Abstract:
A system for testing objects such as electronic devices and mechanical components to see how they can withstand thermally hard circumstances created by a thermal agent supplied from a supplying system communicating with a testing section by and through an inlet flow path and an outlet flow path, wherein heat exchange is effected between the incoming agent and the outgoing agent, so that the remaining heat content, worm or cold, is taken and utilized for later uses.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a system for testing to see how mechanical or electronic objects can function under thermally hard circumstances created by using a thermal medium or agent, from which heat content, warm or cold, is taken. The thermal agent is hereinafter called “agent.” 
       BACKGROUND ART 
       [0002]    Among mechanical components and electronic appliances, cellphones and personal computers have occasions where they are used under thermally hard circumstances. This requires that their mechanical and electronic component parts, such as integrated circuits, should be previously checked to see if they can function properly in the anticipated hard circumstances. For testing machines for such use, there are some proposals disclosed in Japanese Patent Laid-open Application No. 2005-45039 and No. H10-288646, which are designed to expose testing objects such as wafers, to high or low temperatures. 
         [0003]    These known testing machines each are provided with a thermal adjuster, such as thermostats, which has a tray, and possibly with an electric heater. A testing object, such as wafers, is placed on the tray. In addition, the testing machine has a cavity through which a warm or cold agent, having a desired temperature is flown to keep the top surface of the tray at a required temperature; for example, when the surface of the tray is to be kept at low temperature, an agent having a corresponding low temperature is flown through the cavity. 
         [0004]    The thermostat maintains the tray at a desired temperature by controlling an electric heater or flowing an agent having a corresponding temperature into the cavity; for example, in order to cool the tray, a cold agent is flown into the cavity. 
         [0005]    In recent years the industry demands a stricter testing standard, and also a larger tray for testing a greater deal of objects in a shorter time. In order to meet these demands, the testing system tends to become large. Accordingly, a large thermal adjuster is required for supplying an agent to the cavity of the testing machine at a desired temperature. Therefore, the inventors devised a testing machine which is independent of the thermal adjuster. 
         [0006]    More specifically, if a cold atmosphere is required for testing, a cold agent having a desired temperature is produced in the agent supplying section, and supplied to the testing section through the inlet flow path, so as to conduct the test in the testing section. 
         [0007]    In the trial testing system it was ascertained that the two-section system considerably enhanced the cooling efficiency, so that the thermal adjuster in the agent supplying section was cooled to a desired temperature. This is a great advantage, but the inventors recognized that the cooled agent undesirably absorbs heat from the atmosphere and becomes warm while passing through the inlet flow path. This trades off the advantage of the increased cooling efficiency. More specifically, the agent required for testing an object must have a temperature of −90° C. or below, but while passing through the inlet flow path, the cold agent unavoidably gains heat from the atmosphere because of the significant difference in temperature between the cold agent and the atmosphere. The inventors have found that the still cold agent from the testing section is discharged with heat contained, and thought with regret that it is the waste of energy. 
         [0008]    The inventors thought that the still warm or still cold agent passing through the outlet flow path from the testing section can be reused, and that if the heat remaining in the outgoing agent is reused, it will contribute to the energy saving. 
         [0009]    Accordingly, the present invention is to provide a system for testing to see how mechanical or electronic objects can function under thermally severe circumstances, which are created by using an agent, liquid or gaseous, from which heat content, warm or cold, is taken, the system being capable of achieving energy saving by reusing the agent which would otherwise be discarded. 
       SUMMARY OF THE INVENTION 
       [0010]    According to a first version embodying the present invention, a testing system includes a testing section for conducting the tests; a thermal adjuster accommodated in the testing section so as to produce and maintain a desired temperature therein; a thermal agent supplying section for supplying an agent cooled or warmed to the testing section, wherein the testing section and the supplying section communicate with each other by and through an inlet flow path and an outlet flow path; a first heat exchanger for effecting heat exchange between an incoming agent from the atmosphere and an outgoing agent from the testing section; and an auxiliary outlet flow path arranged side by side with the outlet flow path so as to effect heat exchange between the agents flowing through the outlet flow path and the auxiliary outlet flow path. 
         [0011]    According to the first version, the heat content of a still cold agent outgoing from the testing section through the outlet flow path, and of a still warm agent outgoing through the outlet flow path is effectively taken for reuse. 
