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 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. A positioning structure extends from at least one of the immovable portion and the movable portion to ensure that the receiving structure is capable of precisely receiving the heat pipe therein. At least a temperature sensor is attached to at least one of the immovable portion and the movable portion to detect a temperature of the heat pipe. An enclosure encloses the immovable portion and the movable portions therein, and defines a space for movement of the movable portion relative to the immovable portion.

Description:
1. FIELD OF THE INVENTION 
   The present invention relates generally to testing apparatuses, and more particularly to a performance testing apparatus for heat pipes. 
   2. 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 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. 
   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. 5 , a performance testing apparatus for heat pipes in accordance with related art 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 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 of the heat pipe  2 . 
   However, in the test, the related 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 affected 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, a large number of performance tests are needed, and the apparatus is used usually over a long period of time; thus, the apparatuses not only requires good testing accuracy, but also requires easy and accurate assembly with the heat pipes to be tested. The testing apparatus affects 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 related 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 removing heat from a condensing section of 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 condensing section of the heat pipe therein. A positioning structure extends from at least one of the immovable portion and the movable portion and avoids the movable portion from deviating from the immovable portion during movement of the movable portion relative to the immovable portion, thereby to ensure the receiving structure being capable of receiving the heat pipe accurately. 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 therein, and defines a space for movement of the movable portion relative to the immovable 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 first embodiment of the present invention; 
       FIG. 2  is an exploded, isometric view of the testing apparatus of  FIG. 1 ; 
       FIG. 3  is an assembled view of a performance testing apparatus for heat pipes in accordance with a second embodiment of the present invention; 
       FIG. 4A  shows an immovable portion and a movable portion of a performance testing apparatus for heat pipes in accordance with a third embodiment of the present invention; 
       FIG. 4B  shows the immovable portion and the movable portion of  FIG. 4A  from a different aspect; 
       FIG. 4C  shows the movable portion of  FIG. 4A  from a different aspect; 
       FIG. 4D  shows the immovable portion of  FIG. 4A  from a different aspect; and 
       FIG. 5  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 comprises an immovable portion  20  and a movable portion  30  movably mounted on the immovable portion  20 . 
   The immovable portion  20  is made of metal having good heat conductivity. 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 corporately define a cooling system for the coolant circulating in the immovable portion  20  to remove heat from a 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 and removing heat from the heat pipe. Two temperature sensors  26  (only one shown in  FIG. 2 ) are inserted into the immovable portion  20  from a bottom thereof so as to position detecting portions (not shown in  FIGS. 1 and 2 ) of the sensors  26  in the cooling groove  24 . The detecting portions of the temperatures sensors  26  are capable of automatically contacting the heat pipe in order to detect a temperature of the condensing section of the heat pipe. 
   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 (not shown in  FIGS. 1 and 2 ) 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 immovable portion  20  has two flanges  25  integrally extending upwardly from two opposite edges thereof and toward the movable portion  30 . The two flanges  25  functions as positioning structure to positioning the movable portion  30  therebetween, which prevents the movable portion  30  from deviating from the immovable portion  30  during test of the heat pipes in mass production, thereby ensuring the grooves  24 ,  32  of the immovable and movable portions  20 ,  30  to always be aligned with each other. Thus, the channel  50  can be always precisely and easily formed for receiving the heat pipe for test. The movable portion  30  slidably contacts the two flanges  25  of the immovable portion  20  when it moves relative to the immovable portion  20 . Alternatively, the movable portion  30  can has two flanges slidably engaging two opposite sides of the immovable portion  20  to keep the immovable portion  20  aligned with the movable portion  30 . 
