VC-90-90-3

PHASE CHANGE Heat Pipe Selection Guide ............................................ 126–131 Vapor Chamber Design Guide ........................................ 132–137 Fluid Phase Change applications, often referred to as “re-circulating,” use closed loop heat pipes to transfer heat quickly through evaporation and condensation within the heat pipe. Because of their high thermal efficiency, heat pipes are often designed into advanced heat sink technologies when increased thermal density or physical size restrictions exist. This similar process is utilized in vapor chamber technology as well. PHASE CHANGE 124 125 PHASE CHANGE PHASE CHANGE HEAT PIPE SELECTION GUIDE WHY USE HEAT PIPES? HEAT PIPE INTRODUCTION Heat pipes are used to transport heat over a distance with very low thermal resistance. This is very helpful when small or distant heat sources need to be dissipated over a larger area or moved to a remote heat exchanger. Heat pipes are a Fluid Phase Change application, often referred to as “re-circulating,” because they use a closed loop to transfer heat quickly through evaporation and condensation within the heat pipe. Heat pipes have proven to be robust and reliable over many years in these types of applications. The next section will give more technical detail on the performance of heat pipes depending on diameter, length, and angle of use. Many thermal systems benefit from the addition of heat pipes, especially when heat sources are dense and/or remote to the final heat exchanger. Computer applications, such as processors, graphics cards and other chip-sets, have high thermally dissipated power in a small area. Fan heat sink combinations used in these applications can offer high-performance dissipation to the ambient, but much of the battle is to bring the heat to the heat exchanger with as little temperature change as possible. Heat pipes excel at this and can transport large heat loads from small areas with very little temperature difference. Heat pipes do not actually dissipate the heat to the environment, but serve to move heat efficiently within a thermal system. A heat pipe is a copper tube with an internal wick structure that is sealed on both ends with a small amount of water inside. As heat is applied to the pipe, the water will boil and turn to a gas, which then travels to the colder section of the heat pipe where it condenses back to a liquid. It is the evaporating and condensing of the water that form a pumping action to move the water (and thus the heat) from end to end of the pipe. There are many types of wick structure that can be used within the heat pipe and they are generally classified into grooved, mesh, powder and hybrid. Heat pipes are used in many harsh environments such as: • • • • Telecommunications Aerospace Transportation Computers and Data Centers KEY FEATURES • • • • Material: Copper Wick Structure: Powder Sintered Copper Light Weight Versatile with high thermal performance HOW HEAT PIPES OPERATE A grooved heat pipe is a copper tube with a series of shallow grooves around the internal perimeter of the heat pipe. While the water is a liquid, it travels in the grooves and while it is a vapor it travels in the open space of the pipe. Grooved pipes can be used in horizontal orientations, but are very limited in performance if used above 15° out of horizontal. GROOVED HEAT PIPE 1 A mesh heat pipe is a smooth wall copper tube with a woven copper mesh installed along the interior of the pipe. The mesh is designed to remain in contact with the walls of the pipe in areas where the pipe may be bent or flattened. Mesh pipes can be used in horizontal and orientations up to 30° out of horizontal. 3 2 5 4 Heat Source MESH HEAT PIPE 1. 2. 3. 4. 5. 6. A powder wick heat pipe can also be known as a sintered heat pipe. During the manufacturing process a mandrel is installed in the center of the pipe and copper powder is poured into the pipe around the mandrel. After the powder is sufficiently packed, the parts are placed into a sintering oven. Once at temperature, the copper powder will stick to the pipe and to itself, forming numerous internal pockets like a sponge. Because of the small pocket sizes, sintered pipes can efficiently move the water and can be used horizontally, vertically and all points in between including upside down. Working fluid absorbs heat while evaporating to vapor Vapor transfers along the cavity to the lower temperature area Vapor condenses back to fluid, discharging heat Fluid is absorbed by the sintered/powdered wick structure Fluid returns to high temperature end via capillary force in the wick structure Natural or forced convection air flow dissipates excess heat to ambient 6 POWDER WICK HEAT PIPE 126 Wakefield-Vette primarily sells sintered, or powder, style heat pipes due to their higher performance and the best heat pipe for your application. 