Heat Pipe Vs. Thermosyphons

1. INTRODUCTION

A heat pipe is a simple mechanism which is use to transfer heat from one point to another point.. It is also referred as the "superconductors" of heat because heat pipe is having extra-ordinary heat transfer capacity and heat transfer from one location to other having rate with no heat loss. Heat pipe was first introduced by R.s.Gagler in 1943.When it is invented that its excellent properties were appreciated and than after a development of heat pipe is started.

In heat pipe design, there is a aluminium or copper container.containers inner surface is having a capillary wick material. In some cases heat pipe is similar to thermosyphon.But only the difference between this two is that in heat pipe capillary system is use to transfer

For circulation of working fluid capillary pumping force is use in the case of heat pipe and gravity forces in the case of two phase thermosyphons to make the fluid in circulation. The wick is for providing the capillary driving force to return back working fluid from the condensate to the evaporator.the wicks are the heart of the process, quality of wick and wick types determines the working of the heat pipe, for this is the heart of the product. There are many types of wicks are used in heat pipes which are depending on the area of application,for which application the heat pipe is used [1].

Working fluid choices are mainly based on the temperature on which the heat pipe work, for example helium is used for extremely low temperature application which is around 2-5 K. than for mercury the temperature range is from 520-930 K. for high temperature ranges sodium and indium are used and temperature range is around 2000-2900 K. but at room temperature in most of the heat pipe ammonia, alcohol and ethanol and water are used, from temperature ranges around 200-350 K. In copper-water heat pipe water behave as a working fluid and having copper envelope, which is operated in the range of 20 to

the invention of heat pipe , gauzler was working on the refridgeration problem at that time. At that time he envisioned that a device in which in evaporator liquid evaporate and above the evaporator there is condenser in which vapour condense but there Is no mechanical work is require for driving the liquid and without any additional work liquid can recycle. So the heat pipe consist of closed tube containing a liquid which would absorb the heat at one point which causes liquid evaporate. Created vapours would then transfer to the condenser section where vapours condensed and it causes latent heat is removed. Liquid would than travel back to evaporator section via wick or capillary. For recycle the liquid back from the higher point , gauzler suggested the wick which consist of sintered iorn wick