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Performance Evaluation of Different Designs of Locomotive Intercoolers 机车中冷器不同设计的性能评价
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25607
V. Rajendran, A. Furman, Barry A. Record
Heat exchangers of two different designs, used for the cooling of turbocharged air for locomotive diesel engines were experimentally studied to characterize the performance as well as to investigate the loss of effectiveness over time. Performance criteria including initial effectiveness, pressure drop and effectiveness degradation due to thermal shocks were characterized for a typical intercooler. Thermal and flow performance tests as well as severe shock tests were conducted in the laboratory at full-scale flow and geometric conditions to study the drop in effectiveness experienced in the field. The inlet Reynolds number for airside, based on the inlet flow conditions and pipe diameter is 2.13 × 105. The inlet Reynolds number for waterside, based on the inlet flow conditions and pipe diameter is 2 × 105. Mechanisms for the effectiveness drop due to thermal transients are discussed. Significant improvements in effectiveness degradation characteristics were achieved with a proposed new design while maintaining initial effectiveness. Overall, the new design was found to be significantly improved compared to the current design.
采用两种不同设计的热交换器,对机车柴油机增压空气的冷却进行了实验研究,以表征热交换器的性能,并研究了热交换器随时间的损耗。性能标准包括初始有效性、压降和热冲击导致的有效性退化。在实验室中进行了全尺寸流动和几何条件下的热工和流动性能测试以及剧烈冲击测试,以研究现场所经历的效率下降。基于进口流动条件和管径计算的空侧进口雷诺数为2.13 × 105。基于进口流动条件和管径的水边进口雷诺数为2 × 105。讨论了热瞬变导致效率下降的机理。在保持初始效能的同时,提出的新设计显著改善了效能退化特性。总的来说,与目前的设计相比,新设计被发现有了显著的改进。
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引用次数: 0
Heat and Mass Transfer Characteristics of a Finned-Tube Evaporator Under Frosting Conditions 结霜条件下翅片管蒸发器的传热传质特性
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25612
Y. H. Kim, Y. J. Park, Yong Chan Kim, S. Shim, S. Oh, J. S. Lee
An experimental study was performed to investigate the heat and mass transfer characteristics of a finned-tube evaporator coil utilized in a domestic refrigerator under frosting conditions. Airside heat transfer coefficient was measured as a function of air temperature, humidity ratio, air velocity, and evaporating temperature. In addition, frost thickness was monitored and measured by visualization tests during frosting operation. Based on the experimental results, the degradation of heat transfer performance due to frost formation was explored as a function of operating parameters. The rate of frost formation on the evaporator increases at relatively high humidity, high airflow rate, low inlet air temperature and low refrigerant temperature. As the frost thickness increases, airflow rate gradually decreases, while the capacity increases at the early stage of frost formation and then significantly drops.
对家用冰箱在结霜条件下翅片管式蒸发器盘管的传热传质特性进行了实验研究。空气侧换热系数作为空气温度、湿度比、空气速度和蒸发温度的函数来测量。另外,通过可视化试验对结霜过程中的霜厚进行了监测和测量。基于实验结果,探讨了结霜对传热性能的影响与运行参数的关系。在相对较高的湿度、较大的气流速率、较低的进风温度和较低的制冷剂温度下,蒸发器上的结霜率增加。随着结霜厚度的增加,风量逐渐减小,而风量在结霜初期增加,然后显著下降。
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引用次数: 0
Recent Developments in High-Performance Refrigeration for the First Compact Cryogenic Freeze-Dryer 第一台紧凑型低温冷冻干燥机高性能制冷的最新进展
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25622
L. Reznikov, D. Sutherland
Lyophilization, a process of drying of frozen materials with sublimation of solvents from frozen products, is one of the key processes in pharmaceutical industry for preparation of dry inert products. Traditionally, refrigeration for operations of freezing, primary and secondary drying of the moist products and for condensing of solvents has been supported by mechanical refrigeration. Development of efficient, reliable cryogenic refrigeration with accurate temperature control and effective heat transfer processes have created premises for design of the first in the world cryogenic pump-free compact unit “Advantage LN2”.