         [0012]    For example, where a cold agent is supplied to the thermal adjuster (e.g. a thermostat) in the testing section, the outgoing agent is still cold below the atmospheric temperature. Where a warm agent is supplied to the testing section, the outgoing agent is still warm above the atmosphere. The heat content, warm or cold, remaining in the agent can be reused. This contributes to energy-saving. 
         [0013]    According to a second version, of the invention, there is a provided a system for supplying a thermal agent to a device for testing objects such as electronic devices and mechanical components to see how they can withstand thermally hard circumstances, includes a testing section for conducting the tests; a thermal agent supplying section, communicating with the testing section by and through an inlet flow path and an outlet flow path; a thermal adjuster accommodated in the testing section so as to produce and maintain a desired temperature therein; a cooling device operable in a cyclic system, having a heat exchanger (A) for cooling an incoming agent to the testing section through the inlet flow path; and an auxiliary inlet flow path located side by side with the inlet flow path so as to effect heat exchange between a coolant flowing through the auxiliary inlet flow path and an incoming agent through the inlet flow path. 
         [0014]    According to a second version, a second heat exchanger is provided so as to take up coldness from a still cold agent outgoing from the testing section. 
         [0015]    According to a third version, a cooling device is provided having a compressor which compresses a coolant. 
         [0016]    The third version effects heat exchange between the still cold agent passing through the outlet flow path and the coolant from the compressor so as to effect heat exchange between the agents flowing through the outlet flow path and the coolant, thereby enable the outgoing agent to condense the coolant. Thus the cooling efficiency is considerably enhanced. 
         [0017]    According to a fourth version, wherein the outlet flow path and the auxiliary outlet flow path include a central tube and an outer flow path covering the central tube so as to constitute a multi-layer structure, thereby enlarging the surface of contact. 
         [0018]    According to the fourth version, the area of contact advantageously becomes large between the outlet flow path and the auxiliary outlet flow path, thereby enhancing the thermal efficiency. 
         [0019]    According to a fifth version, wherein the central tube of the fourth version, includes an inserted pipe open in the depth of the central tube, so as to introduce or discharge a cold or warm agent into or from the central tube. 
         [0020]    According to the fifth version, the agent, cold or warm, can reach and return from, the deepest part of the central tube, so that the stay of the agent in the central tube is prolonged, and therefore, the efficiency of heat exchange is enhanced. 
         [0021]    According to a sixth version, wherein the thermal adjuster includes a cavity, and the thermal agent is a gas to stay therein. 
         [0022]    According to a seventh version, wherein each of the first to the sixth version, receives a cold agent by and from the thermal adjuster, such as a thermostat. 
         [0023]    The seventh version contributes to the energy saving by providing the possibility of reusing the coldness of the still cold agent outgoing from the testing section. 
         [0024]    The embodiments mentioned above ensure that the heat energy, warm or cold, remaining in the agent can be effectively utilized. This leads to the energy saving. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective view showing a testing system of the present invention, including a testing section and an agent supplying section; 
           [0026]      FIG. 2  is a diagram showing the piping indicated in  FIG. 1 ; 
           [0027]      FIG. 3  is a diagram particularly showing in detail an inlet flow path in the piping shown in  FIG. 2 ; 
           [0028]      FIG. 4  is a sectional view throughout the inlet flow path shown in  FIG. 3 ; 
           [0029]      FIG. 5  is a sectional view throughout the outlet flow path in the piping shown in  FIG. 1 ; 
           [0030]      FIG. 6  (A) is a partly cross-sectional perspective view showing a modified inlet flow path; 
           [0031]      FIG. 6  (B) is a partly cross-sectional perspective view showing a modified outlet flow path; and 
           [0032]      FIG. 7  is a diagram showing a piping in another version of the invention in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     General: 
       [0033]    In the following description the above-mentioned first heat exchanger for adjusting the temperature of a warm agent will be referred to as “heat exchanger (A)”, and likewise the second heat for taking up coldness from a coolant will be referred to as “heat exchanger (B)”. Referring to  FIG. 1 , the illustrated testing machine  1  includes a testing section  3  and an agent supplying section  5 , wherein the agent is a substance from which heat energy, warm or cold, can be taken. The testing section  3  includes a thermal plate or tray  2 . The piping shown in  FIG. 2 , wherein the frame (A) shows a part of the piping located in the testing section  3 , and the frame (B) shows a part of it located in the agent supplying section  5 . The two sections  3  and  5  are communicatively connected to each other by an inlet tube  7  and an outlet tube  8 , wherein the tubes can be cylindrical or rectangular in its cross-section. 
