HEAT TRANSFER DEVICE AND AN ASSOCIATED METHOD OF FABRICATION

Abstract

A heat transfer device includes a casing and a wick disposed within the casing. The wick includes a first sintered layer and a second sintered layer. The first sintered layer includes a plurality of first sintered particles, having a first porosity and a plurality of first pores. The first sintered layer is disposed proximate to an inner surface of the casing. The second sintered layer includes a plurality of second sintered particles, having a second porosity and a plurality of second pores. The second sintered layer is disposed on the first sintered layer. The heat transfer device includes at least one first sintered particle smaller than at least one second pore and the first porosity is smaller than the second porosity.

Description

This invention was made with Government support under contract number N66001-08-C-2008 awarded by U.S. Department of Defense. The Government has certain rights in the invention.

BACKGROUND

The present disclosure relates generally to a heat transfer device and more particularly, to a vapor chamber or a heat pipe having a spatially controlled porosity or pore size and an associated method of fabrication.

A heat transfer device is used to transfer heat from a source to a sink. Such heat transfer devices may include a hot end and a cold end to enable transfer of the heat from the hot end to the cold end. Generally, the heat transfer device combines the principle of a thermal conductivity and a phase transition of a working fluid to transfer the heat. In one example, the heat transfer device is a sealed tube or a sealed chamber, fabricated using a material having a high thermal conductivity. The heat transfer device includes the working fluid within the sealed chamber to transfer the heat effectively. Typically, such heat transfer device may further include a wick to enable heat transfer by condensation and evaporation of the working fluid i.e. by changing phase of the working fluid within the sealed chamber.

The conventional wick includes a plurality of mono-dispersed sintered particles distributed along the longitudinal direction of the heat transfer pipe. Typically wicks are designed to provide a high fluid transport and phase change capability of the working fluid. Such functions are achieved by designing the wick having a very large pores combined with high surface area for phase change processes. However, such conventional wicks are less effective in performing phase change of the working fluid, because the design and fabrication process are based on mono-dispersed particles. Further, such wick structures provide solid conduction thermal resistance due to low contact area with the chamber walls, or casing material and/or low porosity.

Such limitations can be addressed by designing the wick, having pore size variation through the use of varying particle sizes. However, the wicks that are designed with varying particle sizes are fabricated using an organic carrier which is burned completely to generate the sintered particles having varied pore size and/or varied porosity. Such fabrication processes may result in contamination of the heat transfer device, limit the wick fabrication temperature to temperatures high enough to burn-away the organics, and also may lead to generation of a non-condensable fluid during prolonged operation of the heat transfer device.

There is a need for an improved heat transfer device and a method for fabricating the heat transfer device.

BRIEF DESCRIPTION

In accordance with one exemplary embodiment, a heat transfer device is disclosed. The heat transfer device includes a casing and a wick disposed within the casing. The wick includes a first sintered layer disposed proximate to an inner surface of the casing and a second sintered layer disposed on the first sintered layer. The first sintered layer includes a plurality of first sintered particles, having a first porosity and a plurality of first pores. The second sintered layer includes a plurality of second sintered particles, having a second porosity and a plurality of second pores. At least one first sintered particle is smaller than at least one second pore and the first porosity is smaller than the second porosity

In accordance with one exemplary embodiment, a method for manufacturing a heat transfer device is disclosed. The method includes filling a mixture of a plurality of first particles and second particles within a first half casing portion. Further, the method includes leveling the plurality of first and second particles within the first half casing portion. The method includes vibrating the first half casing portion to segregate the plurality of first particles from the plurality of second particles such that a first layer portion having the plurality of first particles and a second layer portion having the plurality of second particles are formed. The first layer portion is disposed proximate to an inner surface of the first half casing portion and a second layer portion is disposed on the first layer portion. Further, the method includes sintering the first layer portion and the second layer portion to generate a first sintered layer portion and a second sintered layer portion. The first sintered layer portion includes a plurality of first sintered particles, having a first porosity and a plurality of first pores. The second sintered layer portion includes a plurality of second sintered particles, having a plurality of second pores and a second porosity greater than the first porosity. Further, the method includes forming at least one first sintered particle smaller than at least one second pore. The method further includes forming a first wick portion having the first sintered layer portion and the second sintered layer. The method further includes repeating the filling, the leveling, the vibrating, and the sintering process in a second half casing portion to form a second wick portion within the second half casing portion. Further, the method includes coupling the first half casing portion to the second half casing portion such that the first wick portion is coupled to the second wick portion to form a heat transfer device.

