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Topic: Heat pipe

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	What is a Heat Pipe?
		The heat transport capability of the heat pipe is raised by increasing the wick thickness.
		Heat pipe has been, and is currently being, studied for a variety of applications, covering almost the entire spectrum of temperatures encountered in heat transfer processes.
		Heat pipes designed to move 75 watts are usually flat with fin stacks from three to six inches, in many cases with fins mounted on each side of the CPU input pad.
	www.cheresources.com /htpipes.shtml (0 words)

	Heat pipe cooled probe - Patent 4485670
		Heat is dissipated from the condenser region and fins 20 causing condensation of the working fluid, which returns to the probe by gravity and the capillary action of the wick 18.
		Heat can be dissipated by any of several means, for this particular application heat is dissipated by radiation and free-convection from fins attached to the cool end of the heat pipe.
		Heat is conducted by the condenser structure 15 and dissipated by convection and radiation from the condenser structure 15 and fins 20 causing the vapor to condense.
	www.freepatentsonline.com /4485670.html (0 words)

	Cooling - Methods and Madness
		One end of the heat pipe is the hot end or evaporator section; the rest of the heat pipe is the cool, or condenser section.
		When it reaches the far end of the pipe, where the pipe is typically embedded in a heat sink, the fluids shed heat as the fluid is condenses into the wicking medium, and the fluid travels back to the hot end through the wick, and the process begins again.
		Heat pipes can even be bent to the desired shape; in fact this is a necessary part of some applications, where the pipe is bent to allow more of the pipe to be in contact with the heat source or sink.
	www.overclockers.com /tips90/index03.asp (0 words)

	Greening EPA: Heat Pipe Effectiveness Study
		A heat pipe dehumidification system is a passive device which uses a series of closed tubes filled with refrigerant to transfer heat from the outside supply air to the supercooled post-cooling coil air.
		By recording heat pipe and cooling coil loads for 15-minute intervals during a two-week monitoring period, it was determined that the heat pipe pre-cooling load, and subsequent reheat load, increases linearly with outside temperature.
		For a seven-day period prior to the heat pipe installation (August 29 - September 4, 1996), the air temperature in room 10 was between 69 F and 73 F, and the relative humidity was between 73% and 80% (average 77.5%).
	www.epa.gov /oaintrnt/content/energy/hpipe.htm (4280 words)

	TRANSTERM Web Site - Overview of Heat Pipe Basics
		The first heat pipe that Grover built used water as the working fluid and was followed shortly by a liquid sodium heat pipe for operation at 1100 °K. Both the high temperature and ambient temperature regimes were soon explored by many workers in the field.
		A heat pipe is a hermetically sealed evacuated tube normally containing a mesh or sintered powder wick and a working fluid in both the liquid and vapor phase.
		The heat pipe, because of its effectiveness in heat transfer, is a prime candidate for applications involving the conservation of energy, and has been used to advantage in heat recovery systems, and energy conversion devices.
	www.transterm.ro /overview.htm (3259 words)

	Heat Pipe Reliability in High-Power Applications
		Heated gas moves to the cold end of the heat pipe at nearly the speed of sound and under nearly isothermal conditions.
		Heat pipes with the ability to move heat with near-zero temperature rise are employed as conduits to eliminate this fin efficiency problem.
		Heat pipes are similar to semiconductor electronics in that they demonstrate higher failure rates at start-up, due to initial infant mortality, and at the end of life, due to wear-out.
	powerelectronics.com /mag/power_heat_pipe_reliability (1839 words)

	OCModShop News - How Does a Heat Pipe Work? Heat Pipes Explained
		Heat pipes are extensively used in many modern computer systems, where increased power requirements and subsequent increases in heat emission have resulted in greater demands on cooling systems.
		Heat pipes are typically used to move heat away from components such as CPUs and GPUs to heat sinks where thermal energy may be dissipated into the environment.
		When heated above a certain temperature, all of the working fluid in the heat pipe will vaporize and the condensation process will cease to occur; in such conditions, the heat pipe's thermal conductivity is reduced to the heat conduction properties of its solid metal casing alone.
	www.ocmodshop.com /news/templates/displayarticle.asp?articleid=3038&zoneid=21 (838 words)

	BRY-AIR ASIA - HEAT PIPE HEAT EXCHANGERS
		Due to the pressure gradients thus created within the heat pipe by the rapid generation of vapour near the surface, the excess vapour is forced to a remote area within the heat pipe having low temperature and pressure.
		Heat is removed from the external surface of the condenser region by conduction, convection or radiation.
		The heat pipe works continuously in a close-loop condensation/evaporation cycle and thus, the capillary pumping force is established within the wick structure that returns the working fluid from the condenser region to the evaporator region.
	www.bryair.com /heat_pipe.htm (620 words)