         [0034]    The tray  2  of disc-shape can function as a chuck in its heated or cooled state, and receives a testing object placed on its top surface  10 . The surface of the tray  2  is kept at a desired temperature, warm or cold, the tray  2  having an electric heater (not shown), and a cavity  11  adapted for being filled with a cold air in circulation so as to keep the tray  2  at a desired low temperature. In addition, the tray  2  is provided with a vacuum device (not shown) for holding a testing object on the top surface  10  under suction. 
         [0035]    As shown in  FIG. 1 , the tray  2  is accommodated in a casing  12  separated from the agent supplying section  5 , and placed on a table  15 . The table  15  can move in the X and Y directions by means of an electric motor (not shown). The casing  12  accommodates pipes  16  and  17  through which the cavity  11  communicates with the atmosphere outside the casing  12 . 
         [0036]    The casing  12  is provided with an air-inlet  18  whose distal portion branches off into two ends, one end being connected to an inlet  78  of the outlet tube  8  through a electromagnet valve  19 , and the other end being open in the atmosphere through an electromagnet valve  13 . 
         [0037]    The air-inlet  18  is connected to a source of dry air  29  (e.g. a compressor) through a pressure reducing valve (not shown). 
       Two Cooling Cycles 
       [0038]    The agent supplying section  5  includes a cooling device for cooling the air introduced therein. The cooling device is operated in two cooling cycles; a first cycle consisting of a first compressor  20 , a first condenser  21 , a flow rate adjuster  22 , a first expanding valve  23 , and a primary side of a heat exchanger (B)  25 , and a second cycle consisting of a second compressor  30 , a second condenser  31 , a secondary side of the heat exchanger (B)  25 , a second expanding valve  33 , and a heat exchanger (A)  35 . 
         [0039]    The two cycles generally receive fluorocarbon or any other agent which is liable to phase change and achieve cooling cycle. More specifically, in the first cycle the agent is compressed by the first compressor  20 , and condensed by the condenser  21  with the help of a fan (not shown). Then the cooled agent flows through the first valve  23 , and gasifies on the primary side of the heat exchanger (B)  25  to take up the heat content, and returns to the first compressor  20  in the form of gas. 
         [0040]    In the second cycle the agent is compressed by the second compressor  30 , and condensed by the second condenser  31  with the help of a fan, thereby obtaining a cold agent. Then, the cold agent enters the secondary side of the heat exchanger (B)  25 , and is more cooled into a liquid under the action of the first cycle. The agent flowing through the second cycle passes through the second expanding valve  33 , and liquefies at the primary side of the heat exchanger (A)  35  to cause the agent to lose more heat. The vaporized agent returns to the compressor  30 . 
         [0041]    As a preferred embodiment, an auxiliary heat exchanger (B)  41  for cooling the agent and a heat-collecting heat exchanger  43  for taking up coldness are provided within the agent supplying section  5 . The secondary flow path of the auxiliary heat exchanger (B)  41  is connected in series to the middle part of the flow path of the first condenser  21 . 
       The Structure and Operation of the Inlet Tube  7   
       [0042]    In  FIG. 3 , the inlet tube  7  has a triple-layer structure with a central tube  50 , an outer tube  51 , and an inserted pipe  52  extending inside the central tube  50 . 
         [0043]    The central tube  50  has a head portion (unnumbered) and a bottom portion  53 , and its greater part is located within the outer tube  51  with the bottom portion  53  extending beyond the outer tube  51 , provided with a coolant outlet  55 . The outside diameter of the central tube  50  is smaller than the inside diameter of the outer tube  51  so as to produce a ring-shaped space therebetween, the space functioning as an inlet flow path  73 . 
         [0044]    The pipe  52  inserted through the bottom portion  53  of the central tube  50  is open near the head of the central tube  50 . The inserted pipe  52  has a smaller outside diameter than the inside diameter of the central tube  50  so as to produce a ring-shaped space therebetween, the space functioning as an auxiliary inlet flow path  72 . In this way the auxiliary inlet flow path  72  is located so closely adjacent to the inlet flow path  73  as to exchange heat easily therebetween; in other words, the flow paths  72  and  73  are arranged side by side along their length. The outer tube  51  has an air-inlet  56  at its proximal end, and an air-outlet  57  at its distal end. 
         [0045]    More specifically, in  FIG. 4  the inlet tube  7  is made of the outer tube  51  having a first coupler  58 , a T-shaped member  59 , a flexible tube  60 , a short pipe  61 , and a second coupler  62 , all of which are successively connected one to another, taking the shape of a thick central portion and opposite slim end portions, and as a whole, being flexible. 
