Graphics Cards Passive Cooling Solution from SPARKLE
 

 

 

 

 

  
  Before refrigeration technology first appeared, people kept cool using natural methods: breezes flowing through windows, water evaporating from springs and fountains as well as large amounts of stone and earth absorbing daytime heat. These ideas were developed over thousands of years as integral parts of building design. Today they are called "passive cooling." Ironically, passive cooling is considered an "alternative" to mechanical cooling that requires complicated refrigeration systems. By employing passive cooling techniques into modern graphics cards products, you can eliminate mechanical cooling, reduce the size and cost of the cooling equipment, such as cooling fans or water block, to create a undisturbed working environments. Now SPARKLE Computer Co., Ltd., the professional VGA card manufacturer and supplier, provides advanced passive cooling technology for SPARKLE Graphics Cards based on GeForce 7 and GeForce 8 series GPUs.

SPARKLE Graphics Cards Cooling Solutions Using Heat Sink
  Aiming at SPARKLE Graphics Cards which have lesser working heat radiation, SPARKLE introduces elaborately made heat sink as passive cooling solution. A heat sink for SPARKLE series graphics card is a object that absorbs and dissipates heat from GPU using thermal direct contact. Heat sinks are used in SPARKLE GeForce 7 series graphics cards wherever efficient heat dissipation is required.

    The most common design of a graphics card heat sink is a metal device with many fins. The high thermal conductivity of the metal combined with its large surface area result in the rapid transfer of thermal energy to the surrounding, cooler, air. This cools the heat sink and whatever it is in direct thermal contact with.
    Graphics Cards' heat sink performance is a function of material, geometry, and overall surface heat transfer coefficient. Generally, forced convection heat sink thermal performance is improved by increasing the thermal conductivity of the heat sink materials, increasing the surface area (usually by adding extended surfaces, such as fins or foam metal).A Graphics Cards' heat sink usually consists of a base with one or more flat surfaces and an array of comb or fin-like protrusions to increase the heat sink's surface area contacting the air, and thus increasing the heat dissipation rate.
    Graphics Cards' heat sinks are made from a good thermal conductor such as copper or aluminum alloy. Copper (401 W/(m¡PK) at 300 K) is significantly more expensive than aluminum (237 W/(m¡PK) at 300 K) but is also roughly twice as efficient as a thermal conductor. Aluminum has the significant advantage that it can be easily formed by extrusion, thus making complex cross-sections possible. The heat sink's contact surface (the base) must be flat and smooth to ensure the best thermal contact with the Graphics Cards' GPUs needing cooling. Frequently thermally conductive grease is used to ensure optimal thermal contact; such compounds often contain colloidal silver. Further, a clamping mechanism, screws, or thermal adhesive hold the heat sink tightly onto the Graphics Cards' PCB, but specifically without pressure that would crush the PCB.
SPARKLE Graphics Cards Cooling Solutions Using Heat Pipe
   With the complexity of GeForce 8 series GPU increase, SPARKLE GeForce 8 series Graphics Cards need greater cooling, and the inherently hotter chips meant more concerns for the enthusiast. More efficient cooling devices are vital to the success of fanless stable operations and overclocking, because the higher a GeForce 8 Graphics Card's cooling rate, the faster the card can operate without instability; generally, faster operation leads to higher performance. SPARKLE now competes to offer the best passive cooling device based on Heat Pipe technology for GeForce 8 and DirectX 10 gaming enthusiasts.

    A heat pipe for SPARKLE GeForece 8 Graphics Cards is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hotter and colder interfaces. Inside a heat pipe, at the hot interface a fluid turns to vapour and the gas naturally flows and condenses on the cold interface. The liquid falls or is moved by capillary action back to the hot interface to evaporate again and repeat the cycle.

    A typical heat pipe used on SPARKLE GeForce 8 series Graphics Cards consists of a sealed hollow tube. A thermo conductive metal such as copper is used to make the tube. The pipe contains a relatively small quantity of a "working fluid" or coolant (such as water, ethanol or mercury) with the remainder of the pipe being filled with vapour phase of the working fluid, all other gases being excluded.

   On the internal side of the tube's side-walls a wick structure exerts a capillary force on the liquid phase of the working fluid. This is typically a sintered metal powder or a series of grooves parallel to the tube axis, but it may in principle be any material capable of exerting capillary pressure on the condensed liquid to drive it back to the heated end. If the heat pipe has a continual slope with the heated end down, no inner lining is needed. The working fluid simply flows back down the pipe. This type of heat pipe is known as a thermosiphon or a Perkins Tube, after Jacob Perkins.

   A typical heat pipe used in SPARKLE GeForce 8 series Graphics Cards contains no moving parts and typically requires no maintenance, though non-condensing gases that diffuse through the pipe's walls, result from breakdown of the working fluid, or exist as impurities in the materials of construction, may eventually reduce the heat transfer effectiveness. This is particularly acute when the working fluid's vapour pressure is low.

  The materials and coolant chosen in design depend on the temperature conditions in which the heat pipe must operate, with coolants ranging from liquid helium for extremely low temperature applications (2-4K) to mercury (523-923K) & sodium (873-1473K) and even indium (2000-3000K) for extremely high temperature conditions. However, the vast majority of heat pipes for low temperature applications use some combination of ammonia (213-373K), alcohol (methanol (283-403K) or ethanol (273-403K)) or water (303-473K) as working fluid.
Hear pipe thermal cycle

1.) Working fluid evaporates to vapour absobing thermal energy.
2.) Vapour migrates along cavity to lower temperature end.
3.) Vapour condenses back to fluid and is absorbed by the wick,releasing thermal energy.
4.) Working fluid flows back to higher temperature end.
 
   The advantage of heat pipe used in SPARKLE GeForce 8 series Graphics Cards heat is its great efficiency in transferring heat. They are actually a vastly better heat conductor than an equivalent cross-section of solid copper. Heat flows of more than 230 MW/m^2 have been recorded (nearly 4 times the heat flux at the surface of the sun). A level of control over the total pressure in the heat pipe can be obtained by controlling the amount of working fluid. Water, for instance, expands 1600 times when it vaporizes at 1 atmosphere. If 1/1600 of the volume of a heat pipe is filled with water, when all the fluid is just vaporized, the pressure will be one atmosphere. If the safe working pressure of the pipe in question is, say, 5 atmospheres, one could use a quantity of water equal to 5/1600 of the total volume. Active control of heat flux can be affected by adding a variable volume liquid reservoir to the evaporator section. Variable conductance heat pipes employ a large reservoir of inert immiscible gas attached to the condensing section. Varying the gas reservoir pressure changes the volume of gas charged to the condenser which in turn limits the area available for vapor condensation. Thus a wider range of heat fluxes and temperature gradients can be accommodated with a single design.