Abstract:
A performance testing apparatus for a heat pipe includes an immovable portion having a heating member located therein for heating 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. At least one temperature sensor is attached to at least one of the immovable portion and the movable portion. The least one temperature sensor has a detecting section exposed in the receiving structure 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 phase changeable working media employed to carry heat is included in the pipe. Generally, according to where the 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 testing 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 in 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]     A typical method for testing the performance of a heat pipe is to first insert the evaporating section of the heat pipe into a liquid at constant temperature; after a period of time the temperature of the heat pipe will become stable, then a temperature sensor such as a thermocouple, a resistance thermometer detector (RTD) or the like can be 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 by this test, and the performance of the heat pipe can not be reflected exactly by this test.  
         [0006]     Referring to  FIG. 7 , a related 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 . At the same time, by controlling flow rate and temperature of cooling liquid entering 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 on the heat pipe  2 .  
         [0007]     However, in the test, the related testing apparatus has the following drawbacks: 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; and, 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 uneven performance test results of the heat pipe. Furthermore, due to awkward 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; therefore, the apparatus 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; therefore, testing accuracy, facility, speed, consistency, reproducibility and reliability need to be considered when choosing the testing apparatus. Therefore, the testing apparatus needs to be improved in order to meet the demand for 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 THE 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 heating member located therein for heating an evaporating section of a heat pipe requiring testing. 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 evaporating section of the heat pipe therein. At least one temperature sensor is attached to at least one of the immovable portion and the movable portion. The at least one temperature sensor has a portion thereof exposed in the receiving structure for thermally contacting the condensing section of the heat pipe in the receiving structure to detect a temperature of the heat pipe. The movable portion is driven by a driving device such as a step motor to move towards or away from the immovable portion. A spring coil is compressed to exert a force on the at least one temperature sensor towards an intimate contact with the evaporating section 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 THE 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 and two temperature sensors of the testing apparatus of  FIG. 2 ;  
         [0016]      FIG. 3B  is an assembled view of  FIG. 3A , viewed from another aspect;  
         [0017]      FIG. 4A  shows a movable portion and two temperature sensors in accordance with a second embodiment of the present invention;  
         [0018]      FIG. 4B  is an assembled view of  FIG. 4A , viewed from another aspect;  
         [0019]      FIG. 5A  shows a movable portion and two temperature sensors in accordance with a third embodiment of the present invention;  
         [0020]      FIG. 5B  is an assembled view of  FIG. 5A ;  
         [0021]      FIG. 6A  shows an immovable portion and two temperature sensors of the testing apparatus of  FIG. 2 ;  
         [0022]      FIG. 6B  is an assembled view of  FIG. 6A , viewed from a different aspect; and  
         [0023]      FIG. 7  is a performance testing apparatus for heat pipes in accordance with related art. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     Referring to  FIGS. 1 and 2 , a performance testing apparatus for heat pipes comprises an immovable portion  20  and a movable portion  30  movably mounted on the immovable portion  20 .  
         [0025]     Referring also to  FIGS. 6A and 6B , the immovable portion  20  has good heat conductivity and is held on a platform of a supporting member such as a testing table or so on. A heating member  22  such as an immersion heater, resistance coil, quartz tube and Positive temperature coefficient (PTC) material or the like is embedded in the immovable portion  20 . The immovable portion  20  defines a hole  23  through a center of a bottom thereof. In the case, the heating member  22  is an elongated cylinder. The heating member  22  is accommodated in the hole  23  of the immovable portion  20 . Two spaced wires  220  extend from an end of the heating member  20  to connect with a power supply (not shown). The immovable portion  20  has a heating groove  24  defined in a top face thereof, for receiving an evaporating section of the heat pipe to be tested therein. Two temperature sensors  26  are inserted into the immovable portion  20  from a bottom thereof so as to position detecting portions  2602  of the sensors  26  in the heating groove  24 . The detecting portions  2602  are capable of automatically contacting the heat pipe in order to detect a temperature of the evaporating section of the heat pipe. In order to prevent heat in the immovable portion  20  from spreading to the supporting member, an insulating plate is disposed on the supporting member for thermally insulating the testing apparatus from the supporting member.  
