CO_2冷风机性能测试实验研究

本文搭建了测试CO_2冷风机性能的实验台,在直接膨胀供液系统和泵供液系统下,通过改变传热温差、库温、循环倍率、迎面风速等参数来研究CO_2冷风机的性能。结果表明:在直接膨胀供液系统中,随着蒸发温度的降低,传热系数和制冷量均呈减小的趋势,蒸发温度从-22℃降低到-47℃时,传热系数从20.2 W/(m2·K)降低到16.6 W/(m2·K),制冷量从7.5 k W降低到6 k W;在泵供液系统中,随着循环倍率的增加,传热系数呈现先增大,达到最大值后缓慢减小的趋势,当循环倍率为3时,传热系数达到最大值,以库温为-20℃时为例,当循环倍率从1增大到3,传热系数增大约13.2%,循环倍率继续增大时,传热系数开始下降,增大到5时,换热系数下降至2%左右。当迎面风速从2.2 m/s变化至2.5 m/s时,传热系数仅增加了2.12%;但迎面风速从2.5m/s变化至3.2 m/s时,增幅为11.4%;当迎面风速从3.2 m/s变化至3.5 m/s时,传热系数增长幅度又变缓,仅增加了0.88%。     

CO_2冷风机换热性能仿真及实验研究

本文利用稳态分布参数法对冷风机建立仿真模型,并利用冷风机性能实验台对冷风机样机进行实验研究,利用实验研究与数值模拟相结合的方法,对冷风机换热性能进行分析研究。在校准箱内温度为-25~0℃范围内,循环倍率在2~5范围内变化时,冷风机总换热系数随着校准箱温度的升高而增大;制冷工质为CO_2时冷风机的制冷量明显高于制冷工质为NH_3时,在校准箱内温度为0℃时高42%,-20℃时高26%;管内侧压降随着循环倍率的增大而增大;换热系数随着循环倍率的增大先增大后逐渐减小,在循环倍率为3左右时,换热系数达到最大。仿真结果与测试结果趋势相同,但存在一定误差。模拟计算得出NH_3换热系数值与测试结果的误差约为16%,CO_2换热系数值与测试结果的误差约为8%。     

泵供液式冷风机性能模拟与实验研究

本文建立了不同流程分布的冷风机模型,对各流程分布冷风机性能进行了模拟研究;采用泵供液式制冷量测试法,对以R717为工质的最优流程分布冷风机进行了性能测试。研究表明,单排管双流程布管方式能够使冷风机的性能最优;存在使冷风机制冷量最大的泵送比,在蒸发温度-25℃工况下,当泵送比为3.5时,冷风机的制冷量最大,为44.3 k W;随着蒸发温度的升高,冷风机的传热系数逐渐增大,当蒸发温度为-25℃时,传热系数为27.4 W/(m~2·K),当蒸发温度为0℃时,传热系数为34.4W/(m~2·K),提高了25.5%;随着蒸发温度的升高,冷风机的制冷量逐渐增大,当蒸发温度为-25℃时,制冷量为44.3 k W,当蒸发温度为0℃时,制冷量为64.3 k W,增大了45.15%。采用泵供液式制冷量测试法,测得在不同实验工况下,冷风机制冷量实验值比模拟值低5%左右,验证了冷风机模型的正确性。     

冷库冷风机传热性能的实验研究

本文对冷风机稳定运行时的性能进行了实验研究,按照ASHRAE标准搭建了冷风机实验室,研究了冷风机的性能随库温、传热温差、循环倍率等因素的变化.结果表明:传热温差为10℃,循环倍率为3时,冷风机传热性能随库温的升高而提高,当库温从-34℃升至10℃时,传热系数由16 W/(m2·℃)增至18.8 W/(m2·℃),增幅达...     

