The machine compressor continuously draws large quantities of refrigerant vapor from the cooler, at a rate determined by the size of the guide-vane opening. This compressor suction reduces the pressure within the cooler, allowing the liquid refrigerant to boil vigorously at a fairly low temperature [typically, 30 to 35°F (−1 to 2°C)].
Liquid refrigerant obtains the energy needed for the change to vapor by removing heat from the water in the cooler tubes. The cold water can then be used in the air-conditioning process.
After removing heat from the water, the refrigerant vapor enters the first stage of the compressor. There, it is compressed and flows into the second stage of the compressor. Here it is mixed with flash-economizer gas and further compressed.
Compression raises the refrigerant temperature above that of the water flowing through the condenser tubes. When the warm [typically 100 to 105°F (38 to 41°C)] refrigerant vapor contacts the condenser tubes, the relatively cool condensing water [typically, 85 to 95°F (29 to 35°C)] removes some of the heat and the vapor condenses into a liquid.
Further heat removal occurs in the group of condenser tubes that form the thermal economizer. Here, the condensed liquid refrigerant is subcooled by contact with the coolest condenser tubes. These are the tubes that contain the entering water.
The subcooled liquid refrigerant drains into a high-side valve chamber. This chamber maintains the proper fluid level in the thermal economizer and meters the refrigerant liquid into a flash economizer chamber. Pressure in this chamber is intermediate between condenser and cooler pressures. At this lower pressure, some of the liquid refrigerant flashes to gas, cooling the remaining liquid. The flash gas, having absorbed heat, is returned directly to the compressor’s second stage. Here, it is mixed with gas already compressed by the first stage impeller. Since the flash gas must pass through only half the compression cycle to reach condenser pressure, there is a savings in power.
The cooled liquid refrigerant in the economizer is metered through the low-side valve chamber into the cooler. Because pressure in the cooler is lower than economizer pressure, some of the liquid flashes and cools the remainder to evaporator (cooler) temperature. The cycle is now complete.