共查询到17条相似文献,搜索用时 98 毫秒
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建立了两级喷射制冷系统和两级喷射器组合的性能分析模型。以水、氨、R290、R600a为工质,研究了两级喷射器组合中间压力分配比与喷射系数的关系,当第一级和第二级喷射器的喷射系数相近时出现使总喷射系数最大的中间压力最佳分配比。探讨了不同工况下最佳分配比与总压缩比和膨胀比之间的关系。膨胀比一定时,最佳分配比随总压缩比的增大先增大,然后减小,最后又逐渐增大;膨胀比对最佳分配比也有一定影响,但与总压缩比的取值区间相关联。绝热指数是影响最佳分配比的重要因素,对处于相同最佳分配比工况的不同工质,绝热指数越大则所需的总压缩比也越大。提出了两级喷射器组合中各级喷射器结构选择方法。 相似文献
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基于工业余热回收利用,提出了一种吸收-喷射复合制冷系统,对系统建立数学模型并进行热力性能分析,分析了发生温度、蒸发温度、冷凝温度、吸收温度及喷射器效率对系统COP的影响。与传统单效式吸收式制冷系统进行对比,得出了吸收-喷射复合制冷系统COP最大时喷射器压缩比最佳值随发生温度的变化规律。研究表明:吸收-喷射复合制冷系统传统单效吸收式制冷系统可利用更低品位的热源,在热源温度为75℃时仍能正常工作;高、低压喷射器压缩比最佳值随发生温度的升高而降低,并逐渐接近于1,且低压喷射器最佳压缩比总是高于高压喷射器的最佳压缩比,在较低热源温度工况下,吸收-喷射复合制冷系统相比传统单效吸收式制冷系统节能效果显著。 相似文献
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本文根据气体动力学方法和定压混合理论,以Visual Basic为工作平台编制了太阳能热虹吸自喷射制冷系统的喷射器喷射系数的计算程序。计算出了以水为制冷工质的各种工况下喷射器的喷射系数。根据计算结果分析得出:喷射系数随发生温度升高而增大,发生温度每升高1℃,喷射系数增加0.007;随蒸发温升高而增大,蒸发温度每升高1℃,喷射系数增加0.031;随冷凝温度的升高而减小,冷凝温度每升高1℃,喷射系数减少0.033。这为提高制冷系统喷射系数提供了有效的途径。 相似文献
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实验探究了蒸气喷射准双级制冷系统中,气体喷射器进出口参数对喷射器喷射系数、COP和制冷量的影响,并与单级蒸气压缩制冷系统进行对比。实验数据显示:随着混合流体出口压力的增加,喷射系数和系统制冷量逐渐减小,而COP则先增加后减小;喷射系数、COP和制冷量随着工作流体压力的增加均呈现先增加后降低的趋势;随着引射流体压力的增加,喷射系数和制冷量均增加,COP先增加后减小;当蒸发温度到-31.4℃时(t_k=35.0℃),单级蒸气压缩式制冷系统将不再产生冷量,而蒸气喷射准双级制冷系统可达到的最低蒸发温度为-36.5℃。 相似文献
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气-液喷射器工作参数的数值模拟 总被引:1,自引:0,他引:1
建立了气-液喷射器工作过程的一维稳态模型。运用数值计算方法对模型进行求解,采用Nabil Beithou等中的定解条件,计算了水为工质时的气-液喷射器内轴向压力分布。计算结果表明,本模型得到的气-液喷射器轴向压力分布与相同条件下Cattadori的实验值吻合较好;以实验结果为基准,本模型蒸汽喷嘴数值模拟结果比Nabil Beithou等的结果大为改善。对太阳能双喷射式制冷系统中的气-液喷射器进行了模拟,得到轴向压力分布和速度分布,结果表明,喷射系数随工作压力的升高而降低。 相似文献
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依据索科洛夫等学者提出喷射器计算的经验公式对喷射器进行优化设计加工,并自行搭建测量喷射器性能实验台。采用N_2、CO_2、R290 3种自然工质,研究了当扩压室直径为定值,实验压力为高压(10 MPa≤P≤100MPa)状态时圆柱形混合室截面直径变化对喷射器性能的影响规律。实验结果表明:当喷射器背压为3.9 MPa、工作流体温度为90℃、工作流体压力变化范围为8.0~10.0 MPa或引射流体压力变化范围为2.4~2.9 MPa、混合室截面直径在1.7~2.1 mm范围变化时,喷射器的喷射系数均随圆柱形混合室截面直径的增大而升高,且在实验工况范围内,以N_2为工质的喷射系数随圆柱形混合室截面直径变化趋势相对平缓。 相似文献
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蒸汽喷射器流动参数与性能的数值分析 总被引:9,自引:0,他引:9
通过二维流动数值计算,分析了以水蒸气为工质的喷射器内工作流体压力、引射流体压力及出口压力对喷射系数的影响;探讨了各工作参数变化对喷射系数产生影响的原因,以及激波产生的条件、激波的位置、强度,产生引射流体雍塞的条件等。结果表明:喷射器存在临界的出口压力pd,当喷射器出口压力大于pd时,喷射器的喷射系数随出口压力升高而降低;当喷射器出口压力小于pd时,喷射器的喷射系数将保持不变。在计算模拟的制冷工况范围内,工作流体压力升高,引起喷射系数降低,pd升高;而引射流体压力升高时,喷射系数与pd都升高。 相似文献
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The performance of a vapour compression system that uses an ejector as an expansion device was investigated. In the analysis, a two‐phase constant area ejector flow model was used. R134a was selected as the refrigerant. According to the obtained results, for any operating temperature there are different optimum values of pressure drop in the suction chamber, ejector area ratio, ejector outlet pressure and cooling coefficient of performance (COP). As the difference between condenser and evaporator temperatures increases, the improvement ratio in COP rises whereas ejector area ratio drops. The minimum COP improvement ratio in the investigated field was 10.1%, while its maximum was 22.34%. Even in the case of an off‐design operation, the performance of a system with ejector is higher than that of the basic system. