金属氢化物热压缩机吸放氢传热传质的对称性研究

Study on Heat and Mass Transfer Symmetry Characteristic of Metal Hydride Thermal Compressor During Absorption/Desorption Process

针对金属氢化物热压缩机(MHTC)在实际应用过程中存在的吸放氢非对称性限制,开展了MHTC传热传质对称性的研究和优化。根据局部热平衡模型,以2D圆环剖面为计算区域,对MHTC多管束反应器实施了模拟,并对模拟过程中的参数及结构进行了优化。优化结果表明:以4层管的多管束反应器为基准,改变吸放氢反应条件能改善反应过程的不对称性特征,即吸、放氢压力分别为2、0.05MPa,温度为293、393K,传热系数为1 000 W/(m2·K)时,吸氢反应分率由0.1上升到0.9;放氢反应分率由0.9降至0.1时,所用时间分别为350和360s,温度变化幅度分别为40和43K,显示出明显的对称性。在反应前20s内,放氢过程中平衡压力的变化剧烈,占平衡压力总变化量的50%以上,为反应过程中的高效反应阶段。

Research and optimization were conducted on heat and mass transfer symmetry of metal hydride thermal compressor （MHTC） between absorption/desorption during the operation of MHTC. On the basis of the local thermal equilibrium model, numerical simulation was performed on a domain with 2D annulus in multi-tube MHTC reactors, and the parameters of the simulation process and structure were also optimized. The results show that for the 4-layer multi-tube reactor, it expends 350 s for the reaction fraction to increase from 0.10 to 0.90 during absorption and 360 s to drop from 0.90 to 0.10 during desorption when the hydrogen pressure, temperature, and heat transfer coefficient are 2/0.05 MPa （absorption/desorption）, 293/393 K, 1 000 W · m-2 · K-1, respectively. The largest temperature differences are 40 K and 43 K, respectively, showing a clear asymmetry between absorption/desorption. The equilibrium pressure inside the multi-tube reactor changes significantly and more than 50% of its total variation occurs in the first 20 s during desorption.