	Benchtest.Com - Heat Pipe 2
		After playing with Heat Pipe 1 for a while, I came to the conclusion that I needed greater fluid capacity in the base.
		The 3/8 NPT and 1/4 NPT refers to pipe threads and are described by the inside diameter of the pipe or fitting, not the external dimensions.
		After filling the the pipe full of R134a, (see heat pipe 1 for the procedure) it weighed 3 pounds (136 kg).
	www.benchtest.com /heat_pipe2.html (1321 words)

	The Heatsink Guide: Heat Pipe information
		However, since heat pipes are tightly sealed tubes, the exact evaporation temperature can be further adjusted to a certain extent by varying the pressure inside the tube (usually reducing it).
		The inside of the heat pipe tube is filled with a capillary structure, often referred to as wick.
		Considering this, the usage of a heat pipe on the CPU cooler, especially when installed in a tower case (vertical orientation of the heat pipe), is rather questionable.
	www.heatsink-guide.com /heatpipes.shtml (0 words)

	Benchtest.Com - Heat Pipe 1
		Heat pipes are generally composed of a tube, closed on each end, with fluid in it.
		The first chart is with the heat pipe and the second is with the Thermaltake attached directly to the heat source without use of the heat pipe.
		Remember that the heat pipe just "moves" the heat to another location and that the results of using a separate heat pipe with a heat sink attached will never be as efficient as using the sink alone.
	www.benchtest.com /heat_pipe1.html (0 words)

	Heat pipe system - Patent 4000776
		Heat pipes are sometimes used to reject heat from components within a missile where heat rejection problems exist.
		When the missile skin is heated to an excessive temperature, the evaporator and condenser sections of the heat pipe reverse and heat would normally be transferred to the component at time when the wall is cool enough to condense the liquid.
		However, heating of the material within the bellows causes the bellows to expand moving the support plate 27 and wick 22 away from heat pipe cover 14, thus effectively eliminating the evaporator for the reverse heat flow system which substantially reduces the heat flow into the component from the missile skin through the heat pipe.
	www.freepatentsonline.com /4000776.html (0 words)

	What Are Heat Pipes?
		A traditional heat pipe is a hollow cylinder filled with a vaporizable liquid.
		Heat is released from the upper part of cylinder to the environment; vapor condenses to liquid phase.
		Because some heat has been removed from the air before encountering the evaporator coil, the incoming air stream section is called the precool heat pipe.
	www.heatpipe.com /heatpipes.htm (0 words)

	Heat pipe, heat pipe structure and principle
		As the heat is lost at the condenser (top), the va pour condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the process.
		Often heat pipes use a wick or capillary system to aid the flow of the liquid, but for the heat pipes used in Apricus solar collectors no such system is required as the interior surface of the copper is extremely smooth, allowing efficient flow of the liquid back to the bottom.
		Heat pipes that are very stiff have not been exposed to such stringent quality testing, and may form an air pocket in the top over time, thus greatly reducing heat transfer performance.
	www.apricus.com /html/solar_collector_heat_pipe.htm (0 words)

	Benchtest.Com - Heat Pipe 2
		Now that the heat pipe project is at a point where thoughts of it don't fill my head all of the time, I hope to turn my attention to building a new tester.
		Heat pipe sink alone, heat pipe sink with a 3½" fan in front of it and a reference test using a stock Pentium III heat sink and fan.
		Since the heat pipe's condensed liquid returns to the block by gravity, the path from the radiator (sink) on top of the case to the block needs to run "down hill" the whole way.
	www.benchtest.com /heat_pipe2_2.html (0 words)

	What is a heat pipe ?
		A heat pipe consists of a sealed aluminum or copper container whose inner surfaces have a capillary wicking material.
		Heat pipes can be built in almost any size and shape.
		Special procedures and testing equipment have been invented for reliable heat pipe manufacture, none of which are available on the open market.
	www.norenproducts.com /Heat_Pipes/what_is.html (0 words)

	What's Heat Pipe ?
		A efficient heat pipe system can be afftected by length of a heat pipe, type of fluid in a heat pipe, return wick type, and the number of bends in a heat pipe.
		A heat pipe is a simple device that can quickly transfer heat from one point to another, which is usually used for cooling an electronic component in air-conditioners, refrigerators, heat exchangers, transistors, capacitors, etc. Heat pipes are also used in laptops to reduce the working temperature for better efficiency.
		As the heat rising to the desired operating temperature, the tube boils the working fluid and turns it into a vapor.
	www.npowertek.com /what.html (475 words)

	heat pipe and heat pipe resources (Site not responding. Last check: )
		Heat Pipe Vacuum Tubes The tube combines double-layed evacuated tube with heat pipe heat pipe.Evacuated tubes absorb,retain heat and heat pipe transfer the coll.
		The heat pipe is a copper pipe, gold plated and sealed at both ends heat pipe.
		The dehumidifying heat pipe is used mostly in commercial and industrial applications heat pipe..
	www.keep-open-space-open.org /heat+pipe.html (405 words)

