Refrigeration cycle apparatus

Abstract

It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range. A refrigeration cycle apparatus uses carbon dioxide as refrigerant and has a compressor, an outdoor heat exchanger evaporator, an expander and an indoor heat exchanger a radiator. An injection circuit for introducing high pressure refrigerant is provided in a halfway of an expansion process of said expander.

1. A refrigeration cycle apparatus using comprising:
 carbon dioxide as refrigerant and having; 
 a refrigerant circuit in which including a compressor, an outdoor heat exchanger a radiator, an expander and an indoor heat exchanger, an evaporator, and an injection circuit which are all connected to one another through pipes, 
 wherein an injection circuit is provided in said refrigerant circuit, and said injection circuit introduces high pressure refrigerant on the side of from an outlet of said outdoor heat exchanger radiator into a halfway of an expansion process of said expander, and simultaneously high pressure refrigerant is introduced into an inflow of said expander, and 
 wherein the refrigerant moves from said expander into said evaporator. 
 
     
     
       2. A refrigeration cycle apparatus according to  claim 1 , further comprising wherein an adjusting valve for adjusting an amount of refrigerant from is provided in said injection circuit. 
     
     
       3. A refrigeration cycle apparatus according to  claim 1 , wherein said expander a pre-expansion valve is provided at its between a refrigerant-inflow side with a pre-expansion valve of said expander and said outlet of said radiator. 
     
     
       4. A refrigeration cycle apparatus according to  claim 1  wherein said expander is provided at its refrigerant-inflow side with a sub-expander is provided between a refrigerant-inflow side of said expander and said outlet of said radiator. 
     
     
       5. A refrigeration cycle apparatus according to  claim 1 , wherein said expander is provided at its refrigerant-outflow side with a sub-expander. 
     
     
       6. A refrigeration cycle apparatus according to  claim 4  or  5 , wherein an electric generator is connected to said sub-expander. 
     
     
       7. A refrigeration cycle apparatus according to any one of  claims 1  to  5 , wherein power recover by said expander is used for driving said compressor 4, comprising a drive shaft of the expander and a drive shaft of the compressor that are connected to each other. 
     
     
       8. A refrigeration cycle apparatus according to any one of  claims 1  to  5 , 4, wherein said compressor is provided at its suction side or discharge side with an auxiliary compressor, and power recover by said expander is used as power for driving said auxiliary compressor. 
     
     
       9. A refrigeration cycle apparatus according to any one of  claims 1  to  5 , 4, further comprising a first four-way valve to which a discharge side pipe and a suction side pipe of said compressor are connected, and a second four-way valve to which a discharge side pipe and a suction side pipe of said expander are connected, wherein refrigerant discharged from said compressor is selectively allowed to flow into said indoor heat exchanger evaporator or said outdoor heat exchanger radiator by said first four-way valve, a direction of refrigerant flowing through said expander is always set in the same direction by said second four-way valve. 
     
     
       10. A refrigeration cycle apparatus according to  claim 8 , further comprising a first four-way valve to which discharge side pipes and suction side pipes of said compressor and said auxiliary compressor are connected, and a second four-way valve to which a discharge side pipe and a suction side pipe of said expander are connected, wherein refrigerant discharged from said compressor and said auxiliary compressor is selectively allowed to flow into said indoor heat exchanger evaporator or said outdoor heat exchanger radiator by said first four-way valve, a direction of refrigerant flowing through said expander and said sub-expander is always set in the same direction by said second four-way valve.