空气源二氧化碳热泵热水器的优化设计

发布时间：2018-07-16 23:46

【摘要】：随着空气源二氧化碳热泵热水器的不断发展,热泵热水器也开始在我国逐步应用。由于二氧化碳热泵热水器应用于商业或者是工业上更具有经济性优势,因此本文就根据GB/T21362--2008《商业或工业用及类似用途的热泵热水机》规定的测试工况,对制冷剂充注量、水的质量流量等影响因素进行了实验,实验结果表明： (1)C02热泵热水系统存在最佳C02充注量,充注过少,通过压缩机和蒸发器的制冷剂流量较小,造成设备浪费,同时所得热水温度过低；充注过多会使操作压力过大,降低系统COP。本文确定了最佳C02充注量为8MPa。 (2)水的质量流量对COP和出口水温的影响是相反的,增大水的流量会增加COP,但会降低出口水温,需综合考虑系统对于COP和热水水温的要求来确定最佳流量。 (3)本文通过实验确定了在CO2充注量为8MPa,水流量为800ml/min、压缩机排气压力为8.5MPa时能够满足GB/T21362—2008的要求。在实验的基础之上,对空气源C02热泵热水器进行了(?)分析,建立了压缩机等系统各部件的(?)分析模型,计算了各个部件的(?)损失和系统的(?)效率。经过计算发现,系统的(?)效率只有27.7%,系统(?)效率较低。同时比较各个部件的(?)损失发现,压缩机的炯损失所占总的(?)损失的百分比最大,其次是节流阀,然后是气体冷却器,蒸发器最小。而且压缩机和节流阀处的(?)损失相差不大,相比较而言,对于节流设备的优化改进不管是从可行性还是经济性上来说都更具优势,因此本文决定利用喷射器来代替节流阀作为节流设备。设计了应用于空气源二氧化碳热泵热水器的喷射器,对喷射器的设计方法、喷射系数、喷射器的结构尺寸等进行了详细的介绍,并利用Visual Basic对喷射器的设计计算过程进行了程序设计,经过计算,喷射器可达到的最大喷射系数为0.7。采用数值模拟的方法对喷射器的内部流场进行了分析。计算得到的喷射系数与理论计算的误差为11.4%。分析了喷射器内部的速度场和压力场,同时还对工作流体压力、引射流体压力等工作参数对超临界C02喷射器的性能影响进行了分析,分析发现,提高混合流体压力会降低喷射系数,在确定喷射器设计参数时,应该兼顾喷射系数和混合流体出口压力的关系,适当降低升压比(Pc/Ph),可以提高喷射器可达到的最大引射能力。
[Abstract]:With the development of air-source carbon dioxide heat pump water heater, heat pump water heater is gradually applied in our country. Since CO2 heat pump water heaters are more economical in commercial or industrial applications, the refrigerant is charged according to the test conditions specified in GB/ T21362--2008 for commercial or industrial heat pump water heaters. The experimental results show that: (1) the optimal charge of CO2 exists in the C02 heat pump hot water system, and the flow rate of refrigerant through compressor and evaporator is small, which results in waste of equipment. At the same time, the temperature of the obtained hot water is too low, too much filling will make the operating pressure too large, and reduce the system COP. In this paper, it is determined that the optimal charge of CO2 is 8 MPA. (2) the effect of water mass flow on cop and outlet water temperature is opposite. Increasing the water flow will increase COP, but decrease the outlet water temperature. The optimal flow rate should be determined by considering the cop and the water temperature of hot water. (3) the experiment results show that the system can meet the requirements of GB / T21362-2008 when the CO _ 2 charge is 8MPa, the water flow is 800ml / min, and the compressor exhaust pressure is 8.5MPa. Based on the experiment, the air source heat pump water heater C02 has been carried out. Analysis and establishment of compressor and other components of the system (?) By analyzing the model, the (?) Loss and system (?) Efficiency. After calculation, it is found that the system's (?) Efficiency is only 27. 7%, system (?) Low efficiency. At the same time, compare the (?) Losses are found to account for the total loss of compressors (?) The percentage loss is highest, followed by throttle valves, then gas coolers, and evaporators the smallest. And compressor and throttle place (?) The loss is not different, compared to the throttling equipment, the optimization and improvement of the throttling equipment is more advantageous in terms of feasibility and economy, so this paper decides to use the ejector instead of the throttle valve as the throttling equipment. The ejector used in air source carbon dioxide heat pump water heater is designed. The design method, ejector coefficient and structure size of ejector are introduced in detail. The design and calculation process of the ejector is programmed by Visual basic, and the maximum ejector coefficient is 0.7. The internal flow field of the ejector is analyzed by numerical simulation. The error between the calculated injection coefficient and the theoretical calculation is 11.4. The velocity field and pressure field inside the ejector are analyzed. The influence of working fluid pressure and ejection fluid pressure on the performance of supercritical C02 injector is also analyzed. When the ejector design parameters are determined, the relationship between the ejection coefficient and the outlet pressure of the mixed fluid should be taken into account, and the maximum ejection capacity of the ejector can be improved by properly reducing the pressure boost ratio (Pc / Ph).
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU822

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