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利用红外热成像技术研究了蒸汽滴状冷凝中液滴合并过程表面温度分布及演化机制,并基于此分析了不同尺寸液滴表面温度随传热通量变化的分布规律。实验结果表明:与蒸汽在微小液滴表面发生连续冷凝不同,液滴合并过程中蒸汽通过四个阶段实现在大液滴表面的周期性冷凝传热;其中,在液滴吸收蒸汽冷凝放热阶段和向壁面传热阶段之间存在一个平衡,高热通量时,蒸汽向液滴表面传热过程占主导,液滴表面温度随尺寸增加而升高;低热通量时,液滴向冷凝壁面传热过程占主导,液滴表面温度随尺寸增加而降低。液滴运动引起的蒸汽在大液滴表面直接冷凝过程为强化低压蒸汽冷凝传热提供了新思路。
Infrared thermography was used to study the surface temperature distribution and evolution mechanism of droplet condensation during the droplet condensation process. Based on this, the distribution of the droplet surface temperature with the heat transfer flux was analyzed. The experimental results show that, unlike the continuous condensation of steam on the surface of micro-droplets, the vapor undergoes periodic condensation heat transfer on the surface of large droplets through the four stages of the droplet consolidation process. In the phase of the droplet absorption steam condensation and heat release And the heat transfer to the wall there is a balance between high heat flux, the steam to the droplet surface heat transfer dominated the droplet surface temperature increases with increasing size; low heat flux, the droplet to the condensation wall surface The thermal process is dominant and the droplet surface temperature decreases with increasing size. The direct condensation of steam caused by droplet movement on the surface of large droplets provides a new idea for enhancing heat transfer in low pressure steam condensing.