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Abstract-Freezer is one of the electrical components that can be found in any building. Like any electrical appliance domestic freezer consumes a significant amount of energy during its working time. During recent decades a lot of solutions have been found to reduce this energy consumption. One of the most usable and appropriate ones is implementation of phase change material (PCM) in a Cold Thermal Energy Storage (CTES) system which can be installed in a household freezer. In this paper numerical investigation of using CTES system in a domestic freezer in order to diminish energy consumption during pick hours (18-22:30), is studied. Regard to the temperature ranges of the freezer, NaCl-H2O is used as a PCM in the CTES system. In a distinct period of time, a large amount of cold thermal energy in latent heat form is stored at low temperature in the PCM, and it is released in the freezer's cabin when the compressor is off. Accordingly, numerical modeling and simulation using Computational Fluid Dynamics (CFD) software on charging and discharging cycle of PCM are done to measure cold storage period and amount of saved energy. The results reveal that using CTES could keep the freezer in the standard thermal condition without using a compressor, for 4.5 hours. These results show that if the PCM used in CTES system for a year, it could reduce energy, fossil fuel consumption and CO2 emission up to 45.7 kWh, 13.7 liters and 32.0 kg, respectively.

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To increase the capacity factor of a concentrated solar thermal power plant (CSTPP) beyond the hours of sunlight, the use of thermal energy storage systems (TES) can be a promising solution. Phase change materials (PCMs) can store latent thermal energy in the course of the melting process and release it when solar energy is not available. Generally, PCMs have low thermal conductivity. One of the most commercially promising solutions is the application of an extended heat transfer surface inside the PCM container. Moreover, the distance of the heat transfer fluid (HTF) to the core of the PCM in a TES system can affect the storage performance. Accordingly, a triplex tube heat exchanger with eight fins is considered in this paper, to investigate the impact of the different velocity of HTF and different entrance pattern in a vertical PCM container. Notably, the middle enclosure of the triplex tube is filled with PCM. Numerical analysis using an enthalpy porosity technique revealed that increasing HTF velocity reduces the charging time. Also, when the HTF enters from the bottom of the container, the storage time will diminish owing to a natural convection side-effect, but if the HTF flows downward, the amount of sensible thermal energy storage is higher than in the other cases.