Abstract:
A performance testing apparatus for a heat pipe includes an immovable portion having a cooling structure defined therein for cooling a heat pipe needing to be tested. A movable portion is capable of moving relative to the immovable portion. A receiving structure is located between the immovable portion and the movable portion for receiving the heat pipe therein. At least a temperature sensor is attached to at least one of the immovable portion and the movable portion for thermally contacting the heat pipe in the receiving structure for detecting temperature of the heat pipe. An enclosure encloses the immovable portion and the movable portions and has sidewalls thereof slidably contacting at least one of the immovable portion and the movable portion.

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 at least a phase changeable working media employed to carry heat is contained in the pipe. Generally, according to positions from which heat is input or output, a heat pipe has three sections, an evaporating section, a condensing section and an adiabatic section between the evaporating section and the condensing section. 
   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 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. 
   Conventionally, a method for testing the performance of a heat pipe is first to insert the evaporating section of the heat pipe into liquid at constant temperature; after a predetermined period of time and temperature of the heat pipe will become stable, then a temperature sensor such as a thermocouple, a resistance thermometer detector (RTD) or the like is used to measure ΔT between the liquid and the condensing section of the heat pipe to evaluate the performance of the heat pipe. However, Rth and Qmax can not be obtained from this test, and the performance of the heat pipe can not be reflected exactly by this test. 
   Referring to  FIG. 6 , a conventional performance testing apparatus for heat pipes is shown. The apparatus has a resistance wire  1  coiling round an evaporating section  2   a  of a heat pipe  2 , and a water cooling sleeve  3  functioning as a heat sink and enclosing a condensing section  2   b  of the heat pipe  2 . In use, electrical power controlled by a voltmeter and an ammeter flows through the resistance wire  1 , whereby the resistance wire  1  heats the evaporating section  2   a  of the heat pipe  2 . Simultaneously, by controlling flow rate and temperature of cooling liquid 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 of the heat pipe  2 . 
   However, in the test, the conventional testing apparatus has drawbacks as follows: a) it is difficult to accurately determine lengths of the evaporating section  2   a  and the condensing section  2   b  which are important factors in determining the performance of the heat pipe  2 ; b) heat transference and temperature measurement may easily be effected by environmental conditions; c) it is difficult to achieve sufficiently intimate contact between the heat pipe and the heat source and between the heat pipe and the heat sink, which results in unsteady performance test results of the heat pipe. Furthermore, due to fussy and laborious assembly and disassembly in the test, the testing apparatus can be only used in the laboratory, and can not be used in the mass production of heat pipes. 
   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; thus, 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; thus testing accuracy, facility, speed, consistency, reproducibility and reliability need to be considered when choosing the testing apparatus. Therefore, the conventional testing apparatus needs to be improved in order to meet the demand for testing during mass production of heat pipes. 
   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 cooling structure defined therein for cooling a heat pipe requiring testing. A movable portion is capable of moving relative to the immovable portion. A receiving structure is located between the immovable portion and the movable portion for receiving the heat pipe therein. At least a temperature sensor is attached to at least one of the immovable portion and the movable portion for thermally contacting the heat pipe with the receiving structure for detecting temperature of the heat pipe. An enclosure encloses the immovable portion and the movable portions, and has sidewalls thereof slidably contacting at least one of the immovable portion and the movable portion. 
