Effects of Flash Gas at Reduced Condensing Temperatures

Energy efficient refrigeration technology by HY-SAVE is based on the operation of the expansion valve, which is directly related to the amount of flash gas or Freon vapour present at the valve, and the pressure difference across the expansion valve.

The effects of flash gas percentage chart (right) shows that 1% vapour (by weight) is formed in the liquid line for each 4 psi pressure drop. Comparing the density of vapour and liquid, shows the relationship between small amounts of flash gas by weight. A 12 psi pressure drop (0.8 bar) in the liquid line will create 3% flash gas by weight of the volume in the liquid line. At 32°C (90F) condensing temperature this will occupy 32% of the volume in the liquid line. At 10°C (50F) condensing temperature this would occupy 48% of the volume of the liquid line. If flash gas is allowed to form, it can significantly reduce the system’s capacity, particularly at lower condensing temperatures.