共查询到20条相似文献,搜索用时 78 毫秒
1.
2.
3.
4.
5.
《制冷与空调(北京)》2021,(6)
分析了微通道蒸发器内制冷剂流动沸腾换热的经验关联式,建立了稳态分布参数和控制单元法的微通道蒸发器数学仿真模型。同时建立不同扁管宽度的微通道蒸发器样机并验证其在不同工况下的传热和压降性能。试验结果表明:微通道蒸发器工作时两相流制冷剂分配不均和冷凝水排除速度慢是造成微通道蒸发器在校核计算时计算值与试验值相差较大的主因。传热试验和修正的仿真模型为今后微通道蒸发器开发计算以及性能优化方面提供了参考。 相似文献
6.
本文根据两相流动换热理论,提出了一个板式换热器的稳态分布参数模型.在此模型基础上,利用分布参数法求解各控制方程,得出了制冷剂的温度、压力、气液相速度以及冷冻水温度、压力沿通道方向上的分布情况.此模型可用于分析换热器的整体性能,为板式换热器的优化设计、制冷系统的匹配提供依据. 相似文献
7.
本文从理论上比较分析了制冷剂物性对于分配性能的影响,R290汽液两相的粘度和密度差别相比R22较小,流量分配特性理论上略好,制冷剂压降也更小。且随着蒸发温度的升高,流量分配特性会变好。通过在两种流程微通道换热器中的对比实验,发现R22和R290在四流程中的分配特性明显好于两流程,蒸发器换热器量提升5%~6%,系统制热量提高1.8%左右,COP提高8%~10%。由于R290分液特性略好,R290的换热量提高幅度略大于R22,且由于R290压降增加更小,更适合于多流程换热器,使得系统COP提升更多。 相似文献
8.
基于分布参数模型建立了微通道平行流环路热管的稳态传热模型,并通过实验验证模型可行性,最大相对误差为10.5%。模拟研究分析了充液率、蒸发器和冷凝器高度差等因素对环路热管传热性能的影响。结果表明:环路热管的最佳充液率为80%~105.4%,换热量为1.27~1.36 kW;蒸发器和冷凝器的高度差从0.4 m增至1.0 m时,换热量约提升8.7%。同时,模型能够预测蒸发器流量分配的不均匀性及扁管内部的两相状态,使模拟结果更加精确,对微通道平行流环路热管的结构设计具有一定的参考价值。 相似文献
9.
本文通过建立以R134a为制冷剂的微通道平行流冷凝器的分布参数模型,使用交复检验非线性法对微通道冷凝器两相区的传热和压降关联式进行修正,并与无修正的仿真模拟结果、传统简单多项式拟合修正法的结果进行了比较。结果表明,运用交复检验非线性法修正的效果要优于无修正及传统简单多项式拟合法,使用前者修正后可将换热量误差减少64. 5%,均方误差控制在3%以内;制冷剂侧压降误差减少82. 05%,均方误差控制在10%以内,该方法为换热量和制冷剂侧压降的修正提供了一种预测精度更高的思路和方法。 相似文献
10.
换热器流量分配不均匀性评价方法的比较 总被引:1,自引:0,他引:1
介绍换热器的流量分配不均匀性的评价方法,对微通道平行流换热器进行流量分配试验,用不同评价方法对试验数据进行处理,对比6种流量分配不均匀性评价方法的优劣。结果表明,采用相对标准方差衡量流量分配的不均匀性最为合理。 相似文献
11.
《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
12.
Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
13.
14.
A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
15.
On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
16.
Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
17.
C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
18.
Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献
19.
《中国标准化(英文版)》2014,(4)
正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from 相似文献
20.
《中国标准化(英文版)》2014,(5)
正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively. 相似文献