小型制冷装置冷凝器的仿真与实验研究

建立了冷凝器的仿真模型,开发冷凝器稳态模型的仿真软件,搭建翅片管式冷凝器的试验装置,得到冷凝器参数随制冷剂质量流量变化的一系列实验数据.经过比较分析,证明实验数据和仿真结果的变化趋势一致,吻合程度较好.     

车用多元平行流冷凝器热力性能及流程布置仿真研究

采用分布参数法建立车用多元平行流冷凝器仿真模型,模拟2种流程布置的冷凝器换热和流动特性,仿真结果表明:与试验结果相比,冷凝器换热量的模拟结果偏差不超过±5%,空气出口温度偏差不超过±10%,制冷剂出口温度偏差不超过±15%,说明仿真模型能够较好地预测多元平行流冷凝器的换热和流动特性。通过50种流程布置方案仿真计算结果发现:车用多元平行流冷凝器的流程数不宜过多,一般以不超过5流程为宜,且最优化的流程布置方案更可能出现在流程数较少的情况下。     

仿真技术在小型空气冷凝器设计中的应用

依据冷凝器设计原理,通过Matlab仿真软件对空冷式冷凝器进行设计研究。计算模型为稳态分布模型,选取的研究对象为目前最为实用的四种肋片管,通过对每一种肋片形式的冷凝器管内制冷剂的不同状态分别做分析,以此达到较高的仿真效果。分别根据管壁肋片的不同形式,综合分析各种肋片在不同空气流速、不同肋间距下换热情况,以及不同制冷剂流量对换热情况的影响。在仿真结果上对比实际冷凝器的换热情况,比较仿真的结果,提出了系列设计意见。     

水冷式冷凝器性能计算机分析系统

水冷式冷凝器广泛应用于制冷行业当中.本文对采用第二工质量热器和变频压缩机的水冷式冷凝器性能实验系统进行了计算机仿真,开发了水冷式冷凝器性能计算机系统软件.利用该软件对水冷却式冷凝器进行了实验性能预测,其结果很好地反映了水冷式冷凝器的性能特征.利用该软件分析预测水冷式冷凝器性能有利于大大减少实验量,缩短冷凝器试制周期.     

降膜蒸发冷凝器建模及仿真

为详细分析降膜蒸发冷凝器传热传质规律,本文将冷凝器等效为所有单管组成的网络,每根单管离散为多个微元,建立了带增膜板的蒸发冷凝器稳态传热传质微元数学模型,并引入了一个新的无量纲准则数Xr,以反映水膜厚度对空气和水膜间传热传质的影响。通过VS 2010软件编程,采用双点弦截法迭代计算,模拟并分析了顺排和叉排结构管束的蒸发冷凝器管外水膜温度、空气温度、空气湿度和管内热流体温度的变化规律。仿真软件能反映并能预测多种结构降膜蒸发冷凝器的性能,为冷凝器的优化提供仿真依据。     

冷凝器阴极保护效果评估与仿真预测研究

为了评估冷凝器系统的阴极保护效果,建立了冷凝器系统样机,通过试验评估了阴极保护系统的保护效果,然后开展了基于边界元法的冷凝器保护电位仿真与优化,优化计算结果与实测结果相一致,从而利用仿真计算预测了多根换热管系统的保护效果,为实际工况提供指导.样机实测结果显示:端盖和管板的保护电位维持在-600～-610 mV左右,得到完全保护;换热管距离管板处30 cm范围内,其电位小于-450 mV,得到完全保护,距离越远保护效果越弱;实测结果与仿真计算结果偏差最大值不超过15％,表明二者具有较好的一致性,仿真可对实际工况具有指导意义.仿真预测表明,27根管模型的端盖和管板得到完全保护,换热管电位低于-450 mV的长度为16.8 cm;63根管模型的端盖和管板也得到完全保护,换热管电位低于-450 mV的长度为13.0 em.综上所述,目前的阴极保护方案可有效保护冷凝器端盖、管板和部分靠近管板的换热管;在牺牲阳极的数量固定的前提下,换热管数量的增加会导致其保护距离逐渐减少.     

