temperature and the rest of the indoor units are controlled by variable superheat degrees. In this control strategy, the target value of evaporation temperature is the lowest value among the upper limits of the evaporation temperatures of all indoor units, and the target values of the superheat degrees of indoor units are predicted according to the cooling demands of rooms. Comparative experiments on room temperature fluctuation and energy consumption among the control strategies of CECS, VECS and VEVS are done. It is shown that both the control strategies of VECS and VEVS achieve smaller room temperature fluctuation and lower energy consumption than those of CECS; compared with the VECS control strategy, the average room temperature fluctuation of the VEVS control strategy is decreased from 1.1 °C to 0.5 °C due to variable superheat degree, and the energy consumption of the VEVS control strategy is reduced by 4.4 %.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"170 ","pages":"Pages 1-18"},"PeriodicalIF":3.5,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.ijrefrig.2024.11.006
Huaqiu Wang, Jiahao Tan
Most enterprise workshop operators frequently adjust the start/stop time of air conditioning systems based on indoor and outdoor temperatures and humidity to accommodate changing demand and weather conditions. However, relying on personal subjective experience for these adjustments often leads to operational delays or energy waste due to the lack of precision in determining optimal timing. Predicting air conditioning system start and stop times is crucial for energy consumption and savings in HVAC systems. Traditional data-driven methods have been insufficient in this regard, as they mainly focus on feature mapping and overlook the dynamic coupling relationships of process variables, resulting in subpar predictions. In response to this challenge, the paper introduces a novel approach known as the Periodicity and Long-Term Convolutional Neural Network (PLCNN). This method converts one-dimensional regression prediction data into two-dimensional data containing time series features to capture the dynamic coupling characteristics of the air conditioning system while maintaining the independent variation relationships of features. Experimental results using real factory floor data have demonstrated the superior performance of the PLCNN method. Specifically, this method achieved a 14.96% lower error rate compared to the traditional method and an 8.18% improvement compared to the deep learning method. Moreover, the implementation of the PLCNN method in the optimal control of air conditioning systems led to a significant 19.43% reduction in total monthly energy consumption. In conclusion, the proposed method offers a promising alternative to traditional approaches to forecasting and provides a solution to the common challenges encountered in traditional prediction tasks.
{"title":"Data-enhanced convolutional network based on air conditioning system start/stop time prediction","authors":"Huaqiu Wang, Jiahao Tan","doi":"10.1016/j.ijrefrig.2024.11.006","DOIUrl":"10.1016/j.ijrefrig.2024.11.006","url":null,"abstract":"<div><div>Most enterprise workshop operators frequently adjust the start/stop time of air conditioning systems based on indoor and outdoor temperatures and humidity to accommodate changing demand and weather conditions. However, relying on personal subjective experience for these adjustments often leads to operational delays or energy waste due to the lack of precision in determining optimal timing. Predicting air conditioning system start and stop times is crucial for energy consumption and savings in HVAC systems. Traditional data-driven methods have been insufficient in this regard, as they mainly focus on feature mapping and overlook the dynamic coupling relationships of process variables, resulting in subpar predictions. In response to this challenge, the paper introduces a novel approach known as the Periodicity and Long-Term Convolutional Neural Network (PLCNN). This method converts one-dimensional regression prediction data into two-dimensional data containing time series features to capture the dynamic coupling characteristics of the air conditioning system while maintaining the independent variation relationships of features. Experimental results using real factory floor data have demonstrated the superior performance of the PLCNN method. Specifically, this method achieved a 14.96% lower error rate compared to the traditional method and an 8.18% improvement compared to the deep learning method. Moreover, the implementation of the PLCNN method in the optimal control of air conditioning systems led to a significant 19.43% reduction in total monthly energy consumption. In conclusion, the proposed method offers a promising alternative to traditional approaches to forecasting and provides a solution to the common challenges encountered in traditional prediction tasks.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"169 ","pages":"Pages 372-382"},"PeriodicalIF":3.5,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.ijrefrig.2024.11.016
Hainan Zhang , Jing Ding , Haichao Liu , Tao Ding , Yanhui Feng
Loop thermosyphon has the ability of heat transfer without external energy input, which has good application potential in many areas. Biomimetic flow channel is an effective way for heat transfer enhancement and resistance optimization, therefore it is a promising method to improve the performance of loop thermosyphon. While currently few studies have been conducted in this field. In this paper, the start-up stages, flow patterns and heat transfer performance of a loop thermosyphon with biomimetic honeycomb-channel evaporator are experimentally investigated, and compared with a loop thermosyphon with parallel-flow evaporator. The results show that the start-up of can be divided into three stages: stage dominated by heat conduction, stage dominated by boiling and stage transited to stable operation; For the steady-state performance, the heating power of the optimal point with the lowest thermal resistance increases from 90 W to 150 W with the increase of the filling ratio from 50 % to 70 %; Compared to loop thermosyphon with parallel-flow evaporator, loop thermosyphon with biomimetic honeycomb evaporator has lower thermal resistance. The decline of thermal resistance is 4.1 %–21.6 %, and is more significant under small heating power. This paper provides a simple and affordable method for heat transfer improvement of loop thermosyphon.
{"title":"Start-up investigation and heat transfer enhancement analysis of a loop thermosyphon with biomimetic honeycomb-channel evaporator","authors":"Hainan Zhang , Jing Ding , Haichao Liu , Tao Ding , Yanhui Feng","doi":"10.1016/j.ijrefrig.2024.11.016","DOIUrl":"10.1016/j.ijrefrig.2024.11.016","url":null,"abstract":"<div><div>Loop thermosyphon has the ability of heat transfer without external energy input, which has good application potential in many areas. Biomimetic flow channel is an effective way for heat transfer enhancement and resistance optimization, therefore it is a promising method to improve the performance of loop thermosyphon. While currently few studies have been conducted in this field. In this paper, the start-up stages, flow patterns and heat transfer performance of a loop thermosyphon with biomimetic honeycomb-channel evaporator are experimentally investigated, and compared with a loop thermosyphon with parallel-flow evaporator. The results show that the start-up of can be divided into three stages: stage dominated by heat conduction, stage dominated by boiling and stage transited to stable operation; For the steady-state performance, the heating power of the optimal point with the lowest thermal resistance increases from 90 W to 150 W with the increase of the filling ratio from 50 % to 70 %; Compared to loop thermosyphon with parallel-flow evaporator, loop thermosyphon with biomimetic honeycomb evaporator has lower thermal resistance. The decline of thermal resistance is 4.1 %–21.6 %, and is more significant under small heating power. This paper provides a simple and affordable method for heat transfer improvement of loop thermosyphon.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":"169 ","pages":"Pages 383-390"},"PeriodicalIF":3.5,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662871","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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