Field Testing of an Advanced Low-Charge Supermarket Refrigeration System

A field test was conducted to compare the performance of multiplex and distributed supermarket refrigeration systems. Two supermarkets in the vicinity of Worcester, Massachusetts were the sites utilized for the field test. One store was equipped with a multiplex refrigeration system that had 3 compressor racks and air-cooled condensers. At the second store, a low-refrigerant-charge distributed refrigeration system was installed that consisted of 10 compressor cabinets. Heat rejection for the compressor cabinets was accomplished through watercooled condensers piped to a fluid loop that used dry fluid coolers. The second store also had water-source heat pumps for space heating and cooling that were piped into the fluid loops. Both sites were instrumented to determine energy consumption, refrigeration and heating, ventilating and air conditioning (HVAC) loads, and numerous system state points to characterize operation. Data were collected for approximately 18 months. A comparison of the performance of the two refrigeration systems was made based on the information gathered. The results showed that the multiplex refrigeration system used less energy and showed better EER than the distributed system. A TEWI comparison between the two refrigeration systems showed significant reductions in atmospheric CO2 generation by the distributed system despite added energy use. Test results also showed that the water-source heat pumps produced energy cost savings for store space heating by recovery of the refrigeration reject heat.