AUTOMATIC GAS PURGERS
Wastage of refrigerant can be reduced by cooling the mixture of gases and thus reducing the ratio. By means of a refrigerated purge device, which cools the mixture down to the evaporator temperature (for example, — 35°C in a blast freezer plant), the ratio would become
Vapour pressure of R407C at — 35°C = 1.5 bar Partial pressure of non-condensible gas = 10.2 bar
The ratio now becomes 10 g of R407C lost per kilogram of air.
Automatic gas purgers comprise a collection vessel for the gas mixture with an inbuilt cooling coil connected to the main suction, or with its own refrigeration system. Condensed refrigerant returns to the condenser, and any gas remaining in the vessel will be non-condensible and can be vented by an inverted bucket trap.
Purging of gases must always be to the open air. The release of ammonia-air mixture is usually made through a flexible tube into a container of water. The water will absorb the ammonia, and any bubbles seen to rise to the surface will be other gases.
Posted in Refrigeration and Air Conditioning