# Patent

## Title
Performance testing apparatus for heat pipes

## 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.

## Background
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 2a of a heat pipe 2, and a water cooling sleeve 3 functioning as a heat sink and enclosing a condensing section 2b 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 2a 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 2a can be removed from the heat pipe 2 by the cooling liquid at the condensing section 2b, whereby a stable operating temperature of adiabatic section 2c of the heat pipe 2 is obtained. Therefore, Qmax of the heat pipe 2 and ΔT between the evaporating section 2a and the condensing section 2b 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 2a and the condensing section 2b 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 3A and 3B, 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.

## Claims

1. A performance testing apparatus for a heat pipe comprising:
an immovable portion having a cooling structure defined therein for cooling a heat pipe requiring testing;
a movable portion capable of moving relative to the immovable portion and having a cooling structure defined therein for cooling the heat pipe;
a receiving structure being located between the immovable portion and the movable portion for receiving the heat pipe therein; and
at least one temperature sensor being 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;
wherein the receiving structure is a channel defined between the immovable portion and the movable portion;
wherein the at least a temperature sensor has a detecting portion thereof exposed to the channel;
wherein at least one of the immovable portion and the movable portion has at least one positioning structure communicating with the channel, the at least one temperature sensor being positioned in the at least one positioning structure;
wherein the at least a temperature sensor comprises two wires, each of the two wires comprising first and second sections and a working section between the first and second sections, the working section being the detecting portion of the at least a temperature sensor;
wherein the at least one positioning structure of one of the immovable portion and the movable portion defines two pairs of through holes therein, and wherein each of the two wires has the first section thereof extending in one of the through holes, the second section fitted in another through hole, and the working section located at a bottom of the positioning structure for contacting with the heat pipe, and wherein an end of the second section extends away from the another through hole for connecting with a monitoring computer; and
wherein the cooling structure of the immovable portion comprises an inlet and an outlet at one end of the immovable portion to allow coolant circulation into or out of the immovable portion.

2. The testing apparatus of claim 1, wherein the at least one temperature sensor is positioned in a positioning socket movably fitted in a through hole of the positioning structure of at least one of the immovable portion and the movable portion.

3. The testing apparatus of claim 2, wherein the positioning socket defines four through apertures therethrough, and wherein each of the wires of the at least one temperature sensor has the first section thereof fitted in one of the through apertures, the second section fitted in another through aperture, and the working section located at a bottom of the socket for contacting with the heat pipe, and wherein an end of the second section extends away from the another through hole for connecting with a monitoring computer.

4. The testing apparatus of claim 3, wherein the positioning socket comprises a square column, a circular column and a circular collar between the square and circular columns, and wherein the through hole of the positioning structure has square and circular sections corresponding to the square column and the circular column of the socket, respectively.

5. The testing apparatus of claim 4, wherein the positioning socket has a spring coil surrounding the circular column of the socket and movably received in the through hole of the positioning portion.

6. The testing apparatus of claim 5, wherein the at least a temperature sensor is fixed in the through hole of the positioning structure via a board covering the positioning structure, and wherein the ends of the wires of the at least one temperature sensor extend through the board.

7. The testing apparatus of claim 5, wherein the at least one temperature sensor is secured in the through hole of the positioning structure via a screw engaged in the through hole, the ends of the wires of the at least a temperature sensor extending through the screw.

8. The testing apparatus of claim 1, wherein the cooling structure of the movable portion comprises an inlet and an outlet at an end of the movable portion for coolant circulation into or out of the movable portion.