An Investigation of Thermal Characteristics of a Sintered-Wick Heat Pipe with Double Heat Sources

Abstract

Heat pipes have been used extensively in the electronic industry for decades especially in laptop computers. For cost-effectiveness, a single heat pipe is designed to simultaneously transfer heat from both the Central Processing Unit (CPU) and the Graphics Processing Unit (GPU) inside the main board to the heat sink. This causes the efficiency of the heat pipe to change without any theoretical prediction. In this research, thermal performance of a sintered-wick heat pipe with double heat sources has been experimentally and numerically investigated by utilizing the Finite Element Method (FEM). The focus being the effect that the distance between the two heat sources and also the power input pattern (heat source#1 (HT1): heat source#2(HT2) has on temperature and thermal resistance of the heat pipe. The first heat source (HT1) was located at one end and the heat sink was located at another end of the heat pipe, while another heat source (HT2) was placed between HT1 and a heat sink. The ratios of heat input power were controlled at 10W:10W, 20W:10W and 30W:10W. Two copper blocks (15×15 mm) were used as heat sources for the evaporator section (Le1, Le2) to electrically supply heat to the bottom half of the heat pipe. A mathematical model using the Finite Element Method (FEM) was established to calculate temperature and thermal resistance. The speed of the cooling fan was adjusted to maintain constant operating temperature at the adiabatic section throughout the tests. The operating temperature was controlled at 60 ± 3°C. It was noted that, when distance between the heat sources was increased from 0 mm to 75 mm, thermal resistance slightly decreased from 0.589-0.53°C/W respectively. Heat source 2, therefore, should be placed as close as possible to the condenser section. Both heat sources should have a distance between them of at least 12 mm, which minimizes heat accumulation. When the power input of HT1 was increased from 10 W to 30W (HT2 was fixed at 10W), thermal resistance slightly increased from 0.56-0.58°C/W. The results from the mathematical model are in good agreement with the experimental data (STD ±2.54%). Therefore, from this study, we are able to design an effective heat pipe for double heat source applications which is very useful for the electronic industry. Finally, a guideline and knowledge were obtained for designing a heat pipe with double heat sources.