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鉴于板式换热器冷热两侧测试阻力降有一定差别,提出评价板式换热器阻力降性能的理论阻力降。考虑到测试水温对物性参数的影响,将理论阻力降转化为定性温度为40℃时的阻力降进行数据分析。通过对数据进行无量纲分析,提出计算板式换热器混装阻力降的三种回归模型即一次、二次、三次回归方程模型。计算结果表明:二次回归方程回归效果最好,精度最高。以试验测试数据为基础,通过理论推导,得出计算板式换热器混装阻力降的一个通用计算方法,即用一个拟合关系式来计算板式换热器混装阻力降。计算数据与试验数据对比表明:拟合关系式计算误差不超过5%,说明了此方法的正确性。 相似文献
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通过对板式换热器传热的理论分析和在干工况、喷淋工况下的实验研究,得出板式换热器在喷淋情形下空气侧喷淋水量对强化对流传热系数的影响关系,进而拟合出喷淋情形下空气侧的对流传热系数的关联式。同时为了综合考虑由于喷淋造成的换热器性能的变化,还对喷淋前后空气侧的阻力变化进行了测试分析。 相似文献
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本文对椭圆管与扁管管板式换热器的充分发展的周期性层流流动与换热特性进行了数值计算分析,给出了在400相似文献
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基于CFD数值模拟的单通道流动分析及结构优化 总被引:1,自引:0,他引:1
为探究板式换热器内流体流动不均匀问题对换热器流体分配的影响,本文利用CFD软件对板式换热器单通道单边流流动和对角流流动进行了模拟分析,发现两种流动中都存在着流动不均匀现象,两种流动中最不均匀流动发生在进出口区与换热区交界附近,相对于平均流量差异最大可达35.9%;对角流流动中相邻截面之间的流量差异最大可达30.8%。针对模拟结果,提出改变单通道分配区域的方法,来消除部分流体分流后的压降和阻力差。优化后单边流流动和对角流流动的最大流体分配差异分别为7.7%和5.5%,极大缓解了流道中分配不均匀的问题。 相似文献
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板壳式换热器传热准则关系式的分析与实验研究 总被引:1,自引:1,他引:0
假设板壳式换热器为特殊板式换热器,介绍了板壳式换热器传热准则关系式的研究方法.分析比较了壁面温度测定法、等雷诺数法、威尔逊法和等流速法等的适用性,确定了利用等流速法来进行实验研究,并分别进行了测定实验和验证实验,测定实验控制进出口流速相同,验证实验控制热侧流速不变,改变冷侧流速,采用实验获得的数据拟合传热准则关系式,计算出传热系数的相对误差.结果表明:传热系数的相对误差小于5%,所得传热准则关系式是合理的,表明板式换热器的研究方法适用于板壳式换热器. 相似文献
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对椭圆钎焊翅片管和双金属轧制翅片管换热器的传热及阻力性能进行试验对比研究,试验得到了一系列工况下的传热数据与管外空气流动阻力数据,给出了相应的传热系数、流动阻力曲线。从总传热系数中分离出管外空气侧的对流换热系数,得到了具有一定应用价值的管外换热的计算关联式;拟合得到了管外阻力计算关联式。结果表明:椭圆钎焊翅片管比双金属轧制翅片管的传热系数约高9%,管外换热系数约高17%,且管外空气流动阻力约低11%。 相似文献
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基于传热学控制方程,采用数值计算方法,对板式换热器单边流动和对角流动时的流动与换热特性进行分析。在分析过程中保持换热器的结构参数不变,只改变进出口的流动方式,结果发现:在相同的流速下,单边流动的总对流换热系数要高于对角流动,而总压降单边流动要低于对角流动,在流速u=0.6 m/s工况下,努谢尔数单边流动比对角流动高出10.87%,压降对角流流动比单边流动高出5.13%。随着进口流速的增大,单边流动与对角流动的冷热流体进出口温差均减小,而且减小的趋势对角流动要大于单边流动,摩擦因子f和传热因子j逐渐减小。单边流动的流动和传热特性要优于对角流动。 相似文献
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为了获得开缝布置方式对开缝翅片管换热器传热与阻力特性的影响规律,对5种不同翅片管换热器进行了数值模拟研究,并进行了模化试验验证。结果表明:增加开缝会提高翅片管换热器的传热性能,但阻力也随之增加;与开缝位置相比,开缝数量对开缝翅片管换热器传热与阻力特性的影响更大;在Re=4800~7500日时,开缝翅片管换热器综合流动传热性能 随着Re数的增大而增大;在5种翅片中,开缝翅片的综合流动传热性能高于普通平直翅片;数值模拟与试验结果偏差较小,采用数值模拟方法能够比较准确地分析开缝翅片管换热器的传热与阻力特性。 相似文献
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Pressure drop characteristics of a gasketed commercial plate heat exchanger configured for single-phase water-to-water flow application are presented. Isothermal pressure drop data are provided for two symmetric 30°/30°, 60°/60° and a nonsymmetric 30°/60° (mixed) chevron plate configuration in the plate heat exchanger. Reynolds number was varied from 500 to 2,500. The experimental data are found to be a strong function of chevron angle and Reynolds number. Experimental results show that mixed plate configuration can be a choice in optimizing the plate heat exchanger design for improved performance. Based on experimental data, correlations are presented for estimation of friction factor. 相似文献
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通过板翅式换热器物流分配问题的实验研究发现,不合理的导流片结构造成板翅式换热器内部物流分配极不均匀,以及在横向与纵向上物流分配不均匀的程度也不相同。同时提出了具有补液腔的新型导流片结构,并定义了新型导流片的结构参数。实验结果表明,采用新型的导流片可以有效的改进换热器内部物流分配不均匀的问题,同时还发现在实验的条件下结构参数为0.2的导流片具有最佳的导流性能,通过实验研究得到了不同导流片结构的物流分配不均匀特性与流体雷诺数之间的关系式。 相似文献
