弦月形狭缝通道内液氮受迫流动沸腾传热强化的研究

研究了液氮在弦月形狭缝通道中受迫流动沸腾时的传热特性。发现液氮在弦月形狭缝通道中的受迫流动沸腾具有很高的换热系数,有显著的强化换热效果。详细分析了弦月形狭缝通道内液氮沸腾传热及流动的偏心特性。研究对于进一步理解狭缝通道沸腾传热强化的机理和狭缝强化传热技术在工程中的应用有着重要的意义。     

新型冷凝蒸发器中沸腾冷凝传热研究

根据两相流微膜热虹吸的理论，设计了一种新型的板翅式冷凝蒸发器，并对它进行了性能测试。它不仅具有很高的冷凝和沸腾传热系数，而且具有很小的传热温差。除此之外，它还具有下述优点：重量轻，体积小，操作简便，运行可靠。实验结果显示，如果它的沸腾侧的传热进一步优化，并与冷凝侧合理匹配，则该冷凝蒸发器的传热性能还会进一步提高。     

杭氧与西交大联合课题“大型制氧装置高效冷凝蒸发器”通过鉴定

20 0 3年 2月 2 6日 ,浙江省科技厅组织的杭州制氧机集团有限公司和西安交通大学联合课题“大型制氧装置高效冷凝蒸发器”的鉴定会在杭州举行。鉴定委员会听取了联合课题组所作的“新型高效冷凝蒸发器及其相关新技术”研究开发报告、研制报告、性能测试报告、用户使用情况报告、科技查新报告等。经过认真讨论 ,一致认为 :(1 )该项目首创特殊通道比例作为基本换热单元 ,构成双沸腾型冷凝蒸发器 ,使冷凝蒸发器的总传热温差得到大幅度降低 ;首创冷凝通道的结构方案 ,显著降低了冷凝蒸发器液氧的平均饱和沸腾温度 ,使主冷传热温差降低到0 6 0K…     

竖直狭缝通道中液氮沸腾强化换热的实验研究

实验表明，狭缝间隙对液氮自然对流核态沸腾换热有明显的影响，在低热流密度下，间隙小的狭缝沸腾换热比间隙大的狭缝明显增强，当狭缝间隙小于实验压力下气泡的脱离直径时，对于同样的热流密度，传热温差减小一个数量级以上，沸腾换热系数提高十几倍到二十倍以上，当热流密度增加一定程度（＞4W/cm^2)时，间隙小的狭缝沸腾换热比间隙大的狭缝有所减弱。     

弦月形通道在太阳能空调系统中的强化传热研究

研究表明，弦月形通道的特殊结构可以有效促进Li—Br溶液的沸腾，降低溶液过热度，强化传热、传质过程，相同工况下的换热量是环形通道的2～3倍，使太阳能小型溴化铿吸收式空调系统在70～80℃宅加热水温度下就可以正常运行。弦月形通道偏心特性尺寸S对通道内Li-Br溶液的流动与换热影响很大，实验结果表明：di＝19mm和do＝32mm的铜管构成的弦月形通道的提升效果较好。     

狭缝沸腾板翅式单元传热性能的实验研究

对采用新型沸腾传热强化措施的工业用板翅式冷凝蒸发器单元试样的传热特性进行了实验研究，实验结果表明：本文的实验单元与现行的６０００ｍ＾３／ｈ空分装置的板翅式主冷凝蒸发器相比，换热系数提高了近一倍，传热温差下降了４０％－５０％。     

冷水机组干式蒸发器中制冷剂沸腾换热与节能途径分析

本文对冷水机组干式蒸发器中制冷剂沸腾换热过程的流动方程、基本参数进行分析，提出了冷水机组干式蒸发器管内制冷剂强化沸腾换热的措施以及节能的途径。     

狭缝微膜热虹吸沸腾自补偿现象的实验研究

对采用狭缝沸腾传热强化措施的工业用板翅式冷凝蒸发器实验单元的危险点壁面温度波动进行了瞬态测试，阐明了狭缝中微膜热虹吸机理具有一定的自动补偿的调节作用它能维持通道处于稳定的良好的传热状态，对于空分装置的稳定和安全运行具有重要地意义。     

窄通道强化沸腾换热的方法综述

利用通道强化沸腾换热是一种既经济又有效地强化传热方法。从核沸腾传热的微液膜蒸发机理出发，通过分析认为；利用窄通道强化沸腾换热，实质是对液膜蒸发过程的强化，并指出扩大微膜面积可强化沸腾换热。针对窄通道沸腾换热临界热负荷小的事实，提出了可通过及时补液的克服方法。     

竖直多孔表面通道内液氮沸腾换热实验研究

在液氮自然循环流动时，对竖直多孔表面管管内沸腾换热及外管单面加热时竖直多孔表面套管内沸腾换热，进行了实验研究，分析并讨论了通道的当量半径、热流密度及含气率对沸腾换热的影响。     

板翅式蒸发器液冷系统设计

为了研究板翅式换热器在沸腾相变换热情况下的传热及压降特性,设计一套采用氟里昂蒸气压缩循环的液体冷却试验系统,其中板翅式换热器作为蒸发器,R22作为制冷剂,热水作为被冷却液体提供制冷剂蒸发所需热量。对该系统的运行工况、参数范围及系统各部件（包括压缩机、冷凝器、毛细管、板翅式蒸发器）进行设计及选择,并介绍所搭建的试验台。     

