variavel0=<b>Mauricio Araujo Zanardi</b> - mzanardi@feg.unesp.br UNESP
<b>Petronio Masanobu Tanisho</b> - tanisho@feg.unesp.br UNESP
<b>Abstract.</b> The heat pipe operation is based on phase-change processes. In this way the return of the condensed fluid to the evaporator section is determinant for the heat tranfer process. If the heat pipe works with the evaporator region above the condenser, the liquid return occurs by wick capilarity effects. The increase of the tilt angle with respect to the horizontal tends to reduce the heat transfered. On the other hand, in the gravity assisted heat pipes the liquid returns to the evaporator by gravity forces and the wick is not essential for the operation. The presence of the wick , although it increases the liquid flow head losses, may cause a better liquid distribution and cause changes in the evaporation and condensation processes increasing the heat transfer performance. Theoretically, performance of the heat pipe in a vertical position would be better than in an inclined position. However, experiences show that this fact is not allways true. There are some tilt angles that provides better performance. An expression that would permit to determine these angles is very hard to be obtained because of the great number of variables involved in the process. In this paper we present an experimental analysis of the influence of the wick porosity in heat pipes operating at different tilt angles. It was used cooper-water heat pipes with screen type wick with mesh nymber varying between 34 and 400. The experimental results permited to determine tilt angles ranges of the heat pipe best performance.
<b>Keywords.</b> Heat Pipes, Inclination Effects.