Pub Date : 2024-09-11DOI: 10.1016/j.ijrefrig.2024.09.005
Ice crystal growth of water and its aqueous solution is the key phenomenon in food freezing. In this research, the effect of static magnetic field (SMF) on single ice crystal growth was investigated combing experiment and simulation. The ice crystal growth of water and NaCl-water solution under 0 - 15 mT SMF intensities were studied. The UV absorbance of water after SMF treatment was measured. Phase field model was adopted to simulate the ice crystal growth. The results show that SMF significantly inhibited the growth rate, while had little effect on the morphology and growth direction of ice crystals. SMF had a certain enhancement effect on the UV absorbance of deionized water. The proposed model could well simulate the ice crystal growth under different SMF intensities. Combining experimental and simulation results, it can be inferred that SMF inhibits ice crystal growth by enhancing original hydrogen bonds and reducing free energy.
{"title":"Experimental and numerical study on single ice crystal growth of deionized water and 0.9 % NaCl solution under static magnetic field","authors":"","doi":"10.1016/j.ijrefrig.2024.09.005","DOIUrl":"10.1016/j.ijrefrig.2024.09.005","url":null,"abstract":"<div><div>Ice crystal growth of water and its aqueous solution is the key phenomenon in food freezing. In this research, the effect of static magnetic field (SMF) on single ice crystal growth was investigated combing experiment and simulation. The ice crystal growth of water and NaCl-water solution under 0 - 15 mT SMF intensities were studied. The UV absorbance of water after SMF treatment was measured. Phase field model was adopted to simulate the ice crystal growth. The results show that SMF significantly inhibited the growth rate, while had little effect on the morphology and growth direction of ice crystals. SMF had a certain enhancement effect on the UV absorbance of deionized water. The proposed model could well simulate the ice crystal growth under different SMF intensities. Combining experimental and simulation results, it can be inferred that SMF inhibits ice crystal growth by enhancing original hydrogen bonds and reducing free energy.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1016/j.ijrefrig.2024.09.007
Vapor injection technology represents a highly promising avenue for enhancing the efficiency of heat pump systems within electric vehicles, especially in challenging cold ambient conditions. Although a simplified isentropic process is commonly employed to assess the thermodynamic functioning of scroll compressors with vapor injection (SCVI), it diverges significantly from actual operational dynamics. This study introduces a sophisticated 1D mathematical model that incorporates key factors such as internal leakage and thermal losses, thereby providing a more accurate representation of SCVI's operational realities. The research includes comprehensive performance evaluations of a short wrap profile SCVI, with a specific focus on low-temperature ambient conditions, supported by rigorous experimental validation. Comparative analyses against non-injection scenarios reveal notable enhancements, including a maximum 17.2 % increase in mass flow, a 10.5 % rise in heating capacity, and a 2.15 % improvement in heating COP. Both the simplified isentropic process calculation model and the enhanced 1D mathematical model are utilized to analyze compressor operations. The integration of internal leakage and heat loss considerations significantly narrows the gap between calculated and experimental results for heating capacity and discharge temperature, reducing discrepancies from nearly 20 % to a mere 4 %. This refined mathematical model demonstrates a high level of alignment with experimental data, achieving an accuracy within 5 % when assessing the compressor's real-world operational dynamics.