翅片管式冷凝器空气侧换热性能研究

建立翅片管式冷凝器性能试验平台,以热水为管内换热介质,通过大量的样机试验数据获得冷凝器空气侧换热及压力损失关联式,并将上述试验关联式应用于冷凝器的仿真计算模型,使用Visual C++编程工具开发翅片管式冷凝器仿真计算程序。试验和仿真结果表明:换热及压力损失关联式和试验数据拟合很好,Nu数的偏差在±10%以内,压力损失的偏差在±15%以内,换热量的偏差在±5%以内。     

R290微通道冷凝器性能优化及其充注量分析

采用仿真方法,以R290家用空调器用微通道冷凝器为研究对象,比较不同流路布置方案对冷凝器性能的影响,并对外形尺寸相同的微通道冷凝器与翅片管冷凝器充注比进行对比。结果表明：流程布置及各流程扁管分配对微通道冷凝器性能有较大影响,存在较优的流程数及流程扁管数;R290微通道冷凝器充注比与Ф5mm单排冷凝器充注比水平相当,经进一步结构优化后,微通道冷凝器将比小管径换热器在降低冷凝器充注比和材料成本方面具有更大的潜力和优势。     

风速对冷凝器换热能力的影响

本文采用分布参数法建立了冷凝器数学模型,在此模型基础上编写了冷凝器仿真程序,对三种管排数的冷凝器进行了模拟.通过计算不同风速下空气侧换热系数和管内外温度的变化,来分析风速对冷凝器换热能力的影响.由计算可知在换热面积相同时2排管冷凝器换热能力要比4排管冷凝器换热能力大2.36%;减少管排数可提高空气侧平均换热因子,减小压降.     

丝管式冷凝器周围空气温度分布的实验研究及仿真

用化学试剂TiCl4对丝管式冷凝器周围空气的流动进行了可视化研究。实验结果表明，丝管式冷凝器周围空气的流动属于紊流。据此，建立了计算冷凝器周围空气温度的数学模型，采用数值模拟的方法，对稳定状态下冷凝器周围空气的温度进行了仿真，并与实验数据进行了对比，验证了所建立数学模型的正确性。这个新模型对冷凝器的优化设计提高设计精度具有一定的指导价值。     

Experimental and numerical study on microchannel and round-tube condensers in a R410A residential air-conditioning system

The effect of different type of condensers on the performance of R410A residential air-conditioning systems was investigated in this study. Two R410A residential air-conditioning systems, one with a microchannel condenser and the other with a round-tube condenser, were examined experimentally, while the other components of the two systems were identical except the condensers. Two condensers had almost same package volumes. The two systems were operated in separate environmental chambers and their performance was measured in ARI A, B, and C conditions. Both the COP and cooling capacity of the system with the microchannel condenser were higher than those for the round-tube condenser in all test conditions. The refrigerant charge amount and the refrigerant pressure drop were measured; the results showed a reduction of charge and pressure drop in the microchannel condenser. A numerical model for the microchannel condenser was developed and its results were compared with the experiments. The model simulated the condenser with consideration given to the non-uniform air distribution at the face of the condenser and refrigerant distribution in the headers. The results showed that the effect of the air and refrigerant distribution was not a significant parameter in predicting the capacity of the microchannel condenser experimentally examined in this study. Temperature contours, generated from the measured air exit temperatures, showed the refrigerant distribution in the microchannel condenser indirectly. The temperature contours developed from the model results showed a relatively good agreement with the contours for measured air exit temperatures of the microchannel condenser.     

An experimental evaluation of a residential-sized evaporatively cooled condenser

In this paper, the performance of an innovative evaporatively cooled condenser is compared with that of a conventional air-cooled condenser for a split heat pump system. The system was tested in an environmentally controlled test chamber that was able to simulate test conditions as specified by ASHRAE Standard 116. Tests to optimize refrigerant charge and short tube restrictor size were conducted using refrigerant HCFC-22. The wheel rotation speed of the evaporative condenser was also optimized experimentally to maximize the coefficient of performance. Using these optimum parameters, steady state and cyclic performance tests were conducted. The experimental results showed that the evaporative condenser has a higher capacity than the air-cooled condenser by 1.8 to 8.1%, a higher COP by 11.1 to 21.6%, and a higher SEER by 14.5%.     

椭圆形套管-管翅式蒸发式冷凝器传热性能实验研究

本文搭建了蒸发式冷凝器性能测试系统,采用控制变量法实验研究了迎面风速、喷淋密度、湿球温度、循环水温度、冷却水流量各参数变化对椭圆形套管-管翅式蒸发式冷凝器传热性能的影响。实验结果表明：该冷凝器实验系统的最佳迎面风速和喷淋密度分别为3.1 m/s和0.005 6 kg/(m·s),冷凝器管外空气压降随迎面风速的增大而迅速增加;随着空气湿球温度升高,冷凝器外传热过程的热流密度(即外热流密度)降低67.5%,而内传热过程的热流密度(即内热流密度)增大47.5%,依靠内传热过程的增强,冷凝器性能良好;随着循环水温度升高,冷凝器的内热流密度降低率高达64.6%,传热性能急剧下降;随着冷却水流量增大,冷凝器的内热流密度大幅提高2.92倍,总热流密度增大21.1%,传热性能显著增强;该冷凝器在低湿球温度、低循环水温度、大冷却水流量的工况下传热性能较优。     

Modelling and optimisation of wire-and-tube condenser

This paper presents the modelling and experimental results of wire-and-tube condensers that are commonly used in vapour compression cycle based domestic refrigerators. A condenser was experimentally tested in a real refrigerator for some operating conditions. A simulation model was developed using the finite element and variable conductance approach, along with a combination of thermodynamic correlations. The condenser capacity per unit weight was optimised using a variety of wire and tube pitches and diameters. An optimisation factor, f_o was defined as ratio of the condenser capacity per unit weight of the optimised design and the present design. The application of this factor led to an improved design with 3% gain in capacity and 6% reduced condenser weight.     

