共查询到20条相似文献,搜索用时 31 毫秒
1.
搭建了扭曲管闭式冷却塔的换热实验平台,在空冷模式下通过测试在不同风机频率以及风机频率固定时不同的管内流体进口温度、空气干球温度情况下闭塔的传热性能、流动阻力和能耗,得到了风机频率、管程体积流量以及管程进口温度、环境温度对综合传热性能和空冷传热量的影响,进而得出优化闭塔空冷换热的方式,并推导出在不同的季节温度下最合理的运行方式。同时本试验拟合了风机频率和风机功率等与迎面风速的试验关联式以及空冷管外空气的传热系数试验关联式,对扭曲管式闭式冷却塔的优化设计有一定的指导作用。 相似文献
2.
将微管道换热器抽象成多孔介质模型,由Brinkman-extended Darcy方程出发,分别按照双方程模型和单方程模型进行求解,以得到微管道内流体的速度场和温度场分布,并对单方程模型和双方程模型的解析解进行了对比,讨论了微管道高宽比和有效导热系数比对流动与传热的影响。证明了由基于多孔介质双方程、单方程模型所得的解析解均可用于预测微管道换热器中的容积平均速度与温度分布。利用基于多孔介质双方程模型还可得出微管道换热器的总热阻和优化设计结构,结合硅衬底上的多路感应耦合等离子体刻蚀工艺加工出了经结构优化的硅制微管道换热器。在满足局部热平衡条件下,基于多孔介质单方程模型更适用于实际工程计算,不必经由预先的试验确定换热系数。 相似文献
3.
高压燃气涡轮叶栅热辐射特性研究 总被引:2,自引:0,他引:2
采用商用软件CFX11.0的不同湍流模型对NASA-Markll高压燃气气冷涡轮叶栅进行气热耦合换热计算,得出最佳湍流模型。针对不同涡轮叶栅前进口总温进行考虑和不考虑热辐射的数值计算,着重分析叶栅流道内热辐射效应随涡轮前入口温度的变化情况,得出在实际的高温高压气冷涡轮叶栅耦合换热计算时,辐射热流应当作为源项加入到方程中。这样能够更准确地得出叶片内部温度分布,为热应力计算以及寿命预估提供准确的边界条件。 相似文献
4.
Jung-In Yoon Oh-Kyung Kwon Choon-Geun Moon Takao Kashiwagi 《Journal of Mechanical Science and Technology》1999,13(3):264-272
This study investigates the effect of additives such as normal octyl alcohol into lithium bromide-water (LiBr/H2O) solutions in the absorption and generation processes of absorption refrigerating machines. The experimental results confirmed
the positive effect of additive use in the absorber. Little is known, however, on the effect of additives on generator performance.
In this study, the authors carried out experiments to investigate the possible positive or negative effects of additive, which
enhances the absorption process, on the generator behavior. The results showed heat transfer at the generator improved as
pressure increased and concentration decreased; the boiling heat transfer coefficient was shown to be more strongly influenced
by concentration than by pressure. The boiling curves showed that the heat transfer of solution in the generator was not significantly
affected by the addition of surfactant. The result of this study showed that the surfactant in absorption heater/chiller made
enhanced absorption effect in the absorber but it didn't give any influence in the generator. Therefore the additive was devoted
to helping high performance in the absorption system. 相似文献
5.
6.
研究了入口空气相对湿度、温度以及风速对风冷热泵蒸发器结霜的影响,获得了各个入口空气参数对蒸发器结霜厚度和换热量的影响规律.研究发现空气入口相对湿度等参数对蒸发器结霜以及换热性能有很大的影响,结霜严重地影响了蒸发器换热性能.计算结果和实验测试的结果吻合良好. 相似文献
7.
提出一种新型太阳能风冷氨水吸收式制冷循环系统,该系统设置精馏器提纯氨蒸汽,并有效回收精馏器精馏热及中温吸收器吸收热,实现对太阳能的有效利用以及机组风冷化和小型化,与传统系统相比其系统性能系数(COP)显著提高。基于能量守恒、溶液质量守恒和氨组分质量守恒建立系统各部件热力学数学模型,在此基础上编写程序对系统循环特性进行理论计算,分析热源温度、蒸发温度、冷凝温度等参数对系统COP的影响,为系统优化设计及建立最优运行方案提供理论支持。 相似文献
8.
Yong H Kim Woo Chong Chun Jin Taek Kim Bock Choon Pak Byoung Joon Baek 《Journal of Mechanical Science and Technology》1998,12(4):709-718
A study of manifold microchannel (MMC) heat sinks for forced air cooling was performed experimentally. The manifold microchannel
heat sink differs from a traditional microchannel (TMC) heat sink in that the flow length is greatly reduced to a small fraction
of the total length of the heat sink. In other words, the MMC heat sink features many inlet and outlet channels, alternating
at a periodic distance along the length of the microchannels while the TMC heat sink features one inlet and one outlet channels.
