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搭建脉冲管制冷机动态参数测试实验台,在脉冲管制冷机整机运行条件下对处于实际温度梯度的回热器进行了动态速度以及动态压力测试。为了测量回热器冷端的动态速度,研究针对低温侧的热线探针进行了低温条件下的标定。实验测量了充气压力3 MPa、运行频率40—60 Hz、冷端温度100 K工况下回热器的相位特性以及阻力特性,并得到了整机运行条件下回热器阻力系数经验公式。研究结果表明,随着频率的提升,回热器冷热端速度-压力相位差增大,相同雷诺数下的阻力系数增大;随着温度降低,相同雷诺数下的阻力系数增大,并且在低雷诺数下变化更加明显。该研究结果是在回热器实际工作条件下测量得到,能够为脉冲管制冷机中的回热器模拟计算以及回热器热力学分析提供必要的数据支持。 相似文献
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分析了在自行研制的双小孔型二级脉管制冷机实验过程中回热器对脉管制冷机性能的影响,给出了合理的回热器布置方式,讨论了回热器形变及压缩机油污染对脉管制冷机性能的影响,指出了羊毛毡在隔离磁性材料Nr3Ni粉尘中所起的重要作用。在优化改进的基础上,该机达到了3.1K的最低无负荷温度。 相似文献
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结合当前最新制冷剂替代政策,以单级蒸气压缩式制冷系统为研究对象,对自然工质(R744、R717、R290、R1270、R600a)、HFCs类过渡工质(R410A、R404A、R32、R152a、R161、R134a)和新型烯烃类制冷剂HFOs(R1234yf、R1234ze)经回热器后对制冷系统性能的影响进行分析。结果显示:回热器对系统COP的提升效果与制冷剂物性、运行工况和回热器效率有关;R717和R32在使用回热器后系统COP降低,当回热器效率为80%时,与回热器效率为30%相比系统COP分别降低了3.90%和2.27%;R161、R152a和R410A受回热器的影响很小;对于其他制冷剂,在使用回热器后,系统COP随蒸发温度和回热器效率的升高均有一定幅度提升,其中R1234yf、R1234ze、R600a和R404A变化最大。当回热器效率为80%的时,与回热器效率为30%相比系统COP分别升高了5.99%、3.94%、4.41%和5.05%。分析结果与相关评估标准较为接近,为现阶段带回热器的蒸气压缩式制冷系统制冷剂的选择提供参考。 相似文献
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在回热器中加入紫铜丝网增加径向导热有利于抑制大功率脉冲管制冷机回热器中的温度不均现象,但紫铜丝网也可能对制冷机性能产生其它的影响。通过数值模拟考察了在没有温度分布不均时,不同的紫铜丝网目数、分布方式、丝网厚度等对制冷机性能的影响。结果表明,在假设回热器温度均匀的情况下,不论如何填充定量的紫铜丝网,总会引起制冷机的效率降低;如果总的紫铜丝网数量一定并且均匀地分布在回热器中,整机制冷性能不会因填充层数的不同而有明显变化;采用与回热器不锈钢丝网目数接近的紫铜丝网要比目数相差较大的丝网可以获得更好的效果。 相似文献
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回热器效率的差分计算 总被引:1,自引:0,他引:1
本文讨论了理想稳流回热器的传热特点和近似的数学描述,根据豪森的数学模型,用有限差分法求解对称情况下的理想回热器传热微分方程,编制了计算稳流回热器效率的通用程序,并使用该程序进行计算,提供了某些对比长度、对比周期下回热器效率的数据。最后探讨了当回热器运行工况考虑变物性时,本文差分计算方法的推广使用。 相似文献
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为了提高无回热器氨-水-溴化锂吸收式制冷实验样机的性能,实验首次提出了单回热器型和双回热器型氨-水-溴化锂吸收式制冷机的概念,并对两种实验样机分别进行了实验研究.实验结果表明,对于单回热器系统,溴化锂的加入大大降低了发生过程中的发生压力,对系统的安全性有利.但是由于吸收器和回热器的直接连通,导致回热器温度高于35℃时,随着回热温度的上升,吸收器压力急剧升高,制冷效果恶化.对于双回热器系统,结构的改进有效地解决了单回热器系统存在的问题,很好地实现了回热功能.相比于无回热器氨-水-溴化锂吸收式制冷实验样机,制冷系数得到明显的提高.在氨质量分数为50%,溴化锂质量分数为15%的情况下,系统的性能系数从无回热器的0.276提高到0.457,增幅达65.35%. 相似文献
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为了快速评估空调器用换热器长期运行后的换热量衰减情况,本文提出一套通过测试换热器加速积尘前后的换热量来预测其换热量衰减率的测试方法。该测试方法中,采用负反馈模式精确调节换热器迎风面的粉尘浓度,能够在加速积尘时间内维持换热器迎风面粉尘浓度的稳定性;通过对加速积尘循环空间与换热量测试风道进行一体化设计,能够在不需要移机时实现加速积尘与换热量测试之间的切换。在入口空气温度为45℃、流速为1. 5 m/s,入口水温为21℃、流速为0. 5 m/s的工况下对该测试方法的可靠性和一致性进行了验证,结果表明:换热器迎风面粉尘浓度能够稳定维持在目标浓度120 mg/m3,波动范围在±20%内;对4种具有不同结构的换热器样件进行了多次换热量衰减率测试,其换热量衰减率相对偏差均在±10%之内,表明该测试方法具有较好的一致性。 相似文献
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地下水源热泵具有显著的经济性,但对地下水资源保护产生不利影响。本文建立地下水源热泵流量分析模型和典型的基准状态,从节能和地下水节约利用两方面综合分析设计工况下板式换热器循环流量和地下水流量最佳范围,以及地下水取用单价的合理范围。结果表明:在基准状态下,板换循环设计温差应在5~6℃左右,比10℃温差工况系统能耗减少2.6%;水电单价比为0.2:1时,水费仅占总费用的9%,经济工况区范围为循环水温差在5~7℃之间,井水温差在10~13℃之间;水电单价比在0.5:1到0.75:1之间对提高地下水利用率较为适合;水电单价比为1.5:1时,地下水源热泵与空气源热泵的运行费用相当。 相似文献
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Woven wire screen matrix heat exchanger (WSMHE) is a kind of compact, light-weight and high-efficiency matrix heat exchanger (MHE) for cryogenic applications. This paper presented a numerical model for the design and thermal analysis of WSMHE. The influence of wall thermal resistance, axial conduction, parasitic heat load and properties variation was taken into account, which is neglected in the traditional effectiveness-NTU method but important for compact cryogenic heat exchangers. The proposed numerical method is verified by effectiveness-NTU method under specific conditions, then it is tested according to experiment data, and a well agreement was obtained. Based on this model, a detailed analysis was performed on WSMHEs. The analysis results show that the axial conduction might result in evident decrease of effectiveness at low flow rate region; the effectiveness of WSMHEs with large flow rate could be remarkably enhanced by increasing its length; the influence of parasitic heat load varied little throughout of the flow rate region. Furthermore, the numerical model presented in this paper can be developed to the design and thermal analysis of small partition wall type heat exchangers. 相似文献
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《低温学》2014