{"title":"Refined one-dimensional modeling and experimental validation of scroll compressor with vapor injection for electric vehicles","authors":"","doi":"10.1016/j.ijrefrig.2024.09.007","DOIUrl":"10.1016/j.ijrefrig.2024.09.007","url":null,"abstract":"<div><div>Vapor injection technology represents a highly promising avenue for enhancing the efficiency of heat pump systems within electric vehicles, especially in challenging cold ambient conditions. Although a simplified isentropic process is commonly employed to assess the thermodynamic functioning of scroll compressors with vapor injection (SCVI), it diverges significantly from actual operational dynamics. This study introduces a sophisticated 1D mathematical model that incorporates key factors such as internal leakage and thermal losses, thereby providing a more accurate representation of SCVI's operational realities. The research includes comprehensive performance evaluations of a short wrap profile SCVI, with a specific focus on low-temperature ambient conditions, supported by rigorous experimental validation. Comparative analyses against non-injection scenarios reveal notable enhancements, including a maximum 17.2 % increase in mass flow, a 10.5 % rise in heating capacity, and a 2.15 % improvement in heating COP. Both the simplified isentropic process calculation model and the enhanced 1D mathematical model are utilized to analyze compressor operations. The integration of internal leakage and heat loss considerations significantly narrows the gap between calculated and experimental results for heating capacity and discharge temperature, reducing discrepancies from nearly 20 % to a mere 4 %. This refined mathematical model demonstrates a high level of alignment with experimental data, achieving an accuracy within 5 % when assessing the compressor's real-world operational dynamics.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1016/j.ijrefrig.2024.09.004
In response to the ongoing optimization of energy systems and the promotion of clean energy, this paper introduces a new high-efficiency cogeneration system based on proton exchange membrane fuel cells (PEMFC). Named the Transcritical Combined Cooling Heating and Power with Subcooling Coupled ORC (CPTSO) system, it undergoes energy, exergy, economic, and environmental (4E) assessments to evaluate its performance in both summer and winter modes. This paper also analyzes the effects of key factors on the new system's performance. The results indicate that the new system performs more effectively overall and achieves faster cost recovery during winter operations. With varying degrees of subcooling (ΔTsubcooling), the system's average energy efficiency, fuel energy saving ratio (FESR), exergy efficiency, and pollutant reduction in winter are 60.97 %, 4.51 %, 17.16 %, and 33.35 % higher, respectively, than in summer. Changes in the main evaporation temperature (Te) result in winter improvements of 74.37 % in energy efficiency, 16.86 % in FESR, 17.6 % in exergy efficiency, and 45.5 % in pollutant reduction compared to summer. Similarly, adjustments to the outlet temperature of the gas cooler (Tg) lead to winter increases of 56.75 % in energy efficiency, 0.49 % in FESR, 17.1 % in exergy efficiency, and 29.3 % in pollutant reduction over summer values.
{"title":"4E Analysis of a new cogeneration system coupling heat pumps and PEMFC in summer and winter modes","authors":"","doi":"10.1016/j.ijrefrig.2024.09.004","DOIUrl":"10.1016/j.ijrefrig.2024.09.004","url":null,"abstract":"<div><div>In response to the ongoing optimization of energy systems and the promotion of clean energy, this paper introduces a new high-efficiency cogeneration system based on proton exchange membrane fuel cells (PEMFC). Named the Transcritical Combined Cooling Heating and Power with Subcooling Coupled ORC (CPTSO) system, it undergoes energy, exergy, economic, and environmental (4E) assessments to evaluate its performance in both summer and winter modes. This paper also analyzes the effects of key factors on the new system's performance. The results indicate that the new system performs more effectively overall and achieves faster cost recovery during winter operations. With varying degrees of subcooling (ΔT<sub>subcooling</sub>), the system's average energy efficiency, fuel energy saving ratio (FESR), exergy efficiency, and pollutant reduction in winter are 60.97 %, 4.51 %, 17.16 %, and 33.35 % higher, respectively, than in summer. Changes in the main evaporation temperature (T<sub>e</sub>) result in winter improvements of 74.37 % in energy efficiency, 16.86 % in FESR, 17.6 % in exergy efficiency, and 45.5 % in pollutant reduction compared to summer. Similarly, adjustments to the outlet temperature of the gas cooler (T<sub>g</sub>) lead to winter increases of 56.75 % in energy efficiency, 0.49 % in FESR, 17.1 % in exergy efficiency, and 29.3 % in pollutant reduction over summer values.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1016/j.ijrefrig.2024.08.027
This paper presents a conventional air source heat pump cycle (CHPC) and two dual-temperature air source heat pump cycles (DTHPC1 and DTHPC2). DTHPC1 employs two condensers, while DTHPC2 adds an extra compressor and combines the ejectors on top of DTHPC1. Compared with the conventional heat pump cycle, the new dual-temperature heat pump DTHPC2 can provide hot water at one additional temperature and still have high performance. In this paper, the refrigerants R1234yf and R1234ze(E) were selected as suitable for the cycle conditions. The cycle performance under different conditions was simulated and compared based on energy analysis methods and exergy analysis methods. The main performance parameters included COPh, ηex, etc. The results demonstrate that the COPh and ηex of DTHPC2 and DTHPC1 are greater than those of CHPC under identical conditions. Specifically, at an ambient temperature of approximately -10 °C, high-temperature hot water of approximately 65 °C, and low-temperature hot water of approximately 35 °C, the COPh of DTHPC2 and DTHPC1 increased by 45% and 32.7%, respectively, in comparison to CHPC. Similarly, the ηex of DTHPC2 and DTHPC1 increased by 27.1% and 28.9%, respectively.
