Experimental study of the effect of geometrical length to diameter ratios and heater orientations on sintered-based heat pipes thermal behavior

Abstract

Recently, many studies have examined conventional heat pipes (CHP) for thermal solutions with higher dissipation rates and improved thermal management. However, several previous studies considered CHP with constant geometrical ratios. Therefore, this study experimentally investigated the time-based transient behaviors of sintered-based CHP with various length to diameter ratios (Lt/do) in the range of 30 to 100. By decreasing the Lt/do ratio from 100 to 30, the CHP thermal resistance was reduced from 0.75 °C/W to 0.05 °C/W. Generally, lower Lt/do ratios obtained by reducing the lengths or increasing the diameters of the CHP promote faster startup time and lower startup temperatures over broader operating conditions. In contrast, the higher Lt/do ratios arising from CHP with longer lengths or narrower diameters incite performance deterioration. Compared to other parameters investigated, the magnitude of heat input significantly governs the transient behavior of CHP. But, the maximum thermal limits depend mainly on the orientation mode. Tilting the CHP at acute and vertical orientations and lowering the Lt/do ratio promote recovery of performance decline. The CHP thermal performance showed exponential temperature responses under the operating parameters investigated. The present results can complement previous efforts, which studied heat pipes performance at fixed geometrical ratios.