Flat plate pulsating heat pipe applicable at various angles and method of manufacturing same

• US 10,264,707 B2
• Filed: 05/22/2015
• Issued: 04/16/2019
• Est. Priority Date: 10/14/2014
• Status: Active Grant

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Kim, Sung Jin, Kwon, Gi Hwan
• Primary Examiner(s): Jonaitis, Justin M
• Application Number:
  US15/518,814
• Publication Number:
  US 20170245393A1
• Time in Patent Office: 1,425 Days
• Field of Search: 16510426, 16510421
• CPC Class Codes: F28D 15/0266 with separate evaporating and condensing chambers connected by at least one conduit; Loop-type heat pipes; with multiple or common evaporating or condensing chambers F28D15/043 takes precedence
• CPC Class Codes: F28D 15/043 forming loops, e.g. capillary pumped loops
• CPC Class Codes: F28D 2015/0225 Microheat pipes
• CPC Class Codes: F28F 13/10 by imparting a pulsating motion to the flow, e.g. by sonic vibration
• CPC Class Codes: H01L 23/427 Cooling by change of state, e.g. use of heat pipes by liquefied gas H01L23/445
• CPC Class Codes: H05K 7/20309 Evaporators
• CPC Class Codes: H05K 7/20318 Condensers
• CPC Class Codes: H05K 7/20336 Heat pipes, e.g. wicks or capillary pumps

Abstract

Disclosed is a flat plate pulsating heat pipe (FP-PHP) serving as a power-free high efficiency heat transfer system for small electronic devices such as mobile phones and laptop computers. The FP-PHP is manufactured using MEMS technology and configured to have a single-turn loop or a multi-turn loop, each having a single diameter channel or a dual diameter channel. Further, since a working fluid used in a flat plate pulsating heat pipe exhibits different characteristics according to the main working temperature, provided is a flat plate pulsating heat pipe which includes a working fluid having optimum efficiency in the main working temperature. In addition, the flat plate pulsating heat pipe applicable at various installation angles, of the present invention which is for achieving the above purpose, includes: a silicon lower wafer plate having a rectangular shape; a capillary tube comprising a channel which has a constant depth on the upper surface of the silicon wafer lower plate and is formed in the form of a straight line along the longitudinal direction of the silicon wafer lower plate, wherein the channel forms a closed loop which is bent at both ends of the silicon wafer lower plate and is connected; a wafer upper plate which is coupled on top of the silicon wafer lower plate and seals the capillary tube; and a working fluid filled inside the capillary tube, wherein the capillary tube is made of a combination of a dual-diameter tube including a pair of channels having different widths and a single diameter tube including a pair of channels having the same width.

Claims

1. A flat plate pulsating heat pipe comprising:

a silicon lower wafer plate having a rectangular shape;

a capillary tube formed in an upper portion of the silicon lower wafer plate and shaped to bend at positions near respective ends of the silicon lower wafer plate to form a closed loop;

an upper wafer plate bonded onto the silicon lower wafer plate to seal the capillary tube;

a working fluid in the capillary tube;

an evaporator provided to an end portion of the capillary tube in a longitudinal direction of the silicon lower wafer plate and located near an external heat source installed outside the silicon lower wafer plate; and

a condenser that is provided to an opposite end portion of the capillary tube in the longitudinal direction of the silicon lower wafer plate and at which the working fluid heated by the external heat source radiates heat outside the capillary tube,

wherein the capillary tube has a larger diameter in a portion from the evaporator to the condenser and a smaller diameter in a portion from the condenser to the evaporator, and

performance of the flat plate pulsating heat pipe is represented by the following figure of merit (M_PHP);

2. The flat plate pulsating heat pipe according to claim 1, wherein the capillary tube has a single-turn loop shape.

3. The flat plate pulsating heat pipe according to claim 1, wherein the capillary tube has a multi-turn loop shape.

4. The flat plate pulsating heat pipe according to claim 1, wherein FC-72 is used as the working fluid when a main operating temperature of the evaporator is 100°

C. or lower but ethanol is used as the working fluid when the main operating temperature of the evaporator is higher than 100°

C.