   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 applied to retain the movable portion  30  together with the immovable portion  20 . 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 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 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 ferroalloy. 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, the supporting frame  10  further comprises a cuboidal enclosure  60  enclosing the immovable and movable portions  20 ,  30  therein. The enclosure  60  comprises a bottom wall  66  positioned on the seat  12  of the supporting frame  10  and two opposite sidewalls and a front wall (not labeled) extending from two opposite sides and a front side of the bottom wall  66  and a top wall (not labeled) interconnecting top ends of the sidewalls and the front wall. The two opposite sidewalls and the bottom wall  66  each extend two parallel spaced ribs  660  from inner faces thereof to prevent the immovable portion  20  from directly contacting these walls, to thereby construct a thermally stable environment for testing the heat pipes. A slot  662  is defined between the two ribs  660  of the bottom wall  66  for extension of wire of the temperature sensors  26  to connect with a monitoring computer. Corresponding to the channel  50  between the immovable and movable portions  20 ,  30 , the front wall of the enclosure  60  defines an opening  62  for extension of the heat pipe therethrough into the channel  50 . Corresponding to the inlet  22  and the outlet  22 , the enclosure  60  defines an entrance  63  opposite to the opening  62 , for the inlet  22  and outlet  22  extending therethrough. A space (not labeled) is left between the movable portion  30  and top wall of the enclosure  60  for movement of the movable portion  30 . The driving device  40  is fixed on the top wall of the enclosure  60 . The top wall of the enclosure  60  defines a through hole  64  for extension of a shaft (not labeled) of the driving device  40  therethrough to engage with a bolt  42  which is secured to a board  34  of the movable portion  30  in the enclosure  60 . 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 . 
   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 shaft of the driving device  40  has a threaded end (not shown) threadedly engaging with the bolt  42  secured to the 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  is moved upwardly or downwardly. Two through apertures (not labeled) are defined in the board  34  of the movable portion  30  for extension of wires (not labeled) of the temperature sensors  36  to connect with the monitoring computer. In use, the driving device  40  drives the movable portion  30  to make accurate linear movement relative to the immovable portion  20 . For example, in the enclosure  60 , the movable portion  30  is 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  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 requirement for the testing, i.e. accuracy, ease of use and speed can be realized by the testing apparatus in accordance with the present invention. 
   It can be understood that positions of the immovable portion  20  and the movable portion  30  can be exchanged, i.e., the movable portion  30  being positioned on the bottom wall  66  of the enclosure  60 , and the immovable portion  20  being located on the movable portion  30 . The driving device  40  is positioned to be adjacent to the immovable portion  20  and drives the immovable portion  20  move relative to the movable portion  30  in the enclosure  60 . Alternatively, 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 . Under the drive of the driving device  40 , the movable portion  30  in the enclosure  60  is then moved to reach the immovable portion  20  so that the condensing section of the heat pipe is tightly fitted in the channel  50 . The sensors  26 ,  36  are in thermal connection with the condensing section of the heat pipe; therefore, the sensors  26 ,  36  can 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  FIG. 3 , a performance testing apparatus for heat pipes in accordance with a second embodiment of the present invention is shown. The apparatus is similar to the first embodiment, the main difference therebetween is that the flanges  25   a  of the immovable portion  20  each further extend a wing  250  abutting against an inner face of a corresponding sidewall of the enclosure  60 , thereby positioning the immovable portion  20  in the enclosure  60 . 
   Referring to  FIGS. 4A-4D , an immovable portion  20  and a movable portion  30  in accordance with a third embodiment of the present invention are illustrated. The immovable portion  20  and the movable portion  30  have two channels  50  defined therein. The two channels  50  are separated from each other in a stepwise manner. Between the two channels  50 , two positioning steps  27 ,  37  are respectively formed on the immovable portion  20  and the movable portion  30 . The positioning steps  27 ,  37  have inclined faces contacting each other when the movable portion  30  moves to the immovable portion  20 . In this case, the positioning steps  27 ,  37  function as positioning structure which avoids the movable portion  30  from deviating from the immovable portion  30  during movement of the movable portion  30  relative to the immovable portion  20 , thereby ensuring that the channels  50  are precisely constructed between the immovable, movable portions  20 ,  30  for receiving the heat pipes for test. Alternatively, the channels  50  can be defined between the immovable and movable portions  20 ,  30  on a same level; correspondingly, the positioning structure (i.e., positioning steps  27 ,  37 ) is formed at edges of the immovable portion  20  and the movable portion  30 . From  FIGS. 4C and 4D , it can be clearly seen that the detecting portions of the temperature sensors  26  and  36  are exposed to the cooling grooves  24  of the immovable portion  20  and the positioning grooves  32  of the movable portion  30 . Thus, when the movable portion  30  is moved to contact with the immovable portion  20 , the condensing sections of the heat pipes received in the channels  50  can have an intimate contact with the detecting portions of the temperature sensors  26 ,  36 , whereby temperature of the heat pipes can be conveniently and quickly decided. 
   Additionally, in the present invention, in order to lower cost of the testing apparatus, the movable portion  30 , the board  34 , and the enclosure  60  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 cooling groove(s)  24  to prevent 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.