Optimization of bent-flattened sintered-grooved wick miniature heat pipe with double heat sources

Abstract

Miniature heat pipes have been widely employed in dissipating heat from electronic circuit boards of laptop computers and other electronic devices. These heat pipes must be bent, flattened, and used with multiple heat sources due to space constraints in these electronic boards. Although there have been previous mathematical models studying the phenomena occurring in these heat pipes in order to predict their thermal performance, high discrepancies were found. This is because these models cannot explain specific internal phenomena especially at the evaporator section and condenser section. Hence, this research has established a mathematical model to describe the heat transfer performance of the heat pipes. Normally, miniature heat pipes using sintered-grooved wick and water as the working fluid are focused. The established model accurately simulates the physical phenomena within the heat pipes. This model includes a three-dimensional calculation of heat and fluid flow within the heat pipe wall, the sintered-grooved wick, and the vapor core at steady-state condition. Additionally, it includes various variables in special cases where there is fluid maldistribution within the sintered-grooved wick, such as fluid receding within the evaporator section and/or excess fluid accumulated in the vapor-core of the condenser section of the heat pipe. From the calculations it was found that, the model effectively describes the phenomena within the heat pipe. The presented model has been verified with previously available mathematical models and good agreement in results were found. Furthermore, the computed results from the mathematical model were validated with experimental results obtained from heat pipes with bending, flattening, with multiple heat sources conditions. This provided important insights into the thermodynamics controlling heat sources and the impact of curved and flattened heat pipes on heat transfer performance. It was found that, they were in good agreement, with STD of 7.43%. Moreover, the results from the model simulation were utilized to determine the optimal design of the bent-flattened-multiple-heat-sources heat pipes, with actual production data from the industrial sector with the controlled function of economic conditions. It was concluded that, heat pipes with a diameter of 6 mm without flattening or bending, and heat source with higher heat flux placed near to the condenser section of the heat pipe, should be manufactured for the optimum criteria.