         [0026]     The movable portion  30 , corresponding to the heating groove  24  of the immovable portion  20 , has a positioning groove  32  defined therein, whereby a testing channel  50  is cooperatively defined by the heating 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 of the sensors  36  are located in the positioning groove  32 . The detecting portions are capable of automatically contacting the heat pipe to detect the temperature of the evaporating section of the heat pipe.  
         [0027]     The channel  50  as shown in the preferred embodiment has a circular cross section enabling it to receive the evaporating section of the heat pipe having a correspondingly circular cross section. Alternatively, the channel  50  can have a rectangular cross section where the evaporating section of the heat pipe also has a flat rectangular configuration.  
         [0028]     In order to ensure that the heat pipe is in close contact with the movable and immovable portions  30 ,  20 , a supporting frame  10  is used to support and assemble the immovable and movable portions  20 ,  30 . The immovable portion  20  is fixed on the supporting frame  10 . A driving device  40  is installed on the supporting frame  10  to drive the movable portion  30  to make accurate linear movement 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 . In this manner, heat resistance between the evaporating section of the heat pipe and the movable and immovable portions  30 ,  20  can be minimized.  
         [0029]     The supporting frame  10  comprises a seat  12  which may be 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 ferrous material. The seat  12  comprises a first plate  14  at a top thereof. A second plate  16  hovers over the first plate  14 . Pluralities 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 second plate  16  and the rods  15  constitute the supporting frame  10  for assembling and positioning the immovable and movable portions  20 ,  30  therein. The immovable portion  20  is fixed on the first plate  14 . In order to prevent heat in the immovable portion  20  from spreading to the first plate  14 , an insulating plate  28  is located at the bottom of the immovable portion  20 . The first plate  14  and the insulating plate  28  define corresponding through holes  140 ,  280  for the wire  220  of the heat member  22  of the immovable portion  20  to extend therethrough, and spaced apertures  142 ,  282  to allow wires  260  of the temperature sensors  26  to extend therethrough to connect with a monitoring computer (not shown).  
         [0030]     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  (also see  FIGS. 3A and 3B ). 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  move upwardly or downwardly. Two through apertures  342  are defined in the board  34  of the movable portion  30  to allow wires  360  of the temperature sensors  36  to extend therethrough to connect with the monitoring computer. In use, the driving device  40  accurately drives the movable portion  30  to move linearly relative to the immovable portion  20 . For example, the movable portion  30  can be driven to depart a certain distance such as 5 millimeters from the immovable portion  20  to facilitate the insertion of the evaporating section of the heat pipe being tested into the channel  50  or withdrawn from the channel  50  after the heat pipe has been tested. Or in another example, the movable portion  30  can be driven to move toward the immovable portion  20  to thereby realize an intimate contact between the evaporating section of the heat pipe and the immovable and movable portions  20 ,  30  during the test. Accordingly, the requirements for testing, i.e. accuracy, ease of use and speed, can be realized by a testing apparatus in accordance with the present invention.  
         [0031]     It can be understood, positions of the immovable portion  20  and the movable portion  30  can be exchanged, i.e., the movable portion  30  is located on the first plate  14  of the supporting frame  10 , and the immovable portion  20  is fixed to the second plate  16  of the supporting frame  10 , and the driving device  40  is positioned to be adjacent to the movable portion  20 . Alternatively, the driving device  40  can be installed to the immovable portion  20 . Otherwise, each of the immovable and movable portions  20 ,  30  may have one driving device  40  installed thereon to move them toward/away from each other.  
