Patent Publication Number: US-2012023893-A1

Title: Cooling device for high temperature fluid, flight vehicle having the same and cooling method for high temperature fluid

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2010-0074259, filed on Jul. 30, 2010, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cooling device operative to cool high temperature fluid, a flight vehicle having the same and a cooling method for high temperature fluid. 
     2. Background of the Invention 
     Cooling devices, which are employed in flight vehicles, such as aircrafts or the like, may be divided into a vapor cycle type using a refrigerant phase change process, and a cooling machine employing type using an adiabatic expansion effect of engine bleed air. 
     The cooling machine employing type separately needs a controller for controlling temperature or pressure of supplied vapor (gas) within a specific range according to application (operation) environments, such as speed, altitude, air temperature, air pressure and the like. However, the separately employed controller increases a fabricating cost of the cooling device, and also an installation space for the cooling device in a flight vehicle should be ensured. 
     Therefore, a new cooling device, which does not need a controller separately is considered to address the problems. 
     SUMMARY OF THE INVENTION 
     Therefore, an aspect of the detailed description is to provide a cooling device capable of being less affected by external application environments, a flight vehicle having the same and a cooling method. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a cooling device including a heat exchanger configured such that fluid is introduced therein to be heat-exchanged with a refrigerant, and configured to vaporize the refrigerant by the heat exchange such that the fluid is discharged at temperature close to vaporization temperature of the refrigerant, a compressor connected to the heat exchanger and configured to compress the fluid discharged out of the heat exchanger, a turbine connected to the compressor and configured to expand the fluid compressed in the compressor to lower temperature of the compressed fluid, and a phase change heat exchanger connected to the turbine, storing a phase change material, and configured to cause heat exchange between the phase change material and the fluid discharged out of the turbine so as to control temperature of the discharged fluid. 
     In accordance with one exemplary embodiment, the heat exchanger may include a main body configured to allow the fluid and the refrigerant to be introduced and discharged therethrough, a refrigerant flow path plate installed within the main body and having a plurality of micro-flow paths for flow of the refrigerant, and a fluid flow path plate having a plurality of micro-flow paths for flow of the fluid, the fluid flow path plate being laminated on the refrigerant flow path plate. The refrigerant discharged out of the heat exchanger may be in a saturated vapor or superheated steam state, and the fluid introduced into the heat exchanger may be air or vapor having temperature higher than vaporization temperature of the refrigerant. 
     In accordance with another exemplary embodiment, the cooling device may further include a second heat exchanger. The second heat exchanger may be disposed between the compressor and the turbine to perform heat exchange using a second refrigerant, and configured such that the second refrigerant is vaporized to cool the fluid discharged out of the compressor such that the temperature of the fluid introduced into the turbine is close to vaporization temperature of the second refrigerant. An impeller of the compressor and the rotor of the turbine may be supported by the same rotational shaft, and the second heat exchanger may be disposed in parallel to the rotational shaft. 
