A novel cascaded absorption/vapor-compression cycle with a high temperature lift was conceptualized and analyzed in this study. A single-effect LiBr-H2O absorption cycle and a subcritical CO2 vapor-compression cycle were coupled together to provide low-temperature refrigerant (-40 °C) for high heat flux electronics applications, medium-temperature refrigerant (5 °C) for space conditioning and other low heat flux applications, and as an auxiliary benefit provide medium-temperature heat rejection (~48 °C) for water heating applications. The cycle was modeled for a naval ship application where the absorption cycle was powered by the exhaust heat from the onboard gas turbine power plants. The performance of the cascaded system was also compared with an equivalent two-stage vapor-compression cycle. For the baseline case, the system COP on total input energy basis, and total-electric input basis was estimated to be 0.594 and 5.685, respectively. The COP of the individual absorption and vapor-compression cycles was estimated to be 0.7803 and 2.173, respectively. With a nominal 200 MW of waste heat input, 82 MW of cooling at 5 °C, and 51 MW of cooling at -40 °C are delivered, with an investment of only 23 MW of compressor power. Parametric analyses on the heat rejection temperature and exhaust heat inlet temperature indicated that the system exhibited a high COP for a wide range of operating conditions. The ability of the system to address pulsed high heat flux loads was also demonstrated and risks of crystallization were explored. When considering waste heat input as "free" energy, the overall COP of the cycle is as high as 8. Compared to an equivalent vapor-compression system, the cascaded absorption/vapor-compression cycle avoids up to 31% electricity demand. The natural refrigerants used in this cycle make it an excellent candidate for use on board naval ships and minimize risk to the environment at large. These analyses show that the cascaded absorption/vapor-compression cycle represents a significant advance in the ability to provide lowtemperature coolant for heat removal at high heat fluxes over large surface areas. The reduction in energy consumption resulting from the utilization of waste heat is not an auxiliary benefit from the absorption system, but rather, is expected to be a critical enabling feature that provides the necessary cooling within the constraints of the limited fuel inventory available on board. The drastic reductions in power consumption will directly minimize fuel requirements, minimize ship weight, increase cruising range, and therefore increase the flexibility in mission and location. Such systems can also be extended to other waste heat recovery applications including long-haul refrigerated trucks, food processing and refrigeration, and others.


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    Title :

    Waste heat driven absorptlon/vapor-compresslon cascade refrigeration system for megawatt scale, high-flux, low-temperature cooling


    Additional title:

    Mit Abwärme betriebene Absorptions/Dampfkompressionskälteanlage (Kaskade) für Hochdurchfluss-Tieftemperaturkühlung im Megawattbereich


    Contributors:

    Published in:

    Publication date :

    2011


    Size :

    10 Seiten, 14 Bilder, 2 Tabellen, 20 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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