What is flash chamber? its significance in vapour compression refrigeration system.

A tank placed between the expansion valve (EV) and evaporator in a refrigeration system to separate and bypass any flash gas formed in the valve.

When liquid refrigerant as obtained from condenser is throttled, there are some vapours. These vapours if carried through the evaporator will not contribute to refrigerating effect. Using a flash chamber at some intermediate pressure, the flash vapour at this pressure can be bled off and fed back to the compression process. The throttling process is then carried out in  stages
. Similarly compression process is also done in two separate compressor stages.