Performance standards for walk-in coolers and freezers in the United States as a function of local weather conditions
Anupindi, Raja Srinivas Rao
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Walk-in coolers and freezers are medium (~35º F) and low (~-10º F to -20º F) temperature commercial food preservation equipment, with high market demand. There is considerable potential for energy savings through implementation of energy efficiency measures such as high-efficiency evaporator/condenser fan motors, feedback control systems, automatic door closers, strip curtains, suction line insulation, optimized envelope insulation design, high efficiency lighting, hot gas defrost, evaporator fan controllers, etc. However, minimum efficiency standards for walk-in coolers and freezers have not yet been developed. Development of performance based standards for walk-in coolers and freezers is tantamount to establishing an effective market system in order to achieve energy savings. Development of minimum energy efficiency standards and performance based rating methods requires energy consumption data and cooling capacity data for various walk-in refrigeration system components as functions of the dry-bulb and wet-bulb temperatures of the ambient air surrounding the walk-in box and the condensing unit. In this project, walk-in cooler and freezer models were developed and their performance was simulated using Pack Calculation II software (Danfoss, 2009), in an effort to determine the annual energy consumption and total cooling for a set of representative climatic zones in the United States. Using this data, a performance metric, referred to as the Annual Energy Efficiency Ratio (AEER), was developed to estimate the annual energy efficiency of walk-in coolers and freezers. A simplified testing method based on two representative condensing temperatures to calculate AEER was developed and demonstrated in this research project, based on the hourly ambient temperature data of twelve representative climatic zones in the United States of America. This technique can also be applied to any geographical location with climatic conditions similar to the twelve locations analyzed in this project. This simplified testing method will provide manufacturers with a practical and cost effective technique to test the annual performance of the walk-in refrigeration equipment and to improve operating efficiency. AEER values of walk-in freezer and cooler designs estimated in the current project using the proposed simulation technique closely matched with EER values published in the Federal Register Vol. 75, No.1, Jan 2010, Department of Energy.
Table of Contents
Introduction -- Energy efficiency standards and testing of walk-ins -- Analytical methods -- Results and discussions -- Future research -- Conclusions -- Appendix A. SAS program to determine the frequency distribution of hourly heat removed and work done by the refrigeration system -- Appendix B. Sample SAS output for frequency distribution of heat removed from a walk-in freezer in New York