Abstract
Lowering the condensing temperature of the Refrigeration and Air-conditioning (RAC) system has been proven to effectively increase the system’s Coefficient of Performance (COP). This paper revolves around evaluating the energy-saving generated by applying a Thermal Diode Tank (TDT) in the RAC systems. The TDT is a novel invention, which is an insulated water tank equipped with gravity heat pipes. If the TDT was placed outdoors overnight, its inside water would theoretically be at the minimum ambient temperature of the previous night. When the TDT water is used to cool the condenser of RAC systems that operate during the daytime, a higher COP of this TDT assisted RAC (TDT-RAC) system could be achieved compared with the baseline system. In this study, a steady-state performance simulation model for TDT-RAC cycles has been developed. The model reveals that the COP of the TDT-RAC cycle can be improved by 10~59% over the baseline cycle depending on the compressor types. The TDT-RAC cycle with a variable speed compressor can save more energy than that with a fixed speed compressor. In addition, TDT-RAC cycles can save more energy with a higher day/night ambient temperature difference. There is a threshold tank size for a given TDT-RAC cycle to save energy, and the energy-saving can be improved by enlarging the tank size. A desk-top case study based on real weather data for Adelaide in January 2021 shows that 9~40% energy could be saved by TDT-RAC systems every summer day on average.
Highlights
Conserving energy is a major global challenge, and one of the most effective methods is to find solutions from energy efficiency improvements
The refrigeration and air-conditioning (RAC) system equipped with a Thermal Diode Tank (TDT) is expected to generate a reduction of up to 40% in its energy consumption
The RAC system equipped with a TDT is expected to generate a reduction of up to 40% in its energy consumption compared with a baseline system in the presence of day and night ambient temcompared with a baseline system in the presence of day and night ambient temperature perature differences
Summary
Conserving energy is a major global challenge, and one of the most effective methods is to find solutions from energy efficiency improvements. This novel condenser achieved an improvement in the COP by about 30% In both researches, the cooling performance of separation condensers is constrained by the ambient temperature; if the ambient temperature was over 40 ◦ C, these systems would even have lower COPs. While utilising the mist generator to supply cold mist for the RAC system’s condenser, Yang et al [17] achieved a considerable COP improvement of 21.3~51.5%, which is higher than those of most evaporative cooling methods. GHPs prevents from from thefrom condenser section tosection the evaporator section bysection conduction the heatbeing fromtransferred being transferred the condenser to the evaporator by even with scorching ambient temperatures If such a device was placed outdoors overnight, the TDT water would theoretically be at the minimum ambient temperature of the last night.
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