冻干是利用冷冻产品中的溶剂升华对冷冻材料进行干燥的过程,是制药工业中制备干燥惰性产品的关键工艺之一。传统上,冷冻、湿产品的一次和二次干燥以及溶剂的冷凝操作的制冷都是由机械制冷支持的。高效、可靠的低温制冷技术的发展,以及精确的温度控制和有效的传热过程,为设计世界上第一个无低温泵紧凑型机组“Advantage LN2”创造了前提。
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引用次数: 0
Forced Convective Heat Transfer From Helicoidal Pipes 螺旋管强制对流换热
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25610
A. Fakheri, Abdelrahman H. A. Alnaeim
Forced convection heat transfer from helicoidal pipes is experimentally investigated over a wide range of operating conditions. Based on the experimental results, a characteristic length incorporating the tube diameter, the coil diameter, and the coil spacing, is proposed as the relevant scale for defining Nusselt and Reynolds numbers. Based on this characteristic length, Nusselt number for helicoidal pipes can be predicated from the correlations available for cylinders in the range of available experimental data. It is shown that the performance of the coils depends on the Reynolds number. At high Reynolds numbers, the heat transfer coefficient is essentially equal to that of the straight pipe and the coil pitch has little influence on the heat transfer rate. On the other hand, at low Reynolds numbers, the heat transfer coefficient is lower than that of a straight pipe and its value is a strong function of the coil spacing.
实验研究了螺旋管在各种工况下的强制对流换热问题。根据实验结果,提出了包含管径、线圈直径和线圈间距的特征长度作为定义努塞尔数和雷诺数的相关尺度。在此特征长度的基础上,螺旋管的努塞尔数可以从可用实验数据范围内圆柱体的相关性中预测出来。结果表明,线圈的性能与雷诺数有关。在高雷诺数时,换热系数与直管换热系数基本相等,盘管间距对换热率的影响较小。另一方面,在低雷诺数下,换热系数低于直管,其值与盘管间距有很强的关系。
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引用次数: 0
Cryogenic Heat Engines for Powering Zero Emission Vehicles 为零排放车辆提供动力的低温热机
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25620
C. Ordonez, M. Plummer, R. Reidy
Progress on advancing the technology of using cold thermal reservoirs for mobile energy storage applications is reported. A heat engine such as a Stirling engine can operate using the cold thermal reservoir as a heat sink and the atmosphere as a heat source. A heat engine as developed by the authors that operates employing a sub-atmospheric temperature thermal reservoir such as liquid nitrogen as a heat sink has been called a “cryogenic heat engine.” With sufficient work produced per unit mass of liquid nitrogen, such a cryogenic heat engine may be suitable for powering short range, non-polluting automobiles.
报道了冷热储技术在移动储能应用中的进展。像斯特林发动机这样的热机可以使用冷热源作为吸热器和大气作为热源来运行。作者开发的利用液氮等亚大气温度热源作为散热器的热机被称为“低温热机”。由于每单位质量的液氮产生足够的功,这种低温热机可能适合为短程、无污染的汽车提供动力。
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引用次数: 12
The Investigation of Distorted and Enhanced Inlet Flow Influence on the Performance of a Centrifugal Compressor Stage 进口气流畸变和增强对离心式压缩机级性能影响的研究
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25602
Yunbae Kim, R. Aungier, A. Engeda, Gregory L. Direnzi
The performance of a centrifugal compressor can be seriously affected by inlet flow distortions due to the unsatisfactory nature of the inlet configuration and the resulting inlet flow structure. In the previous work, experimental tests were carried out for the comparison of a centrifugal compressor stage performance with two different inlet configurations: one of which was a straight pipe with constant cross-sectional area as an ideal model and the other is a 90-degree curved pipe with nozzle shape as an actual model. The comparative test results indicated significant compressor stage performance difference between the two different inlet configurations. In addition, the numerical simulation part of the previous work clearly showed that the inlet flow distortion is caused by the pressure driven secondary flow developed in the curved section in the case of the bend inlet, resulting in locally concentrated incidence at the impeller inlet and thus the compressor stage performance degradation. An improved inlet model with the design method has been proposed based on the comparisons of the designated flow properties. In the present work, further numerical simulations on the compressor stage including the impeller and the diffuser with three different inlets are carried out to investigate the performance behavior of the compressor exposed to different inlet configurations. The three different inlet systems include the original bend inlet as well as the proposed inlet model based on the developed design method. Since the flow from the bend inlet is not axisymmetric due to the circumferential and radial distortion on the cross-section, the impeller and the diffuser are modeled with fully 360-degree passages, which accommodates the inlet flow distortion and the impeller-diffuser interaction influence on the entire flow passage of the compressor. The stage performance with the different inlet systems are evaluated and compared with the previous experimental result. The diffuser performance and the flow properties in the vaneless region are compared among those inlet models. The proposed inlet system indicated the benefit of performance improvement over the original inlet system.