The present study primarily focused to investigate the effects of geometrical parameters on the thermal performance of the
manifold microchannel heat sinks for optimal design. Also, the thermal resistances of the MMC heat sinks were compared with
those of the TMC heat sinks. Experimental results showed the thermal resistances of MMC heat sinks were affected strongly
by the pumping power, the microchannel width and the manifold inlet/outlet channel width, but weakly by the microchannel thickness-width
ratio and the microchannel depth coorporated with the manifold inlet/outlet channel width. However, it was found that there
existed the optimum values of the latter parameters. Under the optimum condition of geometrical parameters in the present
study, the thermal resistance of the MMC heat sink was approximately 35% lower than that of a TMC heat sink, which clearly
demonstrated the effectiveness of using a manifold. 相似文献
9.
溴化锂吸收式制冷机新型镍合金强化传热管的实验研究 总被引:3,自引:0,他引:3
对一种新型镍合金强化传热管在210-250℃高温溴化锂水溶液中的耐腐蚀性、传热、传质、抗拉强度、耐磨性、胀管气密性等进行了实验研究。结果表明,在高温溴化锂水溶液中,该管具有很强的耐腐蚀性,其传热、传质及工艺性优良,可以用作三效溴化锂吸收式制冷机传热管。 相似文献
10.
对发生在吸收器内的二元溶液两相流动传热传质过程进行了深入细致的描述。结合实际运行情况,将流动过程划分为3个区域,给出了不同区域的控制微分方程,建立了溶液滴状降膜吸收模型。基于Matlab平台进行求解,分析了水平管束式吸收器溶液温度、浓度的变化以及不同结构参数及运行工况下,溶液质量流量、润湿率WR、蒸发温度等变量对吸收器蒸气吸收能力、吸收器热负荷及蒸发器制冷量的影响。所得结果对于吸收器等热力部件的结构计算具有一定的参考作用。 相似文献
11.
S. S. Sehgal Krishnan Murugesan S. K. Mohapatra 《Journal of Mechanical Science and Technology》2012,26(9):2985-2994
Microchannels based heat sinks are considered as potential thermal management solution for electronic devices. The overall thermal performance of a microchannel heat sink depends on the flow characteristics within microchannels as well as within the inlet and outlet plenum and these flow phenomena are influenced by channel aspect ratio, plenum aspect ratio and flow arrangements at the inlet and outlet plenums. In the present research work an experimental investigation has been carried out to understand how the heat transfer and pressure drop attributes vary with different plenum aspect ratio and channel aspect ratio under different flow arrangements. For this purpose microchannel test pieces with two channel aspect ratios, 4.72 and 7.57 and three plenum aspect ratios, 2.5, 3.0 and 3.75 have been tested under three flow arrangements, namely U-, S- and P-types. Test runs were performed by maintaining three constant heat inputs, 125 W, 225 W and 375 W in the range 224.3 ?? Re ?? 1121.7. Reduction in channel width (increase in aspect ratio, defined as depth to width of channel) in the present case has shown about 126 to 165% increase in Nusselt number, whereas increase in plenum length (reduction in plenum aspect ratio defined as width to length of plenum) has resulted in 18 to 26% increase in Nusselt number. 相似文献
12.
搭建了一套测试微通道性能参数的循环换热试验系统,介绍了组成该系统的微通道换热器、模拟芯片、微型泵、恒温装置以及控制测量等部件.以水为介质,对三种不同结构型式微通道换热器的传热及流动性能进行了试验研究,测量了进出微通道换热器的冷却液流量、温度和压差以及模拟芯片表面多个测点的温度等参数,获得了微通道换热器内的流动阻力和传热特性. 相似文献
13.
冷却水对废热驱动型双效溴化锂吸收式制冷机组性能影响的仿真研究 总被引:1,自引:0,他引:1
随着能源使用的日益紧张,各类冷热电联供技术尤其是废热驱动型吸收式制冷机组的性能研究越来越受到关注。针对废热驱动型双效溴化锂吸收式制冷机组性能特点,建立了该机组在小扰动条件下的数学模型,并编制了相应的仿真程序。根据仿真结果分析了冷却水进口温度和流量的变化对废热驱动型吸收式机组的性能影响。 相似文献
14.