{"title":"Thermodynamic analysis of a new tandem dual-temperature air source heat pump with ejector","authors":"","doi":"10.1016/j.ijrefrig.2024.08.027","DOIUrl":"10.1016/j.ijrefrig.2024.08.027","url":null,"abstract":"<div><div>This paper presents a conventional air source heat pump cycle (CHPC) and two dual-temperature air source heat pump cycles (DTHPC1 and DTHPC2). DTHPC1 employs two condensers, while DTHPC2 adds an extra compressor and combines the ejectors on top of DTHPC1. Compared with the conventional heat pump cycle, the new dual-temperature heat pump DTHPC2 can provide hot water at one additional temperature and still have high performance. In this paper, the refrigerants R1234yf and R1234ze(E) were selected as suitable for the cycle conditions. The cycle performance under different conditions was simulated and compared based on energy analysis methods and exergy analysis methods. The main performance parameters included COP<sub>h</sub>, <em>η<sub>ex</sub></em>, etc. The results demonstrate that the COP<sub>h</sub> and <em>η<sub>ex</sub></em> of DTHPC2 and DTHPC1 are greater than those of CHPC under identical conditions. Specifically, at an ambient temperature of approximately -10 °C, high-temperature hot water of approximately 65 °C, and low-temperature hot water of approximately 35 °C, the COP<sub>h</sub> of DTHPC2 and DTHPC1 increased by 45% and 32.7%, respectively, in comparison to CHPC. Similarly, the <em>η<sub>ex</sub></em> of DTHPC2 and DTHPC1 increased by 27.1% and 28.9%, respectively.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-07DOI: 10.1016/j.ijrefrig.2024.08.018
Extremely cold climates subject residential heat pumps to significant temperature differences between the heat source and the ambient being heated, which may lead to system failure and reduced compressor performance. The present study considers the possibility of improving the performance of heat pump systems that are simultaneously used for residential space and domestic water heating while subjected to climates varying from -25 °C to 5 °C by exploring the use of zeotropic mixtures. CO2-based binary mixtures composed of low-GWP (global warming potential) refrigerants are considered – R32, R1234yf, and R290 – aiming to benefit from environmentally friendly and flame suppressants characteristics of CO2, as well as the improved thermal efficiency granted by the addition of a secondary refrigerant. A thermodynamic model was developed for a standard vapor-compression heat pump cycle and used to maximize the coefficient of performance limited by the minimum pinch point in the heat exchangers. Our analysis explores the effect of several parameters, such as, the mixture components, mass fractions, space and water heating demands, and heat source temperature on the heat pump's performance. For cold climates, the mixture of R32 (90%)/CO2 (10%) yields the highest COP and CO2-rich mixtures exhibit the lowest. However, by increasing the mass fraction of CO2 within the zeotropic mixture, the pressure ratio of the heat pump was improved. When considering combined performance criteria, such as the volumetric heating effect and the total heat delivered related to heat pump size, CO2-rich mixtures tend to allow more compact systems, especially in colder climates.
