Patent Publication Number: US-2017350631-A1

Title: Pressure reducing device for cooling system and cooling system

Description:
TECHNICAL FIELD 
     The present invention relates to a pressure reducing device for a cooling system and a cooling system. 
     BACKGROUND ART 
     Conventionally, it is known that a refrigerant vaporized by taking evaporation heat from an object to be cooled in a heat exchanger is liquefied in a compressor and a condenser, and then is reused through a pressure reducing valve (see Patent Document 1). 
     RELATED ART DOCUMENT 
     Patent Document 
     Patent Document 1: PCT International Publication No. WO 2014/041654 
     SUMMARY 
     Problems to be Solved by the Invention 
     In recent years, as a heat exchanger of a cooling system for cooling a fluid, a stacked type heat exchanger in which a first plate having a flow path through which a fluid to be cooled flows and a second plate having a flow path through which a refrigerant flows are alternately stacked has become known. Such a stacked type heat exchanger is small in size and has high heat exchange efficiency because it has a plurality of thin flow paths. However, when the refrigerant being introduced into the thin flow paths of such a stacked type heat exchanger is a flow of a vapor-liquid mixed phase, since it is difficult for the refrigerant to be evenly introduced into each flow path, there is a possibility of degradation in heat exchange performance. 
     In order to allow only a liquid phase portion of the refrigerant to be introduced into the heat exchanger, providing a separator for separating the refrigerant in a vapor-liquid mixed phase flow in a stage subsequent to a pressure reducing valve into a vapor phase and a liquid phase in a stage ahead of the heat exchanger can be conceived. However, since the separator has a container for accommodating the refrigerant therein and separating it into a vapor phase and a liquid phase, the separator tends to be large. Thus, there is room for improvement in miniaturization of the cooling system using the heat exchanger with thin flow paths for the refrigerant. 
     That is, the present invention is directed to providing a compact cooling system with high heat exchange efficiency and a pressure reducing device thereof. 
     Means for Solving the Problem 
     An aspect of the present invention provides a pressure reducing device for a cooling system including a pressure reducing valve disposed in a stage subsequent to a condenser for a refrigerant, and a microscopic bubble formation unit disposed inside a flow path for the refrigerant from the condenser to a heat exchanger and configured to form a vapor phase of the refrigerant into microscopic bubbles to be dispersed into a liquid phase of the refrigerant. 
     According to the present invention, since the microscopic bubble formation unit forms the vapor phase of the refrigerant that has become a flow of a vapor-liquid mixed phase into microscopic bubbles using the pressure reducing device and the microscopic bubbles are dispersed into a liquid phase and introduced into the heat exchanger, a heat exchange performance is higher than when a flow of the vapor-liquid mixed phase is directly introduced into the heat exchanger. Further, according to the present invention, since the microscopic bubble formation unit is disposed inside the flow path for the refrigerant, it is possible to reduce a size of the cooling system compared with a case in which a separator for separating the liquid phase of the refrigerant is provided in a stage ahead of the heat exchanger. 
     In the pressure reducing device for a cooling system of the aspect described above, the microscopic bubble formation unit may include an opening member in which a plurality of through hole portions which constitute a plurality of microscopic flow paths having a flow path cross-sectional area smaller than a cross-sectional area of the flow path are formed. 
     In this case, since the vapor phase becomes microscopic bubbles in the process of the flow of the vapor-liquid mixed phase passing through the plurality of through hole portions, the configuration can be simple. 
     In the pressure reducing device for a cooling system of the aspect described above, an opening diameter at least on a discharge side of each through hole in the plurality of through hole portions may be 1 mm or less. 
     In the pressure reducing device for a cooling system of the aspect described above, each through hole in the plurality of through hole portions may have an elongated opening having a width of 1 mm or less. 
     In these cases, since the bubbles in the refrigerant become microscopic bubbles and the microscopic bubbles cannot easily grow until the microscopic bubbles in the refrigerant are introduced into the heat exchanger, it becomes easier for the refrigerant to be evenly introduced into each flow path of the heat exchanger and heat exchange performance cannot easily degrade. 
     In the pressure reducing device for a cooling system of the aspect described above, the microscopic bubble formation unit may be disposed inside the pressure reducing valve. 
