Improved of effective wetting area and film thickness on a concentric helical bank of a generator for an absorption heat transformer
Improved of effective wetting area and film thickness on a concentric helical bank of a generator for an absorption heat transformer
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DOI：
10.1016/j.applthermaleng.2016.06.127
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发表时间：
2016-08
影响因子：
6.4
通讯作者：
Y. Lazcano-Véliz;J. Hernández;D. Juárez-Romero;A. Huicochea-Rodríguez;A. Alvarez‐Gallegos;J. Siqueiros
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文献类型：
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作者：
Y. Lazcano-Véliz;J. Hernández;D. Juárez-Romero;A. Huicochea-Rodríguez;A. Alvarez‐Gallegos;J. Siqueiros
该工作在一种用于水净化的吸收式热变压器（AHT）的发生器上进行，该变压器具有两个同心螺旋线圈。AHT采用降膜换热，以55%重量的LiBr-H2O进行换热。本研究的目的是确定发电机的运行条件。分析了不同的降膜形式：滴型、液柱型和射流型。通过数字图像处理，测定了0.003、0.008、0.014、0.019 kg/s 4种工况下，两螺旋盘管的有效换热面积、润湿效率和实验膜厚度。测量了理论膜厚，并与用努塞尔方程计算的膜厚进行了比较。0.008 kg/s的流量保持滴落型分布，有利于沿螺旋试验滩均匀下降。湿化效率达99.52%，建议作为发电机的运行流程。该流的理论膜厚为0.289 cm，通过数字图像处理实验得到的膜厚为0.293 cm。结果表明，降膜交换器的降膜分布更有利于提高降膜交换器的效率。
This work was performed in the generator of an absorption heat transformer (AHT) applied for water purification, which has two concentric helical coils. The AHT used LiBr-H2O to 55%wt for the heat transfer through a heat exchange by falling film. The objective of this study was to define the operating condition of the generator. Different falling film regimes were analyzed: drop mode, liquid column, and jet mode. The effective area of heat transfer of the two helical coils, wetting efficiency, and experimental film thickness were determined for the four operating flows (0.003, 0.008, 0.014, 0.019 kg/s) through digital image processing. The theoretical film thickness was measured and compared with the one calculated by the Nusselt equation. The flow of 0.008 kg/s maintained a drop mode distribution favoring a homogeneous fall along the helical test bank. A wetting efficiency of 99.52% was obtained, so it is proposed as operating flow in the generator. The theoretical film thickness for this flow was 0.289 cm and the one obtained experimentally through digital image processing was 0.293 cm. It was concluded that the distribution in the drop mode was more favorable for a better efficiency in the values of the falling film exchangers.