DRAWINGS

These and other features and aspects of embodiments of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic sectional view of a heat transfer device, for example a vapor chamber in accordance with an exemplary embodiment;

FIG. 2a is a sectional view of a first half casing portion of a vapor chamber in accordance with an exemplary embodiment;

FIG. 2b is a sectional view of a second half casing portion of a vapor chamber in accordance with an exemplary embodiment;

FIG. 3 is a schematic sectional view of a portion of a vapor chamber having a first sintered layer, a second sintered layer, and a third sintered layer in accordance with an exemplary embodiment;

FIG. 4a is a perspective view of a portion of a wick having a plurality of first sintered particles and a plurality of second sintered particles in accordance with an exemplary embodiment;

FIG. 4b is a perspective view of the portion of the wick in FIG. 4a having a plurality of third sintered particles in accordance with an exemplary embodiment;

FIG. 4c is a perspective view of a portion of a wick having a plurality of third sintered particles in accordance with another exemplary embodiment;

FIG. 5a is a schematic view of a portion of a wick having a first sintered layer with a uniform thickness of and a second sintered layer having a non-uniform thickness in accordance with another exemplary embodiment;

FIG. 5b is a schematic view of the portion of the wick in FIG. 5a having a third sintered layer having a non-uniform thickness in accordance with another exemplary embodiment;

FIG. 6 is a schematic flow diagram illustrating a method of manufacturing a first sintered layer and a second sintered layer within a casing in accordance with an exemplary embodiment;

FIG. 7 is a schematic flow diagram illustrating a method of manufacturing a third sintered layer portion on a second sintered layer portion within a first half casing portion in accordance with an exemplary embodiment;

FIG. 8 is a schematic flow diagram illustrating a method of manufacturing a second sintered layer portion having a non-uniform thickness along an evaporator section, a transport section, and a condenser section in accordance with another exemplary embodiment;

FIG. 9 is a schematic flow diagram illustrating a method of manufacturing a second sintered layer portion having a non-uniform thickness along an evaporator section, a transport section, and a condenser section in accordance with yet another exemplary embodiment; and

FIG. 10 is a schematic flow diagram illustrating a method of manufacturing a third sintered layer portion having a non-uniform thickness along an evaporator section, a transport section, and a condenser section in accordance with another exemplary embodiment.

DETAILED DESCRIPTION

While only certain features of embodiments have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as falling within the spirit of the invention.

Embodiments discussed herein disclose a heat transfer device and associated methods for manufacturing the heat transfer device. More particularly, certain embodiments disclose a vapor chamber. The vapor chamber includes a casing and a wick having a first sintered layer and a second sintered layer disposed within the casing. The first sintered layer includes a plurality of first sintered particles having a first porosity and a plurality of first pores. The first sintered layer is disposed proximate to an inner surface of the casing. The second sintered layer includes a plurality of second sintered particles having a second porosity and a plurality of second pores. The second sintered layer is disposed on the first sintered layer. At least one first sintered particle is smaller than at least one second pore and the first porosity is smaller than the second porosity.

Certain embodiments disclose a method of manufacturing a heat transfer device. More specifically, certain embodiments disclose a method of manufacturing a vapor chamber. The method includes filling a plurality of first particles and second particles within a first half casing portion and leveling the plurality of first and second particles. Further, the method includes vibrating the first half casing portion so as to segregate the plurality of first particles from the plurality of second particles to form a first layer portion and a second layer portion. The segregated first layer portion includes the plurality of first particles disposed proximate to an inner surface of the first half casing portion and the segregated second layer portion includes the plurality of second particles disposed on the first layer portion. The method further includes sintering the first layer portion and the second layer portion to generate a first sintered layer portion and a second sintered layer portion. The first sintered layer portion and the second sintered layer portion together form a first wick portion.

Further, the method includes repeating the filling, the leveling, the vibrating, and the sintering process in a second half casing portion to form a second wick portion within the second half casing portion. The method further includes coupling the first half casing portion to the second half casing portion such that the first wick portion is coupled to the second wick portion to form the vapor chamber.

FIG. 1 is a schematic sectional view of a heat transfer device 100 in accordance with an exemplary embodiment. In the illustrated embodiment, the heat transfer device 100 is a vapor chamber. It should be noted herein that the terms “heat transfer device” and “vapor chamber” are used interchangeably. In some other embodiments, the heat transfer device is a heat pipe.

