International Journal of Refrigeration-revue Internationale Du Froid最新文献_第4页

A method to calculate the two-phase distribution in a microchannel heat exchanger 计算微通道热交换器中两相分布的方法

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-30 DOI: 10.1016/j.ijrefrig.2024.09.027

Maldistribution seriously impacts the heat transfer performance of the microchannel heat exchanger (MCHX). Fully understanding the two-phase distribution in the heat exchanger is important for advancing academic research and engineering applications. This study introduces a novel method for quantifying two-phase distribution in a microchannel heat exchanger. An experimental setup was developed to measure the local vapor mass fraction in the heat exchanger header. Capacitance signals were measured under inlet vapor mass fractions from 0 to 1, and inlet flow rates of 10, 15, and 25 g s⁻¹ corresponding to a mass flux of 17.47, 26.2, and 43.66 kg m⁻²s⁻¹, respectively. The local vapor mass fraction in the header was estimated using the capacitance measurements. The mass flow rate in the header, the microchannel tube, and the vapor mass fraction in the tube were calculated using the proposed model. The calculation model was validated against literature data, and the results were analyzed. The analysis reveals the characteristics of vapor mass fraction and mass flow rate distribution in the MCHX and further elaborates on the effects of phase separation, entrainment ratio, and pressure drop balance on the distribution. The proposed method can evaluate distribution in the header and tubes of microchannel heat exchangers, and it is also applicable to other types of two-phase flow devices.

分布不良严重影响了微通道换热器（MCHX）的传热性能。充分了解热交换器中的两相分布对于推进学术研究和工程应用非常重要。本研究介绍了一种量化微通道热交换器中两相分布的新方法。研究人员开发了一种实验装置，用于测量热交换器集管中的局部蒸汽质量分数。在入口蒸汽质量分数为 0 至 1，入口流速为 10、15 和 25 g s-1 的情况下测量电容信号，对应的质量通量分别为 17.47、26.2 和 43.66 kg m-2s-1。集管中的局部蒸汽质量分数是通过电容测量值估算出来的。利用提出的模型计算了集管、微通道管中的质量流量和管中的蒸汽质量分数。计算模型与文献数据进行了验证，并对结果进行了分析。分析揭示了 MCHX 中蒸汽质量分数和质量流量分布的特点，并进一步阐述了相分离、夹带比和压降平衡对分布的影响。所提出的方法可以评估微通道热交换器集管和管道中的分布，也适用于其他类型的两相流设备。

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引用次数: 0

Numerical investigation of ammonia boiling heat transfer in rectangular microchannel under high pressure 高压下矩形微通道中氨沸腾传热的数值研究

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-29 DOI: 10.1016/j.ijrefrig.2024.09.025

Ammonia boilers are commonly used as expendable radiators during the return phase of spacecraft. The aim of this study is to investigate the bubble behavior and heat transfer characteristics within a vertical rectangular microchannel of a plate-fin ammonia boiler under gravity at an absolute pressure of 354–615 kPa. In order to achieve this, a single rectangular microchannel unit was intercepted from the ammonia boiler structure to construct a simulation model, and the high-pressure boiling process of ammonia in the rectangular microchannel was numerically investigated using the VOF model. Good agreement was obtained by comparing the numerical results with the experimental data with the error within 8 %. The results show that the wake flow at the lower end of the primary bubbles has an enhanced effect on the heat transfer, which is about 50–60 %. The maximum horizontal dimension of primary bubbles increases with increasing superheat, and significant bubble coalescence occurs when 45 % of the rectangular microchannel spacing is exceeded. In addition, the effect of different saturation temperatures on the heat transfer performance on the hot high temperature wall was investigated. Significant heat transfer deterioration was found to occur at saturation temperatures below 4 °C (superheat above 15 °C). The reason found in this study was that bubble coalescence significantly increases the percentage of gas-phase contact area on the high-temperature wall (from 25 % to 54 %) and weakens the wake enhancement effect.