极度寒冷的气候会使住宅热泵的热源与被加热环境之间存在显著温差，从而可能导致系统故障和压缩机性能下降。本研究考虑了通过探索使用各向异性混合物来提高同时用于住宅空间和生活热水加热的热泵系统性能的可能性，这些热泵系统所处的气候条件从 -25 °C 到 5 °C 不等。研究考虑了由低全球升温潜能值（GWP）制冷剂（R32、R1234yf 和 R290）组成的二氧化碳二元混合物，目的是利用二氧化碳的环保和阻燃特性，以及通过添加辅助制冷剂提高热效率。为标准蒸汽压缩热泵循环开发了一个热力学模型，用于最大限度地提高受热交换器最小夹点限制的性能系数。我们的分析探讨了几个参数对热泵性能的影响，如混合物成分、质量分数、空间和水加热需求以及热源温度。在寒冷气候条件下，R32（90%）/CO2（10%）混合物的 COP 值最高，而富含 CO2 的混合物的 COP 值最低。不过，通过增加各向同性混合物中二氧化碳的质量分数，热泵的压力比得到了改善。如果考虑到综合性能标准，例如与热泵尺寸相关的容积加热效果和总热量输送，富含二氧化碳的混合物往往能使系统更加紧凑，尤其是在寒冷的气候条件下。
{"title":"Performance assessment of residential heat pumps operating in extreme cold climates using zeotropic mixtures","authors":"","doi":"10.1016/j.ijrefrig.2024.08.018","DOIUrl":"10.1016/j.ijrefrig.2024.08.018","url":null,"abstract":"<div><div>Extremely cold climates subject residential heat pumps to significant temperature differences between the heat source and the ambient being heated, which may lead to system failure and reduced compressor performance. The present study considers the possibility of improving the performance of heat pump systems that are simultaneously used for residential space and domestic water heating while subjected to climates varying from -25 °C to 5 °C by exploring the use of zeotropic mixtures. CO<sub>2</sub>-based binary mixtures composed of low-GWP (global warming potential) refrigerants are considered – R32, R1234yf, and R290 – aiming to benefit from environmentally friendly and flame suppressants characteristics of CO<sub>2</sub>, as well as the improved thermal efficiency granted by the addition of a secondary refrigerant. A thermodynamic model was developed for a standard vapor-compression heat pump cycle and used to maximize the coefficient of performance limited by the minimum pinch point in the heat exchangers. Our analysis explores the effect of several parameters, such as, the mixture components, mass fractions, space and water heating demands, and heat source temperature on the heat pump's performance. For cold climates, the mixture of R32 (90%)/CO<sub>2</sub> (10%) yields the highest COP and CO<sub>2</sub>-rich mixtures exhibit the lowest. However, by increasing the mass fraction of CO<sub>2</sub> within the zeotropic mixture, the pressure ratio of the heat pump was improved. When considering combined performance criteria, such as the volumetric heating effect and the total heat delivered related to heat pump size, CO<sub>2</sub>-rich mixtures tend to allow more compact systems, especially in colder climates.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-07DOI: 10.1016/j.ijrefrig.2024.08.017
Brazed plate heat exchanger (BPHE) has gained more advantages of refrigerant inventory reduction and high efficiency due to smaller chevron channel. This paper experimentally investigates the heat transfer and pressure drop of R32 and R410A flow boiling in BPHEs with 1 mm chevron depth and W– and V– chevron patterns. Variations in heat transfer coefficient (HTC) and frictional pressure drop (FPD) with mass flux (15 − 40 kg m−2 s−1 for R32 and 25 − 60 kg m−2 s−1 for R410A) and imposed heat flux (from 6 − 14 kW m−2) are analyzed for each combination of the two refrigerants and two types of plate patterns. The HTC of R32 is approximately 10 % and 30 % higher than that of R410A at same mass flux in W– and V–shaped plates, respectively, which has an equivalent friction factor. The V–shaped plate is found more suited for R32 compared to the W–shaped plate. The existing available transition criterions fail to predict the flow boiling heat transfer mechanism in microscale channel, and convective boiling seems dominant in 1 mm chevron depth channel under the present working conditions, particularly for R32. The HTC correlations of Hsieh and Lin, and Palmer et al. fit the measured data relatively well with 96 and 80 % data within the deviation of ±20 %, respectively. Huang et al. correlation exhibits fare predictability for FPD, with more than 80 % data within the deviation of ±25 %.
