Experimental Investigation and Advanced Exergy Analysis of Different Factors That Can Affect Seasonal Performance in an R410A Chiller

Due to the new energy regulations, there is an increased demand for higher efficiency HVAC&R equipment. Improvements in compressors and heat exchangers (BPHX) can lead to a higher system COP. Compressors are compared using efficiency and BPHX are evaluated based on their LMTDs and pressure drops. It is difficult to compare the contribution of these two on the system COP using traditional first law analysis. Advanced exergy analysis (AEA) can help with this estimation by using exergy destruction as a metric. In the current paper, AEA framework is used to analyze the different factors that can impact the system performance and seasonal performance. The study is done on an 8-kW R410A water ethylene glycol chiller (WEG) and the results from seasonal performance of three different scroll compressors are used for this analysis. Three factors included are compressor motor efficiency, condenser size and compressor capacity modulation strategy. AEA shows that optimizing the compressor followed by condenser has the highest potential of improving system performance. \({\dot{E}}_{D}^{EX,total}\) drops by 18% with upgraded compressor while it drops by 28% with oversized condenser showing that that the condenser has higher impact on the exergy destruction. AEA comparison of a two-stage compressor and a variable speed compressor show that \({\dot{E}}_{D}^{EN}\) of the two-stage compressor is 39% higher indicating that variable speed compressor is more efficient at matching the cooling load. Based on the relative magnitude of \({\dot{E}}_{D}^{AV,EN}\) , compressor upgrade and condenser upgrade would yield higher system performance in two-stage and variable speed compressor systems respectively.