流速对盘管内冰浆流动及换热特性的影响研究

Study on Influence of Flow Velocity on Flow and Heat Transfer Characteristics of Ice Slurry in Coil Tubes

冰浆作为一种性能优越的潜热蓄能和输送介质,在蓄冷空调中具有极大的应用潜力。但由于冰浆输运、储存过程中受到诸多因素的影响呈现复杂的流动特征,如分层、聚集等,容易堵塞管道,目前仍未大规模应用。文章模拟研究了一定冰浆含冰率以及管外径条件下入口速度对盘管内冰浆流动及换热特性的影响。结果表明:冰浆在盘管的流动过程中,弯管部位都会出现与单相液体流动一样的二次流,速度越大、二次流现象越明显。入口速度对冰浆在盘管内流动与换热特性影响较大,流速过小,管道顶部冰粒子聚集易形成滞留层,不利于冰浆流动,但有利于冰粒子的相变释放潜热;流速过大时,管道内冰粒子均匀悬浮,流动状态好,但冰浆在管道内持续的时间短,不利于相变释放潜热,针对本文条件,冰浆在末端设备流动入口速度不应超过0.5 m/s,比较理想的入口速度为0.25 m/s左右。

As a kind of latent heat storage and transport medium with superior performance, ice slurry has great application potential in storage air conditioning. However, due to the influence of many factors in the process of ice slurry transportation and storage, it presents complex flow characteristics, such as stratification and aggregation, which are easy to block the pipeline. So far, it has not been applied in a large scale. In this paper, the effects of the inlet velocity on the flow and heat transfer of ice slurry in the tube under the condition of ice content and diameter of the ice slurry are studied. The results show that in the flow process of the ice slurry in the coil, the secondary flow of the pipe appears as same as the single phase liquid flow;the greater the velocity is, the more obvious the secondary flow phenomenon is. The inlet velocity has great influence on the flow and heat transfer characteristics of ice slurry in the coil. When the flow velocity is too small, the accumulation of ice particles at the top of the pipe is easy to form a stagnant layer, which is not conducive to the flow of ice pulp, but it is beneficial to release the latent heat of the ice particles. When the flow velocity is too large, the ice particles in the pipe are suspended evenly and the flow state is good, but the duration of the ice slurry in the pipeline is short, which is not conducive to release the latent heat of the phase change. According to the conditions of this paper, the inlet speed of ice slurry in terminal equipment should not exceed 0.5 m/s, and the ideal inlet speed is about 0.25 m/s.