钎焊板式热交换器（BPHE）因其较小的楔形通道而在减少制冷剂库存和提高效率方面获得了更多优势。本文通过实验研究了 R32 和 R410A 在楔形槽深度为 1 毫米、楔形槽形状为 W 形和 V 形的钎焊板式热交换器中流动沸腾时的传热和压降。分析了两种制冷剂和两种板型的传热系数（HTC）和摩擦压降（FPD）随质量通量（R32 为 15 - 40 kg m-2 s-1，R410A 为 25 - 60 kg m-2 s-1）和外加热通量（6 - 14 kW m-2）的变化情况。在具有等效摩擦因数的 W 形板和 V 形板中，在相同质量通量下，R32 的 HTC 分别比 R410A 高约 10 % 和 30 %。与 W 形板相比，V 形板更适合 R32。现有的过渡标准无法预测微尺度通道中的流动沸腾传热机理，在目前的工况条件下，对流沸腾在 1 毫米楔形深度的通道中似乎占主导地位，尤其是对于 R32。Hsieh 和 Lin 以及 Palmer 等人的 HTC 相关性较好地拟合了测量数据，分别有 96% 和 80% 的数据偏差在 ±20% 以内。Huang 等人的相关性显示了 FPD 的可预测性，80% 以上的数据在 ±25 % 的偏差范围内。
{"title":"Thermal−hydraulic characteristics of R32 and R410A flow boiling in plate heat exchangers with 1 mm chevron depth","authors":"","doi":"10.1016/j.ijrefrig.2024.08.017","DOIUrl":"10.1016/j.ijrefrig.2024.08.017","url":null,"abstract":"<div><div>Brazed plate heat exchanger (BPHE) has gained more advantages of refrigerant inventory reduction and high efficiency due to smaller chevron channel. This paper experimentally investigates the heat transfer and pressure drop of R32 and R410A flow boiling in BPHEs with 1 mm chevron depth and W– and V– chevron patterns. Variations in heat transfer coefficient (HTC) and frictional pressure drop (FPD) with mass flux (15 − 40 kg m<sup>−2</sup> s<sup>−1</sup> for R32 and 25 − 60 kg m<sup>−2</sup> s<sup>−1</sup> for R410A) and imposed heat flux (from 6 − 14 kW m<sup>−2</sup>) are analyzed for each combination of the two refrigerants and two types of plate patterns. The HTC of R32 is approximately 10 % and 30 % higher than that of R410A at same mass flux in W– and V–shaped plates, respectively, which has an equivalent friction factor. The V–shaped plate is found more suited for R32 compared to the W–shaped plate. The existing available transition criterions fail to predict the flow boiling heat transfer mechanism in microscale channel, and convective boiling seems dominant in 1 mm chevron depth channel under the present working conditions, particularly for R32. The HTC correlations of Hsieh and Lin, and Palmer et al. fit the measured data relatively well with 96 and 80 % data within the deviation of ±20 %, respectively. Huang et al. correlation exhibits fare predictability for FPD, with more than 80 % data within the deviation of ±25 %.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142264480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1016/j.ijrefrig.2024.09.001
In this study, a numerical model of the Active Magnetic Regenerator (AMR) cycle, implemented in the reciprocal demonstrator, was developed using COMSOL Multiphysics. A nested Halbach cylinder (NHC) array served as the magnetic field source. Additional simulation of an operation of the NHC array was carried out. To eliminate the discrepancies between the heat exchange duration of the heat transfer medium (HTM) and the hot and cold ends of the regenerator, an adequate time dependence of the inner cylinder rotation angle was calculated. The latter provides the symmetrical sinusoidal form of time dependence of the magnetic flux density in the gap of NHC array, which is important for enhancing the performance of a magnetic refrigerator. It was established that in order to achieve a maximal temperature span, it is necessary to shift the phases of the magnetic field insertion/removal and heat transfer fluid pumping processes by nearly half of the operating cycle period. The latter brings the simulated cycle closer to the ideal AMR cycle.
