Refrigeration system with intermediate pressure vapor supply valve

1. A refrigeration system, comprising:

a compressor having an inlet and an outlet of refrigerant fluid in vapor form;

a condenser having a vapor inlet connected to the outlet of the compressor and a liquid outlet;

a high-expansion device having an inlet connected to the liquid outlet of the condenser and an outlet;

a separating means having a first inlet connected to the liquid outlet of the condenser and a vapor outlet connected to the inlet of the compressor and a liquid outlet;

a low-expansion device having an inlet connected to the liquid outlet of the separating means and an outlet;

an evaporator having a vapor-liquid mixture inlet receiving refrigerant fluid from the separating means through the outlet of the low-expansion device and a vapor-liquid mixture outlet; and a selecting valve having: a first vapor inlet connected with the vapor-liquid mixture outlet of the evaporator; a second vapor inlet connected to the vapor outlet of the separating means; and a vapor outlet connected to the inlet of the compressor, said selecting valve maintaining the refrigerant fluid in the second vapor inlet of the selecting valve and in the interior of the separating means at a first suction pressure higher than a second suction pressure in the first vapor inlet of the selecting valve and in the vapor outlet of the evaporator and being operated to selectively and alternatingly communicate the first and second vapor inlets of the selecting valve with the vapor outlet of the selecting valve, so as to allow the compressor to draw refrigerant vapor from the separating means, in said first suction pressure, and refrigerant vapor from the evaporator, in said second suction pressure; and a control unit operatively associated with the selecting valve, so as to operate the selecting valve for maintaining the level of the liquid refrigerant fluid in the interior of the separating means within predetermined values.

2. The system, as set forth in claim 1 , characterized in that the control unit comprises a timer which determines communication times between each of the first and second vapor inlets of the selecting valve and the vapor outlet of the latter, said communication times being designed to maintain the level of the liquid refrigerant fluid in the interior of the separating means within said predetermined values.

3. The system, as set forth in claim 2 , characterized in that the control unit commands the operation of the selecting valve from variable communication times which are switched between the first and second vapor inlets and the vapor outlet of the selecting valve, said communication times being defined from at least one operational condition associated with the components of the refrigeration system and/or with the environment external to the refrigeration system.

4. The system, as set forth in claim 1 , characterized in that the control unit commands the operation of the selecting valve from a level sensor capable of detecting predetermined maximum and minimum values of the liquid refrigerant fluid level in the interior of the separating means.

5. The system, as set forth in claim 1 , characterized in that the high-expansion device and low-expansion device are operatively associated with the control unit, so as to be commanded by the control unit to vary the degree of restriction in the refrigerant fluid flow and the pressure in the interior of the separating means and of the evaporator.