127 PHASE CHANGE PHASE CHANGE HEAT PIPE SELECTION GUIDE FLATTENING HEAT PIPES HEAT PIPE BASICS When selecting the diameter and length of heat pipe it is important to consider the orientation with respect to gravity and overall heat load for the thermal system. The transport of vapor within the heat pipe is responsible for the thermal conduction from one end to the other. A larger diameter heat pipe can transport more vapor, translating into a larger heat carrying capacity. Also, the orientation of the pipe with respect to gravity plays a role in the thermal capacity of a heat pipe. HEAT PIPE BASICS • • • • • Picking the correct pipe Transport General parameters Bending Flattening When selecting the diameter and length of heat pipe it is important to consider the orientation with respect to The thermal capacity is increased when the heat source is lower than the condenser (or ambient heat exchanger) because gravity assists the return of condensed water back to the heat source. The opposite is also true as the thermal capacity is reduced when the condensed water must move by capillary forces back to the heat source against gravity. This effect is exaggerated with longer heat pipes and testing has shown that the gravity effect can nearly the double the thermal capacity in the advantageous direction and cut the capacity in half in the deleterious direction from the heat pipe in the horizontal orientation. In the short heat pipe extreme (3”-4” length), this effect is nearly zero, so please consult with Wakefield-Vette engineers to find the right solution for your application. MAXIMUM HEAT TRANSFER TABLE (POWDER TYPE) Qmax Out Diameter Type Ф3mm Flatten 13.2 W t=2.0mm Flatten 13.2 W t=2.5mm Flatten 13.1 W t=3.0mm Round Pipe 13.2 W HEAT PIPE LENGTH = 150MM Out Diameter Out Diameter Ф4mm Ф5mm 16.6 W 20.5 W 19.8 W 23.6 W 34.0 W 51.5 W 19.8 W 28.4 W 39.2 W 67.5 W 19.8 W 30.1 W 48.1 W 74.2 W MAXIMUM HEAT TRANSFER TABLE (POWDER TYPE) Qmax Out Diameter Type Ф3mm Flatten 7.2 W t=2.0mm Flatten 8.1 W t=2.5mm Flatten 8.2 W t=3.0mm Round Pipe 9.0 W Out Diameter Out Diameter Ф6mm Ф8mm SIZE OF FLATTED HEAT PIPES Diameter (mm) 4mm 5mm 6mm 8mm Thickness (mm) 3 2.5 2 3.5 3 2 4 3.5 6 5 4 3 Width (mm) 4.65 5 5.23 5.97 6.25 6.83 7.3 7.58 9.35 9.95 10.5 10.99 Tolerance (mm) +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 +/- 0.15 Bending radius for heat pipes of different diameters depending on the method of bending. BENDING By Hand: • 4mm: 4 x diameter • 6mm: 4 x diameter • 8mm: 5 x diameter Tooling: • 4mm: 3 x diameter • 6mm: 3 x diameter • 8mm: 4 x diameter HEAT PIPE LENGTH = 250MM Out Diameter Out Diameter Ф4mm Ф5mm 10.1 W 12.2 W Out Diameter Out Diameter Ф6mm Ф8mm 11.2 W 13.1 W 16.5 W 23.0 W 12.1 W 14.1 W 22.0 W 37.0 W 12.3 W 15.6 W 29.3 W 45.0 W wakefield-vette.com 128 Flattening is another aspect of heat pipes that effect their performance. Often it is necessary to flatten a heat pipe to fit into a desired shape or gap or to increase the contact area of the pipe with the heat. Since flattening reduces the effective cross-sectional area of the round pipe, the thermal capacity is reduced, just as if a smaller diameter pipe was being used. The larger diameter of the starting heat pipe, the larger reduction of thermal capacity is seen when flattening. Also, the larger diameter pipes cannot be flattened to the same ultimate dimension as the smaller pipes without disrupting heat flow altogether. This is also true for bending of pipes. The radius of bending is usually 3-5x the diameter of the heat pipe depending on the pipe diameter and the process of bending the pipe. The potential danger is to collapse the pipe, effectively cutting off vapor and thermal transport. Contact us: (603) 635-2800 129 PHASE CHANGE PHASE CHANGE HEAT PIPE SELECTION GUIDE HEAT PIPE ASSEMBLIES WAKEFIELD-VETTE STANDARD HEAT PIPES Interfacing heat pipes with plates and heat exchangers is predominately about maximizing contact area while adhering to the flattening and bending guidelines mentioned above. In most cases, the