Environmental simulation chamber and respective method of operation

Abstract

Environmental simulation chamber ( 100 ) comprising a refrigeration apparatus ( 1 ) equipped with a refrigeration device ( 10 ) having a closed circuit (C) within which a refrigerant fluid circulates, said closed circuit (C) being equipped with at least one compressor ( 2 ), cooling means ( 3 ) for said refrigerant fluid, expansion means ( 4 ) for said refrigerant fluid and evaporation means ( 5 ), said chamber ( 100 ) further comprising an insulated space ( 20 ) into which a specimen ( 21 ) to be tested is inserted and wherein said evaporation means ( 5 ) are adapted to regulate the internal temperature of said insulated space ( 20 ), said simulation chamber being characterised in that said refrigerant fluid is carbon dioxide.

1 . Environmental simulation chamber ( 100 ) comprising a refrigeration apparatus ( 1 ) comprising a refrigeration device ( 10 ) having a closed circuit (C) within which a refrigerant fluid circulates, said closed circuit (C) comprising at least one compressor ( 2 ), cooling means ( 3 ) for said refrigerant fluid, expansion means ( 4 ) for said refrigerant fluid and evaporation means ( 5 ), said chamber ( 100 ) further comprising an insulated space ( 20 ) adapted to receive a specimen ( 21 ) to be tested therein and wherein said evaporation means ( 5 ) are adapted to regulate an internal temperature of said insulated space ( 20 ) and said refrigerant fluid is carbon dioxide. 
     
     
         2 . The environmental simulation chamber ( 100 ) according to  claim 1 , wherein said closed circuit further comprises an expansion reservoir ( 30 ) for said carbon dioxide, said expansion reservoir ( 30 ) arranged operatively along a first length (T) arranged between said evaporation means ( 5 ) and said at least one compressor ( 2 ), and filling and releasing means ( 6 ) for allowing the filling of refrigerant fluid from said first length (T) to said expansion reservoir ( 30 ) and the release of refrigerant fluid from said expansion reservoir ( 30 ) to said first length (T). 
     
     
         3 . The environmental simulation chamber according to  claim 2 , wherein said compressor ( 2 ) has intermittent operation in case of partial loads. 
     
     
         4 . The environmental simulation chamber according to  claim 2 or 3 , further comprising at least one control unit that, based on said internal temperature to be regulated within said insulated space, turns on or off said compressor ( 2 ), said refrigerant fluid present in said expansion reservoir ( 30 ) feeding said circuit (C) and/or being filled by said circuit (C). 
     
     
         5 . The environmental simulation chamber ( 100 ) according to  claim 4 , wherein said filling and releasing means ( 6 ) comprise a connecting conduit ( 61 ). 
     
     
         6 . The environmental simulation chamber ( 100 ) according to  claim 5 , wherein said connecting conduit ( 61 ) comprises a first shut-off valve ( 43 ) and said control unit opens or closes said first valve ( 43 ) to allow or disallow the inflow/outflow of said refrigerant fluid into/from said expansion reservoir ( 30 ) depending on the pressure at an outlet from the evaporation means ( 5 ). 
     
     
         7 . The environmental simulation chamber ( 100 ) according to  claim 2  wherein said closed circuit (C) further comprises a storage reservoir ( 70 ) of said refrigerant fluid in liquid form, which is arranged in a second length (T 2 ) of said closed circuit between said cooling means ( 3 ) and said expansion means ( 4 ). 
     
     
         8 . The environmental simulation chamber ( 100 ) according to  claim 1 , further comprising at least one auxiliary line ( 50 ) which directly or indirectly connects said closed circuit (C) to said insulated space ( 20 ), said auxiliary line ( 50 ) having an inlet section ( 51 ) for said refrigerant fluid arranged along a first length (T) of said closed circuit (C) between said evaporation means ( 5 ) and said at least one compressor ( 2 ), an outlet section ( 52 ) for said refrigerant fluid, and an opening/closing valve ( 55 ) for allowing or preventing passage of said refrigerant fluid along said auxiliary line, said outlet section ( 52 ) connected to said insulated space ( 20 ) for the inflow of carbon dioxide in gaseous form into said insulated section ( 20 ). 
     
     
         9 . The environmental simulation chamber ( 100 ) according to  claim 8 , further comprising detecting means ( 80 ) for detecting an ignition of a fire within said insulated space ( 20 ), said detecting means ( 80 ) operatively connected to said opening/closing valve ( 55 ) to control its opening or closing. 
     
     
         10 . The environmental simulation chamber ( 100 ) according to  claim 1 , wherein said refrigeration apparatus ( 1 ) comprises a further refrigeration device ( 10 ′) having a further closed circuit (C′) within which a further refrigerant fluid circulates, said further closed circuit (C′) comprising at least one further compressor ( 2 ′), further cooling means ( 3 ′) for said refrigerant fluid, further expansion means ( 4 ′) for said refrigerant fluid and further evaporation means ( 5 ′) adapted to operate in cooperation with said cooling means ( 3 ) of said refrigeration device ( 10 ), said further refrigeration device ( 10 ′) operating in a temperature range higher than that at which said refrigeration device ( 10 ) operates. 
     