The vapor chamber 100 includes a casing 102 and a wick 104. Further, the wick forms a sealed chamber 106 filled with a working fluid 108. The working fluid 108 transfers the heat from one end 116 to another end 118 of the vapor chamber 100. Further, the vapor chamber 100 includes an evaporator section 110 disposed proximate to the end 116, a condenser section 112 disposed proximate to the end 118, and a transport section 114 disposed between the evaporator section 110 and the condenser section 112. The evaporator section 110 is used to absorb heat from a source (not shown in FIG. 1) by evaporating the working fluid 108. The condenser section 112 is used to release heat to a sink (not shown in FIG. 1) by condensing the working fluid 108. The transport section 114 is used to conduct the heat from one end 116 to the other end 118 via the working fluid 108. The vapor chamber 100 is fabricated using a material having high thermal conductivity. The material of the vapor chamber 100 may be copper or aluminum nitrate, for example. The vapor chamber 100 has a rectangular shape and a length “L₁” in the range of five to ten meters, for example.

The casing 102 includes a first half casing portion 102a and a second half casing portion 102b. Each half casing portion 102a, 102b includes an inner surface 120 and an outer surface 122. Each half casing portion 102a, 102b has a U-shape. The first half and second half casing portions 102a, 102b are coupled to each other by brazing, soldering, or the like. The wick 104 is disposed proximate to the inner surface 120 of the casing 102. The wick 104 includes a first sintered layer 126 and a second sintered layer 128. Specifically, the first sintered layer 126 is disposed proximate to the inner surface 120 of the casing 102. The second sintered layer 128 is disposed on the first sintered layer 126. The first sintered layer 126 includes a first sintered layer portion 126a disposed in the first half casing portion 102a and another first sintered layer portion 126b disposed in the second half casing portion 102b. Similarly, the second sintered layer 128 includes a second sintered layer portion 128a disposed on the first sintered layer portion 126a and another second sintered layer portion 128b disposed on the other first sintered layer portion 126b.

The first and second sintered layers 126, 128 have a uniform thickness “T₁” and “T₂” respectively across the length “L₁” of the vapor chamber 100. The casing 102 may be made of a first material and the first sintered layer 126 and the second sintered layer 128 are made of a second material different from the first material. The casing 102, the first sintered layer 126, and the second sintered layer 128 may be made of the same material.

FIG. 2a is a sectional view along (2A-2A) of the first half casing portion 102a in accordance with the embodiment of FIG. 1. The first half casing portion 102a includes a first wick portion 104a and a coating portion 130a.

The first wick portion 104a includes the first sintered layer portion 126a disposed proximate to the inner surface 120 of the first half casing portion 102a and the second sintered layer portion 128a disposed on the first sintered layer portion 126a. The coating portion 130a is disposed between the inner surface 120 of the first half casing portion 102a and the first sintered layer portion 126a. The coating portion 130a may include one or more layers depending on the application and design criteria. The coating portion 130a may be made of a material having high thermal conductivity such as copper, aluminum nitrate, or the like. The first half casing portion 102a may be made of a first material and the coating portion 130a, the first sintered layer portion 126a, and the second sintered layer portion 128a may be made of a second material different from the first material.

FIG. 2b is a sectional view along (2B-2B) of the second half casing portion 102b in accordance with the embodiment of FIG. 1. The second half casing portion 102b includes a second wick portion 104b and a coating portion 130b.

The second wick portion 104b includes the first sintered layer portion 126b disposed proximate to the inner surface 120 of the second half casing portion 102b and the second sintered layer portion 128b disposed on the first sintered layer portion 126b. The coating portion 130b is disposed between the inner surface 120 of the second half casing portion 102b and the first sintered layer portion 126b. The coating portion 130b includes a material having high thermal conductivity such as copper, aluminum nitrate, or the like. The second half casing portion 102b may be made of a first material and the coating portion 130b, the first sintered layer portion 126b, and the second sintered layer portion 128b may be made of a second material different from the first material.

FIG. 3 is a schematic sectional view of a portion of the vapor chamber 100. In the illustrated embodiment, the vapor chamber 100 includes the casing 102, the first sintered layer 126, the second sintered layer 128, and additionally a third sintered layer 140. The third sintered layer 140 is disposed on the second sintered layer 128. The third sintered layer 140 has a uniform thickness “T₃” along the length of the vapor chamber 100. The third sintered layer 140 includes a material having high thermal conductivity, such as copper, aluminum nitrate, or the like.