heat pipes are slotted into channels/grooves in the plate to maximize contact. The heat pipe can be secured into the groove using solder or thermal epoxy, which also augments the contact area of the heat pipe. The heat pipe can also be clamped between two plates with matching channels/ grooves which are fastened together. In the clamped configuration, thermal grease can be used to increase the contact of the heat pipe to the plates to reduce the thermal resistance of the contact interface, just as the thermal epoxy and solder did in the prior example. Vapor transports heat from evaporator to condenser. Condensed liquid flows back to evaporator through capillary action. Heat pipe dissipates thermal power to fins/ heat exchanger and condenses vapor to liquid. Wakefield-Vette offers individual Heat Pipes through distribution. These most common offerings are a great option for testing, sampling, and validating your heat pipe solution into eventual production. When building or testing your heat sink assembly please feel free to contact one of Wakefield Vette’s authorized distributors to purchase. Always remember to contact us for free consultation on assembly design or parameter questions. Wakefield-Vette Part Number 121686 121687  121688 110578 110579 110580 110581 110582 121968  110583 110584 110585 121689 121690 121691  121692  121716 121717 121718 121719 121720 121721 121722 121723 121724 121725 121726 121727  121728  121729  120231 120229 Description Round Heat Pipe 4 x 70mm Round Heat Pipe 4 x 100mm Round Heat Pipe 4 x 150mm  Round Heat Pipe 6 x 100mm Round Heat Pipe 6 x 150mm Round Heat Pipe 6 x 200mm Round Heat Pipe 6 x 250mm Round Heat Pipe 6 x 300mm Round Heat Pipe 8 x 100mm Round Heat Pipe 8 x 200mm Round Heat Pipe 8 x 250mm Round Heat Pipe 8 x 300mm Round Heat Pipe 10 x 100mm Round Heat Pipe 10 x 200mm Round Heat Pipe 10 x 250mm Round Heat Pipe 10 x 300mm Flat Heat Pipe 2.5 x 100mm Flat Heat Pipe 2.5 x 150mm Flat Heat Pipe 2.5 x 200mm Flat Heat Pipe 2.5 x 250mm Flat Heat Pipe 3 x 100 mm Flat Heat Pipe 3 x 150 mm Flat Heat Pipe 3 x 200 mm Flat Heat Pipe 3 x 250 mm Flat Heat Pipe 3 x 300 mm Flat Heat Pipe 4.5 x 100mm Flat Heat Pipe 4.5 x 150 mm Flat Heat Pipe 4.5 x 200 mm  Flat Heat Pipe 4.5 x 250 mm  Flat Heat Pipe 4.5 x 300 mm  Ultra Thin 6MM DIA X 1.50MM Ultra Thin 5MM DIA X 1.00MM Embedded heat pipe in plate absorbs heat through vaporization of liquid. wakefield-vette.com 130 Contact us: (603) 635-2800 131 PHASE CHANGE PHASE CHANGE VAPOR CHAMBER DESIGN GUIDE WHY USE VAPOR CHAMBERS? VAPOR CHAMBER INTRODUCTION Vapor Chambers are used to transport heat over a distance with very low thermal resistance. This is very helpful when small heat sources need to be dissipated over a larger area. Vapor chambers are a Fluid Phase Change application because they use a closed loop to transfer heat quickly through evaporation and condensation within the chamber. The particular aspect useful in designs is that vapor chambers transport heat in a plane, more effectively “spreading heat” compared to a heat pipe which transports heat over a distance in a straight line. Vapor chambers, like heat pipes, do not actually dissipate the heat to the environment, but serve to move heat efficiently within a thermal system. A vapor chamber is made from copper plates (top and bottom) with an internal wick structure that is sealed around the perimeter with a small amount of water inside. As heat is applied to the chamber, the water will boil and turn to a gas, which then travels to the colder section of the vapor chamber, where heat is dissipated through an external heat exchanger, where it condenses back to a liquid. It is the evaporating and condensing of the water that form a pumping action to move the water (and thus the heat) from the area of the heat source to all other areas of the vapor chamber. There are a few types of wick structure that can be used within the vapor chamber, but most commercial chambers are classified as mesh or powder. In both cases, the powder or mess line the copper plate surfaces to allow water flow to/from all directions within the area of the vapor chamber. Often, when mesh is used as the wick structure, different sized meshes are used together to promote condensation or transport of liquid depending on the void size. Vapor chambers are best used in horizontal orientations. The effects of gravity may vary depending on application and orientation, but one must consider lower