5. The flat plate pulsating heat pipe according to claim 1, wherein the figure of merit (M_PHP) of the flat plate pulsating heat pipe is 10¹² kg/(m·

s)(W/m³) or higher.

6. The flat plate pulsating heat pipe according to claim 1, wherein a thickness of the flat plate pulsating heat pipe is 2 mm or less.

7. The flat plate pulsating heat pipe according to claim 1, further comprising two through-holes provided to respective side surfaces of the silicon lower wafer plate, the two through-holes communicating with the capillary tube and used such that the working fluid is charged into and discharged from the capillary tube through the two through-holes.

8. A flat plate pulsating heat pipe comprising:

a silicon lower wafer plate having a rectangular shape;

a capillary tube including a channel formed to have a predetermined depth in an upper portion of the silicon lower wafer plate, the channel linearly extending in a longitudinal direction of the silicon lower wafer plate and bending at positions near respective ends of the silicon lower wafer plate, thereby forming a closed loop;

an upper wafer plate bonded to the silicon lower wafer plate to seal the capillary tube; and

a working fluid in the capillary tube,

wherein the capillary tube is a combination of a dual diameter channel including a pair of channels with respectively different widths and a single diameter channel including a pair of channels with a same width.

9. The flat plate pulsating heat pipe according to claim 8, wherein a diameter of the capillary tube is represented by the following equation:

10. The flat plate pulsating heat pipe according to claim 9, wherein two diameters of the dual diameter channel satisfy the following condition:

0.3≤

Δ

D/D_avg≤

0.5

where Δ

D is difference between two diameters and D_avg is average of two diameters.

11. The flat plate pulsating heat pipe according to claim 8, wherein the capillary tube includes a plurality of dual diameter channels, and

wherein a proportion of a number of dual diameter channels with respect to a total number of channels in the entire capillary tube is 60% or higher.

12. The flat plate pulsating heat pipe according to claim 8, wherein a performance of the flat plate pulsating heat pipe is represented by the following figure of merit (M_PHP2):

13. The flat plate pulsating heat pipe according to claim 12, wherein the figure of merit (M_PHP2) is a value of 2×

10⁵ kg/(m³·

s) or greater.

14. A method of manufacturing a flat plate pulsating heat pipe using a Micro Electro Mechanical System (MEMS) manufacturing process, the method comprising:

(a) depositing a photoresist layer on an upper surface of a silicon wafer having a rectangular shape;

(b) patterning the photoresist layer into to a pattern corresponding a shape of a capillary tube, the capillary tube being bent at positions near respective ends of the silicon wafer, thereby having a closed loop shape;

(c) forming the capillary tube by etching the silicon wafer;

(d) removing the photoresist layer remaining on the etched silicon wafer; and

(e) bonding an upper wafer plate onto an upper surface of the etched silicon wafer,

wherein in the step (b), the patterning is performed such that two through-holes extending to respective side surfaces of the silicon wafer and communicating with the capillary tube are formed.

15. The method according to claim 14, wherein in the step (b), the capillary tube has a multi-turn loop shape.

16. The method according to claim 14, wherein in the step (b), the capillary tube is a combination of a dual diameter channel including a pair of channels with respectively different widths and a single diameter channel including a pair of channels with a same width.

17. The method according to claim 16, wherein the capillary tube includes a plurality of dual diameter channels, and

wherein a proportion of a number of dual diameter channels with respect a total number of channels in the entire capillary tube is 60% or higher.

18. The method according to claim 15, wherein performance of the flat plate pulsating heat pipe is represented by the following figure of merit (M_PHP):

19. The method according to claim 16, wherein performance of the flat plate pulsating heat pipe is represented by the following figure of merit (M_PHP2):