风速对不同流程数CO2蒸发器性能的影响

为研究迎面风速对不同流路数CO₂翅片管蒸发器性能的影响,本文建立分布参数模型对蒸发温度为-25℃,风速为0.5～4 m/s条件下5种流路数CO₂翅片管蒸发器的制冷剂压降、换热量、温度分布及传热系数的变化进行分析,并通过实验验证了蒸发器模型的可靠性。蒸发器模型的换热量、制冷剂压降和风侧压降等参数模拟值与相同工况下实验值的误差均在±4%以内。结果表明:同一流路数蒸发器的换热量、制冷剂压降及传热系数均随风速的增大而增大,而其涨幅随风速增大而减小,综合考虑换热效果和能耗可得最佳风速范围为2.5～3.5 m/s;在一定风速条件下,蒸发器设计时在合理范围内选择较多流路数可有效提升蒸发器换热性能并增强换热均匀性,本次实验中24流路蒸发器为最佳设计方案。     

两组冷风机并联的重力再循环蒸发器运行特性实验

针对传统重力再循环制冷系统冷量损失的问题,采用两组冷风机并联的方式,减小供液高度,将气液分离器放置在冷库内部并采用卧式的形式。实验研究了不同库温和不同冷凝温度下蒸发器的各种运行特性。结果表明:随冷凝温度的降低,传热温差上升速率加快,在冷凝温度为45℃,40℃,35℃,30℃时,上升速率分别为2. 47%,4. 4%,4. 5%,4. 9%。传热系数随库温及冷凝温度的降低有增长趋势且增长幅度减慢。当循环倍率从3增加到3. 5,库温-30℃工况下传热系数增加率最为明显为7. 01%,采用两组冷风机并联的重力再循环制冷系统蒸发器的运行性能得到了提高,且在低库温下性能更好。     

环境参数对蒸发式冷却换热器性能影响的实验研究

本文利用由焓差室控制环境参数的水-水蒸发式冷却换热器实验台,研究喷淋密度、迎面风速和环境参数对其传热传质性能的影响。当改变喷淋密度和迎面风速时,测得最佳喷淋密度为0.031 4 kg/(m·s),最佳迎面风速为3.22 m/s;在最佳喷淋密度和最佳迎面风速的条件下,改变环境参数,测得湿球温度从22℃上升至28℃时,总传热系数降低约4.2%,传质系数降低约9.3%;相对湿度从85%降低至55%时,总传热系数上升约10%,传质系数上升约13.7%。     

蒸发式冷凝器传热传质性能研究

建立单级压缩制冷循环蒸发式冷凝器实验台,研究逆流状态下,迎面风速和喷淋密度对传热传质的性能影响。通过调节水泵和风机的频率改变风水量的配比关系,得出蒸发式冷凝器的传热传质性能变化情况。分析数据得出,当迎面风速为2.96 m/s,喷淋密度为0.057 kg/(m·s)时,总传热系数达最优值628 W/(m2·K),传质系数随风速的增大而增大,随喷淋密度的变化不明显。此外,通过实验数据回归得到传质系数计算关联式。     

CO_2/R290应用于复叠制冷低温环路浓度配比实验研究

在复叠制冷实验台上对由CO_2/R290组成的不同配比的二元混合制冷剂进行了低温循环性能实验.实验结果表明,随着CO_2含量增大,二元混合物的压比减小,制冷量增大,耗功减少,COP增加,制冷速率增大.但随着CO_2含量增大,二元混合物的排气温度也升高,当CO_2在混合物中的组分达到71%时,蒸发温度为-61℃时,压缩机的排气温度接近115℃.因此,混合物中CO_2含量不宜超过71%.混合物中R290降低了CO_2凝固点温度,同时也降低了CO_2较高的冷凝压力,对扩展CO_2在低温区域的应用很有益处.     

磁力泵驱动两相冷却复合制冷系统特性分析和实验研究

为降低数据中心制冷系统的能耗,搭建了一种磁力泵驱动的两相冷却复合制冷装置,并对其进行了实验研究。结果表明,室外温度15℃时,泵循环模式的EER随冷凝器迎面风速先增大后减小,当风速为1 m/s时EER获得最大值。在热负荷为7.3 k W条件下,实验获得了两种运行模式的最佳转换温度;最后以哈尔滨和石家庄地区为例,模拟计算出泵驱动模式的全年最佳运行时间比。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

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.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

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.……     

Optimum-Simulation von Ernteprozessen

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.     

A study of centrifugal cast high boron high speed steel

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.     

Brainstorming for ISO Strategy 2016-2020

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     

CNAS Passes APLAC's PTP Review

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.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to