Experimental examination of utilizing novel radially grooved surfaces in the evaporator of a thermosyphon heat pipe

The application of heat pipes with flat evaporators in cooling electronic devices has attracted a lot of attention in recent years. Increasing the rate of heat transfer in their evaporator by utilizing structured surfaces is considered as a prominent method for reducing the thermal resistance of the heat pipes. In this study, the performance of a thermosyphon heat pipe with novel radially rectangular-grooved and radially inclined triangular-grooved evaporator surfaces was evaluated experimentally. It is hypothesized that the radial grooves may enhance the performance by inducing rotational motions and increasing the heat transfer coefficients. Based on the results, the optimum filling ratio of the heat pipe was 20% for all of the considered surfaces. The average thermal resistance of radially rectangular-grooved and radially inclined triangular-grooved surfaces with the same heat transfer area improved by 22.9% and 36.13%, respectively, compared to the smooth surface. Further, experimental heat transfer coefficients on the proposed radially inclined triangular grooves can be predicted by theoretical correlations with an average deviation of less than 4%. Visualization of the boiling process of droplets on different surfaces indicated the existence of the rotational flow of droplets on the radially inclined triangulargrooved surface.