         [0032]     Referring to  FIGS. 3A and 3B , the movable portion  30  and two temperature sensors  36  in accordance with a first embodiment of the present invention are illustrated. In this case, the two sensors  36  which work independently are substantially vertically mounted in two different places on the movable portion  30 . Each of the sensors  36  has two wires  360  inserted in two pairs of through apertures  37  vertically extending through the movable portion  30 , wherein working (detecting) sections  3602  of the two wires  360  are located in a concave  370  communicating with the groove  32 . Each of the two wires  360  has two vertical sections  3601  extending into a corresponding pair of apertures  37  of the movable portion  30 . The working section  3602  interconnects bottom ends of two corresponding vertical sections  3601 . One the of vertical sections  3601  of each wire  360  has an upper extension extending through a corresponding aperture  342  in the board  34  to connect with the monitoring computer.  
         [0033]     In use, the evaporating section of the heat pipe is received in the channel  50  when the movable portion  30  moves away from the immovable portion  20 . The evaporating section of the heat pipe is put in the heating groove  24  of the immovable portion  20 . Then the movable portion  30  moves to reach the immovable portion  20  so that the evaporating section of the heat pipe is tightly fitted into the channel  50 . The sensors  26 ,  36  are in thermal contact with the evaporating section of the heat pipe; therefore, the sensors  26 ,  36  work to accurately send detected temperatures from the evaporating 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 quickly decided.  
         [0034]     In the embodiment, in order to help the evaporating section of the heat pipe to have an intimate contact with the working sections  3602  of the sensors  36 , each of the working sections  3602  is formed to have a curved configuration with a curvature corresponding to that of the evaporating section of the heat pipe.  
         [0035]     Referring to  FIGS. 4A and 4B , the movable portion  30  and two temperature sensors  36  in accordance with a second embodiment of the present invention are shown. The difference from the first embodiment is that the movable portion  30  has two through holes  38  substantially vertically extending therethrough, and a temperature sensor  36  is inserted into each of the two through holes  38 . In this embodiment, the through holes  38  communicate with the positioning groove  32  in different positions of the movable portion  30 . Each of the two temperature sensors  36  comprises a positioning socket  362  and a pair of thermocouple wires  360  fitted in the socket  362 . The socket  362  comprises a square column  3620 , a circular column  3622  above the square column  3620 , and a circular collar  3624  between the square column  3620  and the circular column  3622 . The socket  362  has two pairs of through apertures  3626  extending from a bottom of the square column  3620  to a top of the circular column  3622 . A spring coil  366  surrounds the circular column  3622  of the socket  362 . Each wire  360  has two vertical sections  3601  extending into the apertures  3626  and the working section  3602  between the two vertical sections  3601  thereof. The working sections  3602  are located at the bottom of the square column  3620  and separated from each other. The vertical sections  3601  are each secured in a corresponding aperture  3626 . The wires  360  extend upwardly from top ends of corresponding vertical sections  3601  through the apertures in  342  in the board  34  to connect with the monitoring computer. The through hole  38  has a portion  382  adjacent to the groove  32  being square to thereby ensure the square column  3620  to be fitted therein, and a round portion (not labeled) above the square portion  382  to ensure the collar  3624  and the spring coil  362  to be fitted therein. When the collar  3624  abuts against top of the portion  382 , the circular column  3622  and a lower portion of spring coil  362  are received in the through hole  38 . The board  34  is secured on the movable portion  30 . The spring coil  366  is compressed between the board  34  and the movable portion  30 . Here, the working sections  3602  of the wires  360  are pushed by the spring coil  366  toward the groove  32 . The use of the testing apparatus having the sensors  36  and movable portion  30  in accordance with the second embodiment is similar to that of the first embodiment.  
         [0036]     In this embodiment, since the temperature sensors  36  are telescopically fitted into the through holes  38  and the working sections  3602  of the temperature sensors  36  are pushed by the spring coils  366  toward the groove  32 , a reliable intimate contact between the working sections  3602  and the evaporating section of the heat pipe can be ensured.  
