Separation Enhancer

Certain refinements of the basic inlets and outlets to the vessel are usually used to facilitate the separation of liquid and vapor. Any of the entrance lines that are carrying liquid are usually turned downward. The vapor line leaving for the compressor usually has an upward turn, as shown in Fig. 10.18a, which requires any liquid drops to travel upward and make a 180° turn to inhibit capture by the suction line. This suction line should be sloped back to the vessel, so a liquid trap develops which can be prevented by drilling a weep hole at the elbow of the pipe.

(a) Separation enhancers including (a) directing inlet flows downard and drawing vapor from the top, and (b) installation of a metal mesh for mist elimination.

Another approach to improved liquid separation is through coalescing the small drops into larger ones by passing the liquid/vapor mixture through eliminator baffles or a mesh, as is shown in Fig. 10.18b. These devices are commonly used for vessels in chemical plants and surely permit the choice of a smallersize vessel. They have the disadvantage of introducing pressure drop which in the view of many refrigeration system designers is a penalty that can be avoided by a larger-size vessel with no obstructions.