FIG. 4a is a perspective view of a portion 134 of the wick 104. The wick 104 includes the first sintered layer 126 and the second sintered layer 128. The first sintered layer 126 has a plurality of first sintered particles 142 and the second sintered layer 128 has a plurality of second sintered particles 144. Further, the first sintered layer 126 has a plurality of first pores 146 and a first porosity 148 and the second sintered layer 128 has a plurality of second pores 150 and a second porosity 152.

Each first sintered particle 142 has a size “S₁” and each second sintered particle 144 has a size “S₂”. Each first sintered particle 142 has the size “S₁” in a range of hundred nanometers to fifty micrometers and each second sintered particle 144 has the size “S₂” in a range of ten micrometers to hundred micrometers. The size “S₂” of each second sintered particle 144 is greater than the size “S₁” of each first sintered particle 142.

Further, each first pore 146 has a size “S₃” and each second pore 150 has a size “S₄”. Each first pore 146 has the size “S₃” in a range of ten nanometers to ten micrometers and each second pore 150 has the size “S₄” in a range of one micrometer to fifty micrometers. Each first sintered particle 142 and each second sintered particle 144 has a spherical or oval or circular shape. The size “S₁” of each first sintered particle 142 is smaller than the size “S₄” of each second pore 150. The size “S₁” of the first sintered particle 142 is at least forty to sixty percent smaller than the size “S₄” of the second pore 150. The first sintered particle 142 having a relatively smaller size than the second pore 150 provides higher heat transfer capability and offers very less thermal resistance along the length of the vapor chamber 100.

The first porosity 148 of the first sintered layer 126 is in a range of five percent to forty percent. The second porosity 152 of the second sintered layer 128 is in a range of eight percent to twenty percent. The first porosity 148 is smaller than the second porosity 152. The second layer 128 having a relatively greater second porosity 152 facilitates to exert a higher capillary pressure on the working fluid along the length of the vapor chamber 100.

FIG. 4b is a perspective view of the third sintered layer 140 in accordance with the exemplary embodiment of FIG. 4a. The third sintered layer 140 includes a plurality of third sintered particles 154. The plurality of third sintered particles 154 is disposed on the plurality of second sintered particles 144. Each third sintered particle 154 has a dendrite shape. Further, the third sintered layer 140 has a plurality of third pores 156 and a third porosity 158. Each third sintered particle 154 has a size “S₅” and each third pore 156 has a size “S₆”. Each third sintered particle 154 has the size “S₅” in a range of hundred nanometers to ten micrometers and each third pore 156 has a size “S₆” in a range of one nanometer to ten micrometers. The third porosity 158 is in a range of twenty percent to eighty percent. The size “S₅” of each third sintered particle 154 is smaller or equal to the size “S₂” of each second sintered particle 144 and the third porosity 158 is smaller than the second porosity 152. The third sintered layer 140 having a relatively smaller third porosity 152 provides a higher heat transfer capability of the wick 104.

FIG. 4c is a perspective view of a third sintered layer 139 in accordance with another exemplary embodiment. The third sintered layer 139 is disposed on a second sintered layer (not shown in FIG. 4c). The third sintered layer 141 includes a plurality of third particles 132 having a spherical shape.

FIG. 5a is a schematic view of a portion 137 of a wick 105 having a first sintered layer 127 and a second sintered layer 129 in accordance with another exemplary embodiment.

The second sintered layer 129 is disposed on the first sintered layer 127. The first sintered layer 127 has a uniform thickness “T₄” along an evaporator section 111, a condenser section 113, and a transport section 115 of a vapor chamber. The second sintered layer 129 has a non-uniform thickness along the evaporator section 111, the condenser section 113, and the transport section 115. Specifically, the second sintered layer 129 has a thickness “T₅” corresponding to the evaporator section 111, a thickness “T6” corresponding to the condenser section 113, and a thickness “T₇” corresponding to the transport section 115. The thickness “T₅” may be in the range of five millimeters to ten millimeters, the thickness “T₆” may be in the range of two millimeters to five millimeters, and the thickness “T₇” may be in the range of five millimeters to eight millimeters, for example. The thickness “T₅” is greater than the thickness “T₆”. The thickness “T₇” is greater than the thickness “T₅”.

FIG. 5b is a schematic view of the portion 137 of the wick 105 having an additional third sintered layer 141 in accordance with the exemplary embodiment of FIG. 5a.