         [0037]     Referring to  FIGS. 5A and 5B , the movable portion  30  and two temperature sensors  36  in accordance with a third embodiment of the present invention are shown. The third embodiment is similar to the second embodiment; the main difference from the second embodiment is that in the temperature sensor  36  the spring coil  366  is compressed by a screw  39  engaged in the hole  38  of the movable portion  30 . The hole  38  has a thread (not shown) in a top of an inner face thereof. The screw  39  has a thread in a periphery face thereof and a through opening  392  extending through a center thereof. The upper ends of the wires  360  extend through the opening  392  of the screw  39  to connect with the monitoring computer. The screw  39  is located upon a corresponding spring coil  366  and engaged in the hole  38 , thereby pushing the spring coil  366  together with the temperature sensor  36  towards the groove  32  of the movable portion  30 . By this design, the board  34  used in the second embodiment can be omitted. And the bolt  42  in the previous embodiments can be directly secured to the movable portion  30  between the temperature sensors  36 , although it is not shown in  FIGS. 5A and 5B .  
         [0038]     According to the third embodiment, the temperature sensor  36  is positioned on the hole  38  of the movable portion  30  via the screw  39  engaging in the hole  38 . Therefore, 1) it is easy to install/remove the temperature sensor  36  to/from the movable portion  30 ; and, 2) it is easy to adjust the compression force of the spring coils to thereby provide suitable force on the working sections  3602  of the wires  360 , whereby the working sections  3602  can have an optimal contact with the evaporating section of heat pipe.  
         [0039]     In all the embodiments of the present invention, the wires  360  are perpendicular to the groove  32 ; and, they can be oriented with other angles in respective to the groove  32 , so long as the wires  360  have an intimate contact with the evaporating section of the heat pipe when the movable portion  30  moves toward the immovable portion  20 .  
         [0040]     The temperature sensors  26  and the immovable portion  20  can have configuration and relationship similar to that of the temperature sensors  36  and the movable portion  30  as illustrated in the second and third embodiments. Referring to  FIGS. 6A and 6B , the temperature sensors  26  are identical to the temperature sensors  36  of the third embodiment and each comprise two wires  260  each having the working section  2602  between two vertical sections (not labeled) thereof; a receiving hole  29  of the immovable portion  20  is identical to the hole  38  of the movable portion  30  in the second embodiment.  
         [0041]     In the present invention, the movable portion  30  has the driving device  40  installed thereon to thereby drive the movable portion  30  to accurately make linear movement relative to the immovable portion  20 ; thus, the evaporating section of the heat pipe needing to be tested can be accurately and quickly positioned between the two portions  20 ,  30 , and can contact with the movable and immovable portions  30 ,  20  intimately, therefore the heat provided by the heating member  22  of the immovable portion  20  can be sufficiently absorbed by evaporating section of the heat pipe. Furthermore, the temperature sensors  26 ,  36  are positioned in the holes of the immovable and movable portions  20 ,  30 , and the temperature sensors  26 ,  36  intimately contact the evaporating section of the heat pipe under optimal conditions, after the movable portion  30  moves to reach the immovable portion  20 . In comparison with the conventional testing apparatuses, the testing apparatus of the present invention can accurately, quickly and easily test the performance of the heat pipe. Therefore, the testing apparatus enables mass production of the heat pipes.  
         [0042]     Furthermore, the apparatus has a plurality of temperature sensors synchronously detecting temperature of the evaporating section of the heat pipe; therefore, an average temperature of the evaporating section can be obtained to indicate the performance of the heat pipe veraciously.  
         [0043]     Additionally, in the present invention, in order to lower cost of the testing apparatus, the immovable portion  30 , the insulating plate  28 , the board  34  and the positioning socket  362  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 the oxidization of the inner face.  
         [0044]     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.