It is usually a copper tube with a diameter of 3-15 mm containing a liquid appropriately selected for the application (liquefied ammonia, acetone, water, ether, freon, methanol, ethanol). The tube is usually covered inside with a porous material that acts as a wick. Heating one end of the tube causes the liquid inside to vaporize, thus absorbing the heat supplied. The vapor then moves to a lower temperature part of the tube where it condenses on the cooler walls of the tube to give up its heat. The condensed liquid flows along the walls by gravity or by seepage in the wick - a porous substance that covers the tube walls - to the part of the tube with the higher temperature. The efficiency of heat transfer by convection combined with evaporation is much more efficient than heat conduction through solids.

The technology is mainly used to cool electronic components, but the spectrum of applications is much broader, from cooling spacecraft engines to solar collectors to cooling Trans-Alaska pipeline structures (so that the heat generated by the flow of crude oil doesn't melt the permafrost in which the structural components are mounted).