3. Conclusions

As the rate of the heat removal from the vapour increases, more condensate returns to the evaporator for another cycle. The effect of cooling water flow

thermosyphon heat pipe [19]. The heat input was fixed at 101 W while five different flow rates ranging from 0.00156 to 0.00611 kg/s were investigated. Temperature and the flow rate readings were recorded for each run and the effects of the cooling water flow rate were evaluated based on the overall thermal resistance, rate of heat transfer to the cooling water, outlet temperature of cooling water, performance of the thermosyphon, etc. The results from such work have shown that the performance of the pipe in terms of heat transfer to the cooling water increases with the increase in the cooling water flow rate. This is due to the mass flow of the cooling water which results in the enhancement of the rate of heat transfer from the pipe wall to the cooling

In addition to the general advantages of heat pipes, thermosyphon type is found to be highly durable, reliable and cost-effective, which make them useful for vari-

II.Liquid circulation: thermosyphon system is used for circulating liquids and volatile gases in heating and cooling systems such as water heaters, furnaces and boilers. It simplifies transfer of liquid or gas without using conventional

III.Cooling applications: thermosyphon is used in cooling of turbine blades, transformers, electronics, internal combustion engines and nuclear reactors [34, 35]. This is due to their ability to dissipate and transfer large amount of

IV.Aircraft cooling: due to their light weight, thermosyphon pipes are used in

rate at constant heat input was investigated on the performance of

Variation of the thermosyphon performance with inclination angle at different heat inputs [17, 19].

water and subsequent increase in the efficiency.

pump which adds cost and complexity to the system.

energy from small area without any significant loss.

2.6 Applications of thermosyphon

I.Solar heating of building [16].

cooling of aircraft and spacecraft.

ous applications, such as:

18

Figure 10.

Recent Advances in Heat Pipes

Several parameters affect the operation of thermosyphon such as fill ratio, working fluid, inclination, geometry, heat input, cooling water flow rate, etc. Experimental and numerical (CFD) studies are usually carried out to enable the investigation of the effects of some of these parameters on the performance of thermosyphon heat pipe for use in various engineering applications. Investigations on the effects of heat input, fill ratio, flow rate of cooling water on the temperature distributions on the wall of the pipe, overall thermal resistance and overall performance of the pipe at vertical orientation were shown to be possible both experimentally and using CFD. Also, the effect of inclination angle of thermosyphon on those parameters was successfully added in the Fluent. Hence, the chapter has shown that volume of fluid (VOF) model's approach in ANSYS together with UDF and other software can fully simulate the complex evaporation and condensation processes taking place in thermosyphon for both vertical and inclined orientations.

Recent Advances in Heat Pipes