         [0046]    The central tube  50  consists of a short pipe  64 , a T-shaped member  65 , another short pipe  66 , and a closed plastics tube  67  successively connected one to another. The outside diameter of the central tube  50  is smaller than the inside diameter of the outer tube  51  so as to produce a space which functions as the inlet flow path  73 . 
         [0047]    A greater part of the short pipe  66  is housed within the outer tube  51 . The short pipe  66  is liquid-tightly closed against the coupler  58 . 
         [0048]    As shown in  FIG. 4 , the inserted pipe  52  consists of a short pipe  70 , and a resilient slender pipe  71  connected to the short pipe  70 . The short pipe  70  partly overlaps with the short pipe  66  of the central tube  50 , and the slender pipe  71  reaches a point near the head of the central tube  50 . 
         [0049]    The inserted pipe  52  has a smaller outside diameter throughout its length than the inside diameter of the central tube  50  so as to produce the auxiliary inlet flow path  72  therebetween. The inserted pipe  52  and the short pipe  64  of the central tube  50  are welded to each other to secure airtight connection. The inlet tube  7  is covered with an insulating material (not shown). 
       The Structure and Operation of the Outlet Tube  8   
       [0050]    As shown in  FIG. 5 , the outlet tube  8  has a double construction with a central tube  75  and an outer tube  76 . The outer tube  76  consists of a first T-shaped pipe  80 , a flexible tube  81 , and a second T-shaped pipe  82  connected one after another. The central tube  75  consists of a first short pipe  83 , a flexible tube  85 , and a second short pipe  86  connected one to another. The central tube  75  and the outer tube  76  are resilient. 
         [0051]    The outside diameter of the central tube  75  is smaller than the inside diameter of the outer tube  76  so as to provide an auxiliary outlet flow path  77 . The central tube  75  functions as an outlet flow path. The outer tube  76  is provided with an air-inlet  78  and an air-outlet  79 . 
         [0052]    As described above, the testing section  3  and the agent supplying section  5  communicate with each other by the inlet tubes  7  and the outlet tube  8 ; that is, each of these tubes  7  and  8  is open within the casing  12  of the testing section  3  and the agent supplying section  5 . 
         [0053]    The casing  12  is provided with an air-inlet flow path having an air-inlet  18  whose distal end branches off, the branching end having an electromagnetic valve  19 . The downstream side of the valve  19  is connected to an air-inlet  78  which is open into the auxiliary outlet flow path  77  of the outlet tube  8 . 
         [0054]    The air-outlet  79  of the outlet tube  8  is connected to a secondary inlet of the heat-collecting heat exchanger  43  whose secondary outlet is connected to a secondary inlet of the heat exchanger (A)  35 . The secondary outlet of the heat exchanger (A)  35  is connected to an air-inlet  56 , which means that the secondary outlet of the heat exchanger (A)  35  is connected to the inlet tube  7 . 
         [0055]    The air-outlet  57  of the inlet tube  7  is connected to an air-inlet of the cavity  11  of the tray  2  whose air-outlet is connected to one end of the central tube  75  in the outlet tube  8  through a piping  17 . More specifically, the air-outlet of the tray  2  is connected to the outlet flow path  8 , thereby causing the used air to flow into the outlet tube  8  through the piping  17 . 
         [0056]    The distal end of the central tube  75  in the outlet tube  8  is connected to a primary inlet of the heat-collecting heat exchanger  43 , which is connected to a primary flow path port of the auxiliary heat exchanger (B)  41  whose primary outlet is open in the atmosphere. 
         [0057]    A part of the secondary cooling cycle branches off, and the branching parts are respectively connected to the coolant inlet and the coolant outlet  55  of the inlet tube  7 . This means that the secondary cold cycle has a bypass  36  to the heat exchanger (A)  35 , and the central tube  50  of the inlet tube  7  is connected to the bypass  36 . 
         [0058]    More specifically, in  FIG. 2  the flow path between the expanding valve  33  in the secondary cold cycle and the heat exchanger (A)  35  branches off, and one of the branching flow path is connected to a coolant inlet of the inlet tube  7  whose coolant outlet  55  is connected to a point between the heat exchanger (A)  35  and the second compressor  30 . Accordingly, the central tube  50  is brought into parallel with the heat exchanger (A)  35 , thereby ensuring that the coolants flowing through the central tube  50  and the heat exchanger (A)  35  has the same temperature. 
