A cutting edge man-portable AVMEC cooling garment was demonstrated to be able to provide sufficient cooling for personnel working at mediate activity loads. Studies were first carried out in a well controlled vacuum desiccator at room temperature to elucidate the effects of several key parameters on the performance of an AVEC device, which was similar to AVMEC except that membrane was not involved. Under the best condition, an average cooling capacity of 179 W/M2 was achieved in a period of four hours and cooling continued at a slowly declining rate for another four hours afterward. The temperature of water was maintained at approximately 12.5 oC after the pseudo steady state was established. Then, it was shown that the AVMEC cooling pads were able to provide a cooling capacity of 277.4 W/m2 in a 37 oC ambient environment (incubator). The temperature of the cooling core surface was maintained in a range of 20 – 21.8 oC in the one-hour test period. No power supply was required except for the initialization stage, which took 5 minutes. Furthermore, human subject tests with or without wearing NWBC (Nuclear Warfare Biological and Chemical) suit demonstrated that, a AVMEC garment composed of 12 cooling pads were able to maintain the core body temperature of the subjects below 38.5 oC for up to 90 minutes while the subject was walking on a treadmill at a speed of 2 miles per hour in an environment of 40 oC and 50% RH (relative humidity). These results indicate that the AVMEC garment is a promising man-portable personal cooling technology.

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Call number: LD2668 .T4 1933 L41

This thesis presents a comprehensive study into the passive thermal management of high-voltage power electronics converters for use in augmented grid assets capable of performing power routing on the electricity grid. The work has focused on the thermal transport of single-phase closed thermosiphon systems incorporating a secondary parallel flow path for cooling an additional, typically smaller, thermal load associated with the power electronics converters. Dual-loop thermosiphon passive thermal management systems were incorporated into a grounded compact dynamic phase angle regulator (GCD-PAR) that aimed to facilitate power routing and reduce line losses on the power grid. The power router utilizes power electronics that reject heat to a planar area, or cold plate, which must be cooled by an entirely passive system to comply with the minimum 30 year mean time between failures (MTBF) consistent with grid reliability requirements. This design includes a secondary-loop cooling path that utilizes the cooling oil already present in the transformer to also cool the power router. An analytical multi-physics thermosiphon model is developed that couples existing fluid dynamic and heat transfer correlations to create a description of the steady state operation of a specific cylindrical 50 kVA transformer augmented with a thermosiphon. The model is validated experimentally and found to solve for steady state baseplate temperatures under maximum load within 2°C in 0.1 seconds. The model is then modified for a specific rectilinear 1 MVA transformer augmented with three thermosiphons. The 1 MVA model is validated experimentally and found to solve for steady state baseplate temperatures under maximum load within 4 °C in 0.2 seconds. The analytical model proves to be accurate and solve quickly with various geometric configurations and thermal loads.

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