New condensate water removal method a plug-in RDC: experimental and regression analysis

Plug-in refrigerated display cabinets (RDCs) are extensively used in supermarkets and constitute a significant portion of global energy consumption. In conventional designs, Positive Temperature Coefficient (PTC) resistance heaters are employed to evaporate condensate water collected in the pan. While effective, this method increases energy consumption and negative environmental impact. This study proposes an alternative condensate water removal method by replacing the PTC heater with an ultrasonic humidifier. The performance of the proposed Ultrasonic Humidifier System (SWUH) was experimentally compared with the conventional PTC System (SWPTC) under the test conditions under the ISO 23953-2:2023. The results indicated that switching to SWUH reduced energy consumption by 15.12 %, decreased lifetime carbon emissions by 6140 kgCO₂, and reduced the EEI (Energy Efficiency Index) of RDC. From an economic perspective, the SWUH investment is expected to achieve payback at the beginning of the 25th month and provide the owner with an additional income of $1000 over its economic lifetime. Statistical analysis showed strong correlations between M-package temperatures within the cabinet compartments in the SWPTC design. The correlation coefficients were 0.69, 0.99, 0.76 respectively. In contrast, the SWUH design exhibited lower correlations (−0.63, 0.52, 0.23). This reflects distinct structural characteristics between the systems. All findings obtained in this study confirm that ultrasonic humidification can be efficient alternative to PTC-based condensate water management in RDCs, providing both energy savings and environmental benefits. Future research will focus on utilizing waste heat from the refrigeration process and enhancing sustainability by meeting the RDC's energy needs with renewable energy technologies.