【作者】 李晓凤；

【导师】 马一太； 李敏霞；

【作者基本信息】 天津大学 ， 工程热物理， 2013， 博士

【摘要】 本文以带膨胀机的跨临界CO2水水热泵系统为对象，以优化CO2膨胀机的运行、提升系统性能为目的，提出在纯CO2中加入添加剂方案，并通过理论和试验研究，分析了添加剂（氮气、氩气、二甲醚和R32）对CO2水水热泵系统性能、膨胀机及气体冷却器的影响。对含添加剂的CO2跨临界带膨胀机循环系统进行了理论分析，结果显示加入氮气和氩气可以提高膨胀机回收功，单位制热量和压缩机比功随着氮气或氩气含量的增加而降低，而COP则随着氮气或氩气含量的增加先增加后降低，系统COP存在最优值。COP随着二甲醚或R32含量的增加而增加，单位制热量和压缩机比功随着二甲醚含量的增加先增加后降低，而随着R32含量的增加而单调增加。本文还对膨胀机内的CO2相变过程进行了理论分析，应用微观液体“准晶格”理论分析得出添加剂可以在相变时作为汽化核心，提高核化率。并从宏观上对含添加剂CO2稀溶液和极限过热度进行了分析，结果表明添加氮气和氩气有利于CO2相变，而添加二甲醚和R32则相反。另外对CO2气体冷却器进行理论分析计算，加入氮气和氩气后，气体冷却器性能下降。而含二甲醚和R32的CO2气体冷却器换热性能增强。设计加工了CO2快速降压试块，对CO2以及含添加剂的CO2快速降压膨胀过程进行了试验。结果显示，氮气可以促进CO2的相变，但是二甲醚则会延缓其相变。最后在带膨胀机的CO2水水热泵系统上进行了含添加剂的试验。试验结果表明，加入氮气和氩气后，膨胀机的回收功增加，制热量随氮气或氩气含量的增加先增加后降低，系统COP在氮气或氩气含量1%时最大。含R32和二甲醚的膨胀机输出功随着添加剂含量的增加先增加后下降，系统COP增加，而且运行压力下降。更多还原

【Abstract】 Based on CO2transcritical water to water heat pump system with expander, aconcept adding additives into CO2heat pump system is put forward in thisdissertation, in order to optimize the operation of the CO2expander and improvesystem performance. The influence of additives, such as nitrogen, argon, dimethylether (DME) and R32, on the performance of the system, the expander and gas coolerin CO2transcritical heat pump system is investigated.The thermodynamics analyses of CO2transcritical cycle with additives areconducted. The recovery power of expander increases using nitrogen and argon asadditives, but the heating capacity and the input power of compressor decrease.However, COP of the system increases first and then decrease with increasing theconcentration of nitrogen or argon, and an optimal COP exists. The heating capacityand the input power of compressor increase at first and then decrease with increasingthe concentration of DME, but for R32, the two parameters monotonically increases.The phase change of CO2with additive in the expander is analyzed with theory.According to the quasicrystal structures theory, the nucleation rate of CO2withadditives increases compared with that of pure CO2. The dilute solution’sthermodynamics performance and the superheat limits of CO2with or withoutadditives are also conducted. The phase change is accelerated with the presence ofnitrogen or argon, but the calculation results show the opposite behavior when DMEand R32are considered. The heat transfer characteristic of CO2with additives in thegas cooler is performed. The heat transfer performance of CO2gas cooler decreaseswith the addition of nitrogen or argon, but that increases with DME or R32.To observe the process of CO2depressurization, a high-pressure CO2test block isdesigned and produced. The rapid depressurization of pure CO2and CO2withnitrogen and DME are tested. The addition of nitrogen accelerate the phase change ofCO2, to the contrary, the phase change of CO2with DME is postponed.At last, the heat pump tests of CO2with and without additives are carried out. Theresults show that the recovery power in the expander of CO2increases with thepresence of nitrogen or argon. The heating capacity increases firstly and then dropwith increasing the concentration of nitrogen and argon. The system gets the maximum COP when the concentration of nitrogen or argon is1%. When R32orDME exists in CO2heat pump system, the recovery power increases at first, and thendescends with increasing the concentration of R32or DME. COP of the systemincreases with the existence of R32or DME.更多还原