Historical Development of Heat Pipes

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Historical Development of Heat Pipes

Operation Principles of Heat Pipes

Types of Heat Pipes

Working Fluids and Temperature Ranges of Heat Pipes

Capillary Wick Designs and Structures in Heat Pipes

Heat Transfer Limitations of Heat Pipes

Heat pipe Start Up

Heat Pipe Characteristics

Heat Pipe Analysis and Simulation

Heat Pipe Applications

Of the many different types of systems which transport heat, the heat pipe is one of the most efficient systems known today [1]. The advantage of using a heat pipe over other conventional methods is that large quantities of heat can be transported through a small cross-sectional area over a considerable distance with no additional power input to the system. Furthermore, design and manufacturing simplicity, small end-to-end temperature drops, and the ability to control and transport high heat rates at various temperature levels are all unique features of heat pipes.

The predecessor of the heat pipe, the Perkins tube, was introduced by the Perkins family from the mid-nineteenth to the twentieth century through a series of patents in the United Kingdom. Most of the Perkins tubes were wickless gravity-assisted heat pipes (thermosyphons), in which heat transfer was achieved by a change of phase (latent heat of evaporation). The Perkins tube design closest to the present heat pipe was patented by Jacob Perkins [2]. This design was a closed tube containing a small quantity of water operating as a two-phase cycle.

The introduction of the heat pipe was first conceived by Gaugler [3] of the General Motors Corporation in the U.S. Patent No. 2350348. Gaugler, who was working on refrigeration problems at that time, envisioned a device which would evaporate a liquid at a point above the place where condensation would occur without requiring any additional work to move the liquid to the higher elevation. His device consisted of a closed tube in which the liquid would absorb heat at one location causing the liquid to evaporate. The vapor would then travel down the length of the tube, where it would recondense and release its latent heat. It would then travel back up the tube via capillary pressure to start the process over. In order to move the liquid back up to a higher point, Gaugler suggested the use of a capillary structure consisting of a sintered iron wick. A refrigeration unit proposed by Gaugler used a heat pipe to transfer the heat from the interior of a compartment to a pan of crushed ice below. His idea, however, was not used by General Motors for the refrigeration problem.

In 1962, Trefethen [4] resurrected the idea of a heat pipe in connection with the space program. Serious development started in 1964 when the heat pipe was independently reinvented and a patent application was filed by Grover at Los Alamos National Laboratory in New Mexico. Grover et al. [5] and Grover [6] built several prototype heat pipes, the first of which used water as a working fluid, and was soon followed by a sodium heat pipe which operated at 1100 K. Grover and his co-workers also demonstrated the effectiveness of heat pipes as a high performance heat transmission device and proposed several applications for their use. In a U.S. patent application filed by Grover on behalf of the U.S. Atomic Energy Commission, Grover [6] coined the phrase “heat pipe” and described a device almost exactly the same as Gaugler’s, stating, “with certain limitations on the manner of use, a heat pipe may be regarded as a synergistic engineering structure which is equivalent to a material having a thermal conductivity greatly exceeding that of any known metal.” In the patent application, Grover [6] gave a very limited theoretical analysis of heat pipes, but presented experimental results obtained from stainless steel heat pipes that incorporated a screen wick with sodium, silver and lithium as working fluids.

The recognition of the heat pipe as a reliable thermal device was initially due to the preliminary theoretical results and design tools that were reported in the first publication on heat pipe analysis by Cotter [7]. Following this publication, research began worldwide. The United Kingdom Atomic Energy Laboratory at Harwell started experimenting with sodium heat pipes to use as thermionic diode converters. In addition, scientists started conducting similar work at the Joint Nuclear Research Center in Ispra, Italy, which soon became the most active research center outside the U.S. Shortly thereafter, other countries such as Germany, France, and the former USSR initiated efforts in this regard.

The early development of terrestrial applications of heat pipes proceeded at a slow pace. Due to capillary action, heat pipes can operate in microgravitational fields without any external force field or pump. Because of this, most early efforts were directed toward space applications. However, due to the high cost of energy, especially in Japan and Europe, the industrial community began to appreciate the significance of heat pipes and thermosyphons in energy savings applications. Today, all developed countries have been actively involved in research, development, and commercialization of heat pipes.

Within the last decade, a major transformation regarding heat pipe technology and application has occurred due to the critical need of electronic cooling and energy systems, as well as the invention of new heat pipes. Several million heat pipes per month are now being manufactured since all modern laptop computers use heat pipe technology to transfer heat away from the processor. Furthermore, research and development for new heat pipes such as loop heat pipes, micro and miniature heat pipes, and pulsating heat pipes, has matured enough for use in various applications.

There is a wealth of published literature: several heat pipe books and monographs, as well as the proceedings of eleven international heat pipe symposiums and seventeen international heat pipe conferences. In addition, there are a large number of archival and non-archival publications and reports related to heat pipes, dating back over the last four decades. A significant amount of basic and applied research & development has been performed since 1985 in the area of heat pipes due to the great potential use of this technology for various applications.


  1. Faghri, A., 1995, Heat Pipe Science and Technology, 1st ed., Taylor & Francis, Washington, D.C.
  2. Perkins, J., 1836, UK Patent No. 7059.
  3. Gaugler, R., 1944, "Heat Transfer Device," U.S. Patent No. 2350348.
  4. Trefethen, L., 1962, "On the Surface Tension Pumping of Liquids or a Possible Role of the Candlewick in Space Exploration," G.E. Tech. Info., Serial No. 615 D114.
  5. Grover, G. M., Cotter, T. P., and Erickson, G. F., 1964, "Structures of very High Thermal Conductance," Journal of Applied Physics, 35(6), 1990-1991.
  6. 6.0 6.1 6.2 Grover, G., 1966, "Evaporation-Condensation Heat Transfer Device," U.S. Patent No. 3229759.
  7. Cotter, T. P., 1965, "Theory of Heat Pipes," Los Alamos Scientific Laboratory Report No. LA-3246-MS.