Abstract

Heat pipes are a popular choice for many industries and research applications to extract heat effectively by maintaining desired device/location at almost isothermal conditions. Pulsating heat pipes, also known as wickless heat pipes, transfers the heat mainly by pumping phenomenon caused by the phase change which set the pulsating vapor-fluid motion. The evaluation of fluid flow and heat transfer characteristics inside the pulsating heat pipe is complex and challenging due to the oscillating two-phase flow between the heat source and heat sink sections. In this paper, a numerical investigation of the closed-loop pulsating heat pipe is performed to study the fluid flow dynamics and evaluate its thermal characteristics. The volume of fluid method is employed to numerically simulate the two-phase unsteady incompressible flow inside the pulsating heat pipe. The heat pipe tube has a 2 mm inside diameter filled with methanol as a working fluid at a preset pressure. The thermal performance of pulsating heat pipe is evaluated for various heat pipe filling ratios (50%, 65%, and 75%) where heat input loads of 5 − 15 W are supplied at the evaporator end for each filling ratio case. The thermal characteristics of the pulsating heat pipe are presented in terms of the thermal resistance, heat transfer coefficient, and effective thermal conductivity, whereas fluid flow dynamics are presented as flow patterns produced inside pulsating heat pipe. The numerical simulations are compared and validated with experimental results. From the present numerical and experimental study, a filling ratio of 65% is an optimized charge quality for the current configuration of the pulsating heat pipe.

摘要

热管是许多行业和研究应用的流行选择，通过将所需的设备/位置保持在几乎等温的条件下来有效地提取热量。脉动热管，也称为无芯热管，主要通过引起脉动蒸汽-流体运动的相变引起的抽吸现象来传递热量。由于热源和散热器部分之间的振荡两相流，脉动热管内流体流动和传热特性的评估是复杂且具有挑战性的。在本文中，对闭环脉动热管进行了数值研究，以研究流体流动动力学并评估其热特性。采用流体体积法对脉动热管内的两相非定常不可压缩流动进行数值模拟。热管管内径为2mm，在预设压力下填充甲醇作为工作流体。脉动热管的热性能针对各种热管填充率（50%、65% 和 75%）进行评估，其中对于每种填充率情况，在蒸发器端提供 5-15 W 的热输入负载。脉动热管的热特性以热阻、传热系数和有效热导率表示，而流体流动动力学则表示为脉动热管内部产生的流动模式。数值模拟与实验结果进行了比较和验证。从目前的数值和实验研究来看，