{"title":"Simulation of an operation of nested Halbach cylinder arrays in regenerative magnetic cooling cycles: The way to maximum thermal span","authors":"","doi":"10.1016/j.ijrefrig.2024.09.001","DOIUrl":"10.1016/j.ijrefrig.2024.09.001","url":null,"abstract":"<div><p>In this study, a numerical model of the Active Magnetic Regenerator (AMR) cycle, implemented in the reciprocal demonstrator, was developed using COMSOL Multiphysics. A nested Halbach cylinder (NHC) array served as the magnetic field source. Additional simulation of an operation of the NHC array was carried out. To eliminate the discrepancies between the heat exchange duration of the heat transfer medium (HTM) and the hot and cold ends of the regenerator, an adequate time dependence of the inner cylinder rotation angle was calculated. The latter provides the symmetrical sinusoidal form of time dependence of the magnetic flux density in the gap of NHC array, which is important for enhancing the performance of a magnetic refrigerator. It was established that in order to achieve a maximal temperature span, it is necessary to shift the phases of the magnetic field insertion/removal and heat transfer fluid pumping processes by nearly half of the operating cycle period. The latter brings the simulated cycle closer to the ideal AMR cycle.</p></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142240063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-01DOI: 10.1016/j.ijrefrig.2024.08.025
The mixtures of R290 (propane) and R1234yf (2,3,3,3-tetrafluoroprop-1-ene), R1243zf (3,3,3-trifluoropropene), or R1234ze(E) (trans-1,3,3,3-tetrafluoropropene) could be potential alternatives for high global warming potential (GWP) refrigerants hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). Obtaining the critical parameters of mixtures is crucial for establishing thermodynamic models, evaluating the highest operating temperature of refrigerants, determining the phase envelope, and confirming the starting point of the Widom line. However, few studies have been made on their critical properties. In this work, the critical properties of three binary systems containing R290 + R1234yf / R1243zf / R1234ze(E) are obtained experimentally with a metal-bellows volume apparatus. The critical state is judged by direct visual observation of critical opalescence and the recurrence of the vapor-liquid phase interface. The extended total uncertainties for the mole fraction, critical pressure, critical temperature, and critical density were below 0.004, 21 kPa, 50 mK, and 0.6 % (k = 2, 0.95 confidence coefficient), respectively. Experimentally obtained critical data are correlated by the Modified Wilson method and the Redlich–Kister method. The critical parameters of the R290 + R1234yf, R290 + R1243zf, and R290 + R1234ze(E) mixtures are predicted using the Correlated Modified Wilson (CMW) method, He et al.’s method, and the Modified Extended Chueh–Prausnitz (MECP) method. The correlated curve and predicted outcomes are employed for comparison with this work's experimental results. Meanwhile, the critical parameters data obtained experimentally are contrasted with the value of REFPROP 10.0 and other open literature. The fitting and prediction curves somewhat agree with the experimental results.