     In accordance with another exemplary embodiment, the phase change heat exchanger may include a storage chamber configured to store the phase change material, and a plurality of channels configured to allow introduction and discharge of the fluid and intersect the storage chamber, at least parts of the plurality of channels being in parallel to each other. A storage space of the storage chamber may be defined as a space without a barrier. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a flight vehicle including a flight vehicle main body, an engine mounted in the main body to generate a propulsive force of the main body and configured to heat fluid introduced into the main body, and a cooling device configured to cool the fluid heated by the engine and discharge the cooled fluid towards an object whose temperature is needed to be adjusted. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a cooling method including cooling fluid using vaporization heat of a refrigerant to lower temperature of the fluid to be close to vaporization temperature of the refrigerant, compressing the temperature-lowered fluid using a compressor, expanding the compressed fluid using a turbine, connected to the compressor, to lower temperature of the compressed fluid, and exchanging heat with the fluid discharged out of the turbine, the heat being emitted or absorbed upon the phase change material being phase-changed, thus to maintain a constant temperature of the fluid discharged out of the turbine. At the cooling step, the fluid having temperature higher than the vaporization temperature of the refrigerant may be introduced into a heat exchanger, and the refrigerant may be heat-exchanged with the fluid within the heat exchanger to be in a saturated vapor or superheated steam state. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a schematic view showing a flight vehicle in accordance with one exemplary embodiment; 
         FIG. 2  is a flowchart showing a cooling method, which is applicable to the flight vehicle of  FIG. 1 ; 
         FIG. 3  is a schematic view of a cooling device shown in  FIG. 1 ; 
         FIG. 4A  is a perspective view of a heat exchanger shown in  FIG. 3 ; 
         FIG. 4B  is a disassembled view of flow path plates installed in the heat exchanger of  FIG. 3 ; 
         FIG. 5  is a sectional view of a compressor and a turbine shown in  FIG. 3 ; and 
         FIG. 6  is a schematic view of a phase change heat exchanger shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of a cooling device for high temperature fluid, a flight vehicle having the same and a cooling method for high temperature fluid in accordance with the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. The expression in the singular form in this specification will cover the expression in the plural form unless otherwise indicated obviously from the context. 
       FIG. 1  is a schematic view showing a flight vehicle in accordance with one exemplary embodiment. 
     A flight vehicle  100  may include, for example, aircraft, missile, rocket and the like, and an aircraft is illustrated in  FIG. 1 . The aircraft may include a main body  110 , an engine  120  and a cooling device  200 . 
     The main body  110  may be formed to suck (absorb) external fluid, for example, external air. The engine  120  may be mounted in the main body  110  not only to generate a propulsive force (thrust) for the main body  110  but also to heat the air introduced in the main body  110 . 
     Since external temperature is extremely low during flight (the external temperature is about 50° below zero upon flying at an altitude of 10 kilometers), a heating device is needed to protect passengers from the low temperature and provide such passengers with a comfortable space. The engine  120  may serve as the heating device. 
     Extremely hot air heated up in the engine  120  may be cooled by the cooling device  200 . The air is cooled down to an appropriate temperature and thereafter introduced into an object ( 130 ), for example, a cabin or the like, whose temperature should be controlled. 
     Ambient environments of the cooling device  200  may drastically change due to flight environments of the flight vehicle. The cooling device  200  related to the detailed description may employ a cooling method, by which high temperature fluid can be cooled down to a predetermined temperature regardless of the changes in the ambient environments. 
     Hereinafter, description will be given of a cooling method applicable to the cooling device  200 . 
       FIG. 2  is a flowchart showing a cooling method, which is applicable to the flight vehicle of  FIG. 1 . 
     First, in order for the temperature of fluid to be lowered close to vaporization temperature of a refrigerant, the fluid is cooled by using vaporization heat of the refrigerant (S 100 ). 
     The fluid may be air or vapor, and introduced into a heat exchanger in a higher temperature state than the vaporization temperature of the refrigerant. The refrigerant is heat-exchanged with the fluid in the heat exchanger to be in a saturated vapor state or a superheated steam state, and the vaporization heat of the refrigerant absorbs heat of the fluid such that the fluid can be less affected by the external environments. Thus, the fluid can always be cooled down to a temperature close to the vaporization temperature of the refrigerant. The heat exchanger may be implemented as an evaporative heat exchanger, for example. 
     More concretely, the cooling step S 100  uses a phenomenon that the temperature of the refrigerant is constantly maintained within a section of the refrigerant being vaporized. 
     The phenomenon of the refrigerant being vaporized with maintaining a certain temperature presents in a refrigerant flow path side and heat is absorbed in the vapor flow path side due to the refrigerant being vaporized at the constant temperature, thereby lowering the temperature. Since the refrigerant flow path is maintained at the constant temperature, then an outlet temperature of the vapor flow path is less affected by the external application environments. 
