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 to be tested. A movable portion is capable of moving relative to the immovable portion and has a cooling structure therein for cooling the heat pipe. A receiving structure is located 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 
   The present invention relates generally to testing apparatuses, and more particularly to a performance testing apparatus for heat pipes. 
   DESCRIPTION OF RELATED ART 
   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. 
   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 high enthalpy vapor 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. 
   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. 
   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, and 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. 
   Referring to  FIG. 7 , 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 . At the same time, 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 on the heat pipe  2 . 
   However, in the test, the conventional 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 effected 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. 
   In mass production of heat pipes, large number of performance testing apparatuses are needed, and the apparatus are used frequently over a long period of time; therefore the apparatuses not only require good testing accuracy, but also require easy and accurate assembly to the heat pipes to be tested. The testing apparatus effects 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 conventional testing apparatus needs to be improved in order to meet the demand for testing during mass production of heat pipes. 
   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 
   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 testing. A movable portion is capable of moving relative to the immovable portion and also has a cooling structure defined therein for cooling the heat pipe. A receiving structure is defined between the immovable portion and the movable portion for receiving the condensing 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 condensing section of the heat pipe. 
   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 
     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. 
       FIG. 1  is an assembled view of a performance testing apparatus for heat pipes in accordance with a preferred embodiment of the present invention; 
       FIG. 2  is an exploded, isometric view of the testing apparatus of  FIG. 1 ; 
       FIG. 3A  shows a movable portion and two temperature sensors of the testing apparatus of  FIG. 2 ; 
       FIG. 3B  is an assembled view of  FIG. 3A , viewed from a bottom aspect; 
       FIG. 4A  shows a movable portion and two temperature sensors in accordance with a second embodiment of the present invention; 
       FIG. 4B  is an assembled view of  FIG. 4A ; 
       FIG. 5A  shows a movable portion and two temperature sensors in accordance with a third embodiment of the present invention; 
       FIG. 5B  is an assembled view of  FIG. 5A ; 
       FIG. 6A  shows an immovable portion and two temperature sensors of the testing apparatus of  FIG. 2 ; 
       FIG. 6B  is an assembled view of  FIG. 6A ; and 
       FIG. 7  is a conventional performance testing apparatus for heat pipes. 
   

   DETAILED DESCRIPTION 
   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 . 
   Referring also to  FIGS. 6A and 6B  and  3 A and  3 B, the immovable portion  20  is made of metal having good heat conductivity. The performance test apparatus 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 to 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 co-operatively 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. 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 cooling groove  24  and be 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. 
   The movable portion  30 , corresponding to the cooling groove  24  of the immovable portion  20 , has a cooling 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 . Cooling passageways (not shown) are defined in an inner portion of the immovable portion  30 , for coolant to flow therein. An inlet  33  and an outlet  33  communicate the passageways with a constant temperature coolant circulating device (not shown); therefore, the passageways, inlet  33 , outlet  33  and the coolant circulating device cooperatively define a cooling system for the coolant to circulate therein to remove heat from the heat pipe during testing. Two temperature sensors  36  are inserted into the movable portion  30  from a top thereof to reach a position wherein detecting portions  3602  of the sensors  36  are located in the positioning groove  32  and are therefore capable of automatically contacting the heat pipe to detect the temperature of the condensing section of the heat pipe. 
   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. 
   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 condensing section of the heat pipe and the movable and immovable portions  30 ,  20  can be minimized. 
   The supporting frame  10  comprises a seat  12  which according to 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 ferrous material. 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 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 extending therethrough communicate with the slot  282 . The through holes  284  and slot  282  allow wires  260  of the temperature sensors  26  to connect with a monitoring computer (not shown). 
   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  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 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 condensing section of the heat pipe being tested 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 requirements for testing, i.e. accuracy, ease of use and speed, can be realized by a testing apparatus in accordance with the present invention. 
   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  30 . 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. 
   The two temperature sensors  36  in accordance with the first embodiment of  FIGS. 3A and 3B  work independently and 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 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 of the 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. 
   In use, the condensing section of the heat pipe is received in the channel  50  when the movable portion  30  moves away from the immovable portion  20 . Then the movable portion  30  moves to reach the immovable portion  20  so that the condensing section of the heat pipe is tightly fitted into the channel  50 . The sensors  26 ,  36  are in thermal contact with the condensing section of the heat pipe; therefore, the sensors  26 ,  36  work to accurately send detected temperatures from 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 quickly decided. 
   In the embodiment, in order to help the condensing 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 condensing section of the heat pipe. 
   Referring to  FIGS. 4A and 4B , a 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 a 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 (not shown) adjacent to the groove  32  being square, which can fittingly receive the square column  3620  therein, and a round portion (not labeled) above the square portion to ensure that the collar  3624  and the spring coil  362  can be fitted therein. When the collar  3624  abuts against top of the square portion of the through hole  38 , 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  to extend part-way into 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. 
   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  into the groove  32 , a reliable intimate contact between the working sections  3602  and the condensing section of the heat pipe can be ensured. 
   Referring to  FIGS. 5A and 5B , a 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, but 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 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 compressing the spring coil  366  towards the groove  32  of the movable portion  30 . By this design, the board  34  used in the second embodiment can be omitted. 
   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 condensing section of heat pipe. In this embodiment, the bolt  42  is directly secured to the movable portion  30 . 
   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 condensing section of the heat pipe when the movable portion  30  moves toward the immovable portion  20 . 
   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 a working (detecting) section  2602  between two vertical sections (not labeled) thereof; a receiving hole  29  of the immovable portion  20  is identical to the square portion of the hole  38  of the movable portion  30  in the second embodiment. 
   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 condensing 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 in the heat pipe can be removed by the movable and immovable portions  30 ,  20  which have the coolant flowing therethrough. 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 condensing 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. 
   Furthermore, the apparatus has a plurality of temperature sensors synchronously detecting temperature of the condensing section of the heat pipe; therefore, an average temperature of the condensing section can be obtained to indicate the performance of the heat pipe veraciously. 
   Additionally, in the present invention, in order to lower cost of the testing apparatus, the immovable portion  30 , the insulating plate  28  and 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 the oxidization of the inner face. 
   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.