倾斜管内R245fa对流冷凝传热的实验研究
发布时间：2018-11-12 20:13
【摘要】：倾斜管内有机工质冷凝换热在工业生产中广泛应用,掌握其传热规律可以优化换热设备,节约能源。当前研究主要集中在小管径的空调管等,而随着ORC等低品位能源的兴起,冷凝管径逐渐增大,因此,本文依托北京市低品位能源与多相流动传热重点实验室,通过实验研究较大管径倾斜管内R245fa冷凝传热。本文在内径14.81mm,长1200mm的倾斜管内进行R245fa对流冷凝传热实验。实验工况为：R245fa质量流速200～700 kg/m2s,入口干度0.1～0.9,相应的弗劳德数为0.174～2.153,实验段入口饱和温度55.5℃,实验段倾角从垂直向下变化到垂直向上,分别为θ=-0°、±4°、±8°、±15°、±30°、±45°、±60°、±900°实验中流型主要为分层流、间歇流和环状流。实验结果表明：冷凝传热系数随倾角增大有上升趋势,且在弗劳德数远小于1时,上升趋势明显,随着弗劳德数增大至1并继续增大,上升趋势逐渐消失。在水平角度及其附近微倾角范围内,无论增大或者减小倾角,其传热系数相对于水平角传热系数均增大。在整个倾角范围内,传热系数随角度成非线性波动趋势。通过可视化分析传热规律得出结论：角度增加时,汽液界面形成强烈的界面波,强化传热。角度下降时,液位降低,热阻减小,强化传热。在不同倾角下,界面波、液位高度、流型、重力、惯性力等多因素共同作用,相互竞争,引起了传热系数的波动趋势。同时,针对传热系数随角度的增大及波动趋势,拟合出关于角度的冷凝传热关联式,其平均误差及均方根误差分别为6.36%、5.97%。
[Abstract]:The condensation and heat transfer of organic working fluid in inclined tube is widely used in industrial production. To master the heat transfer law can optimize the heat transfer equipment and save energy. At present, the research is mainly focused on the air conditioning tubes with small pipe diameter, but with the rise of low-grade energy sources such as ORC, the condensing pipe diameter is gradually increasing. Therefore, this paper relies on the Beijing key Laboratory of Low-grade Energy and Multiphase flow Heat transfer. The condensation heat transfer of R245fa in inclined tube with large diameter was studied experimentally. In this paper, R245fa convection condensation heat transfer experiments are carried out in an inclined tube with an inner diameter of 14.81 mm and a long 1200mm. The experimental conditions are as follows: the inlet dryness of the R245fa mass flow rate 200,700 kg/m2s, is 0.1g / 0.9, the corresponding Froude number is 0.174n2.153, and the inlet saturation temperature of the experiment section is 55.5 鈩，
本文编号：2328098
[Abstract]:The condensation and heat transfer of organic working fluid in inclined tube is widely used in industrial production. To master the heat transfer law can optimize the heat transfer equipment and save energy. At present, the research is mainly focused on the air conditioning tubes with small pipe diameter, but with the rise of low-grade energy sources such as ORC, the condensing pipe diameter is gradually increasing. Therefore, this paper relies on the Beijing key Laboratory of Low-grade Energy and Multiphase flow Heat transfer. The condensation heat transfer of R245fa in inclined tube with large diameter was studied experimentally. In this paper, R245fa convection condensation heat transfer experiments are carried out in an inclined tube with an inner diameter of 14.81 mm and a long 1200mm. The experimental conditions are as follows: the inlet dryness of the R245fa mass flow rate 200,700 kg/m2s, is 0.1g / 0.9, the corresponding Froude number is 0.174n2.153, and the inlet saturation temperature of the experiment section is 55.5 鈩，
本文编号：2328098
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