   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 preferred embodiment of the present invention; 
       FIG. 2  is an exploded, isometric view of the testing apparatus of  FIG. 1 ; 
       FIG. 3  shows an enclosure of  FIG. 2  in an inverted manner; 
       FIG. 4  is an assembled view of a performance testing apparatus for heat pipes in accordance with an alternative embodiment of the present invention; 
       FIG. 5  is an exploded, isometric view of the testing apparatus of  FIG. 5 ; and 
       FIG. 6  is a conventional performance testing apparatus for heat pipes. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-3 , 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 immovable portion  20  has good heat conductivity and is held on a platform of a supporting member such as a testing table (not shown) or so on. Cooling passageways (not shown) are defined in an inner portion of the immovable portion  20 , to allow coolant flow therein. An inlet  22  and an outlet  22  communicate the passageways with a constant temperature coolant circulating device (not shown); therefore, the passageways, inlet  22 , outlet  22  and the coolant circulating device corporately define a cooling system for the coolant circulating therein to remove heat from the heat pipe in test. The immovable portion  20  has a cooling groove  24  defined in a top face thereof, for receiving a condensing section of the heat pipe to be tested therein. Two temperature sensors  26  are inserted into the immovable portion  20  from a bottom thereof so as to position detecting portions 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 is disposed at a bottom of the immovable portion  20 . 
   The movable portion  30 , corresponding to the cooling groove  24  of the immovable portion  20 , has a positioning groove  32  defined therein, whereby a testing channel  50  is cooperatively defined by the cooling groove  24  and the positioning groove  32  when the movable portion  30  moves to reach the immovable portion  20 . Thus, an intimate contact between the heat pipe and the movable and immovable portions  30 ,  20  defining the channel  50  can be realized, thereby reducing heat resistance between the heat pipe and the movable and immovable portions  30 ,  20 . Two temperature sensors  36  are inserted into the movable portion  30  from a top thereof to reach a position wherein detecting portions of the sensors  36  are located in the positioning groove  32  and capable of automatically contacting the heat pipe to detect the temperature of the condensing section of the heat pipe. 
   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. 
   Generally, in order to ensure that the heat pipe is in close contact with the movable and immovable portions  30 ,  20 , a supporting member  10  is used to support and assemble the immovable and movable portions  20 ,  30 . The immovable portion  20  is fixed on the supporting member  10 . A driving device  40  is installed on the supporting member  10  to drive the movable portion  30  to make accurate linear movements relative to the immovable portion  20  along a vertical direction, thereby realizing the intimate contact between the heat pipe and the movable and immovable portions  30 ,  20 ; thus, heat resistance between the condensing section of the heat pipe and the movable and immovable portions  30 ,  20  can be micro-controlled. 
   The supporting member  10  comprises a seat  12  which may be an electromagnetic holding chuck, using which the testing apparatus can be easily fixed at any desired position which is provided with a platform made of ferroalloy. A first plate  14  is secured on the seat  12 ; a second plate  16  hovers over the first plate  14 ; a plurality of supporting rods  15  interconnect the first and second plates  14 ,  16  for supporting the second plate  16  above the first plate  14 . The seat  12 , the first and second plates  14 ,  16  and the rods  15  constitute a mainframe 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 , the 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 (not labeled) vertically extend therethrough and communicate with the slot  282 , for extension of wires (not shown) of the temperature sensors  26  to connect with a monitoring computer (not shown). 
   In order to ensure that the immovable portion  20  and the movable portion  30  have good linear movement relative to each other, and keep the grooves  24 ,  32  of the immovable and movable portions  20 ,  30  in positions corresponding to each other, a cuboid enclosure  60  without bottom covers the immovable and movable portions  20 ,  30 , and is located between the first and second plates  14 ,  16  of the supporting member  10 . The enclosure  60  has four sidewalls (not labeled) thereof slidably contacting side faces of the immovable portion  20  all along. One of the sidewalls of the enclosure  60  defines an opening  62  located corresponding to the channel  50  between the immovable and movable portions  20 ,  30 , for disposing the heat pipe into the channel  50  therefrom. An opposite one of the sidewalls of the enclosure  60  defines an arced hatch  63  for the inlet and outlet  22  extending therethrough. A ceiling of the enclosure  60  contacts a top face of the movable portion  30  and defines therein a through hole (not shown) and two apertures  66  located at two sides of the through hole. 
