The continually increasing heat generation rates in high performance electronics, radar systems and data centers require development of efficient heat exchangers that can transfer large heat loads. In this paper, we present the design of a new high-performance heat exchanger capable of transferring 1000 W while consuming less than 33 W of input electrical power and having an overall thermal resistance of 0.05 K/W. The low thermal resistance is achieved by using a loop heat pipe with a single evaporator and multiple condenser plates that constitute the array of fins. Impellers between the fins are driven by a custom permanent magnet synchronous motor in a compact volume of 0.1 × 0.1 × 0.1 m to maximize the heat transfer area and reduce the required airflow rate and electrical power. The design of the heat exchanger is developed using analytical and numerical methods to determine the important parameters of each component. The results form the basis for the fabrication and experimental characterization that is currently under development.Index Terms-Air cooling, heat exchanger, loop heat pipe, thermal management.
Thermal management of modern electronics is rapidly becoming a critical bottleneck of their computational performance. Air-cooled heat sinks offer ease and flexibility in installation and are currently the most widely used solution for cooling electronics. We report the characterization of a novel loop heat pipe (LHP) with a wick in the condenser, developed for the integration into an air-cooled heat sink. The evaporator and condenser are planar (102 mm  102 mm footprint) and allow for potential integration of multiple, stacked condensers. The condenser wick is used to separate the liquid and vapor phases during condensation by capillary menisci and enables the use of multiple condensers with equal condensation behavior and performance. In this paper, the thermal-fluidic cycle is outlined, and the requirements to generate capillary pressure in the condenser are discussed. The LHP design to fulfill the requirements is then described, and the experimental characterization of a single-condenser version of the LHP is reported. The thermal performance was dependent on the fan speed and the volume of the working fluid; a thermal resistance of 0.177 C/W was demonstrated at a heat load of 200 W, fan speed of 5000 rpm and fluid volume of 67 mL. When the LHP was filled with the working fluid to the proper volume, capillary pressure in the condenser was confirmed for all heat loads tested, with a maximum of 3.5 kPa at 200 W. When overfilled with the working fluid, the condenser was flooded with liquid, preventing the formation of capillary pressure and significantly increasing the LHP thermal resistance. This study provides the detailed thermal-fluidic considerations needed to generate capillary pressure in the condenser for controlling the condensation behavior and serves as the basis of developing multiplecondenser LHPs with low thermal resistance.
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