     In this case, since the microscopic bubble formation unit is inside the pressure reducing valve, the pressure reducing device can be small-sized. 
     The pressure reducing device for a cooling system of the aspect described above may further include a horizontal pipe having a refrigerant flow path which connects the microscopic bubble formation unit and the heat exchanger horizontally and in a straight line. 
     In this case, since the refrigerant in a state in which microscopic bubbles are dispersed therein due to having passed through the microscopic bubble formation unit is sent to the heat exchanger through the horizontal pipe horizontally and in a straight line, growth of the microscopic bubbles and vapor-liquid separation cannot easily occur. 
     Another aspect of the present invention provides a cooling system including a compressor which compresses a refrigerant, a condenser disposed in a stage subsequent to the compressor and configured to liquefy at least a portion of the refrigerant, a heat exchanger disposed in a stage subsequent to the condenser and having a flow path through which the refrigerant flows, and a pressure reducing device for a cooling system of the aspect described above. 
     According to the present invention, since the microscopic bubble formation unit forms the vapor phase of the refrigerant that has become a flow of a vapor-liquid mixed phase into microscopic bubbles using the pressure reducing device and the microscopic bubbles are dispersed into a liquid phase and introduced into the heat exchanger, a heat exchange performance is higher than when a flow of the vapor-liquid mixed phase is directly introduced into the heat exchanger. Further, according to the present invention, since the microscopic bubble formation unit is disposed inside the flow path for the refrigerant, it is possible to reduce a size of the cooling system compared with a case in which a separator for separating the liquid phase of the refrigerant is provided in a stage ahead of the heat exchanger. 
     Advantage of the Invention 
     According to the present invention, it is possible to provide a compact cooling system with high heat exchange efficiency and a pressure reducing device thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a cooling system of a first embodiment of the present invention. 
         FIG. 2  is a schematic view illustrating a pressure reducing valve of the cooling system. 
         FIG. 3  is a schematic view illustrating a microscopic bubble formation unit attached to a pressure reducing valve of the cooling system. 
         FIG. 4  is a schematic view illustrating a heat exchanger of the cooling system. 
         FIG. 5  is a schematic view of a cooling system of a second embodiment of the present invention. 
         FIG. 6  is a schematic view illustrating a microscopic bubble formation unit attached to a refrigerant pipe of the cooling system. 
         FIG. 7  is a schematic view illustrating an example of a shape of through hole portions in the microscopic bubble formation unit. 
         FIG. 8  is a schematic view illustrating another example of a shape of through hole portions in the microscopic bubble formation unit. 
         FIG. 9  is a schematic view of a cooling system of a third embodiment of the present invention. 
         FIG. 10  is a graph illustrating a correlation between a configuration of a microscopic bubble formation unit and an average bubble diameter of microscopic bubbles in an example of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present invention will be described.  FIG. 1  is a schematic view of a cooling system of the present embodiment.  FIG. 2  is a schematic view illustrating a pressure reducing valve of a cooling system.  FIG. 3  is a schematic view illustrating a microscopic bubble formation unit attached to pressure reducing valve of a cooling system.  FIG. 4  is a schematic view illustrating a heat exchanger of a cooling system. 
     As illustrated in  FIG. 1 , a cooling system  1  of the present embodiment includes a compressor  2 , a condenser  3 , a pressure reducing device  4 , and a heat exchanger  14 . 
     The compressor  2  compresses a refrigerant  40  (see  FIG. 2 ) that has been vaporized in the heat exchanger  14  to be described below and sends it to the condenser  3 . A configuration of the compressor  2  is not particularly limited. 
     The condenser  3  liquefies the refrigerant  40  that has been compressed by the compressor  2  and sends it to the pressure reducing device  4 . A configuration of the condenser  3  is not particularly limited. 
     The pressure reducing device  4  illustrated in  FIG. 2  is a pressure reducing device for a cooling system configured to reduce a pressure of the refrigerant  40  which has been partially liquefied by the condenser  3  in the cooling system of the present embodiment. As illustrated in  FIG. 2 , the pressure reducing device  4  includes a pressure reducing valve  5  and a microscopic bubble formation unit  20 . 
