Theoretical analysis on expansion mechanism in carbon dioxide expander
Theoretical analysis on expansion mechanism in carbon dioxide expander
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DOI：
10.1007/s11431-011-4328-x
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发表时间：
2011-04
期刊：
影响因子：
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通讯作者：
H. Tian;Yitai Ma;Minxia Li;Mei Zhang
中科院分区：
文献类型：
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作者：
H. Tian;Yitai Ma;Minxia Li;Mei Zhang
从理论上分析了二氧化碳膨胀机的膨胀机理。亚稳平衡机理分析表明，相变过程中存在势垒。也就是说，当新界面由初生相形成时，需要能量来克服势垒。液体的膨胀系数是相变的动力，随流体饱和温度的升高呈指数下降。分析还表明，在相变过程中存在一个临界半径。当气泡半径大于临界值时，气泡长大，反之，气泡消失。在考虑亚稳态相变的情况下，膨胀过程中PandV的计算表明，随着压力的降低，相变会延迟，即滞后现象。相变延迟时间随初始温度的升高而减小。当初始温度接近临界温度时，延迟时间接近于零。相变延迟带来的能量损失随着初始温度的升高而减小，其减小比例也有减小的趋势。当初始压力为10 MPa时，初始温度为10°C时的能量损失为1.06 W，初始温度为20°C时的能量损失为0.34 W。
The expansion mechanism inside carbon dioxide expander is analyzed theoretically in this paper. The mechanism analysis of metastable equilibrium indicates that there is a potential barrier during phase change process. That is to say energy is required to overcome the potential barrier when the new interface is formed from primary phase. The superheat of liquid is the impetus of phase change and has an exponential decrease with the increase of the saturated temperature of fluid. The analysis also indicates that there is a critical radius during the phase change process. The bubble will grow up when its radius is larger than the critical value, otherwise, will disappear. When considering the metastable phase change, calculation ofPandVduring expansion process indicates that the phase-change will be delayed with the decline of pressure, which is called lag phenomenon. The phase-change delay time decreases with the increase of initial temperature. When the initial temperature is close to the critical temperature, the delay time is close to zero. The phase-change delay brings energy losses, which decrease with the increase of initial temperature and its decrease ratio also has a decrease trend. When the initial pressure is 10 MPa, the energy loss will be 1.06 W with an initial temperature of 10°C while 0.34 W with that of 20°C.