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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This paper presents a computer‐based first law and exergy analysis applied to vapour compression refrigeration systems for determining subcooling and superheating effects of environmentally safe new refrigerants. Three refrigerants are considered: R134a, R407c and R410a. It is found that subcooling and superheating temperatures directly influence the system performance as both condenser and evaporator temperatures are affected. The thermodynamic properties of the refrigerants are formulated using artificial neural network (ANN) methodology. Six ANNs were trained to predict various properties of the three refrigerants. The training and validation of the ANNs were performed with good accuracy. The correlation coefficient obtained when unknown data were used to the networks were found to be equal or very near to 1 which is very satisfactory. Additionally, the present methodology proved to be much better than the linear multiple regression analysis. From the analysis of the results it is found that condenser and evaporator temperatures have strong effects on coefficient of performance (COP) and system irreversibility. Also both subcooling and superheating affect the system performance. This effect is similar for R134a and R407c, and different for R410a. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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在比较制冷工质的优劣时,不仅应考虑系统COP,还应考虑循环泵的耗功及压力容器中的压力水平。根据饱和蒸气压将八种环境友好型制冷工质分为四组(R141b&R123,R600a&R142b,R134a&R152a,R290&R717),分组的依据是每组制冷工质的饱和蒸气压曲线非常相近。比较结果表明,R123和R141b、R142b和R600a的热力性能都非常相近,但R123和R600a对环境的影响更小;R152a相比R134a,具有更低的压力和循环泵功、更小的环境影响,但性能系数却更大。 相似文献
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This study presents a comparison of energetic and exergetic performance of a vapor compression refrigeration system using pure hydrocarbon (HC) refrigerants. In this study, four different pure HCs propane (R290), butane (R600), isobutane (R600a) and isopentane (R1270) are used in theoretical analysis. R22 and R134a are also used in the analysis. For the analysis, EES package program was used for solving thermodynamic equations of the refrigerants. Results have been presented graphically. According to results, differences of coefficient of cooling performance values of these refrigerants are quite small. Energetic and exergetic efficiency values obtained with R1270 and R600 are higher than R600a and R290. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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This paper describes an innovative ejector enhanced Joule‐Thomson cycle for low‐temperature refrigerators. Since an ejector is introduced into the cycle, the cycle performance is profoundly affected by the pressure lift ratio and entrainment ratio of the ejector. As a case study, the performance characteristic of the novel cycle refrigerator using the non‐azeotropic refrigerant mixture R14/R23 with the molar fraction of 0.6/0.4 is theoretically investigated in detail. The theoretical results show that in a typical refrigeration temperature range from −65°C to −95°C, the novel cycle refrigerator has 24.4%–41.5% improvement in coefficient of performance and 60%–220% enhancement in refrigeration capacity when compared to a basic Joule‐Thomson cycle low‐temperature refrigerator. This achieves a significant advantage as the use of the novel cycle is applied to low‐temperature refrigerators for the medical and commercial applications. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献