The recuperative heat exchanger governs the overall performance of the mixed refrigerant Joule–Thomson cryocooler. In these heat exchangers, the non-azeotropic refrigerant mixture of nitrogen–hydrocarbons undergoes boiling and condensation simultaneously at cryogenic temperature. Hence, the design of such heat exchanger is crucial. However, due to lack of empirical correlations to predict two-phase heat transfer coefficients of multi-component mixtures at low temperature, the design of such heat exchanger is difficult.The present study aims to assess the existing methods for prediction of flow boiling heat transfer coefficients. Many correlations are evaluated against available experimental data of flow boiling of refrigerant mixtures. Silver-Bell-Ghaly correlation and Granryd correlation are found to be more suitable to estimate local heat transfer coefficients. A modified Granryd correlation is recommended for further use. 相似文献
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微通道换热器在空调器上的应用研究 总被引:1,自引:0,他引:1
试验研究空气流量和流路设计对微通道换热器换热量的影响。测试结果表明,空气流量增加47%后,换热量增加10.6%;流路设计变化后,换热能力差别1.8%。将某机型铜管换热器更换成微通道换热器后,A工况能效提高0.22w/w,功耗降低4%,制冷剂充注量减少21.4%。指出整机的通风设计对微通道换热器有很大的影响,顶出风和侧出风机型需要采用不同的微通道结构设计。认为微通道换热器是应对国家2级能效要求的一个很好的技术解决方案;分析限制微通道换热器推广使用的一些因素。 相似文献
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Experimental study on a new internally cooled/heated dehumidifier/regenerator of liquid desiccant systems 总被引:2,自引:0,他引:2
Yonggao Yin Xiaosong Zhang Geng Wang Lei Luo 《International Journal of Refrigeration》2008,31(5):857-866
For providing good performance of dehumidifier and regenerator with certain dimensions, a new type of internally cooled/heated dehumidifier/regenerator based on the plate–fin heat exchanger (PFHE) was designed. To investigate the behavior of the new equipment, an experimental setup was established in an environment chamber with regulable temperature and humidity air. By the internally cooled dehumidification testing, effects of the cooling water temperature, the air flow rate and the desiccant temperature on the dehumidification performance and the cooling efficiency were presented. The behavior of internally cooled dehumidification process was compared with that of the adiabatic dehumidification process. The results suggested that the cooling efficiency decreased with the increasing of the cooling water temperature and desiccant with low temperature could bring more mass transfer coefficients. There is an optimal air flow rate to achieve the maximum absolute humidity decrease of the air. By the internally heated regeneration testing, effects of the air flow rate and the desiccant inlet temperature on the regeneration performance and air outlet parameters were discussed and also compared with those of the adiabatic regeneration process. It was concluded that the regeneration efficiency of internally heated regeneration was more than that of the adiabatic regeneration, and the internally heated regenerator could offer better thermal performance. 相似文献
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YPON-12500/7130型液化装置氧氮换热器中抽管道不畅通,导致氧氮换热器温差过大,冷量损失严重。通过优化操作流程,使氧氮换热器中抽管道畅通,不仅解决了氧氮换热器温差过大、冷量损失大的问题,而且大大提高了设备运行的安全性。简介液化装置流程,分析优化操作的具体措施,通过计算分析取得的经济效益。 相似文献
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Liquid refrigerant injection technique can be a very effective method for controlling subcooling and the compressor discharge temperature of a refrigeration system at high ambient temperatures. In this study, the effects of liquid refrigerant injection on the performance of a refrigeration system with an accumulator heat exchanger were investigated by varying the liquid injection rate at the conditions of constant expansion valve opening in the evaporator and constant total flow rate. During the tests, the ambient temperature was maintained at 43 °C. With the increase of the liquid injection rate, the subcooling at the inner heat exchanger outlet increased and the superheat at the accumulator outlet decreased. However, unacceptable results such as the increase of the compressor discharge pressure and decrease of the system performance were also observed depending on the control method applied. To obtain high system performance and reliability, optimum control methods for liquid injection in the accumulator heat exchanger are suggested. The liquid injection technique for the refrigeration system with an accumulator heat exchanger was found to be an effective method for controlling adequate subcooling and the compressor discharge temperature of the refrigeration system at high ambient temperatures. 相似文献