{"title":"Experimental study and correlation of critical parameters for three binary mixtures containing R290 and hydrofluoroolefins","authors":"","doi":"10.1016/j.ijrefrig.2024.08.025","DOIUrl":"10.1016/j.ijrefrig.2024.08.025","url":null,"abstract":"<div><p>The mixtures of R290 (propane) and R1234yf (2,3,3,3-tetrafluoroprop-1-ene), R1243zf (3,3,3-trifluoropropene), or R1234ze(E) (<em>trans</em>-1,3,3,3-tetrafluoropropene) could be potential alternatives for high global warming potential (GWP) refrigerants hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). Obtaining the critical parameters of mixtures is crucial for establishing thermodynamic models, evaluating the highest operating temperature of refrigerants, determining the phase envelope, and confirming the starting point of the Widom line. However, few studies have been made on their critical properties. In this work, the critical properties of three binary systems containing R290 + R1234yf / R1243zf / R1234ze(E) are obtained experimentally with a metal-bellows volume apparatus. The critical state is judged by direct visual observation of critical opalescence and the recurrence of the vapor-liquid phase interface. The extended total uncertainties for the mole fraction, critical pressure, critical temperature, and critical density were below 0.004, 21 kPa, 50 mK, and 0.6 % (<em>k</em> = 2, 0.95 confidence coefficient), respectively. Experimentally obtained critical data are correlated by the Modified Wilson method and the Redlich–Kister method. The critical parameters of the R290 + R1234yf, R290 + R1243zf, and R290 + R1234ze(E) mixtures are predicted using the Correlated Modified Wilson (CMW) method, He et al.’s method, and the Modified Extended Chueh–Prausnitz (MECP) method. The correlated curve and predicted outcomes are employed for comparison with this work's experimental results. Meanwhile, the critical parameters data obtained experimentally are contrasted with the value of REFPROP 10.0 and other open literature. The fitting and prediction curves somewhat agree with the experimental results.</p></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142240064","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 : 2024-08-31DOI: 10.1016/j.ijrefrig.2024.08.028
Addressing the urgent need for environmentally sustainable and efficient refrigeration systems, this study investigates the performance of low-GWP refrigerants R1234yf and R513A in comparison to the high-GWP refrigerant R134a, focusing on the heat transfer coefficient (HTC) and pressure drop during flow boiling in smooth and microfin tubes. The experimental setup involves tubes with a 6.14 mm internal diameter and 500 mm length. Data were collected across a broad range of operating conditions, including mass fluxes from 170 to 495 kg/m² s, heat fluxes from 10 to 40 kW/m², saturation temperatures of 15 °C and 25 °C, and vapor qualities from 0.15 to 1.0. In a specific case with a mass flux of 170 kg/m² s, heat flux of 23 kW/m², and a saturation temperature of 15 °C, the results indicate that the microfin tube achieves an HTC enhancement of up to 64 % compared to smooth tubes. However, R134a exhibits a higher HTC than R1234yf and R513A, approximately 5 % and 3 % higher, respectively. In contrast, R134a presents a higher pressure drop than R1234yf by about 8 %. While the pressure drop for R134a is slightly higher than R513A in the smooth tube, the microfin tube shows similar trends but more pronounced differences. This study comprehensively explores microfin tube performance with these refrigerants, offering critical insights for designing advanced refrigeration systems that balance environmental responsibility with energy efficiency. These findings were validated against predicted correlations, showing good agreement.
