RETA Breeze_MayJune_Final_2025

EVOLUTION OF THE RECEIVER

O ur receiver designs have pro gressed over the years as we sought greater efficiencies. As Milt Garland said “Since the 1850s, there has been no change to the basic refrigera tion cycle. Changes have come in the form of efficiencies and feed rates.” The evolution of the receiver is a story of the hunt for greater efficiencies. In the early days, there was no receiver. Early systems were “critically charged.”That is, they had a small charge, and the majority of the refrigerant charge was on the low side of the system. It’s important to re- member that our early refrigeration systems were block ice makers. They were turned on, they built ice, then they were turned off. There was no load fluctuation in the early ice making systems. They ran “all out” or were shut off. PILOT/STORAGE RECEIVERS Early ice-making systems tended to leak a little. To have replacement refrigerant available quickly, some would keep ammonia onsite. Eventually, some facilities installed a tank onsite that allowed ammonia to be immediately available. This was quicker than adding refrigerant from cylinders. These tanks were called “nurse tanks” or “pilot receivers.”They were used for charging efficiency, not production efficiency. We mention them here for clarity. When the industry began to transition from the removal of heat from water (ice

production) to the removal of heat from spaces (air cooling), loads began to vary. Cold areas would need maximum refriger- ation when warm product was first intro- duced to the space. But once the doors were closed and the product was down to temperature, the refrigeration system would do less work. These varying loads had the potential to either starve the refrigeration system (less liquid refriger ant than needed for the load), or flood back (having more refrigerant than needed). To allow for varying loads, it became necessary to have a liquid stor- age vessel, and so the receiver was born. HIGH PRESSURE RECEIVERS (HPR) The original high-pressure receiver was simply a place for unneeded ammonia to be stored. Originally, these were pass- through type receivers, meaning all of the refrigerant passed through it as part of the refrigeration cycle. As systems got larger, the pass-through type receivers became much larger. The next innovation was the overflow or surge type receiver. The surge-type high- pressure receiver varied from the pass through type in that the liquid refrigerant did not pass through the surge-type receiver as part of the refrigeration cycle. Liquid “backed up” into the surge receiver through a bottom connected pipe when the low side did not need it. Liquid flowed out of the surge-type receiver to the low side when additional refrigerant was

A common question I receive is: “Why do we have so many types of receivers?” The short answer may be: “Because we need several different types of receivers.” That is far too simple of an answer.

By Vern M. Sanderson, CIRO, CRST

22 RETA.com