Abstract:
A performance testing apparatus for a heat pipe includes an immovable portion having a cooling structure defined therein for cooling a heat pipe requiring test. A movable portion is capable of moving relative to the immovable portion. A receiving structure is defined between the immovable portion and the movable portion for receiving the heat pipe therein. A concavo-convex cooperating structure is defined in the immovable portion and the movable portion for avoiding the movable portion from deviating from the immovable portion to ensure the receiving structure being capable of precisely receiving the heat pipe. At least a temperature sensor is attached to at least one of the immovable portion and the movable portion for thermally contacting the heat pipe in the receiving structure to detect a temperature of the heat pipe.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to testing apparatuses, and more particularly to a performance testing apparatus for heat pipes.  
       DESCRIPTION OF RELATED ART  
       [0002]     It is well known that a heat pipe is generally a vacuum-sealed pipe. A porous wick structure is provided on an inner face of the pipe, and at least a phase changeable working media employed to carry heat is contained in the pipe. Generally, according to positions from which heat is input or output, a heat pipe has three sections, an evaporating section, a condensing section and an adiabatic section between the evaporating section and the condensing section.  
         [0003]     In use, the heat pipe transfers heat from one place to another place mainly by exchanging heat through phase change of the working media. Generally, the working media is a liquid such as alcohol or water and so on. When the working media in the evaporating section of the heat pipe is heated up, it evaporates, and a pressure difference is thus produced between the evaporating section and the condensing section in the heat pipe. The resultant vapor with high enthalpy rushes to the condensing section and condenses there. Then the condensed liquid reflows to the evaporating section along the wick structure. This evaporating/condensing cycle continually transfers heat from the evaporating section to the condensing section. Due to the continual phase change of the working media, the evaporating section is kept at or near the same temperature as the condensing section of the heat pipe. Heat pipes are used widely owing to their great heat-transfer capability.  
         [0004]     In order to ensure the effective working of the heat pipe, the heat pipe generally requires test before being used. The maximum heat transfer capacity (Qmax) and the temperature difference (ΔT) between the evaporating section and the condensing section are two important parameters for evaluating performance of the heat pipe. When a predetermined quantity of heat is input into the heat pipe through the evaporating section thereof, thermal resistance (Rth) of the heat pipe can be obtained from ΔT, and the performance of the heat pipe can be evaluated. The relationship between these parameters Qmax, Rth and ΔT is Rth=ΔT/Qmax. When the input quantity of heat exceeds the maximum heat transfer capacity (Qmax), the heat cannot be timely transferred from the evaporating section to the condensing section, and the temperature of the evaporating section increases rapidly.  
         [0005]     Conventionally, a method for testing the performance of a heat pipe is first to insert the evaporating section of the heat pipe into liquid at constant temperature; after a predetermined period of time, temperature of the heat pipe will become stable and then a temperature sensor such as a thermocouple, a resistance thermometer detector (RTD) or the like is used to measure ΔT between the liquid and the condensing section of the heat pipe to evaluate the performance of the heat pipe. However, Rth and Qmax can not be obtained from this test, and the performance of the heat pipe can not be reflected exactly by this test.  
         [0006]     Referring to  FIG. 5 , a conventional performance testing apparatus for heat pipes is shown. The apparatus has a resistance wire  1  coiling round an evaporating section  2   a  of a heat pipe  2 , and a water cooling sleeve  3  functioning as a heat sink and enclosing a condensing section  2   b  of the heat pipe  2 . In use, electrical power controlled by a voltmeter and an ammeter flows through the resistance wire  1 , whereby the resistance wire  1  heats the evaporating section  2   a  of the heat pipe  2 . Simultaneously, by controlling flow rate and temperature of cooling liquid flowing through the cooling sleeve  3 , the heat input at the evaporating section  2   a  can be removed from the heat pipe  2  by the cooling liquid at the condensing section  2   b,  whereby a stable operating temperature of adiabatic section  2   c  of the heat pipe  2  is obtained. Therefore, Qmax of the heat pipe  2  and ΔT between the evaporating section  2   a  and the condensing section  2   b  can be obtained by temperature sensors  4  at different positions of the heat pipe  2 .  