performance if used above 15° out of horizontal. TOP COPPER PLATE TOP WICK (COPPER MESH) COPPER COLUMNS WORKING FLUID BOTTOM WICK (COPPER MESH) BOTTOM COPPER PLATE wakefield-vette.com 132 During the manufacturing process copper columns are used throughout the vapor chamber to support the plates that act as the lids and contain the liquid and vapor. The copper mesh is oriented within the chamber pressed against the copper plates. The plates are sealed around the perimeter via diffusion bonding. In some cases, soldering or welding are used, but diffusion bonding allows for the strongest and highest temperature compatible seal for the vapor chamber. The diffusion bonding process also allows the mesh to bond to the copper plates as well. Vapor chambers have proven to be robust and reliable over many years in these types of applications. The next section will give more technical detail on the performance of vapor chambers depending on thickness and area. Many thermal systems benefit from the addition of vapor chambers, especially when heat sources are dense and the final heat exchanger is much larger and the heat from the source must be spread to a larger area effectively to efficiently use the heat exchanger. Computer applications, such as processors, graphics cards and other chip-sets, have high thermally dissipated power in a small area. Fan heat sink combinations used in these applications can offer high-performance dissipation to the ambient, but much of the battle is to spread the heat to the heat exchanger with as little temperature change as possible. Vapor chambers excel at this and can transport large heat loads from small areas with very little temperature difference. Vapor chambers are used in many harsh environments such as: • Computers and Data Centers • Telecommunications • Aerospace • Transportation KEY FEATURES • • • • Material: Copper Wick Structure: Copper Mesh Light Weight Versatile with high thermal performance HOW VAPOR CHAMBERS OPERATE COOLING HEAT EXCHANGER FINS VAPOR CHAMBER HEAT SOURCE COPPER COLUMN MESH WICK Contact us: (603) 635-2800 133 PHASE CHANGE PHASE CHANGE VAPOR CHAMBER DESIGN GUIDE VAPOR CHAMBERS THERMAL CAPACITY VAPOR CHAMBER BASICS VAPOR CHAMBER BASICS When considering the use of a vapor chamber in your application, it is important to consider the orientation with respect to gravity and overall heat load for the thermal system. The transport of vapor within the vapor chamber is responsible for the thermal conduction from one area to the other. A thicker vapor chamber can transport more vapor, translating into a larger heat carrying capacity. Although vapor chambers can have complex shapes and mounting features, they are not typically bent and integration can be more direct with the heat source than with heat pipes. • Comparison to Heat Pipes • Transport • General parameters VAPOR CHAMBER HEAT PIPE Theory 2-Phase heat transfer 2-D heat distribution. Spreading heat by a single vapor chamber. Suitable for large heat flux and high power. Complex shape in X and Y direction with pedestal. Mounted with through-holes in vapor chamber Direct contact. Mounting pressure to 90PSI T=5mm > 400W; T=3mm > 200W; T=1mm > 60W Vapor chamber has larger tooling cost so high volume applications can lower cost to ~2X heat pipe. However, solution may need only 1 vapor chamber compared to many heat pipes and fixture/base plates. Much like heat pipes, the ultimate dimension in determining heat carrying capacity of a vapor chamber is the volume of the vapor space. This is determined by the thickness and area of the vapor chamber. For most applications, the thickness of the vapor chamber does not exceed 3mm, however pedestals and other surface features can be used to contact specific heat sources while leaving clearance for other board mounted objects. These pedestals can be extended 5mm from the vapor chamber lid plate. Mounting holes can also be integrated within the area of the vapor chamber for better integration with the heat source and locating the heat source a the center of the vapor chamber with good pressure application. Application Shape Fixtures Heat Source Contact Qmax Cost 2-Phase heat Transfer 1-D heat distribution. Using one or more heat pipes to spread heat. Suitable for long distance between heat source and heat exchanger. HEAT CARRYING CAPACITY (Q-MAX) BY VAPOR CHAMBER THICKNESS Round, flattened or bent in any direction. Additional fixure plates needed to mount heat pipes. A base plate required to contact the heat source unless flattened/machined. Ø5 > 20W; Ø6 > 40W; Ø8 > 60W Lower cost for a single heat pipe, but may also need tooling cost for bending/flattening.  