2001 TSE: NSF/EPA Partnership for Environmental Research: A Theoretical and Experimental Approach to Rapid Screening and Design of Secondary Refrigerants (TSE01-C)

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Hydrofluorocarbon (HFC) emissions from the refrigeration and air conditioning sector in the U.S. currently amount to approximately 13 million metric tons of carbon equivalent (MMTCE). This number is expected to grow to 27 and 38 MMTCE in 2005 and 2010, respectively. Second only to automotive refrigeration systems, retail food refrigeration accounts for 25% of these emissions: a typical supermarket leaks about 1 ton of refrigerants every year. Secondary refrigeration loops have the potential to reduce primary refrigerant charges to as little as 10% of that required in a traditional refrigeration system. Nonetheless, secondary refrigeration has found acceptance in only about 200 out of over 30,000 supermarkets and 300,000 convenience stores in the U.S. With profit margins comparable to their electric bills, retail food enterprises are concerned that secondary refrigerants may not be as energy-efficient as the HFCs that are currently used in direct refrigeration. Improving the energy efficiency in this sector is of government concern as well since the retail food industry currently accounts for approximately 4% of electricity consumption in the nation. The primary goal of this project is to work towards addressing the following questions: (a) What are the families of compounds that can act as secondary refrigeration fluids? (b) What is the energy efficiency of these compounds and how does it compare to that of the HFCs that are currently used in direct refrigeration? (c) Are these compounds safe and environmentally benign? Towards answering these questions, this project integrates theoretical and experimental research that will: (1) develop a mathematical model which selects the atomic composition of a refrigerant in such a way that environmental and chemical constraints are satisfied while the energy efficiency, total warming impact of the refrigerant life-cycle, and other economic and environmental objectives are optimized; (2) devise an algorithmic procedure to solve the above model in a way that overcomes the combinatorial difficulty of the problem as well as difficulties associated with nonlinearities in property prediction estimation techniques; (3) establish an experimental procedure for calibrating the mathematical model through measurement of physical properties of potential refrigerants; (4) verify experimentally the theoretical findings through laboratory synthesis of compounds identified by the model and measurement of their thermal transfer properties in actual refrigeration equipment.