{"title":"Experimental comparison of flow boiling heat transfer in smooth and microfin tubes using R134a, R1234yf, and R513A","authors":"","doi":"10.1016/j.ijrefrig.2024.08.028","DOIUrl":"10.1016/j.ijrefrig.2024.08.028","url":null,"abstract":"<div><div>Addressing the urgent need for environmentally sustainable and efficient refrigeration systems, this study investigates the performance of low-GWP refrigerants R1234yf and R513A in comparison to the high-GWP refrigerant R134a, focusing on the heat transfer coefficient (HTC) and pressure drop during flow boiling in smooth and microfin tubes. The experimental setup involves tubes with a 6.14 mm internal diameter and 500 mm length. Data were collected across a broad range of operating conditions, including mass fluxes from 170 to 495 kg/m² s, heat fluxes from 10 to 40 kW/m², saturation temperatures of 15 °C and 25 °C, and vapor qualities from 0.15 to 1.0. In a specific case with a mass flux of 170 kg/m² s, heat flux of 23 kW/m², and a saturation temperature of 15 °C, the results indicate that the microfin tube achieves an HTC enhancement of up to 64 % compared to smooth tubes. However, R134a exhibits a higher HTC than R1234yf and R513A, approximately 5 % and 3 % higher, respectively. In contrast, R134a presents a higher pressure drop than R1234yf by about 8 %. While the pressure drop for R134a is slightly higher than R513A in the smooth tube, the microfin tube shows similar trends but more pronounced differences. This study comprehensively explores microfin tube performance with these refrigerants, offering critical insights for designing advanced refrigeration systems that balance environmental responsibility with energy efficiency. These findings were validated against predicted correlations, showing good agreement.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428514","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 : 2024-08-30DOI: 10.1016/j.ijrefrig.2024.08.026
In certain extreme conditions characterized by ultra-low water vapor content and ultra-low temperatures (e.g. cryogenic wind tunnel), trace water vapor frosting can also pose significant hazards. Considering the crucial role of initial nucleation on subsequent frosting processes, this study firstly investigated and compared the nucleation characteristics of frosting at different water vapor contents (0.1−1000 ppmv) from humid air to trace water vapor based on classical nucleation theory. The preferred nucleation phase diagrams and critical nucleation conditions were analyzed. Sensitivity of the nucleation mass transfer rate, as well as the frosting pathways were further identified. Results show that the nucleation characteristics of trace water vapor frosting (<100 ppmv) is significantly different from that of humid air frosting (>1000 ppmv). Trace water vapor frosting is more inclined towards desublimation nucleation due to its lower nucleation temperature and larger critical contact angle. The critical contact angles for 1000 ppmv, 100 ppmv and 0.1 ppmv are 49°, 75° and 120°, respectively. Furthermore, trace water vapor nucleation requires a greater subcooling degree, has a smaller critical nucleation radius, and is highly sensitive to surface contact angle and further-subcooling degree. At a surface contact angle of 120°, the nucleation subcooling degree of 0.1 ppmv is 2.9 K greater than that of 1000 ppmv. This study helps understanding the nucleation characteristics under different water vapor content conditions, which indicates that reducing subcooling degree and increasing contact angle are more effective anti-frosting methods than reducing water vapor content for trace water vapor frosting.
{"title":"Theoretical analysis of the initial nucleation characteristics of trace water vapor frosting on a cryogenic surface","authors":"","doi":"10.1016/j.ijrefrig.2024.08.026","DOIUrl":"10.1016/j.ijrefrig.2024.08.026","url":null,"abstract":"<div><div>In certain extreme conditions characterized by ultra-low water vapor content and ultra-low temperatures (e.g. cryogenic wind tunnel), trace water vapor frosting can also pose significant hazards. Considering the crucial role of initial nucleation on subsequent frosting processes, this study firstly investigated and compared the nucleation characteristics of frosting at different water vapor contents (0.1−1000 ppmv) from humid air to trace water vapor based on classical nucleation theory. The preferred nucleation phase diagrams and critical nucleation conditions were analyzed. Sensitivity of the nucleation mass transfer rate, as well as the frosting pathways were further identified. Results show that the nucleation characteristics of trace water vapor frosting (<100 ppmv) is significantly different from that of humid air frosting (>1000 ppmv). Trace water vapor frosting is more inclined towards desublimation nucleation due to its lower nucleation temperature and larger critical contact angle. The critical contact angles for 1000 ppmv, 100 ppmv and 0.1 ppmv are 49°, 75° and 120°, respectively. Furthermore, trace water vapor nucleation requires a greater subcooling degree, has a smaller critical nucleation radius, and is highly sensitive to surface contact angle and further-subcooling degree. At a surface contact angle of 120°, the nucleation subcooling degree of 0.1 ppmv is 2.9 K greater than that of 1000 ppmv. This study helps understanding the nucleation characteristics under different water vapor content conditions, which indicates that reducing subcooling degree and increasing contact angle are more effective anti-frosting methods than reducing water vapor content for trace water vapor frosting.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428508","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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