45*45 90*90 120*120 150*150 200*200 250*250 300*300 1.0mm 10W 40W 40W 1.2mm 15W 50W 50W 1.5mm 2.0mm 2.3mm 2.5mm 3.0mm >3.0mm 20W 25W 60W 80W 100W >100W 80W 100W 150W 180W 250W >300W 80W 100W 160W 200W 275W >300W 80W 100W 170W 220W 300W >300W 100W 175W 225W >300W >300W 180W 240W >300W >300W >300W Note: Heat source = 30*30mm This table is for reference. Q-max is related to heat source power density and effectiveness of final heat exchanger. In many applications, the decision to use a vapor chamber is frequently compared to a thermal solution using heat pipes. In both cases, 2-phase transport is used as a vapor moves heat within the chamber or pipe and the liquid is condensed at the heat exchanger and transported back to the heat source. However, the main aspects of applications that differentiate vapor chambers from heat pipes are: • • High power density: when the heat source is small but heat generation is large, vapor chambers can more easily transport the heat to a larger area. A heat pipe solution would require multiple pipes, which may be difficult to integrate within the footprint of the heat source. High power: when the application must dissipate large wattage, a vapor chamber spreads the heat to a large area efficiently with similar temperatures of the chamber surface. This allows more efficient use of the final heat exchanger since hot spots are minimized. Heat pipes can also spread the heat, but unless many are ganged together, the hot spots may still persist. wakefield-vette.com 134 Contact us: (603) 635-2800 135 PHASE CHANGE PHASE CHANGE VAPOR CHAMBER DESIGN GUIDE WAKEFIELD-VETTE STANDARD VAPOR CHAMBERS VAPOR CHAMBER ASSEMBLIES Interfacing vapor chambers with plates and heat exchangers is predominately about maximizing contact area. In most cases, the vapor chambers are soldered to heat exchanger fins for air cooled applications. The vapor chambers can also be soldered to liquid cold plates to take advantage of spreading the heat before final heat exchange with the liquid. In many cases, the vapor chambers are also integrated with heat pipes to take the heat that has spread in the plane of the vapor chamber and extend it in the vertical dimension to more efficiency interact with cooling fins. Integrating with the heat source is most commonly done with pressure, up to 90 psi, and the use of a thermal grease or other interface material to maximize surface area contact to the source. Wakefield-Vette offers individual vapor chambers through distribution. These most common offerings are a great option for testing, sampling, and validating your vapor chamber solution into eventual  production. When building or testing your heat sink assembly please feel free to contact one of Wakefield-Vette’s authorized distributors to purchase. Always remember to contact us for free consultation on assembly design or parameter questions. WKV Part # VC-1131-8175-517 VC-90-90-3 VC-106-70-3 VC-106-82-3 Product Description Thermal Resistance Length Width Thickness qMax Standard Vapor Chamber 113.1mm x 81.75mm X 5.17mm 0.145 113.1 81.75 5.7 180W~ Standard Vapor Chamber 90mm x 90mm x 3.00mm 0.143 90 90 3 150W~ Standard Vapor Chamber 106mm x70mm x 3mm 0.150 106 70 3 150W~ Standard Vapor Chamber 106mm x 82mm x 3mm 0.140 106 82 3 150W~ PART NUMBER VC-1131-8175-517 Product Info Description Dimension(mm): L: 113mm / W: 81.8mm / T: 5.7mm Operation Power: 180W~ Product Info Details Thermal Resistance: 0.145°C/W Operation Temp: 40~130°C Platform : VGA PART NUMBER VC-90-90-3 Product Info Description Dimension(mm): L: 90mm / W: 90mm / T: 3mm Operation Power: 150W~ PART NUMBER VC-106-70-3 2 TYPES OF FILLING PORTS (7MM MAXIMUM): RETRACTED Product Info Details Thermal Resistance: 0.143°C/W Operation Temp: 40~140°C Platform : Intel 2011 Square CHAMFER Product Info Description Dimension(mm): L: 106mm / W: 70mm / T: 3mm Operation Power: 150W~ Product Info Details Thermal Resistance: 0.150°C/W Operation Temp: 40~140°C Platform : Intel 2011 Narrow PART NUMBER VC-106-82-3 Product Info Description Dimension(mm): L: 106mm / W: 82mm / T: 3mm Operation Power: 150W~ wakefield-vette.com 136 Product Info Details Thermal Resistance: 0.140°C/W Operation Temp: 40~140°C Platform : Intel 2011 Narrow Contact us: (603) 635-2800 137