The third sintered layer 141 is disposed on the second sintered layer 129. The third sintered layer 141 has a non-uniform thickness along the evaporator section 111, the condenser section 113, and the transport section 115 of the vapor chamber. Specifically, the third sintered layer 141 has a thickness “T₈” corresponding to the evaporator section 111, a thickness “T₉” corresponding to the condenser section 113 and a thickness “T₁₀” corresponding to the transport section 115. The thickness “T₈” may be in the range of two millimeters to three millimeters, the thickness “T₉” may be in the range of one millimeter to two millimeters, and the thickness “T₁₀” may be in the range of two millimeters to five millimeters, for example. The thickness “T₈” is greater than the thickness “T₉”. The thickness “T₁₀” is greater than the thickness “T₈”.

FIG. 6 is a schematic flow diagram illustrating a plurality of steps involved in a method 160 of manufacturing the first sintered layer 126 and the second sintered layer 128 within the casing 102 in accordance with the embodiment of FIGS. 1, 2a, and 2b.

The method 160 includes a step 162 of disposing the first half casing portion 102a and a step 168 of applying the coating portion 130a on the inner surface 120 of the first half casing portion 102a. A plurality of first particles 164 and a plurality of second particles 166 are filled in the first half casing portion 102a. The first half casing portion 102a is made of a first material and the coating portion 130a, the plurality of first particles 164, and the plurality of second particles 166 includes a second material different from the first material.

In another embodiment, a coating portion 130a may not be applied to the inner surface 120 of the first half casing portion 102a and the plurality of particles 164, 166 are filled directly within the first half casing portion 102a such that the plurality of particles 164, 166 are in contact with the inner surface 120 of the first half casing portion 102a. The first half casing portion 102a, the plurality of first particles 164, and the plurality of second particles 166 include the same material.

A step 170 includes leveling the plurality of first particles 164 and the plurality of second particles 166 within the first half casing portion 102a. The plurality of first and second particles 164, 166 is leveled using a squeegee device 172. A uniform contact surface 171 of the squeegee device 172 is used to level the plurality of first particles 164 and the plurality of second particles 166 to generate a uniform thickness. The squeegee device 172 may be made of a material such as nickel-cobalt ferrous alloy or ceramics such as aluminum nitrate, alumina, silicon carbide, silicon nitride or the like.

The method 160 further includes a step 174 of vibrating the first half casing portion 102a to segregate the plurality of first particles 164 from the plurality of second particles 166 such that a first layer portion 176a and a second layer portion 178a is formed within the first half casing portion 102a. The first half casing portion 102a is vibrated using a vibrator device 180. The vibrator device 180 is clamped to the first half casing portion 102a and powered via mechanical elements to vibrate the first half casing portion 102a. The first layer portion 176a having the plurality of first particles 164 is disposed proximate to the inner surface 120 of the first half casing portion 102a and the second layer portion 178a having the plurality of second particles 166 is disposed on the first layer portion 176a. The first layer portion 176a has a uniform thickness “T₀₁” and the second layer portion 178a has a uniform thickness “T₀₂”. In another exemplary embodiment, the step 174 of vibrating the half casing portion may be optional.

The method 160 further includes a step 182 of sintering the first layer portion 176a and the second layer portion 178a. The step 182 includes disposing a sintering spacer 184 over the second layer portion 178a and filling an additional amount of the plurality of second particles 166 in the spaces formed between the sintering spacer 184 and the inner surface 120 of the first half casing portion 102a. The sintering spacer 184 has a uniform contact surface 187 contacting the second layer portion 178a. The step 182 further includes disposing the first half casing portion 102a with the sintering spacer 184, in a sintering device 188 to sinter the first layer portion 176a and the second layer portion 178a so as to generate the first sintered layer portion 126a and the second sintered layer portion 128a having a uniform thickness as shown in step 190.

The first sintered layer portion 126a includes the plurality of first sintered particles 142 having the first porosity 148 and the plurality of first pores 146 (as shown in FIG. 4a). The second sintered layer portion 128a includes the plurality of second sintered particles 144 having the plurality of second pores 150 and the second porosity 152 (as shown in FIG. 4a). The sintering step 182 is performed in a controlled environment i.e. at a predefined temperature and pressure so as to generate at least one first sintered particle 142 smaller than at least one second pore 150. The sintering process is controlled to generate at least forty to sixty percent of the first sintered particles 142 having a size smaller than the plurality of second pores 150. The sintering pressure is in a range of 50 bars to 60 bars and the sintering temperature is in a range of 648.89 degrees Celsius to 815.56 degrees Celsius. The sintering spacer 184 may be made of a material such as nickel-cobalt ferrous alloy or ceramics including aluminum nitrate, alumina, silicon carbide, and silicon nitride.

