在一台三吨级分体式热泵上对五台L/D比为7.5～11.9的短管制冷剂膨胀装置进行了试验。试验结果表明，在液体过冷温度为22.2℃（40.0℉）时，发生了一级阻塞。然而，没有迹象表明发生过第二阶段窒息。根据测试结果，形成了两个相关性。一种是孔板模型，孔板常数是压差和液体过冷度的函数。该模型适用于低于22.2摄氏度（40.0华氏度）的液体过冷。另一个是一级阻塞模型，适用于22.2 C°（40.0 F°）以上的液体过冷度。引用:ASHRAE交易，第88卷，第2部分，加拿大多伦多

Five short-tube refrigerant expansion devices, with L/D ratios from 7.5 to 11.9, were tested on a three-ton split-system heat pump. The test results show that first-stage choking has occurred at the liquid subcooling temperature of 22.2 C° (40.0 F°). However, there is no indication that second-stage choking has ever occurred.Based on the test results, two correlations were formed. One is an orifice model with the orifice constant as a function of the pressure differential and the level of liquid subcooling. This model is for liquid subcooling less than 22.2 C° (40.0 F°). The other is a first-stage choking model, which is for a level of liquid subcooling above 22.2 C° (40.0 F°).