氨锅炉通常用作航天器返回阶段的消耗性散热器。本研究的目的是研究在绝对压力为 354-615 kPa 的重力条件下，板翅式氨锅炉垂直矩形微通道内的气泡行为和传热特性。为此，从氨锅炉结构中截取了一个矩形微通道单元来构建模拟模型，并利用 VOF 模型对氨在矩形微通道中的高压沸腾过程进行了数值研究。通过将数值结果与实验数据进行比较，得到了良好的一致性，误差在 8% 以内。结果表明，初级气泡下端的唤醒流对传热有增强作用，约为 50-60%。原生气泡的最大水平尺寸随着过热度的增加而增大，当超过矩形微通道间距的 45% 时，就会出现明显的气泡凝聚现象。此外，还研究了不同饱和温度对高温热壁传热性能的影响。研究发现，当饱和温度低于 4 °C（过热度高于 15 °C）时，传热性能会显著下降。这项研究发现的原因是气泡凝聚显著增加了高温壁上气相接触面积的百分比（从 25% 增加到 54%），削弱了唤醒增强效应。

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引用次数: 0

Investigating dehumidification and heating performance in a dual evaporator heat pump system for electric vehicles 研究电动汽车双蒸发器热泵系统的除湿和加热性能

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-27 DOI: 10.1016/j.ijrefrig.2024.09.024

In cold, moisture-rich winter environments, window fogging represents a substantial safety hazard for drivers. Electric vehicles often incorporate heat pump systems to address challenges such as dehumidification and heating specific to cold weather. Therefore, it is essential to evaluate the dehumidification and heating efficiency of these systems through focused research. This study presents a dual-evaporator heat pump system designed specifically for electric vehicles, equipped with two distinct modes for dehumidification and heating. The research examines how factors such as inlet air volume and the degree of opening of the electronic expansion valve affect the system's dehumidification and heating performance. Experimental analyses were conducted to explore the system's response under various conditions of inlet air humidity and compressor speed in both modes. Results suggest that increasing inlet air volume improves dehumidification effectiveness but may reduce heating performance. Likewise, a wider opening of the electronic expansion valve enhances heating but could decrease dehumidification efficiency. Importantly, the study indicates that when the relative humidity of the inlet air exceeds 70 %, a single evaporator mode is more effective for dehumidification. However, when the relative humidity is below 70 %, the dual evaporator mode is more advantageous, showing better heating performance.

在寒冷、湿度大的冬季环境中，车窗起雾对驾驶员的安全构成了极大的威胁。电动汽车通常采用热泵系统来应对寒冷天气下的除湿和加热等挑战。因此，有必要通过重点研究来评估这些系统的除湿和加热效率。本研究介绍了专为电动汽车设计的双蒸发器热泵系统，该系统配备两种不同的除湿和加热模式。研究探讨了进气量和电子膨胀阀开启程度等因素如何影响系统的除湿和制热性能。研究人员进行了实验分析，以探讨系统在两种模式下不同的进气湿度和压缩机转速条件下的反应。结果表明，增加进气量可以提高除湿效果，但可能会降低制热性能。同样，电子膨胀阀开度越大，制热效果越好，但可能会降低除湿效率。重要的是，研究表明，当入口空气的相对湿度超过 70% 时，单蒸发器模式的除湿效果更好。然而，当相对湿度低于 70% 时，双蒸发器模式更具优势，显示出更好的制热性能。

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引用次数: 0

Experimental performance comparison of various expansion devices for small-capacity subcritical R744 vapour-compression refrigeration units 小容量亚临界 R744 蒸汽压缩制冷机组各种膨胀装置的实验性能比较

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-26 DOI: 10.1016/j.ijrefrig.2024.09.015

The target of this study is to experimentally compare the performance of three different expansion devices for small-capacity subcritical R744 vapour-compression refrigeration units. The first considered expansion device was the conventional high-pressure expansion valve, which was selected as the baseline. The second assessed expansion device was a two-phase ejector for expansion work recovery whose refrigerant flow was modulated via the pulse-width modulation (PWM) strategy. Finally, the PWM approach was employed for controlling the refrigerant flow of the ejector motive nozzle while the refrigerant was not permitted to be drawn by the ejector suction nozzle. The results showed that the motive nozzle controlled via PWM effect offers similar effectiveness to a conventional high-pressure expansion valve in the subcritical regime. Furthermore, it was observed that the PWM ejector is able to control the high pressure effectively while increasing the coefficient of performance (COP) by up to 5.3 % without and by up to 7.9 % with overfed evaporator compared to the baseline in the transition regime. The results also showed that the installation of the conventional high-pressure expansion valve is not necessary. Finally, the yearly performance of the aforementioned expansion devices was assessed in five different locations, i.e., Athens (Greece), Phoenix (USA), New Delhi (India), Riyadh (Saudi Arabia) and Bangkok (Thailand). The outcomes revealed that the PWM ejector allows for a higher in yearly average COP (COP_{yearly avg}) from 4.9 % (in Athens) to 11.8 % (in Bangkok) over the baseline.

