In an evaporator with a double riser, which pipe has a trap and which incorporates an inverted trap?

In a double riser evaporator system, the purpose of an inverted trap is primarily to ensure that refrigerant vapor can rise freely while preventing any liquid refrigerant from flooding the riser. The larger riser typically serves as the main vapor return path to the compressor, and it is here that the trap is positioned. This trap is installed to facilitate the return of vapor while ensuring that any liquid refrigerant that might inadvertently accumulate is allowed to drain back to the evaporator.

Conversely, the smaller riser is usually designed to accommodate some liquid refrigerant, and an inverted trap there would not be practical. This is because if the smaller riser were to collect liquid, the design should allow for vapor to continue moving freely in the larger riser. Therefore, having the trap in the larger riser helps maintain the efficiency of the evaporator by ensuring that the return to the compressor is primarily vapor with minimal liquid.

This configuration is essential for the proper operation of the refrigerant cycle, optimizing performance, and preventing issues like compressor damage due to liquid slugging. By understanding the roles of the traps in these risers, it becomes clear why the larger riser is the one that incorporates a trap.