     The pressure reducing valve  5  includes an inlet  6  connected to a pipe  31  connected to the condenser  3 , an outlet  7  connected to a refrigerant pipe  32  connected to the heat exchanger  14 , and a throttle portion  8 . 
     The throttle portion  8  includes a cylinder  9 , a piston  12 , and an operating unit  13 . 
     The cylinder  9  includes the microscopic bubble formation unit  20  for introducing the refrigerant  40  from the inlet  6  into the cylinder  9  and an outlet opening  11  through which the refrigerant  40  flows out from the cylinder  9  to the outlet  7 . 
     As illustrated in  FIG. 3 , the microscopic bubble formation unit  20  is formed with a plurality of through hole portions  22  penetrating through a wall surface of the cylinder  9  by processing means such as electrical discharge machining, laser machining, drilling, or three-dimensional shaping. 
     The through hole portions  22  have a flow path cross-sectional area smaller than a cross-sectional area of the inlet  6  of the pressure reducing valve  5  (see  FIG. 2 ). The through hole portions  22  communicate with the inside and the outside of the cylinder  9  in a state in which the microscopic bubble formation unit  20  is formed in the cylinder  9 . In the through hole portions  22  of the present embodiment, each of the through hole portions  22  has a circular opening end having an inner diameter of 1 mm or less at least on a discharge side thereof. 
     The refrigerant  40  passing through the through hole portions  22  becomes a flow of a vapor-liquid mixed phase during the pressure reducing process due to a pressure difference in the refrigerant  40  between the outside of the cylinder  9  and the inside of the cylinder  9  illustrated in  FIG. 2  but is formed into bubbles when a vapor phase  41  of the refrigerant  40  is sheared at the opening ends on the discharge side of the through hole portions  22 . Thus, the refrigerant  40  changes from a flow of a vapor-liquid mixed phase with a large bubble diameter generated in a pressure reducing process of a conventional pressure reducing device which does not have each of through hole portions  22  having a circular opening end having an inner diameter of 1 mm or less to a state in which microscopic bubbles  41   a  are dispersed in a liquid phase  42  (a bubble flow). The microscopic bubbles  41   a  generated by the microscopic bubble formation unit  20  of the present embodiment have become microscopic bubbles smaller than a milli-bubble and are dispersed into the liquid phase  42  unlike the flow of the vapor-liquid mixed phase upstream from the microscopic bubble formation unit  20 . 
     In the present embodiment, when carbon dioxide is employed as the refrigerant  40 , for example, when a supercritical liquid of carbon dioxide which is in a supercritical state in a state in which a difference of 20 atmospheres or more is generated between the inside and outside of the cylinder  9  passes through the through hole portions  22  of the microscopic bubble formation unit  20 , it is possible to generate a bubble flow including bubbles having an average bubble diameter of 0.2 mm. 
     The piston  12  illustrated in  FIG. 2  is a member which is moved forward and backward in the cylinder  9  by the operating unit  13 . The piston  12  changes an opening degree of the through hole portions  22  by closing a portion of the through hole portions  22  of the cylinder  9 . A flow rate of the refrigerant  40  is changed due to a portion or all of the through hole portions  22  being closed by the piston  12 . 
     The operating unit  13  adjusts a position of the piston  12  in the cylinder  9  so that the refrigerant  40  flowing out from the outlet  7  to the outside of the pressure reducing valve  5  has a constant flow rate set in advance. 
     As illustrated in  FIGS. 1 and 4 , the heat exchanger  14  includes a first conduit  16  which constitutes a flow path through which a fluid substance to be cooled flows and a second conduit  18  which constitutes a conduit through which the refrigerant  40  (see  FIG. 2 ) flows. 
     The heat exchanger  14  of the present embodiment includes a first plate  15  having a plurality of first conduits  16  and a second plate  17  having a plurality of second conduits  18 . The first plate  15  and the second plate  17  are alternately stacked. In the present embodiment, heat exchange is performed between the first plate  15  and the second plate  17 . 
     An operation of the cooling system  1  of the present embodiment will be described. 
     In the operation of the cooling system  1  of the present embodiment illustrated in  FIG. 1 , the refrigerant becomes a flow of a vapor-liquid mixed phase in which at least a portion is liquefied or a liquid phase by the compressor  2  and the condenser  3  and is introduced into the pressure reducing device  4 . 