The first sintered layer 126a has a uniform thickness “T₁” corresponding to an evaporator section 110, a condenser section 112, and a transport section 114. Similarly, the first sintered layer 128a has a uniform thickness “T₂” corresponding to the evaporator section 110, the condenser section 112, and the transport section 114. The step 190 further involves removing the sintering device 188 and the sintering spacer 184 such that the first wick portion 104a is formed within the first half casing portion 102a. The first wick portion 104a includes the first sintered layer portion 126a and the second sintered layer portion 128a.

Similarly, the method further includes a step 192 of repeating the steps 162, 168, 170, 174, 182, and 190 in the second half casing portion 102b to form a second wick portion 104b. The second wick portion 104b includes the first sintered layer portion 126b disposed proximate to the inner surface 120 of the second half casing portion 102b and the second sintered layer portion 128b disposed on the first sintered layer portion 126b. The method also includes applying the coating portion 130b on the inner surface 120 of the second half casing portion 102a.

The method 160 further includes a step 194 of coupling the first half casing portion 102a to the second half casing portion 102b such that the first wick portion 104a is coupled to the second wick portion 104b to form the heat transfer device 100. A sealed chamber 106 is formed between the first half casing portion 102a and the second half casing portion 102b. The heat transfer device 100 includes a casing 102 having a wick 104 disposed within the casing 102. The first half and second half casing portions 102a, 102b are coupled to each other by brazing, soldering, or the like.

FIG. 7 is a schematic flow diagram illustrating the method 360 of manufacturing an additional third sintered layer portion 140a on the second sintered layer portion 128a within the first half casing portion 102a in accordance with the embodiment of FIGS. 2a, 2b, and 3.

The method 360 includes a step 196 of disposing the first half casing portion 102a having the first sintered layer portion 126a and the second sintered layer portion 128a. The method 360 further includes a step 200 of filling the plurality of third particles 198 within the first half casing portion 102a. Specifically, the plurality of third particles 198 are filled on the second sintered layer portion 128a. The method 360 further includes a step 202 of leveling the plurality of third particles 198 within the first half casing portion 102a so as to form a third layer portion 204a having a uniform thickness T₀₃. The squeegee device 172 having the uniform contact surface 171 is used for leveling the plurality of third particles 198.

The method 360 further includes a step 206 of sintering the third layer portion 204a. The sintering step 206 includes disposing the sintering spacer 184 on the third layer portion 204a and disposing the first half casing portion 102a including the sintering spacer 184, in the sintering device 188 to sinter the third layer portion 204a so as to generate the third sintered layer portion 140a. The sintering spacer 184 having a uniform contact surface 187, is used to generate the third sintered layer portion 140a having the uniform thickness “T₃”. The third sintered layer portion 140a includes the plurality of third sintered particles 154 having the third porosity 158 and the plurality of third pores 156 (as shown in FIG. 4b). The sintering process is performed in a controlled environment so as to generate the third porosity 158 smaller than the second porosity 152. The third sintered particle 154 has a size less than or equal to the size of the second sintered particle 144.

The steps 196, 200, 202, and 206 are repeated in the second half casing portion 102b to generate another third sintered layer portion 140b.

FIG. 8 is a flow diagram illustrating a method 208 of manufacturing the second sintered layer portion 129a having a non-uniform thickness in accordance with the embodiment of FIG. 5a.

The method 208 includes a step 210 of forming a second layer portion 179a having a non-uniform thickness on a first layer portion 177a having a uniform thickness “T₀₄”. The step 210 includes leveling a plurality of second particles 167 using a squeegee spacer 212 having a uniform contact surface 214. Two smaller squeegee spacers 173, 175 are disposed on the second layer portion 179a corresponding to the position of the evaporator section 111 and the condenser section 113. The squeegee spacer 212 is disposed on the second layer portion 179a and contacting the two smaller squeegee spacers 173, 175 so as to form the second layer portion 179a having a non-uniform thickness. The second layer portion 179a has a thickness “T₀₅” for the evaporator section 111, a thickness “T₀₆” for the condenser section 113, and a thickness “T₀₇” for the transport section 115. The squeegee spacers 212, 173, 175 may be made of a material including nickel-cobalt ferrous alloy or ceramics such as aluminum nitrate, alumina, silicon carbide, and silicon nitride.