         [0007]     However, in the test, the conventional testing apparatus has drawbacks as follows: a) it is difficult to accurately determine lengths of the evaporating section  2   a  and the condensing section  2   b  which are important factors in determining the performance of the heat pipe  2 ; b) heat transference and temperature measurement may easily be affected by environmental conditions; c) it is difficult to achieve sufficiently intimate contact between the heat pipe and the heat source and between the heat pipe and the heat sink, which results in unsteady performance test results of the heat pipes. Furthermore, due to fussy and laborious assembly and disassembly in the test, the testing apparatus can be only used in the laboratory, and can not be used in the mass production of heat pipes.  
         [0008]     In mass production of heat pipes, a large number of performance tests are needed, and the apparatus is used frequently over a long period of time; thus, the apparatuses not only requires good testing accuracy, but also requires easy and accurate assembly to the heat pipes to be tested. The testing apparatus affects the yield and cost of the heat pipes directly; thus testing accuracy, facility, speed, consistency, reproducibility and reliability need to be considered when choosing the testing apparatus. Therefore, the conventional testing apparatus needs to be improved in order to meet the demand for testing during mass production of heat pipes.  
         [0009]     What is needed, therefore, is a high performance testing apparatus for heat pipes suitable for use in mass production of heat pipes.  
       SUMMARY OF INVENTION  
       [0010]     A performance testing apparatus for a heat pipe in accordance with a preferred embodiment of the present invention comprises an immovable portion having a cooling structure defined therein for removing heat from a condensing section of a heat pipe requiring test. A movable portion is capable of moving relative to the immovable portion. A receiving structure is defined between the immovable portion and the movable portion for receiving the condensing section of the heat pipe therein. A concavo-convex cooperating structure is defined in the immovable portion and the movable portion for avoiding the movable portion from deviating from the immovable portion to ensure the receiving structure being capable of accurately receiving the heat pipe. At least a temperature sensor is attached to at least one of the immovable portion and the movable portion for thermally contacting the heat pipe in the receiving structure for detecting temperature of the heat pipe.  
         [0011]     Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]     Many aspects of the present apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
         [0013]      FIG. 1  is an assembled view of a performance testing apparatus for heat pipes in accordance with a preferred embodiment of the present invention;  
         [0014]      FIG. 2  is an exploded, isometric view of the testing apparatus of  FIG. 1 ;  
         [0015]      FIG. 3A  shows a movable portion of the testing apparatus of  FIG. 2 ;  
         [0016]      FIG. 3B  shows an immovable portion of the testing apparatus of  FIG. 2 ;  
         [0017]      FIG. 4A  shows a movable portion of a performance testing apparatus for heat pipes in accordance with an alternative embodiment of the present invention;  
         [0018]      FIG. 4B  shows an immovable portion of the testing apparatus in accordance with the alternative embodiment of the present invention; and  
         [0019]      FIG. 5  is a conventional performance testing apparatus for heat pipes. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Referring to  FIGS. 1-3B , a performance testing apparatus for heat pipes in accordance with a preferred embodiment of the present invention comprises an immovable portion  20  and a movable portion  30  movably mounted on the immovable portion  20 .  
         [0021]     The immovable portion  20  is made of metal having good heat conductivity and is held on a platform of a supporting member (not shown) such as a testing table or so on. Cooling passageways (not shown) are defined in an inner portion of the immovable portion  20 , to allow coolant flow therein. An inlet  22  and an outlet  22  communicate the passageways with a constant temperature coolant circulating device (not shown); therefore, the passageways, inlet  22 , outlet  22  and the coolant circulating device corporately define a cooling system for the coolant circulating therein to remove heat from the heat pipe in test. The immovable portion  20  has a cooling groove  24  defined in a top face thereof, for receiving a condensing section of the heat pipe to be tested therein and removing heat from the heat pipe. Two temperature sensors  26  are inserted into the immovable portion  20  from a bottom thereof so as to position detecting portions (not labeled) of the sensors  26  in the cooling groove  24 . The detecting portions of the sensors  26  are capable of automatically contacting the heat pipe in order to detect a temperature of the condensing section of the heat pipe. In order to prevent heat in the immovable portion  20  from spreading to the supporting member, an insulating plate (not shown) is disposed between the performance testing apparatus and the supporting member.  
