<p>Increasing average atmospheric temperature demands air conditioning in several fields such as human thermal comfort to increase workability, prolong the life of beverages and food products, effective execution of the industrial processes, etc. A district cooling (DC) is superior to conventional air conditioning as it helps to reduce energy consumption and to protect the environment by reducing carbon dioxide emissions. District cooling is a scheme to provide thermal comfort to the end-user through a centralized chiller plant and complex distribution network. &nbsp;Currently, many DC plants around the world operate with vapor compression refrigeration (VCR) chillers which significantly consume high grade energy and degrades the environment due to both burnings of fossil fuels to generate electricity and the use of refrigerants. The use of fossil fuels increases the emission of greenhouse gases and the use of refrigerants in the VCR with high global warming potential values, both contribute to global warming. The advantages of the district cooling plant can further be improved by integrating the VCR system with the vapor absorption refrigeration system (VAR). The implementation of VAR, either alone or with integration, allows effective use of the low grade energy such as waste heat or renewable energy, which otherwise be wasted. Another aspect of interest is the search for novel combinations of refrigerant/absorbent mixtures, which improve the ABR thermodynamic performance, reduce environmental impact, and curtail handling risks compared to the widely used ammonia-water. In this context, this paper presents the comparative assessment of the VCR chiller and two configurations of the VCR and VAR integrated chiller: parallel configuration and cascade configuration. Two refrigerant-absorbent mixtures in the VAR system will be considered namely; the conventional ammonia-water and the novel acetaldehyde-N,N-dimethylformamide. The energy, exergy, environmental and economic analysis of the systems have been performed considering the coefficient of performance, the exergy efficiency, the total equivalent warming impact, and the cost rate as performance indicators, respectively. Actual data from a DC plant are used to develop a model of the configurations under consideration. In the parallel configuration, the total refrigerating load will be divided equally between the VCR system and the VAR system (chilled water enters first in the VAR and then pass through VCR). Whereas the refrigerating effect in the cascade arrangement will be achieved from the evaporator of the VCR alone, but the heat rejected in the condenser of the VCR will be dissipated through the evaporator of the VAR system. A detailed comparative investigation on the performance indicators for all three configurations considering direct and indirect impact will be presented.</p>

Thermodynamic, Environmental and Cost Evaluation of Compression-Absorption Parallel and Cascade Refrigeration Chiller

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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