The method 208 further includes a step 216 of generating the second sintered layer portion 129a having a non-uniform thickness over the first sintered layer portion 127a having the uniform thickness “T₄”. The step 216 includes replacing the squeegee spacer 212 with a first sintering spacer 213 having a uniform contact surface 218 and the two smaller squeegee spacers 173, 175 with second sintering spacers 183, 185. The process further includes sintering the second layer portion 179a having non-uniform thickness to form the second sintered layer portion 129a. The second sintered layer portion 129a has the thickness “T₅” for the evaporator section 111, the thickness “T₆” for the condenser section 113, and the thickness “T₇” for the transport section 115. The sintering spacers 213, 183, 185 may be made of a material including nickel-cobalt ferrous alloy or ceramics such as aluminum nitrate, alumina, silicon carbide, and silicon nitride.

FIG. 9 is a flow diagram illustrating a method 220 for manufacturing a second sintered layer portion 229a having a non-uniform thickness in accordance with another embodiment.

The method 220 includes a step 222 for forming a second layer portion 228a having a non-uniform thickness, using a squeegee device 226 having a non-uniform contact surface 224. The non-uniform contact surface 224 of the squeegee device 226 is disposed over the second layer portion 228a and the squeegee device 226 is actuated so as to form the second layer portion 228a having a non-uniform thickness. The second layer portion 228a has a thickness “T₀₁₁” corresponding to the position of an evaporator section 221, a thickness “T₀₁₂” corresponding to the position of a condenser section 223, and a thickness “T₀₁₃” corresponding to the position of a transport section 225. The squeegee device 226 having the non-uniform contact surface 224 may be manufactured by milling.

The method 220 further includes a step 230 of generating the second sintered layer portion 229a having a non-uniform thickness. The process 230 includes replacing the squeegee device 226 with a sintering spacer 232 having a non-uniform contact surface 234 and sintering the second layer portion 228a in a sintering device to form the second sintered layer portion 229a having the non-uniform thickness. The second sintered layer portion 229a has a thickness “T₁₁” corresponding to the evaporator section 221, a thickness “T₁₂” corresponding to the position of the condenser section 223, and a thickness “T₁₃” corresponding to the position of the transport section 225. The sintering spacer 232 having the non-uniform contact surface 234 may also be manufactured by milling

FIG. 10 is a schematic flow diagram illustrating a method 236 of manufacturing a third sintered layer portion 141a having a non-uniform thickness in accordance with the embodiment of FIG. 5b.

The method 236 includes a step 238 of forming a third layer portion 240a having a non-uniform thickness. A plurality of third particles 246 is disposed on the second sintered layer portion 129a. A squeegee device 244 having a non-uniform contact surface 242, is actuated over the plurality of third particles 246 so as to form a third layer portion 240a having a non-uniform thickness. The third layer portion 240a has a thickness “T₀₈” corresponding to the position of the evaporator section 111, a thickness “T₀₉” corresponding to the position of the condenser section 113, and a thickness “T₀₁₀” corresponding to the position of the transport section 115. The method 236 further includes a step 248 of generating the third sintered layer portion 141a having a non-uniform thickness. The step 248 includes replacing the squeegee device 244 with a sintering spacer 252 having a non-uniform surface 254 for sintering the third layer portion 240a to form the third sintered layer portion 141a. The third sintered layer portion 141a has the thickness “T₈” corresponding to the position of the evaporator section 111, the thickness “T₉” corresponding to the position of the condenser section 113, and the thickness “T₁₀” corresponding to the position of the transport section 115.

Embodiments of the present disclosure discussed herein facilitate easy and economic manufacturing of the heat transfer device. Further, the heat transfer device of the present disclosure provides lower thermal resistance, higher thermal conductivity, and higher heat transport capability.

Claims

1. A heat transfer device comprising:

a casing having an inner surface and an outer surface; and

a wick disposed within the casing; wherein the wick comprises: a first sintered layer comprising a plurality of first sintered particles, having a first porosity and a plurality of first pores, disposed proximate to the inner surface of the casing; and a second sintered layer comprising a plurality of second sintered particles, having a second porosity and a plurality of second pores, disposed on the first sintered layer; wherein at least one first sintered particle is smaller than at least one second pore and the first porosity is smaller than the second porosity.

2. The heat transfer device of claim 1, wherein each first pore has a size in a range of ten nanometers to ten micrometers.

3. The heat transfer device of claim 1, wherein each second pore has a size in a range of one micrometer to fifty micrometers.