         [0022]     The movable portion  30 , corresponding to the cooling groove  24  of the immovable portion  20 , has a positioning groove  32  defined therein, whereby a testing channel  50  is cooperatively defined by the cooling groove  24  and the positioning groove  32  when the movable portion  30  moves to reach the immovable portion  20 . Thus, an intimate contact between the heat pipe and the movable and immovable portions  30 ,  20  defining the channel  50  can be realized, thereby reducing heat resistance between the heat pipe and the movable and immovable portions  30 ,  20 . Two temperature sensors  36  are inserted into the movable portion  30  from a top thereof to reach a position wherein detecting portions (not labeled) of the sensors  36  are located in the positioning groove  32  and capable of automatically contacting the heat pipe to detect the temperature of the condensing section of the heat pipe.  
         [0023]     The movable portion  30  has a plurality of cylindrical posts  35  extending downwardly integrally from a bottom face thereof towards the immovable portion  20 . The cylindrical posts  35  are evenly located at two sides of the groove  32  of the movable portion  30 . Corresponding to the posts  35  of the movable portion  30 , the immovable portion  20  has a plurality of positioning holes  25  defined in a top face thereof. The posts  35  are slidably inserted into the corresponding holes  25 . The posts  35  are entirely embedded in the holes  25  when the movable portion  30  moves to the immovable portion  20 ; therefore, the bottom face of the movable portion  30  contacts the top face of the immovable portion  20 . The posts  35  and the holes  25  concavo-convexly cooperate to avoid the movable portion  30  from deviating from the immovable portion  30  during test of the heat pipes, thereby ensuring the grooves  24 ,  32  of the immovable, movable portions  20 ,  30  to precisely align with each other. Accordingly, the channel  50  can be accurately formed for precisely receiving the heat pipe therein for test. Alternatively, the immovable portion  20  can have a plurality of posts while the movable portion  30  can have a plurality of holes corresponding to the posts.  
         [0024]     The channel  50  as shown in the preferred embodiment has a circular cross section enabling it to receive the condensing section of the heat pipe having a correspondingly circular cross section. Alternatively, the channel  50  can have a rectangular cross section where the condensing section of the heat pipe also has a flat rectangular configuration.  
         [0025]     Generally, in order to ensure that the heat pipe is in close contact with the movable and immovable portions  30 ,  20 , a clamping member is applied to retain the movable portion  30  together with the immovable portion  20 . The immovable portion  20  is fixed on a supporting frame  10 . A driving device  40  is installed on the supporting frame  10  to drive the movable portion  30  to make accurate linear movements relative to the immovable portion  20  along a vertical direction, thereby realizing the intimate contact between the heat pipe and the movable and immovable portions  30 ,  20 ; thus, heat resistance between the condensing section of the heat pipe and the movable and immovable portions  30 ,  20  can be minimized.  
         [0026]     The supporting frame  10  comprises a seat  12  which in accordance with the preferred embodiment is an electromagnetic holding chuck, by which the testing apparatus can be easily fixed at any desired position which is provided with a platform made of ferroalloy. A first plate  14  is secured on the seat  12 ; a second plate  16  hovers over the first plate  14 ; a plurality of supporting rods  15  interconnect the first and second plates  14 ,  16  for supporting the second plate  16  above the first plate  14 . The seat  12 , the first and second plates  14 ,  16  and the rods  15  constitute the supporting frame  10  for assembling and positioning the immovable and movable portions  20 ,  30  therein. The first plate  14  has the immovable portion  20  fixed thereon. In order to prevent heat in the immovable portion  20  from spreading to the first plate  14 , an insulating plate  28  is disposed between the immovable portion  20  and the first plate  14 . The first plate  14  has a top face defining a positioning concave  145  therein in which the insulating plate  28  is positioned. The insulating plate  28  defines a pond  285  in a top face thereof in which a bottom of the immovable portion  20  is positioned. The insulating plate  28  has an elongated slot  282  defined in a bottom face thereof, wherein the bottom face abuts the first plate  14 , and two through holes  284  vertically extend therethrough and communicate with the slot  282 . The through holes  284  and slot  282  are used for extension of wires (not shown) of the temperature sensors  26  to connect with a monitoring computer (not shown).  