	Heat Pipes
		The vapor then travels to the other end of the heat pipe (the high end), which is placed in the stream of cold air that is produced by the air conditioner.
		Heat is removed from the warm upstream air and rerouted to the cool downstream air.
		One method is to arrange several heat pipes in parallel banks with the evaporator coil separating the pipes' evaporator ends and condenser ends.
	www.tropickool.com /heatpipes.htm (1629 words)

	Advanced Packaging - Heat pipe simulation
		The maximum heat transport capability of the heat pipe is governed by several limiting factors (which are a function of the heat pipe operating temperature): viscous, sonic, capillary pumping, entrainment/flooding and boiling (Table 1).
		The heat pipe transfers the high heat flux at the die interface to a large condenser area where the heat is dissipated by forced convec-tion using fans with 3 cfm of airflow.
		It is common for heat pipes to be soldered or epoxied to the evaporator plate and/or the heat sink.
	ap.pennnet.com /Articles/Article_Display.cfm?Section=Articles&Subsection=Display&ARTICLE_ID=129170 (1967 words)

	dehumidifying heat pipe
		One technology that addresses this problem is the dehumidifying heat pipe, a device that enables an air conditioner to dehumidify better and still efficiently cool the air.
		A dehumidifying heat pipe resembles two heat exchangers, located on either side of the air conditioner's evaporator coil.
		Although the heat pipes don't use any electricity directly, they cause the conditioned air to leave the system slightly warmer than it would have in the absence of the heat pipe, so it takes more energy to cool your home.
	www.daviddarling.info /encyclopedia/D/AE_dehumidifying_heat_pipe.html (437 words)

	Heat Pump
		A heat pipe is a synergistic engineering structure which, within certain limitations on the manner of use, is equivalent to a material having a thermal conductivity greatly exceeding that of any known metal.
		Applying heat at any point along the surface of the heat pipe causes the liquid at that point to boil and enter a vapor state.
		The heat pipe could also be attached to other physical components suitable as a heat sink to dissipate heat.
	www.colorado.edu /ASEN/asen5519/11heatpump_files/Heat-Pump-Text.htm (2649 words)

	Facing Thermal Solutions with Heat Pipe Technology
		The walls of the heat pipe are lined with a wick structure that allows liquid to travel from one end of the heat pipe to the other via capillary action.
		Heat added to one end of the heat pipe, called the evaporator end, causes the working fluid to evaporate or change phase from liquid to vapor.
		Thus, you can use heat pipes to carry heat away from the heat-sensitive components to the finned array or a heatsink located in an area where more space for heat dissipation is allowed — leaving room for electronics layout flexibility.
	powerelectronics.com /mag/power_facing_thermal_solutions/index.html (876 words)

	Electronics Cooling: heat pipes for electronics cooling applications (Site not responding. Last check: )
		The total thermal resistance of a heat pipe is the sum of the resistances due to conduction through the wall, conduction through the wick, evaporation or boiling, axial vapor flow, condensation, and conduction losses back through the condenser section wick and wall.
		Assume the heat pipe is dissipating 75 watts with a 5 cm evaporator and a 5 cm condenser length.
		Heat pipes are used to transfer heat from the chip to a fin stack large enough to convect the heat to the supplied air stream.
	www.electronics-cooling.com /Resources/EC_Articles/SEP96/sep96_02.htm (1986 words)

	Heat Pipes (Site not responding. Last check: )
		The heat is conducted through the walls of the heat pipe to a working fluid inside.
		Due to small pressure gradients internal to the heat pipe, the vapor at the evaporator flows to the condenser where the vapor is condensed on the internal walls, green arrow.
		The heat transfer coefficient for the convection elements is simply the inverse of the thermal resistance of the heat pipe per unit external surface area.
	www.harvardthermal.com /products/TAS/ExampleModels/heatpipes.htm (484 words)

	Heat pipe - Basics heat pipe, Ferraz Shawmut Thermal Management
		As a consequence, heat pipe thermal resistance is not dependent only on the air flow rate but also on the dissipated power as illustrated on the following curve.
		Most of the heat pipes used are thermosiphons or thermosiphon loops where the liquid returns from the condenser to the evaporator by natural gravitational flow.
		For heat pipes working in natural convection, with a rising vertical air flow, typical heat pipe designs are as follows.
	www.fs-thermalmanagement.com /html/technical_support_heatpipe.htm (294 words)

	Swales Aerospace - Products - Heat Pipes
		Heat pipes are two-phase heat transfer devices circulating a working fluid, such as ammonia, that evaporates and condenses to transport waste heat.
		Heat pipes can be embedded within a honeycomb panel and bonded to the interior side of the facesheets.
		Heat pipe panels often have hundreds of inserts and serve as equipment shelves transferring heat from electronics base plates.
	www.swales.com /products/heatpipes.html (285 words)

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