离心式压缩机的性能会受到进口气流畸变的严重影响,这是由于进口配置的不满意性质和由此产生的进口气流结构。在之前的工作中,对两种不同进口结构下的离心压气机级性能进行了实验测试,其中一种是理想模型为等截面积的直管,另一种是实际模型为喷嘴形状的90度弯曲管。对比试验结果表明,两种不同进口结构的压气机级性能存在显著差异。此外,前面工作的数值模拟部分清楚地表明,在弯曲进口的情况下,进口流动畸变是由压力驱动的二次流在弯曲截面发展引起的,导致叶轮进口局部集中入射,从而导致压气机级性能下降。在对指定流动特性进行比较的基础上,提出了一种改进的进气道模型。在本工作中,进一步对压气机级包括叶轮和扩压器进行了三种不同进口的数值模拟,以研究不同进口配置下压气机的性能行为。三种不同的进气道系统包括原始的弯曲进气道以及基于所开发的设计方法提出的进气道模型。由于截面上的周向和径向畸变导致弯曲进口的流动不是轴对称的,因此叶轮和扩压器采用全360度通道进行建模,以适应进口流动畸变和叶轮-扩压器相互作用对压气机整个流道的影响。对不同进气系统下的级性能进行了评价,并与前人的实验结果进行了比较。比较了不同进气道模型的扩压器性能和无叶区流动特性。所提出的进气系统表明,性能改进优于原来的进气系统。
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引用次数: 0
Experimental Measurement of the Natural Convection Heat Transfer for Horizontal Helicoidal Pipes 水平螺旋管自然对流换热的实验测量
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25609
Getnet S. Kidane, A. Fakheri
The natural convection heat transfer coefficient for the helicoidal coils are experimentally measured and compared with those for horizontal cylinders. It is found that when the coil pitch to pipe diameter ratio is less than around 1.2, the heat transfer coefficient of the coils approaches that of a horizontal cylinder having a diameter equal to the coil diameter. For the P/d ratio greater than 1.4, the heat transfer coefficient approaches that for horizontal cylinder of diameter d. A modified characteristic, length which incorporates the tube diameter, the coil diameter, and the coil spacing, is used to define Nusselt and Rayleigh numbers. Using the proposed characteristic length, it is shown that the Nusselt number for horizontal helicoidal pipes can be determined using the available Nusselt and Rayleigh number correlation for straight horizontal cylinders in the range of the experimental and available data, Ra ≤ 105, within a maximum deviation of 15.4%.
实验测量了螺旋盘管的自然对流换热系数,并与水平圆柱的自然对流换热系数进行了比较。研究发现,当盘管节距与管径比小于1.2左右时,盘管的换热系数接近于直径与盘管直径相等的水平圆柱体的换热系数。当P/d比大于1.4时,换热系数接近直径为d的水平圆柱体的换热系数。采用一种改进的特性,即长度,它包含了管径、盘管直径和盘管间距,用于定义努塞尔数和瑞利数。利用所提出的特征长度,可以利用直线水平圆柱体的可用Nusselt和Rayleigh数相关性在实验和可用数据Ra≤105范围内确定水平螺旋管的Nusselt数,最大偏差在15.4%以内。
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引用次数: 0
Second Law Analysis of a Stirling Cryocooler With Optimal Design of the Regenerator and Losses 斯特林制冷机蓄热器及损耗优化的第二定律分析
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25621
E. Rogdakis, N. A. Bormpilas
The aim of the research in this paper is a second law analysis of a Stirling cryocooler. A one-dimensional model is proposed for the simulation of the gas flow in the expansion space, the regenerator, the warm-end, the compression space and the compressor. Helium gas is selected as the working medium. An algorithm has been developed considering parametrically the most from the main operational tasks of the thermodynamic cycle. Performance indices such as heat input, efficiency, external dimensions of the engine and technical requirements are taken into account as constraints. Engine operating parameters i.e. speed, external temperature, mean pressure are fixed. The regenerator loss has a critical influence on the cryocooler efficiency and the reduction of this kind of internal irreversibilities is extremely difficult due to the generator is subject to rapidly cycling flows accompanied by steep temperature gradients and large pressure variations. The second flow analysis of the regenerator identifies two principal losses, the irreversible internal heat transfer into the solid matrix and the hydraulic resistance. An optimization technique leads to entropy generation charts, extremely useful for a good design of the regenerator. Finally the main thermodynamic characteristics (net refrigeration, power input and the coefficient of performance) of the cryocooler are given both cases with and without external and internal irreversibilities.
