Chung-Lung Chen

Operating Characteristic Investigations in Pulsating Heat Pipe

Pulsating heat pipe (PHP) is an interesting heat transfer device. In this paper we focus on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both the total temperature differences (from the evaporator to condenser) and the evaporator temperature fluctuations are relevant to operating temperature. The minimal total temperature difference and temperature fluctuation appear at an operating temperature ranging from 120°C to 160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large total temperature difference and temperature fluctuation. Phase change proportion increases at the optimal operating temperature. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus the operating temperature.

Experimental Investigations of an Avionics Cooling System for Aerospace Vehicle

DOI: 10.2514/1.16051 With extensive use of high-power electronic devices in avionics systems, more effective heat transfer systems must bedeveloped tomeet highload heattransfer requirements. Inthis article, acoolingsystemin terms of pulsatingheat pipetechnology ispresented andtestedforthepurposeofheattransferenhancementinavionicssystems.Toachieve the enhancement, pulsating heat pipes with 1.65 mm internal diameter are fabricated and mounted with printed circuit boards onto the avionics chassis wall so that a quick heat transfer path is constructed from the electronic devicestotheexternalheatsink.Experimentalresultsindicatethatpulsatingheatpipeiscapableoflongdistanceand high-powerheattransferfornewgenerationavionicssystems,andtemperaturedifferencesaresignificantlyreduced compared to traditional thermal systems. Pulsating heat pipe performance characteristics, such as temperature fluctuation and orientation, are explored and discussed in this application as well.

Heat Transfer Enhancement of Planar Pulsating Heat Pipe Device

Heat pipes are widely used heat transfer devices in the electronic cooling area. In this paper, a novel pulsating heat pipe (PHP) design, which combines features of PHP and capillary microstructures, is presented to enhance heat transfer of electronic printed circuit boards (PCB). Test prototype fabrication is initiated by making dual-radius serpentine channels on a 4.0mm thick aluminum plate, followed by compressing 4.67mm diameter copper tube into the grooves, and completed by generating a millimeter sized liquid channel with micro-grooves in the PHP along the longitudinal direction. Because of this design, the planar PHP is able to circulate operating liquid by both capillary pump and oscillation motions, which eliminate the dry state in the evaporator section and supply sufficient coolant at high heat loads. Demonstrations of heat transfer performance indicate that the planar PHP has high effective thermal conductivity and low evaporator temperature fluctuations, and oscillation continuity is the key factor to reduce the temperature difference between the evaporator and condenser.Copyright

Applications of Advanced Cooling Technology in Avionics System for Aerospace Vehicle

With extensive applications of high power electronic devices in modern avionics systems, more effective heat transfer technology has to be developed and applied to solve high heat flux/load cooling issues. Pulsating heat pipe (PHP), an advanced passive cooling technology, which has a simple internal structure, lower manufacture cost, lightweight, and high heat transfer capability, is selected to improve the avionics system thermal management in this paper. Investigation efforts are focused on reducing thermal resistance from heat sources on print circuit board (PCB) to external heat sink of avionics chassis by employing PHP technology. Experimental results indicate that the PHP is capable of longer distance and higher power heat transfer, and temperature gradients are significantly reduced comparing to traditional thermal designs. Additionally, the PHP performance characteristics, such as temperature fluctuation, orientation and transient effects are explored and analyzed in this application.

Multilayer Wick Structure of Loop Heat Pipe

Loop heat pipe (LHP) is known as a two-phase heat transfer device that utilizes the evaporation and condensation of an operating fluid to transfer heat. At the LHP low operating temperatures, heat leakage induced by saturated temperature differences between the evaporator and compensation chamber is more serious than at high operating temperatures, due to inherent thermophysical properties of the operating liquid. The serious heat leakage at the low operating temperature not only causes high liquid subcooling requirement but also leads to high total temperature difference and degraded heat transfer performance. In this paper, research efforts are placed on reducing the heat leakage by introducing a multilayer wick structure into the LHP. Based on the previous research results of LHP non-metallic wick structures, the multilayer wick LHP combines advantages of both metallic and non-metallic wick structures, retains good heat conduction from the evaporator case to the liquid/vapor interface and inhibits the reverse heat transfer from the interface to compensation chamber. By demonstrating the concept on a methanol LHP, experimental results exhibit a significant enhancement in reducing heat leakage and the total heat transfer resistance.Copyright