分体管壳式余热锅炉内摩擦及局部压降

摘要

The calculation of frictional and local pressure drops inside lower shell tubes upon a vapor-liquid two-phase flow running through horizontal tube bundles was studied on a visualizable experimental platform of split shell-tube waste heat recovery boiler. PIV flow velocity measurement technique was combined with traditional differential pressure method to measure cross-sectional vapor fraction in vertical upward tubes. A new method for calculating cross-sectional vapor fraction was proposed according to the bubble flow pattern. A new bubble-slug flow pattern was defined with vapor mass fractionx=10−4as the boundary condition to distinguish bubble flow and bubble-slug flow in vertical upward tubes. Based on the similarity of their occurrences under a circumstance of a vapor-liquid two-phase flow running through horizontal tube bundles, both frictional and local pressure drops were analyzed integrally. A new correlation equation to calculate frictional and local pressure drops was obtained after processed experimental data by the Chisholm method and studied calculation of frictional and local pressure drops. Validation of the correlation equation with experimental data showed an error within±20%, indicating that the equation could meet the needs of engineering calculation.%通过搭建可视化分体管壳式余热锅炉实验平台，对其下部管壳内汽液两相横向冲刷水平管束时摩擦及局部压降的计算进行了研究。在测量竖直上升管内截面含汽率时，将粒子图像测速（PIV）技术与传统压差法相结合，针对上升管中出现的泡状流型，给出了计算截面含汽率的新方法；在竖直上升管内定义了一种泡状-段塞流的新流型，并分析得出将质量含汽率x=10−4作为区分泡状流与泡状-段塞流的边界。根据汽液两相横向冲刷管束时摩擦压降与局部压降类似的产生规律，将两者作为整体分析，通过借鉴Chisholm计算方法对实验数据进行处理，重点对汽液两相横向冲刷管束时摩擦及局部压降的计算进行研究，得到了可用于计算摩擦及局部压降的关联式。对所得实验数据验证计算后发现，误差在±20%以内，能够较好地满足工程计算需要。