共查询到20条相似文献,搜索用时 83 毫秒
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近年来,由于良好的环境效益和高温出水能力,跨临界CO2循环在制冷热泵领域得到了广泛应用。但较高的回水温度会限制系统的整体性能,因此有必要进行技术改善,提升跨临界CO2循环系统性能。其中,在气体冷却器出口对工质进行过冷就是一种良好的办法。过冷的形式包含多种,如添加回热器、经济器、闪蒸罐及双系统过冷等,其中双系统又分成热电模块、辅助循环以及其他新型组合方式。研究结果表明,以上方式均可以提高跨临界循环系统性能。回热器可使系统获得10%以上的COP增量,而双系统过冷则可以达到20%以上。本文详细讨论了3种过冷方法的应用特点,为学术研究及工程应用提供了参考。 相似文献
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为利用CO2跨临界循环气体冷却器放热段较大的温度滑移,减小节流部分的膨胀功损失,提高系统性能,可在制冷系统中利用CO2跨临界循环与NH3喷射循环复合实现压缩/喷射复叠式系统。在对系统进行热力学分析的基础上,建立了相应的模型。计算结果表明:NH3循环喷射器引射流体温度和出口的冷凝温度对引射系数影响很大,在较高引射流体温度和较低冷凝温度下,CO2跨临界压缩/喷射制冷循环可以得到较高的循环性能。在较低CO2跨临界循环蒸发温度和压缩机效率时,此循环相对基本循环有明显优势。降低发生器温差也是提高循环性能的途径之一。 相似文献
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介绍了一种新型商用跨临界CO2循环压缩机,并对此压缩机的关键部件,如壳体和连杆的设计及其应力分布进行分析,同时对压缩机内的油路进行设计,保证压缩机内油压平衡.在自行设计的跨临界CO2压缩机性能测试试验台对跨临界CO2压缩机及其热泵系统进行了系列实验研究,根据实验数据拟合出压缩机的等熵效率和容积效率公式.研究结果表明,在吸气压力为4.0 MPa,气冷器排气温度为25℃工况时,压缩机制热量在58~65 kW之间,制冷量在49~52 kW之间.跨临界CO2热泵系统在按照"一次加热"方式进行实验时,名义工况下出水温度分别为55℃和85℃时,热泵系统制热系数COPh分别为3.46和2.82.系统性能系数随着气体冷却器出水温度的升高而降低,但却随着蒸发器进水温度的升高而升高.冷却水进水温度越高,热泵系统效率越低,因此热泵热水器系统更适于"一次加热"供水系统. 相似文献
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介绍了一种新型商用跨临界CO2热泵空气干燥系统.首先建立了热泵干燥系统所需的翅片式气冷器的物理和数学模型,对气冷器的换热面积进行了计算,同时根据超临界状态下CO2放热特性对气冷器的结构进行设计.在此基础上,建立了跨临界CO2热泵空气干燥系统,并对该系统进行了性能试验研究.试验结果表明,该系统可将常温空气“一次性”加热到100℃,此种工况下空气流量为2.26 m3/h,系统性能系数COP为3.80. 相似文献
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Clarence W.DE SILVA 《Instrumentation》2019,(4):72-84
An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t... 相似文献
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A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load. 相似文献
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针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。 相似文献
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The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci... 相似文献
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针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。 相似文献
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针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。 相似文献
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交通荷载作用下桥梁结构参数识别方法 总被引:2,自引:1,他引:1
应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别. 相似文献
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30 keV Ga+ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z2, and shows a non-monotonic relationship between contrast and Z2. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z2, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory. 相似文献
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RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication. 相似文献
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This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an... 相似文献