压缩式制冷空调机组壳管式换热器的传热强化研究进展

冷凝器和蒸发器是压缩式制冷空调机组中的重要设备,其传热系数的高低直接影响机组的效率和成本。采用强化传热技术是提高冷凝器与蒸发器传热性能的关键。对于管外冷凝传热强化,在Turbo-C管的基础上,将翅片从翅顶到翅根完全割裂,形成断裂的三维翅片管,以减少表面张力作用下冷凝液在传热管表面粘滞特性对传热的影响。采用螺旋隔板替代冷凝器和干式蒸发器的弓型隔板,能改善壳程流体的流动与传热性能;针对降膜蒸发器的降膜蒸发区与满液蒸发区的不同特点,应分别采用不同类型的强化管,以提高蒸发器传热系数。     

Heat transfer in the evaporator of an advanced two-phase thermosyphon loop

As heat generation from electronic components increase and the limit of air-cooling is reached, the interest for using liquid cooling for high heat flux applications has risen. Thermosyphon cooling is an alternative liquid cooling technique, in which heat is transferred as heat of vaporization from evaporator to condenser with a relatively small temperature difference.The effect of fluid properties, the structure of wall surfaces, and the effect of system pressure was investigated and reported previously by the author. In this paper, the influence of heat flux, system pressure, mass flow rate, vapor fraction, diameter of evaporator channel and tubing distance between evaporator and condenser on the heat transfer coefficient of an advanced two-phase thermosyphon loop is reported. The tested evaporators were made from small blocks of copper with 7, 5, 4, 3 and 2 vertical channels with the diameters of 1.1, 1.5, 1.9, 2.5, and 3.5 mm, respectively and the length of 14.6 mm. Tests were done with isobutane at heat fluxes ranging between 28.3 and 311.5 kW/m².     

竖直矩形可视化流动沸腾换热实验台的设计及初步研究

为了了解矩形窄通道内流动沸腾及传热现象的机理,建立了单面加热竖直矩形窄通道可视化流动沸腾换热实验台进行了实验。实验结果表明:矩形窄通道流动沸腾过程的换热系数存在最大值;随着干度的增加(即热流密度的增加)其换热系数逐渐降低,转为以液膜蒸发为主的流动沸腾换热,此时需控制热流密度,避免干涸现象的发生。     

Measurement and prediction of heat transfer coefficient on ammonia flow boiling in a microfin plate evaporator

Thermal characteristics of ammonia flow boiling in a microfin plate evaporator are experimentally investigated. Titanium microfin heat transfer surface is manufactured to enhance boiling heat transfer. Longitudinally- and laterally-microfined surfaces are used and those performances are compared. Heat transfer coefficient of microfin plate evaporator is also compared with that of plain-surface plate evaporator. The effects of mass flux, heat flux, channel height, and saturation pressure on heat transfer coefficient are presented and discussed. The experiments are conducted for the range of mass flux (5 and 7.5 kg m⁻² s⁻¹), heat flux (10, 15, and 20 kW m⁻²), channel height (1, 2, and 5 mm), and saturation pressure (0.7 and 0.9 MPa). Heat transfer coefficient is compared with that predicted by available empirical correlations proposed by other researchers. Modified correlations using Lockhart-Martinelli parameter to predict heat transfer coefficient are developed and they cover more than 87% of the experimental data.     

Visualization study of the interface between superheated He II and superheated He I in a two-dimensional narrow channel by using the shadowgraph method

Dynamic behavior of superheated He II-superheated He I interface as a result of heating in a narrow channel between parallel walls that simulates cooling channels of superconducting magnets was investigated using a shadowgraph visualization method. It was confirmed that a superheated state could be created in the narrow channel without preparing a special calm environment. A superheated He II-superheated He I interface transiently appeared between 2.0 K and lambda temperature when applying a small heat flux. The boiling state accompanying the superheated He II-superheated He I interface was repeatedly generated and collapsed. This boiling mode was anticipated to have a high heat transfer coefficient.     

Mechanical refrigeration using an ejector-injector to transfer the working fluid from the evaporator to the condenser

The refrigeration plant described in this paper uses an ejector-injector instead of a compressor to pump the freezing mixture from the evaporator to the condenser. A pump draws the liquid from the condenser and pumps it to another vessel. Before the ejector-injector, a heat exchanger preheats the refrigerating fluid to speed up the mixing with steam ejected from the evaporator. The steam is compressed using kinetic energy in the ejector-injector and the pump supplies a discharge pressure to operate the plant. The heat transfer fluid, the condensing and evaporating pressures and the energy losses determine the operating features of the plant. Energy saving is obtained using such an ejector-injector and it provides a simple method of refrigeration. The operating conditions were optimized in this study and the feasibility of the plant was confirmed.     

板式升膜蒸发器蒸发换热特性的实验研究

升膜蒸发利用被蒸发溶液在受热沸腾汽化产生的蒸气带动料液上升,形成一个稳定的液膜,从而加快蒸发,提高了传热系数.针对蒸发器液位、换热温差、加热蒸气的流量等因素对板式升膜蒸发传热系数的影响进行了实验研究,实验结果表明随着蒸发器内液位的降低升膜蒸发传热系数明显提高,此外,换热温差、加热蒸气的流量等因素对升膜蒸发换热性能也有明...