4. The heat transfer device of claim 1, wherein each first sintered particle has a size in a range of hundred nanometers to fifty micrometers.

5. The heat transfer device of claim 1, wherein each second sintered particle has a size in a range of ten micrometers to hundred micrometers.

6. The heat transfer device of claim 1, wherein the first porosity is in a range of five percent to forty percent.

7. The heat transfer device of claim 1, wherein the second porosity is in a range of eight percent to twenty percent.

8. The heat transfer device of claim 1, wherein the wick further comprises a third sintered layer including a plurality of third sintered particles, having a third porosity and a plurality of third pores, disposed on the second sintered layer

9. The heat transfer device of claim 8, wherein each third pore has a size in a range of one nanometer to ten micrometers.

10. The heat transfer device of claim 8, wherein the third porosity is in a range of twenty percent to eighty percent.

11. The heat transfer device of claim 8, wherein each third sintered particle has a size in a range of hundred nanometers to ten micrometers.

12. The heat transfer device of claim 8, wherein a size of each third sintered particle is less than or equal to a size of each second sintered particle.

13. The heat transfer device of claim 8, wherein the casing, the plurality of first sintered particles, the plurality of second sintered particles, and the plurality of third sintered particles comprise a same material.

14. The heat transfer device of claim 1, wherein the first sintered layer is disposed contacting the inner surface of the casing.

15. The heat transfer device of claim 1, further comprising a coating disposed between the first sintered layer and the inner surface of the casing.

16. The heat transfer device of claim 15, wherein the casing comprises a first material and the first sintered layer, the second sintered layer, and the coating comprises a second material different from the first material.

17. The heat transfer device of claim 1, further comprising an evaporator section, a transport section, and a condenser section within the casing, wherein the wick has a uniform thickness extending along the evaporator section, the transport section, and the condenser section.

18. The heat transfer device of claim 1, further comprising an evaporator section, a transport section, and a condenser section within the casing, wherein the wick has a non-uniform thickness extending along the evaporator section, the transport section, and the condenser section.

19. A method comprising:

filling a plurality of particles within a first half casing portion, wherein the plurality of particles comprises a plurality of first particles and a plurality of second particles;

leveling the plurality of first and second particles within the first half casing portion;

vibrating the first half casing portion to segregate the plurality of first particles from the plurality of second particles such that a first layer portion having the plurality of first particles, is disposed proximate to an inner surface of the first half casing portion and a second layer portion having the plurality of second particles is disposed on the first layer portion;

sintering the first layer portion and the second layer portion to generate a first sintered layer portion including a plurality of first sintered particles, having a first porosity and a plurality of first pores, and a second sintered layer portion including a plurality of second sintered particles, having a plurality of second pores and a second porosity greater than the first porosity, wherein at least one first sintered particle is smaller than at least one second pore, and the first sintered layer portion and the second sintered layer portion together form a first wick portion;

repeating the filling, the leveling, the vibrating, and the sintering process in a second half casing portion to form a second wick portion within the second half casing portion; and

coupling the first half casing portion to the second half casing portion such that the first wick portion is coupled to the second wick portion to form a heat transfer device.

20. The method of claim 19, wherein the leveling further comprises forming a uniform thickness of the plurality of first and second particles along an evaporator section, a transport section, and a condenser section of the first half casing portion.

21. The method of claim 19, wherein the leveling further comprises forming a non-uniform thickness of the plurality of first and second particles along an evaporator section, a transport section, and a condenser section of the first half casing portion.

22. The method of claim 19, wherein the sintering further comprises disposing a sintering spacer having a non-uniform contact surface on the second layer portion.

23. The method of claim 19, wherein the sintering further comprises:

disposing a first sintering spacer having a uniform contact surface on the second layer portion; and

disposing at least one second sintering spacer between the uniform contact surface of the first sintering spacer and the second layer portion.

24. The method of claim 19, further comprises performing filling, leveling, and sintering of a third layer portion having a plurality of third particles disposed on the second sintered layer portion to generate a third sintered layer portion including a plurality of third sintered particles, having a plurality of third pores, and a third porosity, on the second sintered layer portion, wherein a size of each third sintered particle is less than or equal to a size of each second sintered particle.

25. The method of claim 19, further comprising applying a coating on the inner surface of the first half casing portion before filling the plurality of first and second particles in the first half casing portion, wherein the first half casing portion comprises a first material and the plurality of first and second particles and the coating comprise a second material different from the first material.