         [0027]     The driving device  40  in this preferred embodiment is a step motor, although it can be easily apprehended by those skilled in the art that the driving device  40  can also be a pneumatic cylinder or a hydraulic cylinder. The driving device  40  is installed on the second plate  16  of the supporting frame  10 . The driving device  40  is fixed to the second plate  16  above the movable portion  30 . A shaft (not labeled) of the driving device  40  extends through the second plate  16  of the supporting frame  10 . The shaft has a threaded end (not shown) threadedly engaging with a bolt  42  secured to a board  34  of the movable portion  30 . The board  34  is fastened to the movable portion  30 . When the shaft rotates, the bolt  42  with the board  34  and the movable portion  30  is moved upwardly or downwardly. Two through apertures (not labeled) are defined in the board  34  of the movable portion  30  for extension of wires (not labeled) of the temperature sensors  36  to connect with the monitoring computer. In use, the driving device  40  drives the movable portion  30  to make accurate linear movement relative to the immovable portion  20 . For example, the movable portion  30  is driven to depart a certain distance such as 5 millimeters from the immovable portion  20  to facilitate the condensing section of the heat pipe which needs to be tested to be inserted into the channel  50  or withdrawn from the channel  50  after the heat pipe has been tested. On the other hand, the movable portion  30  can be driven to move toward the immovable portion  20  to thereby realize an intimate contact between the condensing section of the heat pipe and the immovable and movable portions  20 ,  30  during which the test is performed. Accordingly, the requirement for the testing, i.e. accuracy, ease of use and speed can be realized by the testing apparatus in accordance with the present invention.  
         [0028]     It can be understood, positions of the immovable portion  20  and the movable portion  30  can be exchanged, i.e., the movable portion  30  being located on the first plate  14  of the supporting frame  10 , the immovable portion  20  being fixed to the second plate  16  of the supporting frame  10 , and the driving device  40  being positioned adjacent to the movable portion  30 . Alternatively, the driving device  40  can be installed to the immovable portion  20 . In a further alternative, each of the immovable and movable portions  20 ,  30  has one driving device  40  installed thereon to move them toward/away from each other.  
         [0029]     In use, the condensing section of the heat pipe is received in the groove  24  of the immovable portion  20  when the movable portion  30  is moved away from the immovable portion  20 . Then the movable portion  30  is moved to the immovable portion  20  with the posts  35  of the movable portion  30  being slidably inserted into the holes  25  of the immovable portion  20  to reach the position wherein the grooves  24 ,  32  of the immovable and movable portions  20 ,  30  accurately constitute the channel  50 . Thus, the condensing section of the heat pipe is tightly fitted in the channel  50 . The sensors  26 ,  36  are in thermal connection with the condensing section of the heat pipe; therefore, the sensors  26 ,  36  work to accurately send detected temperatures of the condensing section of the heat pipe to the monitoring computer. Based on the temperatures obtained by the plurality of sensors  26 ,  36 , an average temperature can be obtained by the monitoring computer very quickly; therefore, performance of the heat pipe can be very quickly decided.  
         [0030]     Referring to  FIGS. 4A and 4B , an immovable portion  20  and a movable portion  30  of a performance testing apparatus for heat pipes in accordance with an alternative embodiment of the present invention are illustrated. The alternative embodiment is similar to the previous preferred embodiment, and the main difference therebetween is that the movable portion of the alternative embodiment has two elongated boards  35   a  extending from a bottom face thereof and toward the immovable portion  30 . The two boards  35   a  are located at two opposite sides of the groove  32  of the movable portion  30 . The immovable portion  20  defines two positioning slots  25   a  in a top face thereof, corresponding to the boards  35   a.  The boards  35   a  are capable of slidably received in the corresponding slots  25   a  so that the movable portion  30  can have an accurate linear movement relative to the immovable portion  20 . Alternatively, the immovable portion  20  can extend boards while the movable portion  30  can define slots receiving the boards.  
         [0031]     Additionally, in the present invention, in order to lower cost of the testing apparatus, the immovable portion  30  and the insulating plate  28 , the board  34  can be made from low-cost material such as PE (Polyethylene), ABS (Acrylonitrile Butadiene Styrene), PF(Phenol-Formaldehyde), PTFE (Polytetrafluoroethylene) and so on. The immovable portion  20  can be made from copper (Cu) or aluminum (Al). The immovable portion  20  can have silver (Ag) or nickel (Ni) plated on an inner face defining the groove  24  to prevent oxidization of the inner face.  
         [0032]     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.