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在低质量流速条件下,对垂直上升内螺纹管内汽水两相流动沸腾传热特性进行了系统的试验研究。试验段采用了材料为SA-213T12的φ32mm×6.3mm四头内螺纹管。试验参数范围为压力p=12～21MPa,质量流速G=232～773kg/(m2·s),内壁热流密度q=132～663kW/m2。试验得到了不同工况下垂直上升内螺纹管的壁温分布特性,分析了压力、内壁热负荷和质量流速变化对内螺纹管传热特性的影响,探讨了传热恶化的发生机制,并给出了能用于工程实际的传热试验关联式。试验结果表明:在亚临界及近临界压力区,垂直上升内螺纹管会发生第2类传热恶化——干涸(dryout),而在试验中未观测到第1类传热恶化——膜态沸腾(departure from nucleate boiling,DNB)。压力与内壁热负荷的增大,以及质量流速的减小,均会导致干涸提前发生和干涸后的壁温飞升值增大。与亚临界压力区相比,内螺纹管在近临界压力区的传热特性变差,管壁温度显著升高,发生传热恶化时的临界焓值减小。
Under the conditions of low mass flow velocity, the boiling heat transfer characteristics of the two-phase flow of soda and water in a vertically rising female tube were systematically studied. The test section uses a material of SA-213T12 φ32mm × 6.3mm four-headed female pipe. The experimental parameters ranged from pressure p = 12-21MPa, mass flow rate G = 232-773kg / (m2 · s) and heat flux density q = 132-663kW / m2. The wall temperature distribution of the vertically rising female pipe under different working conditions was obtained. The influence of pressure, wall heat load and mass flow rate on the heat transfer characteristics of the female pipe was analyzed. The mechanism of heat transfer deterioration was also discussed. Out of the heat transfer test can be used in engineering related. The experimental results show that in the subcritical and near critical pressure zone, the vertical rise of the internally threaded tube occurs in the second type of heat transfer deterioration - dryout (Dryout), while in the test did not see the first type of heat transfer deterioration - the membrane state Departure from nucleate boiling (DNB). Pressure and wall heat load increases, as well as the mass flow rate decreases, will lead to dry-up in advance and dry wall temperature soaring value increases. Compared with the subcritical pressure zone, the heat transfer characteristics of the internally threaded tube in the near critical pressure region deteriorate, the temperature of the tube wall significantly increases, and the critical enthalpy decreases as the heat transfer deteriorates.