Browsing by Author "Saygan, S."

Now showing 1 - 3 of 3

Open Access
Capillary boosting for enhanced heat pipe performance through bifurcation of grooves: Numerical assessment and experimental validation
(2022-10) Saygan, S.; Akkus, Y.; Dursunkaya, Z.; Cetin, Barbaros
In this study, an enhanced heat pipe performance for grooved heat pipes has been demonstrated through capillary boosting with the introduction of the bifurcation of grooves. Wider grooves regularly branch to narrower grooves such that the total cross-sectional liquid flow area remains approximately the same. Following the computational framework drawn by a recently developed heat pipe analysis toolbox (H-PAT), we develop a numerical model for the heat pipes with tree-like groove architecture. Then we utilize the model to design a flat-grooved heat pipe with one step groove bifurcation at the evaporator. To verify our numerical findings, two heat pipes with and without groove bifurcation are manufactured and experimented under the same conditions. Experimental results show that the numerical model can predict the thermal performance quite accurately. The results reveal that groove bifurcation can be a viable option for a better thermal performance than that of heat pipes with standard grooved heat pipes with straight grooves which leads to at least 25% higher maximum heat transport capacity. The effect of number of branching on the temperature flattening across the heat pipe is also demonstrated for different evaporator lengths.
Open Access
Effect of liquid-vapor interaction on the thermal performance of a flat grooved heat pipe
(Begell House Inc., 2023-03) Derebaşı, B.; Saygan, S.; Çetin, Barbaros; Dursunkaya, Z.
Flat grooved heat pipes (FGHP) are predominantly used in electronics cooling due to their ability to transfer high heat loads with small temperature differences and superior reliability. Modeling the underlying physics is challenging due to the presence of multiple simultaneous physical phenomena, including phase change, free surface, two-phase flow and heat transfer. In this study, a recently developed modeling tool H-PAT [1] is extended by including the interaction at the interface between the two phases of the FGHP's working fluid. The vapor phase is assumed to be saturated, eliminating the need to solve the energy equation for the vapor. Analytical solutions of liquid and vapor flows are used, and the steady-state energy equation is solved via a thermal resistance network to get the temperature distribution. Interface heat transfer is modeled using the fundamental findings of kinetic theory. The model is exercised to quantify the effect of vapor spacing on the thermal performance of a flat grooved heat pipe. The results show that liquid-vapor interaction on the interface enhances the evaporation performance in the micro-region, resulting in a more uniform temperature distribution.
Open Access
Performance assessment of commercial heat pipes with sintered and grooved wicks under natural convection
(TIBTD, 2019) Atay, Atakan; Sarıarslan, Büşra; Kuşçu, Yiğit F.; Saygan, S.; Akkuş, Y.; Gürer, A. T.; Çetin, Barbaros; Dursunkaya, Z.
Heat pipes are widely used in thermal management of high heat flux devices due to their ability of removing high heat loads with small temperature differences. While the thermal conductivity of standard metal coolers is approximately 100–500 W/m.K, effective thermal conductivities of heat pipes, which utilize phase-change heat transfer, can reach up to 50,000 W/m.K. In industrial applications, commercially available heat pipes are commonly preferred by thermal engineers due to their low cost and versatility. Thermal performance of a heat pipe is functions of heat pipe type and operating conditions. Selection of the appropriate heat pipe complying with the operating conditions is critical in obtaining satisfactory thermal management. One key point for the utilization of heat pipes is to avoid dryout operation condition in which heat pipes operate no more at the desired heat transport capacity. In the current study, the performance of cylindrical heat pipes with sintered and grooved wick structures, which are among the most commonly used types, is experimentally tested at different heat loads, gravitational orientations and ambient temperatures. Dryout limits of the heat pipes are determined and the relationship between the dryout onset and operating conditions is elucidated. The results reported in the present study are expected to guide thermal engineers for the proper selection and operation of conventional heat pipes.