制冷机运行效果测试及评价

对某水源热泵在制冷工况下的运行效果进行了测试,将系统运行参数修正到设计工况进行了定量的评价.结果表明机组的制冷能力衰减62％.在对冷凝器进行检查清洗后,机组在制冷设计工况下的制冷能力可达92％.说明冷凝器结垢是性能衰减的主要原因;地下水抽取后直接进入冷凝器是结垢的主要原因.因此需要经常对冷凝器进行清洗或对抽取的地下水进行过滤除砂等措施后再进入冷凝器进行冷却.     

新型套管蒸发式冷凝器的理论研究

提出一种新型套管蒸发式冷凝器，在蒸发式冷凝器的基础上在换热管中再加入一根内管，使得制冷剂可以在管的内部进行换热，提高冷凝器的传热系数，进而改善换热性能。针对此冷凝器介绍其结构形式和运行原理，并在相同状况下与蒸发式冷凝器进行数值计算比较，指出套管蒸发式冷凝器具有更好的换热性能。     

Failure of Titanium Condenser Tubes After 24 Years Power Plant Service

The titanium condenser has been in operation for 24 years at Amager unit 3 power plant. In February 2012, the plant was contaminated by seawater due to a failed condenser tube and some tubes were plugged. A month later, the plant tripped again. Small leaks were found again and finally approx. 200 tubes were plugged before the condenser was in service again. A series of inspections, NDT, and destructive examinations were conducted to try and understand the cause of failure in the tubes within the condenser. After such investigations, degradation mechanisms such as inner fouling, steam impingement, and fretting/erosion around the supports could be discounted. Ductile cracks were found in the tube within the tubesheet. From circumstantial evidence, it was concluded that failure was caused by a semi-filled condenser which led to a mismatch in expansion coefficients of filled tubes and unfilled tubes during a plant trip. In addition, small amounts of titanium hydride were revealed to be present in the tubes within the tubesheet indicating that the carbon steel tubesheet was corroding due to ingress of salt water. Although this was not the reason for the failure, it indicated the need for repair of the epoxy coating in the waterbox.     

蒸发式冷凝器和水冷式冷凝器的能耗比较及经济性分析

本文分析了蒸发式冷凝器和水冷式冷凝器在同一冷凝温度下对应于相同冷凝负荷的能耗量。并用实例比较了蒸发式冷凝器、立式水冷式冷凝器和卧式水冷式冷凝器各自对应于900kW冷凝负荷的能耗量和初投资。比较的结果说明了蒸发式冷凝器比水冷式节能，也显示了卧式水冷式冷凝器不管在节省初投资和节能方面，均优于立式水冷式。     

Freeze Condensing Vacuum Systems Offer Advantages. Vakuum‐Tiefkühlkondensation bietet Vorteile

A freeze condenser ahead of a ejector system can improve performance of a process in a number of ways. The condenser will trap unwanted vapors so they don't entire an ejector system. That eliminates the need for alterate motive fluids, such as ethylene glycol or monochlorobenzene. The process is able to stay onstream longer because ejector plugging due to product buildup is avoided. Additionally, by removing the vapors in a freeze condenser the ejector system becomes less expensive and requires less utility consumption. Furthermore, the production of waste water and vent streams is less, so the environmental impact from a particular process is improved. Freeze condensation technology is not well known and may be often overlooked. It should be considered when evaluating vacuum system design criteria. Successful freeze condenser installations are in bisphenol‐A, phenol, fatty alcohols, polyester resin, 1,3‐propanediol, 1,4‐butanediol and edible oil applications. Be certain to specify the freeze condenser and ejector system as single unit. Proper freeze condenser performance comes from matching the ejector system to the condenser. An ejector should be designed to ensure it does not control freeze condenser operating pressure, the ejector system simply supports the condenser. The best vacuum is obtained when a freeze condenser is unrestrained by the ejector system. By specifying the freeze condenser and ejector system as a single unit, the likelihood of discontinunity between the two is eliminated. Conversion factors for converting between U.S. engineering and S.I. units of measure