Thermally activated miniaturized cooling system
Determan, Matthew Delos
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A comprehensive study of a miniaturized thermally activated cooling system was conducted. This study represents the first work to conceptualize, design, fabricate and successfully test a thermally activated cooling system for mobile applications. Thermally activated systems have the ability to produce useful cooling from waste heat streams or directly from the combustion of liquid fuels. Numerous concepts of miniaturized or mobile, active cooling systems exist in the literature but up to this point, successful fabrication and testing has not been documented. During this study, a breadboard absorption heat pump system was fabricated from off the shelf or in-house, custom-built components. The breadboard system was used to validate the feasibility of operating an absorption heat pump with a cooling capacity of about 300 W. Subsequently, a flexible and scalable design methodology for designing miniaturized absorption heat pumps was developed. A miniaturized, 300 W nominal cooling capacity ammonia/water absorption heat pump cycle with overall dimensions of 200 × 200 × 34 mm and a mass of 7 kg was then fabricated and tested. Testing of the absorption heat pump was conducted over a range of heat sink temperatures (20 ≤ T ≤ 35°C) and desorber thermal input rates (500 ≤ Q ≤ 800 W). Evaporator coolant heat duties in the study ranged from 136 to 300 W, while system COPs ranged from 0.247 to 0.434. At a nominal rating condition of 35°C heat sink temperature, the maximum thermal input of 800 W produced a cooling effect of 230 W. This represents a cycle COP of 0.29. Analysis of the experimental data indicated that future work should focus on improved desorber and rectifier designs to improve refrigerant purity. It is estimated that a system similar to the one in this study, with all fluid connections made internal to the system, could achieve the same cooling capacity with a system mass of 2.5 - 3.5 kg in an envelop of 120 × 120 × 25 mm.