本研究的目标是通过实验比较小容量亚临界 R744 蒸汽压缩制冷装置的三种不同膨胀装置的性能。首先考虑的膨胀装置是传统的高压膨胀阀，并将其作为基准。第二个评估的膨胀装置是用于膨胀功回收的两相喷射器，其制冷剂流量通过脉宽调制（PWM）策略进行调节。最后，采用 PWM 方法控制喷射器动力喷嘴的制冷剂流量，同时不允许喷射器吸气喷嘴吸入制冷剂。结果表明，在亚临界状态下，通过 PWM 效果控制的动机喷嘴与传统的高压膨胀阀具有相似的效果。此外，还观察到 PWM 喷射器能够有效控制高压，同时与过渡工况下的基线相比，在不使用超喂蒸发器的情况下，性能系数（COP）最高可提高 5.3%，在使用超喂蒸发器的情况下，性能系数（COP）最高可提高 7.9%。结果还表明，无需安装传统的高压膨胀阀。最后，在希腊雅典、美国凤凰城、印度新德里、沙特阿拉伯利雅得和泰国曼谷五个不同地点对上述膨胀装置的年度性能进行了评估。结果表明，与基线相比，PWM 喷射器可使年平均 COP（COPyearly avg）从 4.9%（雅典）提高到 11.8%（曼谷）。

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引用次数: 0

Theoretical analysis of the optimal ejector operation and design within an ejector-based refrigeration system 基于喷射器的制冷系统中喷射器最佳运行和设计的理论分析

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-24 DOI: 10.1016/j.ijrefrig.2024.09.020

Optimal operation and design of ejectors are the subject of recent concerns, especially for the enhancement of refrigeration and heat pump cycles based on natural refrigerants like carbon dioxide. In this study, a thermodynamic analysis of an ejector-based refrigeration cycle is performed to determine both what operating pressures lead to the highest physically possible performance depending on the ambient conditions, and what are the main dimensions of the ejector leading to the best performance at a given ambient temperature. A state-of-the-art thermodynamic model for the prediction of the ejector performance is for the first time utilized to generate reliable operation and performance maps of the ejector cycle. Most notably, it is found that the optimal coefficient of performance is not necessarily found when the ejector operates at critical conditions but mostly when the device is under off-design regime, depending on the ejector internal efficiency and the hot side temperature. In addition, the analysis reveals that the performance of the cycle is not highly sensitive to the throat area ratio of the ejector given that the latter lies within an acceptable range. Those findings contribute to getting a better understanding of how the cycle benefits from the ejector and define design and control strategies for the cycle.

喷射器的最佳运行和设计是近期关注的主题，特别是在增强基于二氧化碳等天然制冷剂的制冷和热泵循环方面。在这项研究中，对基于喷射器的制冷循环进行了热力学分析，以确定在给定的环境温度下，什么样的工作压力能使物理性能达到最高，以及喷射器的主要尺寸能使其达到最佳性能。预测喷射器性能的最先进热力学模型首次用于生成可靠的喷射器循环运行和性能图。最值得注意的是，研究发现，最佳性能系数并不一定是在喷射器在临界状态下运行时找到的，而主要是在设备处于非设计状态时找到的，这取决于喷射器的内部效率和热侧温度。此外，分析表明，如果喷射器的喉管面积比在可接受的范围内，则循环性能对喉管面积比的敏感度并不高。这些发现有助于更好地了解循环如何从喷射器中获益，并确定循环的设计和控制策略。

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引用次数: 0

Optimisation of cooling performance and water consumption of a solid desiccant-assisted indirect evaporative cooling system using response surface methodology 利用响应面方法优化固体干燥剂辅助间接蒸发冷却系统的冷却性能和耗水量

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-24 DOI: 10.1016/j.ijrefrig.2024.09.023

