重力热管内部相变及传热传质过程的数值模拟

Simulation of the phase change and heat mass transfer in a gravitational thermosyphon

中文关键词: 重力热管  气液两相流  VOF  蒸发冷凝  数值模拟

英文关键词: gravity thermosyphon  liquid gas two-phase flow  VOF  evaporation-condensation  numerical simulation

中文摘要:

      重力热管内部包含复杂的两相流动以及相变传热过程,传统理论分析及实验手段不能直观给出其内部流动、相变、热质传递的详细信息。作者采用VOF(volume of fluid)多相流模型对重力热管内气液两相流动及传热进行模拟,捕捉到蒸发段气泡产生、合并、长大、上升,以及冷凝段壁面附近液滴形成、合并、下滑、汇集到液池的全过程,得到的壁温分布与实验测量值对比体现良好一致性,表明数值模拟的正确性。同时,以热阻、传热量和热效率为评价标准,研究不同充液率和倾斜角度下对重力热管运行性能的影响。结果表明：在所研究的参数范围内,随着充液率的增加,热阻逐渐减小,冷凝段传热量逐渐增大。且工质初始充注量充满蒸发段时热管性能较好；倾角对热阻的影响不明显,冷凝段传热量和热效率均随倾角增加而增长。

英文摘要:

      The fluid flow, heat and mass transfer in the gravity thermosyphon are very complex, and it is difficult to obtain the detail information within the thermosyphon theoretically or experimentally. Simulation of vapor-liquid two-phase flow and heat transfer in a thermosyphon is conducted using the VOF (volume of fluid) model to obtain the whole process which includes the producing, merging, growing and rising of bubbles in the evaporation section, and the forming, merging, sliding and flowing into the liquid pool of droplet in the condensation section. A good agreement is obtained which verified the correctness of numerical simulation by comparing CFD wall temperature to experimental measurements. The thermal resistance, heat transfer of condenser and thermal efficiency are defined as performance criteria simultaneously to assess the effects of filling ratio and inclination angle on the operating performance. The results show that, in the range of studied parameters, the thermal resistance gradually decreases with the increase of the filling ratio, whereas the heat transfer of condenser increases. The performance of the thermosyphon is better when the initial charge volume of the working fluid is full of evaporation section. Influence of inclination angle on thermal resistance is not obvious, while, the heat transfer of condenser and the thermal efficiency rise as the inclination angle increases.