     As illustrated in  FIG. 2 , the refrigerant  40  introduced into the pressure reducing device  4  is introduced from the inlet  6  into the cylinder  9  through the through hole portions  22 . In the present embodiment, since the through hole portions  22  are formed as the microscopic bubble formation unit  20 , the refrigerant  40  being introduced from the inlet  6  into the cylinder  9  passes through the through hole portions  22  (see  FIG. 3 ) of the microscopic bubble formation unit  20 . A vapor phase portion of the refrigerant  40 , which has become a flow of a two-phase vapor-liquid in the pressure reducing process of passing through the through hole portions  22 , is sheared at the opening ends on the discharge side of the through hole portions  22  such that it becomes microscopic bubbles  41   a  smaller than the milli-bubble illustrated in  FIG. 2 . 
     The refrigerant  40  after passing through the microscopic bubble formation unit  20  is in a state in which the microscopic bubbles  41   a  are dispersed into the liquid phase  42  of the refrigerant  40 . The refrigerant  40  in which the microscopic bubbles  41   a  are dispersed is sent to the heat exchanger  14  illustrated in  FIG. 1  while the microscopic bubbles  41   a  are maintained as bubbles with no change. 
     Inside the heat exchanger  14  illustrated in  FIGS. 1 and 4 , heat exchange is performed between a substance to be cooled and the refrigerant  40 . That is, heat is transferred from the first conduit  16  constituting the flow path through which the substance to be cooled flows to the refrigerant  40  in the second conduit  18 . The refrigerant  40  is heated by the heat transferred from the first conduit  16  and is vaporized, thereby taking as much heat from the substance to be cooled as the heat of vaporization of the refrigerant  40 , and is discharged from the heat exchanger  14  to be returned to the compressor  2  (see  FIG. 1 ) through a pipe  33 . 
     In the refrigerant  40  introduced into the second conduit  18 , the vapor phase of the refrigerant  40  has become the microscopic bubbles  41   a . Therefore, in the second conduit  18 , the microscopic bubbles  41   a  are substantially evenly dispersed throughout the entire second conduit  18 . As a result, since the vaporization of the refrigerant  40  occurs in all regions of the second conduit  18 , a heat exchange efficiency becomes higher compared to a case in which only the vapor phase of the refrigerant  40  is introduced into a portion of the second conduit  18 . 
     As described above, in the cooling system  1  and the pressure reducing device  4  of the present embodiment, the microscopic bubble formation unit  20  can disperse the vapor phase  41  of the refrigerant  40  into the liquid phase  42  as the microscopic bubbles  41   a  and send it to the heat exchanger  14  instead of separating the vapor phase  41  from the flow of a two-phase mixed phase of the refrigerant  40 . Thus, it is possible to obtain the same heat exchange efficiency as that in the case of introducing only the liquid phase  42  of the refrigerant  40  into the heat exchanger  14 , without needing to retrieve only the liquid phase  42  by providing a separator in a container shape having a certain volume for separating the refrigerant  40  into the vapor phase  41  and the liquid phase  42 . 
     In the present embodiment, since the microscopic bubble formation unit  20  is disposed inside the flow path for the refrigerant  40  from the condenser  3  to the heat exchanger  14 , particularly in the present embodiment, inside the pressure reducing valve  5 , it is possible to reduce a size of the pressure reducing device  4  compared with the case in which the separator is provided. Therefore, it is also possible to reduce the overall size of the cooling system  1 . 
     Second Embodiment 
     A second embodiment of the present invention will be described. Further, in the embodiment described below, components the same as the components disclosed in the first embodiment are designated by the same reference signs as in the first embodiment, and duplicated description and illustration thereof will be omitted. 
       FIG. 5  is a schematic view of a cooling system of the present embodiment.  FIG. 6  is a schematic view illustrating a microscopic bubble formation unit attached to a refrigerant pipe of the cooling system.  FIG. 7  is a schematic view illustrating an example of a shape of through hole portions in a microscopic bubble formation unit.  FIG. 8  is a schematic view illustrating another example of a shape of the through hole portions in the microscopic bubble formation unit. 
     A cooling system  1 A of the present embodiment illustrated in  FIG. 5  includes a pressure reducing device  4 A having a different configuration from the pressure reducing device  4  disclosed in the first embodiment in place of the pressure reducing device  4  disclosed in the first embodiment. 