Solid desiccant-assisted dew-point indirect evaporative cooling (SD-DPIEC) systems have gained considerable attention as a potential eco-friendly alternative to vapour-compression cooling systems in building cooling applications. However, one major drawback of these systems is their substantial water consumption during evaporative cooling. To tackle this issue, this study aims to improve the cooling efficiency and water utilisation of an SD-DPIEC system using response surface methodology (RSM). This research focuses on optimising four key parameters: supply air temperature, humidity ratio, water consumption rate and coefficient of performance (COP). The independent variables encompass the ambient temperature, relative humidity, regeneration temperature, and recirculation air ratio. Employing a multi-objective optimisation approach via the desirability function, the optimised SD-DPIEC system is subsequently tested in two prevalent weather patterns in Australia. The results demonstrated that the regression models derived from RSM exhibited commendable predictive capability, with the determination coefficient

R^{2}

and Adequate Precision exceeding 0.97 and 40.46, respectively. The outcomes revealed that the system attained its optimal performance with a supply air temperature of 20.36 °C, humidity ratio of 12.56 g kg^-1, a water consumption rate of 3.11 kg/hr, and COP of 2.03 under the ambient temperature of 33.79 °C, relative humidity of 68.48 %, regeneration temperature of 51.78 °C, and recirculation air ratio of 60 %. Based on the optimisation results, a case study was undertaken to evaluate the system's applicability in representative Australian climates. The results demonstrated that the system could uphold air conditions with the supply air temperature below 19 °C and humidity ratio below 11.51 g kg^-1 under the studied Australian climates.

固体干燥剂辅助露点间接蒸发冷却（SD-DPIEC）系统作为建筑冷却应用中蒸汽压缩冷却系统的潜在环保型替代品，已获得了广泛关注。然而，这些系统的一个主要缺点是在蒸发冷却过程中会消耗大量的水。为解决这一问题，本研究旨在利用响应面方法（RSM）提高 SD-DPIEC 系统的冷却效率和水利用率。研究重点是优化四个关键参数：送风温度、湿度比、耗水量和性能系数（COP）。自变量包括环境温度、相对湿度、再生温度和再循环空气比率。通过可取函数采用多目标优化方法，优化后的 SD-DPIEC 系统随后在澳大利亚的两种常见天气模式下进行了测试。结果表明，由 RSM 得出的回归模型表现出值得称赞的预测能力，确定系数 R2 和适当精度分别超过 0.97 和 40.46。结果显示，在环境温度为 33.79 °C、相对湿度为 68.48 %、再生温度为 51.78 °C、再循环空气比率为 60 % 的条件下，系统的最佳性能为送风温度为 20.36 °C、湿度比率为 12.56 g kg-1、耗水量为 3.11 kg/hr、COP 为 2.03。根据优化结果，进行了一项案例研究，以评估该系统在澳大利亚代表性气候条件下的适用性。结果表明，在所研究的澳大利亚气候条件下，该系统可以维持供气温度低于 19 °C、湿度比低于 11.51 g kg-1 的空气条件。

{"title":"Optimisation of cooling performance and water consumption of a solid desiccant-assisted indirect evaporative cooling system using response surface methodology","authors":"","doi":"10.1016/j.ijrefrig.2024.09.023","DOIUrl":"10.1016/j.ijrefrig.2024.09.023","url":null,"abstract":"<div><div>Solid desiccant-assisted dew-point indirect evaporative cooling (SD-DPIEC) systems have gained considerable attention as a potential eco-friendly alternative to vapour-compression cooling systems in building cooling applications. However, one major drawback of these systems is their substantial water consumption during evaporative cooling. To tackle this issue, this study aims to improve the cooling efficiency and water utilisation of an SD-DPIEC system using response surface methodology (RSM). This research focuses on optimising four key parameters: supply air temperature, humidity ratio, water consumption rate and coefficient of performance (COP). The independent variables encompass the ambient temperature, relative humidity, regeneration temperature, and recirculation air ratio. Employing a multi-objective optimisation approach via the desirability function, the optimised SD-DPIEC system is subsequently tested in two prevalent weather patterns in Australia. The results demonstrated that the regression models derived from RSM exhibited commendable predictive capability, with the determination coefficient <span><math><msup><mrow><mi>R</mi></mrow><mn>2</mn></msup></math></span> and Adequate Precision exceeding 0.97 and 40.46, respectively. The outcomes revealed that the system attained its optimal performance with a supply air temperature of 20.36 °C, humidity ratio of 12.56 g kg<sup>-1</sup>, a water consumption rate of 3.11 kg/hr, and COP of 2.03 under the ambient temperature of 33.79 °C, relative humidity of 68.48 %, regeneration temperature of 51.78 °C, and recirculation air ratio of 60 %. Based on the optimisation results, a case study was undertaken to evaluate the system's applicability in representative Australian climates. The results demonstrated that the system could uphold air conditions with the supply air temperature below 19 °C and humidity ratio below 11.51 g kg<sup>-1</sup> under the studied Australian climates.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428367","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}

