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EVALUATION OF A MULTIFUNCTIONAL VALVE ASSEMBLY IN A DIRECT EXPANSION REFRIGERATION SYSTEM REPORT
Citation:
Gage*, C L. AND G. S. Kazachki. EVALUATION OF A MULTIFUNCTIONAL VALVE ASSEMBLY IN A DIRECT EXPANSION REFRIGERATION SYSTEM REPORT. U.S. Environmental Protection Agency, Washington, DC, 2004.
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Description:
The report describes the performance, including energy consumption, of a refrigeration system incorporating a multifunctional valve (MXV assembly). The MXV assembly (consisting of additional liquid line, an XTC valve, and a larger thermostatic expansion valve) was installed on all display cases of an instrumented supermarket refrigeration test rig. The refrigeration test rig includes two low- temperature single-deck display refrigerators; two 2-door reach-in cases; and a condensing unit with three unequal compressors, a water-cooled condenser, a water-cooled subcooler, an oil management system, and a programmable controller. Tests were performed at various combinations of evaporating temperature (-30 or -27 degrees F), condensing temperature (75 or 105 degrees F), and defrost schedules (once per 24 or 48 hours) under either temperature or pressure control. Results were compared to tests at the same conditions on the baseline system. Lower package temperatures were achieved under pressure control with the MVX assembly due to the lower superheats specified by the MXV manufacturer, but this reduction came at an energy penalty. Under temperature control, the control methodology used in field applications, there was no energy or product temperature benefit seen with the MXV valve assembly. Although coil pull-down times after defrost were shorter, there was no impact on daily energy use. Both the MXV and baseline system performed well with one defrost per 48 hours, and each had about 4% energy savings compared to a more frequent defrost schedule. However, at this condition, MXV showed no added benefit over baseline.