     Afterwards, the temperature-lowered fluid is compressed using a compressor (S 200 ). The compressed fluid is expanded using a turbine connected to the compressor so as to lower the temperature of the compressed fluid (S 300 ). The compressed fluid by the compressor is in a high temperature compressed state and adiabatically expanded by the turbine such that the temperature of the fluid can be decreased. 
     Finally, in order to maintain a constant temperature of the fluid discharged out of the turbine, heat, which is emitted or absorbed upon a phase change of a phase change material, is exchanged with the fluid discharged out of the turbine (S 400 ). 
     If the cooling device is in a good operation condition and thus the outlet temperature of the turbine is satisfactorily lowered by virtue of an expansion effect, the phase change material emits accumulated energy as low temperature vapor to be solidified. Here, if the temperature of the vapor is lower than a temperature within a target temperature range, the temperature of the fluid is increased by the energy of the phase change material. 
     In addition, if the cooling device is not in a good operation condition and thus the outlet temperature of the turbine exceeds the target temperature range, energy contained in the high temperature fluid is delivered to the phase change material, thereby lowering the temperature of the fluid being discharged. That is, the fluid discharged out of the turbine is heat-exchanged with the phase change material, for example, in the phase change exchanger, which allows the temperature of the fluid discharged to be controlled. 
     Hereinafter, the cooling device to which the cooling method is applied will be described in more detail with reference to  FIGS. 3 to 6 .  FIG. 3  is a schematic view of a cooling device shown in  FIG. 1 ,  FIG. 4A  is a perspective view of a heat exchanger shown in  FIG. 3 ,  FIG. 4B  is a disassembled view of flow path plates installed in the heat exchanger of  FIG. 3 ,  FIG. 5  is a sectional view of a compressor and a turbine shown in  FIG. 3 , and  FIG. 6  is a schematic view of a phase change heat exchanger shown in  FIG. 3 . 
     Referring to  FIG. 3 , the cooling device  200  may include a heat exchanger  210 , a compressor  220  and a turbine  230 . 
     The heat exchanger  210  may be configured such that fluid is introduced therein to be heat-exchanged with a refrigerant. Also, the heat exchanger  210  may be configured to vaporize the refrigerant so as for the fluid to be discharged at a temperature close to vaporization temperature of the refrigerant. 
     Referring to  FIGS. 4A and 4B , a main body  211  of the heat exchanger  210  may be configured such that the fluid and the refrigerant can be introduced and discharged, respectively. 
     Especially, the main body  211  may include a low temperature refrigerant inlet  212   a  for allowing a refrigerant in a low temperature liquid state, stored in a refrigerant storing tank (not shown), to be introduced therein, a high temperature fluid inlet  213   a  formed at an opposite side to the low temperature refrigerant inlet  212   a  for supplying high temperature fluid, a low temperature refrigerant outlet  212   b  formed at an opposite side to the low temperature refrigerant inlet  212   a  for discharging a refrigerant in a saturated vapor or superheated steam state, and a high temperature fluid outlet  213   b  for discharging fluid cooled through heat-exchange with the refrigerant in the liquid state. 
     The refrigerant may be, for example, natural water, cooling water or the like, and the high temperature fluid supplied via the high temperature fluid inlet  213   a  may be air or vapor having a temperature higher than the vaporization temperature of the refrigerant. 
     Micro-flow path plates  214  and  215  installed in the main body  211  may include a refrigerant flow path plate  214  through which the refrigerant flows, and a fluid flow path plate  215  through which the high temperature fluid flows. The refrigerant flow path plate  214  and the fluid flow path plate  215  may be alternately laminated by interposing a barrier plate  216  therebetween. 
     The refrigerant flow path plate  214  may be connected between the low temperature refrigerant inlet  212   a  and the low temperature refrigerant outlet  212   b , and the fluid flow path plate  215  may be connected between the high temperature fluid inlet  213   a  and the high temperature fluid outlet  213   b.    