     The pressure reducing device  4 A of the present embodiment includes a pressure reducing valve  5 A and a microscopic bubble formation unit  20 A. 
     In the present embodiment, a known configuration can be appropriately selected and employed for the pressure reducing valve  5 A. 
     The microscopic bubble formation unit  20 A of the present embodiment is disposed in a refrigerant pipe  32  connecting the pressure reducing valve  5 A and a heat exchanger  14 . 
     As illustrated in  FIGS. 6 and 7 , the microscopic bubble formation unit  20 A is formed with an opening member including a plate-shaped frame body portion  21 A having a shape corresponding to a cross-sectional shape of the refrigerant pipe  32  and a plurality of through hole portions  22 A having a smaller opening area than the cross-sectional area of the refrigerant pipe  32 . 
     The through hole portions  22 A have an inner diameter of 1 mm or less as in the first embodiment. The through hole portions  22 A serve as flow paths connecting an upstream side and a downstream side of the microscopic bubble formation unit  20 A in the refrigerant pipe  32  in a state in which the microscopic bubble formation unit  20 A is attached to the refrigerant pipe  32 . 
     Also, a shape of an opening of the through hole portions  22 A in the microscopic bubble formation unit  20 A of the present embodiment may not be a circular opening. As another configuration example, as illustrated in  FIG. 8 , an elongated slit  22 B having a width of 1 mm or less may be formed in the frame body portion  21 A, for example. In addition, a shape of the through hole portions  22 A is not particularly limited as long as there is a pressure-loss body constituting a flow path gap of 1 mm or less in the refrigerant pipe  32 . 
     An operation of the cooling system  1 A of the present embodiment will be described. 
     The microscopic bubble formation unit  20 A of the pressure reducing device  4 A of the cooling system  1 A illustrated in  FIG. 5  is disposed in a portion of the refrigerant pipe  32 . For example, as illustrated in  FIG. 6 , the refrigerant pipe  32  is divided into an upstream portion  32 - 1  and a downstream portion  32 - 2  which sandwich the microscopic bubble formation unit  20 A therebetween and is fixed with the microscopic bubble formation unit  20 A sandwiched therebetween. 
     The refrigerant  40  passing through the pressure reducing valve  5 A illustrated in  FIG. 5  and flowing in the refrigerant pipe  32  is a flow of a vapor-liquid mixed phase or a flow of a liquid phase with no change from the state in which a portion of the refrigerant  40  is liquefied in a condenser  3  until it reaches the microscopic bubble formation unit  20 A. When the flow of the vapor-liquid mixed phase or the flow of the liquid phase passes through the plurality of through hole portions  22 A of the microscopic bubble formation unit  20 A and the pressure is reduced, as in the first embodiment, a vapor phase  41  of the refrigerant  40  is dispersed into a liquid phase  42  of the refrigerant  40  as microscopic bubbles  41   a.    
     As described above, in this embodiment, as in the first embodiment, it is possible to obtain the same heat exchange efficiency as that in the case of introducing only the liquid phase  42  of the refrigerant  40  into the heat exchanger  14 , without needing to retrieve only the liquid phase  42  by providing a separator. 
     Also, since a known pressure reducing valve  5  can be appropriately selected and employed in the present embodiment, production of the cooling system  1 A is facilitated and a degree of freedom in designing the cooling system  1 A is high. 
     Third Embodiment 
     A third embodiment of the present invention will be described.  FIG. 9  is a schematic view of a cooling system of the present embodiment. 
     A cooling system  1 B of the present embodiment illustrated in  FIG. 9  is distinguished from the configuration of the above-described second embodiment in that the pressure reducing device  4  disclosed in the above-described second embodiment further includes a horizontal pipe  32 A which connects a microscopic bubble formation unit  20 A and a heat exchanger  14  horizontally and in a straight line. 
     That is, in the present embodiment, regarding refrigerants pipes  32  on opposite sides of the microscopic bubble formation unit  20 A, a pipe on the downstream side of the microscopic bubble formation unit  20 A is straight. 