本文的研究目的是对斯特林制冷机的第二定律进行分析。提出了一维气体在膨胀空间、蓄热器、暖端、压缩空间和压缩机内流动的模拟模型。选择氦气作为工质。从热力学循环的主要操作任务出发,提出了一种考虑参数化的算法。性能指标,如热输入,效率,发动机的外部尺寸和技术要求被考虑为约束。发动机运行参数,即速度,外部温度,平均压力是固定的。蓄热器损失对制冷机效率有重要影响,由于蓄热器处于快速循环流动中,且温度梯度大、压力变化大,因此降低这种内部不可逆性极为困难。再生器的第二个流动分析确定了两个主要损失,不可逆的内部热量传递到固体基质和水力阻力。一种优化技术可以生成熵生成图,这对再生器的良好设计非常有用。最后给出了冷冻机的主要热力学特性(净制冷量、功率输入和性能系数),以及有无外部不可逆和内部不可逆的情况。
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引用次数: 0
Simulations, Analysis and Thermoeconomical Synthesis of Heat Transfer Elements 传热元件的模拟、分析及热经济合成
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25623
L. Reznikov, T. Morosuk
Problems of analysis and design of intricate heat transfer elements are traditional for various industrial and experimental heat transfer units, including multichannel heat exchangers and multi-component fins. Authors suggest and introduce unified method of analysis and synthesis for these classes of heat transfer objects. Authors’ method of simulations for such class of objects is based on step-by-step integration of local tangential and longitudinal heat flows with sequential computations of temperature fields in cycles of iterations and specific selection of boundary conditions. Variations of selected key factors provide arrays of design parameters for synthesis of new and optimized heat transfer objects.
复杂传热元件的分析和设计问题是各种工业和实验传热装置的传统问题,包括多通道换热器和多部件翅片。作者提出并介绍了对这类传热物体进行统一分析和综合的方法。作者对这类物体的模拟方法是基于局部切向和纵向热流的逐步整合,在迭代循环和特定边界条件选择的温度场的顺序计算。选定的关键因素的变化为合成新的和优化的传热对象提供了一系列的设计参数。
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引用次数: 0
Design Point Performance Trends for Water Vapor Compressors 水蒸汽压缩机设计点性能趋势
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/pid-25605
N. D’Orsi, S. Wight, T. Yoshinaka
A design study of various water vapor compressor configurations — including single and multistage centrifugal compressors and multistage axial compressors — is used to determine geometry and performance trends as a function of design speed, compressor configuration, and intercooling method. The intercooled multistage centrifugal machines led to the lowest required power levels, though the large outer diameter of these machines and the addition of an intercooler may reduce their appeal. The non-intercooled multistage axial configurations offered high design point performance and a much smaller outer diameter than the centrifugal machines, though at the expense of large overall axial length and limited flow range. Ultimately, the selection of the right machine for a given application is a tradeoff between the performance and geometry trends illustrated in this paper, as well as the cost of the machine.
对各种水蒸汽压缩机配置的设计研究——包括单级和多级离心式压缩机和多级轴向压缩机——用于确定几何形状和性能趋势作为设计速度、压缩机配置和中间冷却方法的函数。中间冷却的多级离心机器导致了最低的所需功率水平,尽管这些机器的大外径和中间冷却器的增加可能会降低它们的吸引力。非中冷多级轴向配置提供了高设计点性能和远小于离心式机器的外径,但代价是大的总轴向长度和有限的流量范围。最终,为给定的应用程序选择合适的机器是在本文所述的性能和几何趋势以及机器的成本之间进行权衡。
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引用次数: 4
期刊
Chemical and Process Industries
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