Abstract
Absorption chillers present opportunities to utilize sustainable fuels in the production of chilled water. An assessment of the steam driven absorption chiller at the University of Idaho, was performed to quantify the current exergy destruction rates. Measurements of external processes and flows were used to create a mathematical model. Using engineering equation solver to analyze and identify the major sources of exergy destruction within the chiller. It was determined that the absorber, generator and condenser are the largest contribution to the exergy destruction at 30%, 31% and 28% of the respectively. The exergetic efficiency is found to be 16% with a Coefficient of performance (COP) of 0.65. Impacts of weak solution concentration of lithium bromide on the exergy destruction rates were evaluated using parametric studies. The studies reveled an optimum concentration that could be obtained by increasing the weak solution concentration from 56% to 58.8% a net decrease in 0.4% of the exergy destruction caused by the absorption chiller can be obtained. The 2.8% increase in lithium-bromide concentration decreases the exergy destruction primarily within the absorber with a decrease of 5.1%. This increase in concentration is shown to also decrease the maximum cooling capacity by 3% and increase the exergy destruction of the generator by 4.9%. The study also shows that the increase in concentration will change the internal temperatures by 3 to 7 °C. Conversely, reducing the weak solution concentration results is also shown to increase the exergetic destruction rates while also potentially increasing the cooling capacity.
Highlights
For building a sustainable system, maximizing the use of resources with minimal environmental impacts is key [1]
Overall the absorption chiller on the University of Idaho campus is responsible for an exergy destruction of 870.1
This study demonstrates the value in analyzing current systems to evaluate for potential improvements
Summary
For building a sustainable system, maximizing the use of resources with minimal environmental impacts is key [1]. A completely sustainable system would require a fully reversible process, a feat that the second law of thermodynamics proves is not possible; indicating that all real processes are irreversible and impact the environment. Approaching sustainability can yield benefits both the current and future environment [2]. Utilization of resources in a responsible fashion and with efficient methods is important when developing new technologies and analyzing current systems [3,4,5,6]. Conventional vapor compression systems and absorption chillers utilize different working fluids. Many of the vapor compression systems use the ozone depleting chlorofluorocarbon refrigerants (CFCs) because of the thermophysical properties offered by them. Many industrial processes often produce a significant amount of thermal
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