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 telescopically mounted in 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. 5 , 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 evaporating 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 the evaporating section of the heat pipe so that a detecting section of the temperature sensor can have 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 an immovable portion and two temperature sensors of the testing apparatus of  FIG. 2 , viewed from another aspect; 
           [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 of the testing apparatus of  FIG. 2 , viewed from another aspect; 
           [0018]      FIG. 4B  is an assembled view of  FIG. 4A , viewed from another aspect; and 
           [0019]      FIG. 5  is a performance testing apparatus for heat pipes in accordance with related art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    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 . The performance testing apparatus is to be held on a platform of a supporting member such as a testing table or so on. 
         [0021]    Referring also to  FIGS. 3A and 3B , the immovable portion  20  is made of material having good heat conductivity. A first 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  has a central portion thereof extending an extension  29  downwardly. The immovable portion  20  defines a hole  23  in the extension  29 . In this case, the first heating member  22  is an elongated cylinder. The first heating member  22  is accommodated in the hole  23  of the immovable portion  20 . Two spaced wires  220  extend beyond the extension  29  from a bottom end of the heating member  22  for connecting 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 sections  2602  of the sensors  26  in the heating groove  24 . The detecting sections  2602  are capable of automatically contacting the heat pipe in order to detect a temperature of the evaporating section of the heat pipe. 
         [0022]    Referring also to  FIGS. 4A and 4B , the movable portion  30  is also made of material having good heat conductivity. The movable portion  30  has an extension  39  extending upwardly from a middle of a top surface thereof. The movable portion  30  defines a hole  33  in the extension  39 . A second heating member  22  is accommodated in the hole  33  of the movable portion  30 . Two spaced wires  220  extend from a top end of the heating member  22  beyond the extension  39  for connecting with the power supply (not shown). The movable portion  30 , corresponding to the heating groove  24  of the immovable portion  20 , has a heating groove  32  defined therein, whereby a testing channel  50  is cooperatively defined by the heating grooves  24 ,  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 sections  3602  of the sensors  36  are located in the groove  32 . The detecting sections  3602  are capable of automatically contacting the heat pipe to detect the temperature of the evaporating section of the heat pipe. A board  34  is positioned over the movable portion  30 . Four columns  150  are secured at corresponding four corners of the movable portion  30  and extend upwardly to engage in corresponding four through holes (not labeled) defined in four corners of the board  34 . A space (not labeled) is left between the extension  39  and the board  34  for extension of the wires  220  of the heating member  22  to connect with the power supply. 
         [0023]    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. 
         [0024]    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. 
         [0025]    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  for extension of the wires  220  and wires  260  of the temperature sensors  26 . The supporting frame  10  has a second plate  16  hovering 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 insulating plate  28 , corresponding to the extension  29  of the immovable portion  20 , defines a concave  289  receiving the extension  29  therein. The first plate  14  and the insulating plate  28  define corresponding through holes  140 ,  280  for the wires  220  of the heat member  22  of the immovable portion  20  to extend therethrough, and spaced apertures  142 ,  282  to allow the wires  260  of the temperature sensors  26  to extend therethrough. The wires  260  are to connect with a monitoring computer (not shown). 
         [0026]    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 the board  34  of the movable portion  30 . When the shaft rotates, the bolt  42  with the board  34  and the movable portion  30  move upwardly or downwardly. 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. 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 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 the testing apparatus in accordance with the present invention. 
         [0027]    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 . In addition, 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. 
         [0028]    Referring to  FIGS. 3A and 3B  again, the immovable portion  20  having two through holes  27  communicating with the heating groove  24  are defined at two opposite sides of the heating member  22 . Each of the two temperature sensors  26  comprises a positioning socket  262  and a pair of thermocouple wires  260  fitted in the socket  262 . The socket  262  comprises a square column  2620 , a circular column  2622  below the square column  2620 , and a circular collar  2624  between the square column  2620  and the circular column  2622 . The socket  262  has two pairs of through apertures (not shown) extending from a top of the square column  2620  to a bottom of the circular column  2622 . A spring coil  264  surrounds the circular column  2622  of the socket  262 . Each wire  260  has two vertical sections (not labeled) extending into the apertures and the detecting section  2602  located between the two vertical sections thereof. The detecting sections  2602  are located at the top of the square column  2620  and separated from each other. The vertical sections are each secured in a corresponding aperture. The through hole  27  has a square portion  272  adjacent to the groove  24  to thereby ensure the square column  2620  to be fitted therein, and a round portion (not labeled) below the square portion  272  to ensure the collar  2624  and the spring coil  264  to be fitted therein. When the collar  2624  abuts against a bottom of the square portion  272 , the circular column  2622  and the spring coil  264  are received in the through hole  27 . The spring coil  264  is compressed by a screw  266  engaged in the hole  27  of the immovable portion  20 . The hole  27  has a thread (not shown) in a bottom of an inner face thereof. The screw  266  has a thread in a periphery face thereof and a through opening  2660  extending through a center thereof. The bottom ends of the wires  260  extend through the opening  2660  of the screw  266  to connect with the monitoring computer. The screw  266  engages in the hole  27  thereby pushing the spring coil  264  together with the temperature sensor  26  towards the groove  24  of the immovable portion  20 . 
         [0029]    According to the preferred embodiment, the temperature sensor  26  is positioned on the hole  27  of the immovable portion  20  via the screw  266  engaging in the hole  27 . Therefore, 1) it is easy to install/remove the temperature sensor  26  to/from the immovable portion  20 ; and, 2) it is easy to adjust the compression force of the spring coils  364  to thereby provide suitable force on the detecting sections  2602  of the wires  260 , whereby the detecting sections  2602  can have an optimal contact with the evaporating section of heat pipe. 
         [0030]    Referring to  FIGS. 4A and 4B  again, the temperature sensors  36  and the movable portion  30  have configuration and relationship similar to that of the temperature sensors  26  and the immovable portion  20  as illustrated in  FIGS. 3A and 3B . The wires  360  of the two temperature sensors  36  each comprise the detecting section  3602  located between two vertical sections (not labeled) thereof; a receiving hole  37  of the movable portion  30  identical to the hole  27  of the immovable portion  20 , receives the temperature sensor  36  therein. 
         [0031]    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. 
         [0032]    In the preferred embodiment of the present invention, the wires  260  are perpendicular to the groove  24 ; however, they can be oriented with other angles in respective to the groove  24 , so long as the wires  260  have an intimate contact with the evaporating section of the heat pipe when the movable portion  30  moves toward the immovable portion  20 . 
         [0033]    Additionally, in the present invention, in order to lower cost of the testing apparatus, the insulating plate  28 , the board  34  and the positioning socket  262  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  and movable portion  30  can be made from copper (Cu) or aluminum (Al). The immovable portion  20  and movable portion  30  can have silver (Ag) or nickel (Ni) plated on an inner face defining the grooves  24 ,  32  to prevent the oxidization of the inner face. 
         [0034]    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.