引用次数: 0

Experimental study of two-phase pressure-drop in horizontal return bends with ammonia 氨水水平回流弯管中两相压力降的实验研究

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-23 DOI: 10.1016/j.ijrefrig.2024.09.021

In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (R/d_o ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m⁻² s⁻¹, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and R/d_o ratio of the bend.

Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.

在制冷和空调系统的蒸发器和冷凝器中，各种直管通过 U 形弯管连接在一起。由于流动干扰和离心效应，这些 U 形弯管会产生较高的压降。准确预测这些弯管中的压降对于可靠的设计和运行至关重要。本研究调查了水平 U 形弯管中氨水在各种实验条件下的两相流压降。使用了三根公称外径在 22.2、15.9 和 9.5 毫米之间的管道，每根管道都有三个弯曲半径（R/do 比），水平配置的弯曲半径在 1.2 和 2.5 之间。试验在 +10 和 -15 °C 饱和温度下进行，质量通量在 10 和 50 kg m-2 s-1 之间变化，蒸汽质量在 0.1 和 0.9 之间变化。与小管子相比，大管子的压降随着质量通量的增加和弯曲率的减小而增大，而小管子的绝对值更高，在两个饱和温度下的整个蒸汽质量范围内的性能更稳定。在高饱和温度和高质量通量下，管子直径的影响较小，而弯曲曲率比则主要影响大直径管子的压降性能。只有当蒸汽质量低于 0.5 时，文献中的一种相关性才能很好地预测数据。对于更宽的质量范围，文献中的现有模型并不适合预测氨 U 形弯管的压降。

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引用次数: 0

Reduced-dimension Bayesian optimization for model calibration of transient vapor compression cycles 用于瞬态蒸汽压缩循环模型校准的降维贝叶斯优化技术

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-20 DOI: 10.1016/j.ijrefrig.2024.09.010

Development and calibration of first-principles dynamic models of vapor compression cycles (VCCs) is of critical importance for applications that include control design and fault detection and diagnostics. Nevertheless, the inherent complexity of models that are represented by large systems of differential–algebraic equations leads to significant challenges for model calibration processes that utilize classical gradient-based methods. Bayesian optimization (BO) is a sample-efficient and gradient-free approach using a probabilistic surrogate model and optimal search over a feasible parameter space. Despite the benefits of BO in reducing computational costs, challenges remain in dealing with a high-dimensional calibration task resulting from a large set of parameters that have significant impacts on system behavior and need to be calibrated simultaneously. This paper presents a reduced-dimension BO framework for calibrating transient VCCs models where the calibration space is projected to a low-dimensional subspace for accelerating convergence of the solution algorithm and consequently reducing the number of transient simulations. The proposed approach was demonstrated via two case studies associated with different VCC applications where 10 parameters were calibrated in each case using laboratory measurements. The reduced-dimension BO framework only required

1 / 8^{th}

of the iterations associated with a standard BO method that deals with high-dimensional calibration parameters for converged solutions and yielded comparable accuracy. Furthermore, both calibrated models revealed significant accuracy improvements compared to uncalibrated models.

蒸汽压缩循环（VCC）第一原理动态模型的开发和校准对于控制设计、故障检测和诊断等应用至关重要。然而，由大型微分代数方程系统表示的模型固有的复杂性给利用经典梯度法进行模型校准的过程带来了巨大挑战。贝叶斯优化（BO）是一种样本效率高、无梯度的方法，它使用概率代理模型和在可行参数空间上的最优搜索。尽管贝叶斯优化法具有降低计算成本的优势，但在处理高维校准任务时仍面临挑战，因为大量参数会对系统行为产生重大影响，而且需要同时进行校准。本文提出了一种用于校准瞬态 VCC 模型的降维 BO 框架，将校准空间投影到低维子空间，以加速求解算法的收敛，从而减少瞬态模拟的次数。我们通过两个与不同 VCC 应用相关的案例研究对所提出的方法进行了演示，每个案例都使用实验室测量结果对 10 个参数进行了校准。缩小维度的 BO 框架所需的迭代次数仅为处理高维度校准参数的标准 BO 方法的 1/8，并获得了相当的精度。此外，与未经校准的模型相比，两种校准模型的精度都有显著提高。