       The Operation of the Testing Section  3   
       [0059]    The testing machine  1  can change a temperature in a range of −65° C. to 200° C. or higher. Especially, the machine  1  is advantageous when it is operated at a low temperature. 
         [0060]    More specifically, in order to chill the top surface  10  of the tray  2 , the first compressor  20  and the second compressor  30  are both put into operation, and a dry air is introduced from the source of dry air  29  like a compressor. Simultaneously as the two compressors  20  and  30  start the operation, the cooling cycle starts, thereby causing a cold coolant to flow through the primary side of the heat exchanger (A)  35 , and to chill the secondary side thereof. 
         [0061]    The coolant flows to the auxiliary inlet flow path  72  through the bypass  36  bypassing the heat exchanger (A)  35 . The bypassed coolant is introduced into the central tube  50  from the end of the inserted pipe  52 , which is open in the depth of the central tube  50  thereby to enable the coolant to reach the depth thereof. 
         [0062]    In this situation, the distal end of the central tube  50  is closed, so that the coolant is caused to flow through the auxiliary inlet flow path  72  and return to the proximal end of the central tube  50 . Evidently, the coolant circles throughout the central tube  50 , and then it is discharged from the outlet  55 . 
         [0063]    As described above, the dry air is introduced into the testing section  3  from the source  29 . Then, it enters the outlet tube  8  through the air inlet  78 , and flows through the auxiliary outlet tube  77  kept in contact with the outlet tube  8 . The air passes through the secondary side of the heat-collecting heat exchanger  43 , and then through the secondary side of the heat exchanger (A)  35 . Furthermore, the air enters the air inlet  56  of the inlet tube  7  and flows through the auxiliary inlet tube  73  to enter the testing section  3 . Then, it enters the cavity  11  of the tray  2  through the piping  16 , and from there, it passes through the central tube  75  of the outlet tube  8 . In this way, the air flows through the primary side of the heat-collecting heat exchanger  43 , and flows through the primary side of the auxiliary heat exchanger (B)  41  to be discharged into the atmosphere. 
         [0000]    Varying Temperatures of the Agent flowing through Each Section 
         [0064]    The agent (air) can have a variety of temperatures at each stage of the flow paths. First, the dry air immediately after having left the source  29  has a room temperature. This air flows through an auxiliary outlet tube  77 , hereinafter called “incoming air”, and in the course of flowing it is cooled by another air (called “outgoing air”) flowing through the central tube  75  of the outlet tube  8 . 
         [0065]    As is evident from the above-mentioned description, the outgoing air has a lower temperature than the incoming air, which means that the outgoing air is colder than the room temperature. Thus, the heat content of the incoming air is taken by contact with the outgoing air through the wall of the outlet flow path  75 . In this way a cold air is obtained. 
         [0066]    The incoming air passes through the auxiliary outlet flow path  77 , and then through the secondary side of the heat-collecting heat exchanger  43 . The incoming air passing through the outlet piping  8  is cooled by exchanging heat with the outgoing air within the heat-collecting heat exchanger  43 . 
         [0067]    More specifically, the outgoing flowing through the primary side of the heat-collecting heat exchanger  43  is colder than the incoming air, thereby robbing the incoming air of its heat. 
         [0068]    The incoming air passing through the heat-collecting heat exchanger  43  enters the heat exchanger (A)  35  where it is cooled by losing its heat. More specifically, the incoming air flows through the secondary side of the heat exchanger (A)  35  which accepts the flow of a coolant cooled by the cooling device. Thus, the incoming air is cooled in the course of flowing through the heat exchanger (A)  35 . 
         [0069]    The air passing through the secondary side of the heat exchanger (A)  35  enters the air inlet  56  of the inlet tube  7 , and flows through the inlet flow path  73  to enter the testing section  3 . During the period of passage the incoming air is cooled by a coolant. 
         [0070]    More specifically, the incoming air flows through the inlet flow path  73 , and on the other hand, a coolant flows through the auxiliary inlet flow path  72 . These flow paths  72  and  73  are arranged side by side with each other so as to ensure that the coolant continues to take heat from the incoming air, thereby keeping the incoming air at a low temperature. 
         [0071]    The temperature of the coolant flowing through the central tube  50  is the same as that of the coolant flowing through the heat exchanger (A)  35 , so that the incoming air has little varying temperatures. The incoming air enters the cavity  11  of the tray  2  and cools the surface of the tray  2  while it rises up in temperature. The air discharged through the cavity  11  remains colder than the room temperature. 
