液体过量供给系统通常用于工业制冷的大吨位应用。ASHRAE手册和产品目录，1973年系统卷l中提供了这些系统的操作原理和设计指南。将蒸发器出口连接到低压接收器或蓄能器的管道称为湿式回流管。它携带液体和蒸汽的混合物，比例由再循环比R决定。通常使用的再循环比在2到1到5到1之间。本研究的目的是改进一种用于确定输送这种气液两相混合物的管道尺寸的方法。之前的一份出版物介绍了关于水平管线中两相压降的实验测量和拟议计算方法的综合文献调查结果。 对AGA/API杜克勒数据库中795个数据点的统计分析，以及关于制冷剂两相流的其他数据表明，Hughmark的相关性3和4产生了最准确的压降计算。根据Hughmark关联式，编制了四种固体制冷剂的设计表，即R-12、R-22、R-502和R-7l7（氨）。总结该研究的出版物2中复制了氨的设计表，涵盖了-40F至+20F（-40°C至-67°C）的蒸发温度和2/1、3/1、4/1和5/1的再循环率。目前的调查是因为制冷系统严重缺乏关于两相压降的准确数据，尤其是在液体过量供给系统中遇到的情况下。赞助商希望测量直管流中的压降，以及大型管道的典型配件和阀门中的压降- 大规模工业制冷应用。由于篇幅和预算的限制，有必要对一个单独的项目进行调查。标称管道回路。由于氨在液体过量供给系统中的应用优势，选择氨作为制冷剂。引文:ASHRAE交易，第82卷，第2部分，华盛顿州西雅图

Liquid overfeed systems are commonly used on large tonnage applications of industrial refrigeration. The principles of operation for these systems and design guidelines are provided in ASHRAE HANDBOOK & Product Directory, 1973 Systems Volume l. The piping which connects the evaporator outlet to the low pressure receiver or accumulator is referred to as a wet return. It carries a mixture of liquid and vapor, the proportion being determined by the recirculation ratio, R. Recirculation ratios generally used are in the range of from 2 to 1 to 5 to 1. An improved method for sizing the piping which carries this two-phase gas-liquid mixture was the object of this investigation. A previous publication presented the results of a comprehensive literature survey made on experimental measurements and proposed calculation methods, for two-phase pressure drop in horizontal lines. A statistical analysis of 795 data points from the AGA/API 'Dukler data bank, together with additional data on refrigerant two-phase flow, showed that Hughmark's correlations3 and 4 produced the most accurate calculations for pressure drop. Design tables for four Sefrigerants, namely, R-12, R-22, R-502, and R-7l7 (ammonia) were prepared, based Qn the Hughmark correlations. The design table for ammonia, covering evaporating temperatures from -40F to +20F (-40°C to -67°C) and recirculation ratios of 2/1, 3/1, 4/1, and 5/1 are reproduced in the publication2 summarizing that study.The present investigation was undertaken because of the serious lack of accurate data from refrigeration systems on two-phase pressure drop, particularly under the conditions encountered in liquid overfeed systems. The desire of the sponsor was for measurements of pressure drop in straight pipe flow and in fittings and valves typical for large-scale industrial refrigeration applications. Limitations of space and budget made it necessary to conduct the ~nvestigation on a one in. nominal piping circuit. Ammonia was selected as the refrigerant because of its predominance in application of liquid overfeed systems.