     
         11 . The environmental simulation chamber ( 100 ) according to  claim 1 , wherein said closed circuit (C) further comprises at least one second high-pressure compressor ( 110 ) arranged in series to said at least one compressor ( 2 ), a bypass circuit ( 112 ) for said cooling means ( 3 ) having at least one control valve ( 113 ) for operating said bypass circuit ( 112 ), an intermediate throttling valve ( 114 ) downstream of said storage reservoir ( 70 ) and a condensation pressure control valve ( 115 ), said intermediate throttling valve ( 114 ) operatively arranged between said storage reservoir ( 70 ) and said second compressor ( 110 ). 
     
     
         12 . The environmental simulation chamber ( 100 ) according to  claim 11  wherein said closed circuit further comprises a heat exchanger ( 200 ) operatively connected to a third length (T 3 ) of said closed circuit (C) between said at least one second compressor ( 110 ), downstream of said bypass circuit ( 112 ), and said storage reservoir of the refrigerant fluid ( 70 ) and means ( 205 ,  206 ) for regulating the flow rate of refrigerant fluid entering said heat exchanger, said heat exchanger ( 200 ) disposed within said insulated space ( 20 ), said heat exchanger ( 200 ) and said evaporation means ( 5 ) disposed in two separate compartments present within said insulated space ( 20 ). 
     
     
         13 . A method for operating an environmental simulation chamber according to  claim 2 , comprising the steps of:
 a) setting at least one temperature, or at least one temperature range, to be obtained within said insulated space ( 20 );   b) activating said at least one compressor ( 2 ) to circulate said refrigerant fluid within said closed circuit (C) of said refrigeration device ( 10 ); and   c) regulating the opening/closing of said expansion means ( 4 ) to vary flow rate of refrigerant fluid passing through said evaporation means ( 5 ) depending on said at least one temperature, or said temperature range, required within said insulated space ( 20 );   wherein said refrigerant fluid is carbon dioxide.   
     
     
         14 . The method according to  claim 13 , further comprising step d) filling at least partially said expansion reservoir ( 30 ) with said refrigerant fluid. 
     
     
         15 . The method according to  claim 14 , wherein, if in said step c) said expansion means operate at partial load and said at least one expansion reservoir ( 30 ) is sized to contain fluctuations of pressures at the outlet of said evaporation means which are lower than 8 bars, said method further comprises step e) making said compressor work intermittently. 
     
     
         16 . The method according to  claim 15 , wherein said step e) comprises
 step e1) reducing the flow rate of the refrigerant fluid passing through said expansion means ( 4 ) to a value lower than that sucked by said at least one compressor ( 2 ) in such a way as to reduce the suction pressure of said at least one compressor to such a pressure value (Ps) to cause it to turn off,   step e2) feeding said expansion reservoir ( 30 ) by said fluid flowing out of said evaporation means until the pressure of said expansion reservoir ( 30 ) has risen to a first pressure value (P 1 ) determined depending on the temperature or the temperature range required within said insulated space ( 20 ) and equal to the suction pressure at which said at least one compressor ( 2 ), in said step e1), starts sucking refrigerant fluid from said expansion reservoir ( 30 ), and   step e3) reactivating operation of said compressor upon exceeding said first pressure value (P 1 ) within said reservoir,   said steps e1), e2) and e3) repeating cyclically.   
     
     
         17 . The method according to  claim 13 , wherein said filling and releasing means ( 6 ) comprise a first shut-off valve ( 43 ) arranged along said connecting conduit ( 61 ), wherein said step a) comprises step a1) rapidly increasing the requirement of required refrigeration load, and wherein said method further comprises step h) reducing the pressure within said expansion reservoir ( 30 ) to a minimum pressure value equal to a minimum suction pressure value (Ps) of said at least one compressor ( 2 ),
 wherein said step h) takes place prior to said step a1) and, subsequent to said step h) and simultaneous with said step a1), the method further comprises step r) keeping open said first shut-off valve ( 43 ) and said expansion means ( 4 ).   
     
     
         18 . The method according to  claim 17 , wherein said step r) continues until the temperature in said insulated space reaches a value 10° K higher than said evaporation temperature, or the suction pressure for said at least one compressor ( 2 ) has reached the maximum operating conditions expected for the operating condition of said at least one compressor ( 2 ) and said at least one first shut-off valve ( 43 ) is closed, said storage reservoir of the refrigerant fluid ( 70 ) and said expansion reservoir ( 30 ) being sized so that during said step r) said liquid-phase refrigerant fluid is not depleted. 
     
     
         19 . The method according to  claim 13 , wherein said refrigerant fluid circulates within said closed circuit under transcritical conditions, and further comprising step l) of flowing refrigerant fluid along said heat exchanger ( 200 ), said step l) carried out simultaneously with said step h) or independently of said step h). 
     
     
         20 . The method according to  claim 13 , further comprising step m) controlling the opening of an opening/closing valve ( 55 ) for passage of said refrigerant fluid along said auxiliary line, and step n) fluidically connecting said closed circuit (C) to said insulated space ( 20 ) by means of said auxiliary line ( 50 ), said auxiliary line ( 50 ) including an inlet section ( 51 ) for said refrigerant fluid arranged along a first length (T) of said closed circuit (C) between said evaporation means ( 5 ) and said at least one compressor ( 2 ), and an outlet section ( 52 ) for said refrigerant fluid, said outlet section ( 52 ) connected to said insulated space ( 20 ) for the inflow of carbon dioxide in gaseous form into said insulated space ( 20 ). 
     
     
         21 . The method according to  claim 20 , wherein said step m) is preceded by step o) detecting ignition of fire within said insulated space ( 20 ).