Patent Document

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 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. 
     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. 
     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. 
     Referring to  FIG. 6 , 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 . 
     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. 
     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. 
     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 
     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 the heat pipe, and a movable portion 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. 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 during the movement of the movable portion relative to the immovable portion to ensure the receiving structure being capable of receiving the heat pipe precisely. At least one 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. 
     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 
       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 first 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 of a performance testing apparatus in accordance with a second embodiment of the present invention; 
         FIG. 3B  shows an immovable portion of the testing apparatus in accordance with the second embodiment of the present invention; 
         FIG. 4A  shows a movable portion of a performance testing apparatus for heat pipes in accordance with a third embodiment of the present invention; 
         FIG. 4B  shows an immovable portion of the testing apparatus in accordance with the third embodiment of the present invention; 
         FIG. 5A  shows a movable portion of a performance testing apparatus for heat pipes in accordance with a forth embodiment of the present invention; 
         FIG. 5B  shows an immovable portion of the testing apparatus in accordance with the forth embodiment of the present invention; and 
         FIG. 6  is a performance testing apparatus for heat pipes in accordance with related art. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a performance testing apparatus for heat pipes in accordance with a first embodiment of the present invention comprises an immovable portion  20  and a movable portion  30  movably mounted on the immovable portion  20 . 
     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 (not labeled) 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 (not shown) through a center of a bottom thereof. In the case, the heating member is an elongated cylinder. The heating member is accommodated in the hole of the immovable portion  20  from bottom of the immovable portion  20 . Two spaced wires  220  of the heating member extend from an end of the heating member 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  at two opposite sides of the heating member from the bottom of the immovable portion  20  so as to position detecting portions (not labeled) of the sensors  26  in the heating groove  24 . The detection portions of the sensors  26  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  28  is disposed on the supporting member for thermally insulating the testing apparatus from the supporting member. 
     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 (not labeled) 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. 
     The movable portion  30  extend two elongated bars  35  downwardly and integrally from a bottom face thereof towards the immovable portion  20 . The elongated bars  35  are located at two sides of the groove  32  of the movable portion  30 . Corresponding to the bars  35  of the movable portion  30 , the immovable portion  20  defines two slots  25  in a top face thereof. The bars  35  are slidably received in the corresponding slots  25 . The bars  35  are always received in the slots  25  when the movable portion  30  moves toward the immovable portion  20  to reach a position wherein the bottom face of the movable portion  30  contacts the top face of the immovable portion  20 . The bars  35  and the slots  25  concavo-convexly cooperate to avoid the movable portion  30  from deviating from the immovable portion  20  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. 
     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. 
     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. 
     The supporting frame  10  comprises a seat  12 . The seat  12  comprises a first plate  14  at a top thereof and two feet  120  depending from the first plate  14 . A space  122  is defined between the two feet  120  of the seat  12  for extension of wires of the temperature sensors  26  and the wires  220  of the heating member. The supporting frame  10  has 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. In order to prevent heat in the immovable portion  20  from spreading to the first plate  14 , the immovable portion  20  is positioned in a pond  285  defined in a top face of the insulating plate  28 . The first plate  14  and the insulating plate  28  define corresponding through holes  140 ,  280  for the wire  220  of the heat member of the immovable portion  20  to extend therethrough to connect with the power supply, and spaced apertures  142 ,  282  to allow wires of the temperature sensors  26  to extend therethrough 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  moves upwardly or downwardly. Two through apertures  342  are defined in the board  34  of the movable portion  30  to allow wires (not labeled) 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. In other hand, 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. 
     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. 
     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 , with the bars  35  of the movable portion  30  sliding in the slots  25  of 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 toward the immovable portion  20  with the bars  35  sliding in the slots  25  until 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. 
     Referring to  FIGS. 3A and 3B , a movable portion  30  and an immovable portion  20  of a performance testing apparatus in accordance with a second embodiment of the present invention are shown. Different from the first embodiment, the movable portion  30  defines two slots  35   a  at two opposite sides of the groove  32  thereof. The immovable portion  20  extends two bars  25   a  slidably received in corresponding slots  35   a  of the movable portion  30 . 
     Referring to  FIGS. 4A and 4B , a movable portion  30  and an immovable portion  20  of a performance testing apparatus in accordance with a third embodiment of the present invention are shown. Different from the first embodiment, the movable portion  30  has a plurality of cylindrical posts  35   b  extending downwardly and integrally from a bottom face thereof towards the immovable portion  20 . The cylindrical posts  35   b  are evenly located at two sides of the groove  32  of the movable portion  30 . Corresponding to the posts  35   b  of the movable portion  30 , the immovable portion  20  has a plurality of positioning holes  25   b  defined in a top face thereof. The posts  35   b  are slidably inserted into the corresponding holes  25   b . The posts  35   b  are always received in the holes  25   b  when the movable portion  30  moves relative to the immovable portion  20 . 
     Referring to  FIGS. 5A and 5B , a movable portion  30  and a immovable portion  20  of a performance testing apparatus in accordance with a forth embodiment of the present invention are shown. Different from the third embodiment, the movable portion  30  defines a plurality of holes  35   c  at two opposite sides of the groove  32  thereof while the immovable portion  20  extends a plurality of posts  25   c  slidably received in corresponding holes  35   c  of the movable portion  30 . 
     Additionally, in the present invention, in order to lower cost of the testing apparatus, the movable 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 a top face thereof defining the groove  24  to prevent oxidization of the top 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.

Technology Category: f