     The cooling system  1 B of the present embodiment is installed so that a center line of the horizontal pipe  32 A is horizontal when the cooling system  1 B is installed. The inside of the horizontal pipe  32 A which is a straight pipe extending horizontally serves as a refrigerant flow path through which a refrigerant  40  flows with microscopic bubbles  41   a . Since stagnation of the refrigerant  40  cannot easily occur in the horizontal pipe  32 A, growth of the microscopic bubbles  41   a  due to the stagnation of the refrigerant  40  is prevented. Thus, uneven flow of the refrigerant  40  in each flow path of the heat exchanger  14  due to a diameter of bubbles growing large can be prevented. 
     Also, in the present embodiment, a refrigerant pipe  32 - 1  upstream with respect to the microscopic bubble formation unit  20 A may not be a straight pipe extending horizontally. When the refrigerant pipe  32 - 1  upstream with respect to the microscopic bubble formation unit  20 A is not a straight pipe, the refrigerant  40  easily stagnates in a bent portion of the refrigerant pipe  32 - 1 . When a vapor phase  41  of the refrigerant  40  stagnates in the portion in which the refrigerant  40  stagnates, a portion of the vapor phase  41  that has stagnated grows to a large bubble and may move toward the horizontal pipe  32 A. In the present embodiment, since this bubble becomes the microscopic bubbles  41   a  due to the microscopic bubble formation unit  20 A, large bubbles are prevented from being directly introduced into the heat exchanger  14 . As a result, in the present embodiment, a degree of freedom in handling the refrigerant pipe  32 - 1  is high. 
     Examples 
     Examples of the present invention will be described.  FIG. 10  is a graph illustrating a correlation between a configuration of a microscopic bubble formation unit and an average bubble diameter of a microscopic bubble. 
     In the present example, when an inner diameter of through hole portions of the microscopic bubble formation unit is 0.2 mm, 0.4 mm, 1.0 mm, and 1.8 mm (see  FIG. 7 ), and when through hole portions of the microscopic bubble formation unit are a slit having a width of 0.2 mm, 0.4 mm, 1.0 mm, and 1.8 mm (see  FIG. 8 ), an average bubble diameter of bubbles in a flow of a two-phase vapor-liquid of carbon dioxide after passing through these through hole portions of the microscopic bubble formation unit is illustrated. 
     As illustrated in  FIG. 10 , when the hole diameter or the slit width in the through hole portions of the microscopic bubble formation unit was 0.2 mm, 0.4 mm, and 1.0 mm, the average bubble diameter was 0.2 mm and microscopic bubbles smaller than a milli-bubble was formed. When the hole diameter or the slit width in the through hole portions of the microscopic bubble formation unit was 1.8 mm, the average bubble diameter was not measurable and microscopic bubbles were not formed after passing through the through hole portion. As illustrated in  FIG. 10 , when the hole diameter or the slit width in the through hole portions of the microscopic bubble formation unit exceeded 1 mm, the average bubble diameter rapidly became larger and it is thought that it was difficult for these to be evenly dispersed into a liquid phase as bubbles. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a cooling system or a gas pressure booster system using a refrigeration cycle. 
     BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS 
     
         
         
           
               1 ,  1 A,  1 B: Cooling system 
               2 : Compressor 
               3 : Condenser 
               4 ,  4 A: Pressure reducing device 
               5 ,  5 A: Pressure reducing valve 
               6 : Inlet 
               7 : Outlet 
               8 : Throttle portion 
               9 : Cylinder 
               11 : Outlet opening 
               12 : Piston 
               13 : Operating unit 
               14 : Heat exchanger 
               15 : First plate 
               16 : First conduit 
               17 : Second plate 
               18 : Second conduit 
               20 ,  20 A: Microscopic bubble formation unit 
               21 A: Frame body portion 
               22 ,  22 A: Through hole portion 
               22 B: Slit (Through hole portion, Elongated opening) 
               31 : Pipe 
               32 : Refrigerant pipe 
               32 - 1 : Upstream portion of refrigerant pipe 
               32 - 2 : Downstream portion of refrigerant pipe 
               32 A: Horizontal pipe 
               33 : Pipe 
               40 : Refrigerant 
               41 : Vapor phase of refrigerant 
               41   a : Microscopic bubble of refrigerant 
               42 : Liquid phase of refrigerant