   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 member  10 . The driving device  40  is fixed to the second plate  16  above ceiling of the enclosure  60 . A shaft (not labeled) of the driving device  40  extends through the second plate  16  of the supporting member  10 . The shaft has a threaded end (not shown) threadedly engaging with a bolt  42  which is secured to the movable portion  30  and extends through the through hole in the ceiling of the enclosure  60 . When the shaft rotates, the bolt  42 , the movable portion  30  and the enclosure  60  move upwardly or downwardly. The temperature sensors  36  have wires (not labeled) thereof extending through the apertures  66  of the enclosure  60  to connect with the monitoring computer. In use, the driving device  40  drives the movable portion  30  and the enclosure  60  to make accurate linear movement relative to the immovable portion  20 . For example, the movable portion  30  and the enclosure  60  can be driven to depart a certain distance such as 5 millimeters from the immovable portion  20  to facilitate the condensing section of the heat pipe which needs to be tested to be inserted into the channel  50  or withdrawn from the channel  50  from the opening  62  of the enclosure  60  after the heat pipe has been tested. Or in another example, the movable portion  30  and the enclosure  60  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. During the movement of the movable portion  30  and the enclosure  60 , the sidewalls of the enclosure  60  slidably contact the side faces of the immovable portion  20 . 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. Furthermore, the enclosure  60  has good adiabatic property, which constructs a steady environment for testing the heat pipes. 
   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 member  10 , and the immovable portion  20  is fixed to the second plate  16  of the supporting member  10 , and the driving device  40  is positioned to be adjacent to the immovable portion  20 . Alternatively, the driving device  40  can be installed to the immovable portion  20 . In a further alternative, each of the immovable and movable portions  20 ,  30  has one driving device  40  installed thereon to move them toward/away from each other. 
   In use, the condensing section of the heat pipe is received in the channel  50  when the movable portion  30  is moved away from the immovable portion  20 . Then the movable portion  30  is moved 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 connection with the condensing section of the heat pipe; therefore, the sensors  26 ,  36  work to accurately send detected temperatures of the condensing section of the heat pipe to the monitoring computer. Based on the temperatures obtained by the plurality of sensors  26 ,  36 , an average temperature can be obtained by the monitoring computer very quickly; therefore, performance of the heat pipe can be very quickly decided. 
   Referring to  FIGS. 4 and 5 , a performance testing apparatus for heat pipes in accordance with a alternative embodiment of the present invention is shown. The performance testing apparatus for heat pipes is similar to the preferred embodiment, the main difference from the first embodiment is that an enclosure  60   a  further comprising a bottom wall  66   a  replaces the enclosure  60  and first and second plates  14 ,  16  of the supporting member  10  of the preferred embodiment. The enclosure  60   a  is directly positioned on the seat  12 . An entrance  63   a  is defined in a side face of the enclosure  60   a . The immovable and movable portions  20 ,  30  are disposed in the enclosure  60   a  from the entrance  63   a . The bottom wall  66   a  defines a slot  662   a  for extension of wire of the temperature sensor  26  to connect with the monitoring computer. The driving device  40  is fixed to a ceiling of the enclosure  60   a . The shaft of the driving device  40  threadedly engages with the bolt  42  which is secured to a board  34  of the movable portion  30  and extends through a through hole  64   a  defined in the ceiling of the enclosure  60   a . When the driving device  40  operates, the shaft rotates, the bolt  42  with the board  34 , and the movable portion  30  move upwardly or downwardly relative to the immovable portion  20  in the enclosure  60   a.    
   According to the embodiments of the present invention, the immovable and movable portions  20 ,  30  are disposed in the enclosure  60 , thereby producing an accurate relative position to the immovable and movable portions  20 ,  30 , therefore the accurate linear movement of the immovable and movable portions  20 ,  30  can be realized when the driving device  40  works. Furthermore, the enclosure  60 ,  60   a  provides a steady environment for testing performance of the heat pipes. 
   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 enclosure  60 ,  60   a  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 in 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.