         [0072]    The air discharged through the cavity  11  passes through the outlet flow path  75  of the outlet tube  8  by way of the piping  17 , and gives its chillness to the incoming air while it rises up in temperature. The air passing through the central tube  75  of the outlet tube  8  flows through the primary side of the heat-collecting heat exchanger  43 , giving its chillness to the incoming air while it rises up in temperature. 
         [0073]    The outgoing air flows through the primary side of the auxiliary heat exchanger (B)  41 , and contributes to condense the coolant in the first cooling cycle. In this way, this embodiment ensures that heat-taking occurs three times, thereby enhancing thermal efficiency. The final exhaust has substantially the same temperature as the room temperature, thereby providing no thermal change. In the conventional system the air discharged through the cavity of the tray or table was discharged into the atmosphere as it was. Therefore, the outlet was covered with dews. According to the present invention, no such problem occurs due to the fact that the exhaust air is kept at the room temperature. 
         [0074]    The embodiment described above allows a coolant to flow through the central tube  50  of the inlet tube  7 , and allows an incoming air to flow through the inlet flow path  73 , wherein the coolant is colder than the incoming air (the atmosphere), thereby preventing the coolant from losing its coldness into the atmosphere. The coolant can reciprocate within the central tube  50 , thereby staying therein so much longer and enhancing the heat exchange efficiency. 
         [0075]    In addition, the flow path is bent within the central tube  50 , so that the fluid flowing therein is liable to a relatively large pressure drag. In contrast, the in let flow path  73  outside the central tube  50  is straight, so that the fluid therein is liable to less pressure drag. This is the reason why the embodiment allows the incoming air to flow through the inlet flow path  73 . However, it is also possible to allow the incoming air through the central tube  50  and the coolant to flow through the inlet flow path. 
         [0076]    Likewise, it is possible to allow an outgoing air to flow through the central tube  75  of the outlet tube  8  and an incoming air to flow round it. It is also possible to allow an incoming air to flow through the central tube  75 , and an outgoing air to flow round it. The reason is that the incoming air is warmer than the outgoing air. 
         [0077]    For illustration&#39;s purpose only,  FIGS. 3 and 4  show that the inlet tube  7  is provided with the incoming and outgoing paths to constitute a double flow path structure, and  FIG. 5  shows that the outlet tube  8  is provided with a straight flow path. However, the invention is not limited to this structure, and the outlet tube  8  can be constructed in the same manner as the inlet tube  7 , wherein the cavity and thereabout must be enclosed by a mantle or the like, and also be provided with a pipe which is open in the depth of the cavity so as to effect the introduction and discharge of a coolant or a liquid. 
       Another Embodiment of the Invention 
       [0078]      FIG. 6  shows another example of the embodiment, characterized by providing a single inlet tube  91  having an inlet tube  92  and an auxiliary inlet tube  93  arranged side by side with each other.  FIG. 6(B)  shows a modified version of the outlet tube  8 ; that is, a single outlet tube  96  is provided in which an outlet tube  97  and an auxiliary outlet flow path  98  arranged side by side with each other. 
         [0079]    In the embodiment described above, the bypass  36  is connected to the central tube  50  of the inlet tube  7 , and bypasses the heat exchanger (A)  35 . Another embodiment will be described by referring to  FIG. 7 , as follows: 
         [0080]    In  FIG. 7 , the central tube  50  of the inlet tube  7  is connected in series to the heat exchanger (A)  35 . In the arrangement shown in  FIG. 7  the central tube  50  of the inlet tube  7  is provided downstream of the expanding valve  33 , and the heat exchanger (A)  35  is provided downstream of the central tube  50 . However, the heat exchanger (A)  35  can be provided ahead of the central tube  50 . 
         [0081]    A middle point between the condenser  31  and the expanding valve  33  can branch off, and one branch can be connected to the central tube  50  of the inlet tube  7 . This arrangement is advantageous in that the inserted pipe  52  of the central tube  50  can function as a capillary tube. In this embodiment a cooling device of a two cycle system is employed, and a coolant produced in the second stage of cycle is introduced into the inlet tube  7 . However, it is also possible to introduce a coolant produced in the first stage of cycle into the inlet tube  7 . In this case, the coolant tends to have a higher temperature than in the first embodiment, and it is necessary to flow a coolant through the outside flow path. 
         [0082]    In the two embodiments described above the agent is a thermally adjusted air intended for introduction into the cavity  11  of the tray  2  but it is also possible to use gas such as nitrogen instead of air, and also liquid.