What is a heat pipe ?

A heat pipe consists of a sealed aluminum or copper container whose inner surfaces have a capillary wicking material. Inside the container is a liquid under its own pressure that enters the pores of the capillary material, wetting all internal surfaces. 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. When that happens, the liquid picks up the latent heat of vaporization. The gas, which then has a higher pressure, moves inside the sealed container to a colder location where it condenses. Thus, the gas gives up the latent heat of vaporization and moves heat from the input to the output end of the heat pipe. Heat pipes have an effective thermal conductivity many thousands of times that of copper. Heat pipes can be built in almost any size and shape.

Even though most people perceive it as a simple technology, heat pipe manufacture has been a difficult area to compete in. Simple in concept, but difficult to apply commercially, the heat pipe is a very elusive technology. Any high school student can make a good performing heat pipe with parts from a hardware store. Many early researchers did just that. All reported a time degradation of their product, concluding that heat pipes inherently decay. That was absolutely right and absolutely wrong. Right, because their heat pipes did decay. Wrong, because they had not discovered the secret to manufacturing heat pipes that last over thirty years.

Special procedures and testing equipment have been invented for reliable heat pipe manufacture, none of which are available on the open market. Since the manufacture of the first Noren Heat Pipe, we have shipped millions of heat pipes to our customers. There have been no reported field failures of a Noren Heat Pipe.

Mega Flats

Flat heat pipes are typically used for cooling printed circuit boards or for heat leveling to produce an isothermal plane. Mega flats are several flat heat pipes sandwiched together. Noren Products has been on the leading edge of both technology development and manufacture of flat heat pipes since 1971, when we manufactured a vapor chamber flat heat pipe for a customer.

Some of the flat heat pipes that Noren Products has designed and manufactured (still in use by its customers) are:

XY Mega Flats: Surface maintained within .01° F isothermal with concentrated load centers; 6" X 6" Mega Flat: Dissipated 850 watts from a printed circuit board; Weight Reduction Mega Flats:

• Standard - aluminum construction.
• Lightweight - 1/2 the weight of aluminum.
• Very light weight - 1/3 the weight of aluminum.

SEM C and SEM E Mega Flats in stock. Low and light weight coefficient of thermal expansion (CTE) Mega Flats - any CTE from 2 to 10. Alloy H: 70% more conductive than, or 40% less weight than copper clad invar.

Flexible Solutions

Noren Products routinely manufactures heat pipes in a multitude of sizes and shapes. Unusual application geometries can be easily accommodated by the heat pipe's versatility to be shaped as a heat transport device.

If some range of motion is required, heat pipes can even be made of flexible material.

We also manufacture heat pipes with a variety of functions, two of the most common are:

• Constant Temperature: The heat pipe maintains a constant temperature or temperature range.
• Diode: The heat pipe will allow heat transfer in only one direction.