This work presents the experimental design and testing of a two-phase, embedded manifold-microchannel cooler for cooling of high flux electronics. The ultimate goal of this work is to achieve 0.025 cm2-K/W thermal resistance at 1 kW/cm2 heat flux and evaporator exit vapor qualities at or exceeding 90% at less than 10% absolute pressure drop. While the ultimate goal is to obtain a working two-phase embedded cooler, the system was first tested in single-phase mode to validate system performance via comparison of experimentally measured heat transfer coefficient and pressure drop to the values predicted by CFD simulations. Upon validation, the system was tested in two phase mode using R245fa at 30°C saturation temperature and achieved in excess of 1 kW/cm2 heat flux at 45% vapor quality. Future work will focus on increasing the exit vapor quality as well as use of SiC for the heat transfer surface upon completion of current experiments with Si.
The present study is an experimental investigation of a set of five additively-manufactured compact, lightweight, low-cost, air-to-water cross-media heat exchangers suitable for liquid cooling applications in desktop computers, among other applications. The heat transfer between the two fluids is facilitated by solid metallic wires arranged in a staggered tube-bank configuration, in direct contact with both fluids separated by polymer walls. Since the liquid flows externally over the wires instead of flowing inside the tubes in conventional tube-bank fin heat exchangers, smaller wires can be used in iCMHXs, resulting in lighter and more efficient units. The additively-manufactured iCMHX units are post-processed using a conformal polyurethane sealant. The units are experimentally studied in two case studies based on their post-processing techniques. The experimental studies include instrumentation calibration as well as uncertainty analysis. The first case study considers three geometrically identical iCMHX units sharing the same post-processing method. The overall iCMHX performances characterized by the thermal and hydrodynamic parameters, such as thermal resistance and pressure drop for both waterside and airside, are compared. Their experimental results are also compared to 2D CFD predictions. To provide probable reasoning behind the differences in the comparisons, a second case study is then carried out by experimentally investigating two iCMHX units but with variable post-processing approaches such as by using a thinned sealant and by using a single layer of sealant.
In order to meet increasing power-dissipation requirements of the electronics industry, compact, low-cost, and lightweight heat exchangers (HXs) are desired. With proper design, materials, and manufacture, polymer composite heat exchangers could meet these requirements. This paper presents a novel crossflow air-to-water, low-cost, and lightweight metal-polymer composite HX. This HX, which is entirely additively manufactured, utilizes a novel cross-media approach that provides direct heat exchange between air and liquid sides by using connecting fins. A robust numerical model was developed, which includes the dimensional effects of additive manufacturing. The study consists of a simplified 3D CFD model based on ellipsoidal-shaped staggered tube banks for the laminar range. It then uses an analytical approach to compute entire HX performance. The model is validated experimentally within 8% for thermal performance, 12% for air-side impedance, and 18% for water-side impedance. Finally, HX is compared with a conventional CPU radiator and performs within 10% of the conventional unit for reasonable flow rates and pressure-drop ranges. Moreover, HX also provides added design and cost advantages over the conventional unit, which makes the HX a potential candidate for electronic cooling applications.
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