考虑制冷剂两相分配不均的微通道蒸发器压降模型 总被引:1,自引:1,他引:0
制冷剂两相分配不均是影响微通道蒸发器压降特性的重要因素,为了准确预测制冷剂两相分配不均影响下的微通道蒸发器压降,开发了新的微通道蒸发器压降模型。模型考虑了从微通道蒸发器进口管到出口管的所有局部和沿程压力损失,引入了简化的微通道管进口干度分布函数来计算微通道蒸发器内各微通道单管的进口状态,提出一种考虑制冷剂两相分配不均的流路压降平衡的仿真算法来迭代求解出微通道蒸发器的压降。该模型适用于制冷剂在蒸发器进口为两相状态(进口干度小于0.45),制冷剂在集流管内质流密度小于764 kg/m2s的条件。模型的仿真结果能较好符合制冷剂在微通道蒸发器中的流量和温度分布趋势,并且与微通道蒸发器压降的试验数据误差小于8%。 相似文献
15.
Jongmin Choi Jongug Jeon Yongchan Kim 《Journal of Mechanical Science and Technology》2008,22(3):575-582
Optimum control of the PCB surface temperature is very important in achieving high performance and operational reliability
of telecommunication equipment with high power density and thermal density. In this study, the performance of a liquid cooling
unit with MPCM slurries (called as “MPCM cooled unit”) was tested and analyzed. In addition, its performance was compared
with that of an air cooled unit and a water cooled unit. The maximum surface temperature and the index of uniform temperature
distribution (IUTD) were introduced to analyze cooling performance. The surface temperature in the unit rack of telecommunication
equipment can be controlled properly by using an MPCM cooled unit instead of an air cooled unit. The maximum surface temperature
and IUTD of the MPCM cooled unit at the inlet temperature of 19°C were lower than those at inlet temperatures of 25°C and
27°C due to the increases of heat capacity and heat transfer rate. The heat capacity of the MPCM cooled unit increased significantly
with the increase of mass flow rate due to high specific heat of MPCM particles with latent heat transfer rate. The cooling
performance of the MPCM cooled unit was superior to that of the water cooled unit. 相似文献
16.
同轴套管式深井换热器是一种开采地热能的有效方式,为了提高其换热器的换热性能,采用有限体积分析方法,开展了同轴套管式深井换热器传热性能研究。通过建立近地热源区域的同轴套管式深井换热器三维传热模型,分析了入口流速、入口温度以及保温管距井底距离等关键因素对换热器采热功率的影响,结果表明:入口流速由0.1 m/s增加到1 m/s,采出温度降低了9.82 K,采热功率增加了7倍;入口温度从288 K增加到308 K,采出温度增加了13.61 K,采热功率下降了17.2%;距井底900 mm距离降低到 100 mm,采出温度增加1.91 K,采热功率增加了6.57%。 相似文献
17.
Kwang Soo Kim Won Tae Kim Ki Baik Lee 《Journal of Mechanical Science and Technology》1998,12(1):132-142
Present study is concerned with forced convective heat transfer of the channel flow with line arrays of heated electronic
components mounted on a printed circuit board. For the assessment of thermal performance in channel flows, three separate
variables are used:channel spacing, row number of the component, and inlet air velocity. The thermal characteristics of a
component due to own power and upstream air heated by components were studied. The experimental results were compared with
those of numerical solution for various conditions: surface temperature of the components, adiabatic temperature rise, and
heat transfer coefficient. The experimental results agree well with the numerical solutions. The study shows that the adiabatic
heat transfer coefficient is significantly affected by the inlet velocity in channel flow and less dependent on the channel
spacing and row number, except for the case ofH/B=3.3. While reviewing the previous literatures, it is found that a little difference in the correlation between Nu and Re
is due to the different geometric ratio of the packaged components. 相似文献
18.
Sung-Jool Kim Ho-Jin Choi Man-Yeong Ha Seok-Ro Kim Seon-Wook Bang 《Journal of Mechanical Science and Technology》2010,24(4):961-969
The present study numerically solves the flow and thermal fields in the full geometry of heat exchanger modeling with frost
layer presence on the heat exchanger surface. The effects of air inlet velocity, air inlet temperature, frost layer thickness,
fin pitch, fin thickness, and heat exchanger shape on the thermo-hydraulic performance of a fin-tube heat exchanger are investigated.
Heat transfer rate rises with increasing air inlet velocity and temperature, and decreasing frost layer thickness and fin
pitch. Pressure drop rises with increasing air inlet velocity and frost layer thickness, and decreasing fin pitch. The effect
of fin thickness on heat transfer and pressure drop is negligible. Based on the present results, we derived the correlations,
which express pressure drop and temperature difference between air inlet and outlet as a function of air inlet velocity and
temperature, as well as frost layer thickness. 相似文献