Thermodynamic analysis for improved HVAC distribution system performance.

摘要

Commercial buildings in the U.S. comprise 12% of the nation's energy consumption. Increasing their efficiency will have marked impact on reducing national consumption. The savings associated with improving commercial-building distribution-system performance are significant, particularly in large buildings with simultaneous heating and cooling loads. Yet, a definition for efficiency does rot exist for the distribution system as it does for energy-consuming building components like luminaires, chillers, or boilers. This results from the energy impact of system design and operating parameters not being limited to individual pieces of equipment that can be isolated and measured.; The objective of this research is to overcome the barriers to characterizing and improving distribution system performance. To meet the objective, distribution-system performance indices are defined to measure efficiency and second-law analysis methods are developed to identify opportunities for making performance improvements. The data needed to characterize distribution system performance are not generally collected even with state-of-the-art energy management and control systems. This study makes recommendations for expanding monitored-building data sets to improve performance characterization and evaluation. Through simulation analysis, a theoretical basis for modifying design and operation evaluation techniques is developed.; Performance indices reduce data from an information-rich process into a form useful for making conservation decisions. The indices proposed in this study measure thermal, mechanical, and overall system performance and are based on a first- and second-law of thermodynamics analysis. Unlike the first law, the second law exposes the sources of irreversibility that occur in a process and reveals the system components with the most potential for improvement. The second-law task efficiency is an example of a distribution system performance index. This index compares the overall performance of the system to an ideal thermodynamic device.; The primary conclusions are that performance indices and second law analysis enhance existing engineering methods used for distribution system design. They encourage performance advances through the quantification and identification of system inefficiencies. In installed-system performance evaluation, performance indices compliment system load and fan energy data but do not supercede their use. To track performance, developing calibrated-models based on energy is simpler and as accurate as developing second-law based models.