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首页> 外文期刊>International Journal of Heat and Mass Transfer >Experimental and theoretical studies on density wave instabilities in helically coiled tubes
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Experimental and theoretical studies on density wave instabilities in helically coiled tubes

机译：螺旋盘管密度波不稳定性的实验和理论研究

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This paper reports on the advancement in the study of thermal-hydraulic dynamic instabilities with reference to the helical-coiled tube geometry. A full-scale open-loop experimental facility simulating a helically coiled steam generator was built and operated at SIET labs in Piacenza(Italy). The facility comprises two helical tubes(1 m coil diameter, 32 m length, 8 m height), connected via lower and upper headers. Nearly 100 flow instability threshold conditions were identified, in a test matrix of pressures(80 bar, 40 bar, 20 bar), mass fluxes(600 kg/m~2 s, 400 kg/m~2 s, 200 kg/m~2 s), inlet subcooling(from -30% up to ～0), and inlet throttling(four different entrance resistance conditions). The long test section feature and the helical-coiled tube geometry render the present facility a quite unique test case in the outline of two-phase flow instability experimental studies. Parametric effects of the operating pressure, flow rate, inlet subcooling and inlet throttling on the threshold power are discussed. The period of oscillations is also discussed. Superimposition of Density Wave Oscillations(DWOs)with Ledinegg flow excursions is finally described. Theoretical modelling of DW0 occurrence in helical pipes was addressed by means of a lumped parameter analytical model, which was exploited to highlight some peculiarities of DWO phenomena and respective stability boundary with respect to classical straight geometry. In the end, numerical simulation results with RELAP5/MOD3.3 code were compared.
机译：本文报道了关于螺旋管几何形状的热工动态不稳定性研究的进展。在意大利皮亚琴察（Piacenza）的SIET实验室建造并运行了一个模拟螺旋盘绕蒸汽发生器的大型开环实验设施。该设施包括两个螺旋管（盘管直径1 m，长度32 m，高度8 m），通过上下集管连接。在压力（80 bar，40 bar，20 bar），质量通量（600 kg / m〜2 s，400 kg / m〜2 s，200 kg / m〜）的测试矩阵中，确定了近100个流量不稳定阈值条件2 s），入口过冷（从-30％到〜0）和入口节流（四种不同的入口阻力条件）。在两相流不稳定性实验研究的概述中，长的测试截面特征和螺旋盘管的几何形状使本设备成为一个非常独特的测试案例。讨论了工作压力，流量，入口过冷和入口节流对阈值功率的参数影响。还讨论了振荡周期。最后描述了具有Ledinegg偏移的密度波振荡（DWO）的叠加。通过集总参数分析模型解决了螺旋管中DW0发生的理论建模问题，该模型用于突出DWO现象的某些特殊性以及相对于经典直线几何的稳定性边界。最后，比较了使用RELAP5 / MOD3.3代码的数值模拟结果。

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