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As fluid flowing through the wavy plate, breaking and destabilizing in the thermal boundary layer are induced. In the present study, the numerical investigation on the heat transfer and flow distributions in the channel with various geometry configuration wavy plates under constant heat flux conditions is considered. A finite volume method with the structured uniform grid system is used to solve the turbulent model. Effects of geometry configuration of wavy plates, wavy plate arrangements, and air flow rates on the temperature and flow developments are considered. The sharp edge of wavy plate has a significant effect on the flow structure and heat transfer enhancement. The results of this study are expected to lead to guidelines that will allow the selected wavy plate geometry configuration for designing heat exchanger which increase thermal performance. 相似文献
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Jeong-Tae KwonDong-Hwi Kim Cheol HuhShigeru Koyama Young-Chul Kwon 《International Communications in Heat and Mass Transfer》2011,38(7):887-892
This study was performed for simulating frosting characteristics that occurred on the surface of plate fins of the outside heat exchanger. Test section with local cooling modules at the central part was made as the rectangular cross sectional passage to imitate the outside heat exchanger. Local frost thickness distributions for test conditions having three experimental parameters (plate wall temperature, air humidity and velocity) were presented. Leading edge effect of the plate was clearly confirmed from the measured frost thickness distributions. The central part of the plate had the highest frost thickness because cooling devices were installed at the center of the plate. Due to different heat and mass transfer characteristics of upstream flow and downstream flow, the frost thickness of upstream area was much higher than that of downstream. The effects of plate surface temperature, humidity and velocity of inlet flow on frost thickness, and sensible and latent heat fluxes were analyzed. 相似文献
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The objective of this study is to investigate the influence of the cooling performance for a water-to-water ground source heat pump (GSHP) by using the counter flow and parallel flow methods. The GSHP uses R-410A as a refrigerant, and its main components are a scroll compressor, plate heat exchangers as a condenser, an evaporator, a thermostatic expansion valve, a receiver, and an inverter. Based on our modeling results, the heat transfer rate of the counter flow evaporator is higher than that of the parallel flow evaporator for a heat exchanger length greater than 0.42 m. The evaporator length of the GSHP used in this study was set to over 0.5 m. The performance of the water-to-water GSHP was measured by varying the compressor speed and source-side entering water temperature (EWT). The cooling capacity of the GSHP increased with increased compressor RPMs and source side EWT. Also, using the counter flow method, compared to the parallel flow method, improves the COP by approximately 5.9% for an ISO 13256-2 rated condition. 相似文献
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