     The refrigerant flow path plate  214  may include a plurality of micro-flow paths along which the refrigerant flows, and the fluid flow path plate  215  may include a plurality of micro-flow paths along which the fluid flows. That is, the heat exchanger  210  may be configured in a layered structure of the plurality of micro-flow path plates each having a thickness within several micrometers (mm). 
     More particularly, the refrigerant flow path plate  214  may be etched to form a plurality of micro-flow paths with predetermined intervals. The refrigerant flows in a direction indicated with an arrow so as to absorb heat transferred from the high temperature fluid. 
     The fluid flow path plate  215  may be etched to form a plurality of micro-flow paths with predetermined intervals. The fluid flows in a direction indicated with an arrow  215   a  to be heat-exchanged with the refrigerant, thereby being cooled. 
     Here, liquid supplied at room temperature absorbs heat from the fluid to be vaporized in the micro-flow paths. Latent heat generated upon vaporization of the liquid is extremely higher than specific heat, so even a less amount of refrigerant can absorb much heat. 
     As shown, the micro-flow paths of the refrigerant flow path plate  214  may have a labyrinthine or zigzag structure that the micro-flow paths are bent (or curved) at least two times. This form of flow path may serve to prevent a refrigerant in a liquid state, which remains non-vaporized due to inertia, from being discharged through the low temperature refrigerant outlet  212   b  immediately when accelerating the heat exchanger mounted in the flight vehicle. 
     Referring to  FIGS. 3 and 5 , the compressor  220  may be connected to the heat exchanger  210  for compressing the fluid discharged from the heat exchanger  210 , and the turbine  230  may be connected to the compressor  220  for expanding the fluid compressed in the compressor  220  so as to lower the temperature of the compressed fluid. 
     The compressor  220  may serve to compress the fluid introduced into the compressor  220  responsive to a rotation of a rotational shaft  240 . The compressor  220  may include a compressor case  221  and an impeller  222 . 
     The compressor case  221  may serve to house the impeller  222  therein, and include a compressor inlet  223  and a compressor outlet  224 . The compressor inlet  223  may be formed towards an axial direction of the rotational shaft  240 , and the compressor outlet  224  may be formed towards a radial direction of the rotational shaft  240 . 
     The impeller  222  may be mounted to one side of the rotational shaft  240 . Accordingly, the impeller  222  may rotate responsive to the rotation of the rotational shaft  240  so as to increase pressure of the fluid introduced into the compressor  220 . 
     The turbine  230  may serve to cool and discharge the fluid from the compressor  220  and also provide a driving force to the rotational shaft  240 . That is, the turbine  230  may have a function of discharging the cooled fluid and a function of serving as a driving source of the compressor  220 . The compressor  220  may compress the fluid introduced therein using energy generated from the turbine  230  and supply the compressed fluid to a turbine inlet  233 . 
     The turbine  230  may include a turbine case  231  and a rotor  232 . 
     The turbine case  231  may serve to house the rotor  232  therein, and include a turbine inlet  233  and a turbine outlet  234 . The turbine inlet  233  may be formed towards the radial direction of the rotational shaft  240 , and the turbine outlet  234  may be formed towards the axial direction of the rotational shaft  240 . 
     The rotor  232  may be mounted to another side of the rotational shaft  240 , and performs a rotation by pressure difference between the turbine inlet  233  and the turbine outlet  234 . The fluid introduced into the turbine  230  may rotate the rotor  232  to generate energy. The fluid flowed through the rotor  232  may be cooled due to expansion, thereby being discharged out through the turbine outlet  234 . As shown, the impeller  222 , the rotor  232  and the rotational shaft  240  may be secured together so as to rotate at once. 
     Referring to  FIG. 5 , a second heat exchanger  250  may be disposed between the compressor  220  and the turbine  230 . 