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引用次数: 0

Essential improvement of the JT cryocooler working at liquid helium temperature for space: Efficient and lightweight 对在液氦温度下工作的 JT 低温冷却器进行了重要改进：高效、轻巧

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-19 DOI: 10.1016/j.ijrefrig.2024.08.006

Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications.

在液氦温度下工作的焦耳-汤姆逊（JT）低温冷却器具有寿命长、振动小和电磁干扰小等优点，已被用于太空。然而，在一定的质量限制下，其冷却能力和热力学效率仍需进一步提高，这是 JT 低温冷却器在太空高效应用的必要改进。因此，本研究对在液氦温度下工作的 JT 低温冷却器进行了优化设计。在对斯特林低温冷却器、脉冲管低温冷却器和 JT 压缩机进行改进的基础上，所开发的 JT 低温冷却器在 4.18 K 时可提供 0.36 W 的冷却能力，而总输入功率和总质量（不含低温恒温器）分别为 1157 W 和 26.8 kg。与文献研究相比，可以发现所开发的 JT 低温冷却器适用于空间应用。

引用次数: 0

Study on the impacts of refrigerant leakage on the performance and environmental benefits of heat pumps using R513A as replacement of R134a 研究制冷剂泄漏对使用 R513A 替代 R134a 的热泵的性能和环境效益的影响

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Refrigeration-revue Internationale Du Froid

Pub Date : 2024-09-19 DOI: 10.1016/j.ijrefrig.2024.09.008

The escalating threat of global warming has highlighted the imperative to address the greenhouse effect. R513A is recognized as a viable substitute for R134a, providing a lower global warming potential (GWP) while preserving similar thermodynamic properties. However, refrigerant leakage is one of the common faults in heat pump equipment. For industrial heat pumps, refrigerant leakage can make the system less stable and affect normal industrial production, while long-term leakage can also affect the carbon emissions of the industry. When substituting refrigerants, it is crucial to consider not only their distinct properties under typical operating conditions but also the stability and environmental impact of the alternative refrigerant in cases of leakage. This paper focuses on experimentally evaluating the impact of using R513A to replace R134a on the performance of refrigeration systems under the condition of rapid refrigerant leakage. Then the life cycle climate performance evaluation (LCCP) theory is used to assist experimental results in evaluating the carbon footprints of R513A and R134a systems at different annual leakage rates. The results show that R513A has better stability than R134a when responding to rapid refrigerant leakage. This paper determines the changes in annual electricity consumption and indirect emissions under several annual leakage rates and finds that the impact of leakage on indirect emissions is also not negligible. During the utilization phase of the equipment, when leakage was taken into account, the carbon emissions of the R134a system were higher.

不断升级的全球变暖威胁凸显了解决温室效应问题的迫切性。R513A 被认为是 R134a 的可行替代品，它具有较低的全球升温潜能值（GWP），同时保持了类似的热力学特性。然而，制冷剂泄漏是热泵设备的常见故障之一。对于工业热泵来说，制冷剂泄漏会使系统稳定性降低，影响正常的工业生产，长期泄漏还会影响工业的碳排放。在替代制冷剂时，不仅要考虑它们在典型运行条件下的不同特性，还要考虑替代制冷剂在泄漏情况下的稳定性和对环境的影响，这一点至关重要。本文主要通过实验评估了在制冷剂快速泄漏的条件下，使用 R513A 替代 R134a 对制冷系统性能的影响。然后，利用生命周期气候性能评估（LCCP）理论辅助实验结果，评估 R513A 和 R134a 系统在不同年泄漏率下的碳足迹。结果表明，在应对快速制冷剂泄漏时，R513A 比 R134a 具有更好的稳定性。本文确定了几种年泄漏率下年耗电量和间接排放量的变化，发现泄漏对间接排放量的影响也不容忽视。在设备使用阶段，如果考虑到泄漏，R134a 系统的碳排放量更高。

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引用次数: 0