     The second heat exchanger  250  may be disposed between the compressor  220  and the turbine  230  such that the temperature of the fluid introduced into the turbine  230  can be close to the vaporization temperature of a second refrigerant. The second refrigerant may cool the fluid discharged out of the compressor  220  during vaporization. That is, the second heat exchanger  250  may be an evaporative heat exchanger, which is the same as or similar to the heat exchanger  210  disposed at the front of the compressor  220 . 
     The second heat exchanger  250  may be disposed in parallel to the rotational shaft  240  so as to sufficiently ensure a cooling flow path and achieve a compact cooling device. 
     The fluid primarily cooled in the heat exchanger  210  increases in temperature and pressure as it undergoes the compression process of the compressor  220 . During this process, the fluid consumes the energy generated from the turbine  230 . In general, for an adiabatic compression process, an outlet temperature of the compressor  220  will be calculated by the following equation. 
     
       
         
           
             
               
                 
                   
                     
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     Here, assuming that the fluid is air and a compression ratio of the compressor  220  is 2, the outlet temperature of the compressor  220  may be increased 1.22 times higher than the inlet temperature thereof. The second heat exchanger  250  may be disposed at the outlet of the compressor  220  to enhance the efficiency of the cooling device. 
     Referring to  FIGS. 3 and 6 , a phase change heat exchanger  260  may be disposed adjacent to the outlet of the turbine  230 . 
     The phase change heat exchanger  260  may store a phase change material. The phase change heat exchanger  260  may be connected to the turbine  230 . The phase change heat exchanger  260  may be formed to cause heat-exchange between the phase change material and the fluid discharged out of the turbine  230  so as to control the temperature of the discharged fluid. 
     In more detail, the phase change heat exchanger  260  may include a storage chamber  261  and a plurality of channels  262   a  and  262   b.    
     The storage chamber  261  may be formed to store the phase change material therein. The phase change material is a material to absorb or emit energy as its phase changes. When the fluid temperature is higher than a phase change temperature of the material, the phase change material absorbs energy for the phase change from the fluid so as to be phase-changed from solid into liquid, while emitting energy as its phase changes from liquid into solid. 
     The phase change material may be filled in a storage space of the storage chamber  261 . The storage space of the storage chamber  261  is a space without a barrier, which allows the phase change material to be smoothly phase-changed from solid to liquid or vice versa. 
     The plurality of channels  262   a  and  262   b  may allow the fluid to be introduced and discharged therethrough, and intersect the storage chamber  261 . The plurality of channels  262   a  and  262   b  may be disposed such that at least parts thereof are in parallel to each other. More concretely, a flow path (passage) of the fluid supplied is provided with micro-channels each having a width within several micrometers (mm), and such micro-channels are layered with each other to create a flow path plate  262 . Such structure can derive an effective heat transfer and optimize efficiency of the heat exchanger. 
     The phase change heat exchanger  260  may increase the temperature of the fluid if the fluid discharged out of the turbine  230  is overcooled while lowering the temperature of the fluid if being insufficiently cooled, according to the operation conditions of the cooling device. 
     Thus, by virtue of employing the evaporative heat exchanger and the phase change heat exchanger using the phase change phenomenon, such as vaporization heat of liquid and melting heat (ambient heat), the cooling device, which is less affected by external operation conditions and is capable of adjusting temperature without a separate controller, can be achieved. 
     In the cooling device with the configuration, the flight vehicle having the same and the cooling method, even when the performance of the cooling device changes responsive to the changes in the operation environments, the temperature of the fluid discharged out of the cooling device can be constantly maintained by the phase change heat exchanger. 
     Also, employment of the heat exchanger using vaporization heat can make the temperature of the fluid, which is discharged out of the outlet of the heat exchanger, maintained close to the temperature of the refrigerant being vaporized, resulting in minimizing the influence of the external operation conditions to the cooling device. 
     The configurations and methods of the cooling device for high temperature fluid, the flight vehicle having the same and the cooling method for the high temperature fluid in the aforesaid embodiments may not be limitedly applied, but such embodiments may be configured by a selective combination of all or part of each embodiment so as to derive many variations. 
     As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.