Thermal energy storage systems for utilization of waste heat

The aim of this study is to decrease electricity consumption and increase conservation through storing and utilization of waste heat at 35-55 °C that is given off from industrial processes and appliances in everyday life. Heat exchangers with different geometries and configurations were designed to be used for thermal energy storage and recovery in Phase Change Materials (PCM). Paraffin RT35 was used as PCM. Storage and recovery experiments were carried out at different temperature and flow rates. Overall heat transfer coefficient (U) and heat storage capacity (Q) increased at higher flow rates. The maximum U values were in the range of 704-854 W/m2ºC for double pipe heat exchanger with graphite fins. The highest Q values were for the compact heat exchanger type with values in the range of 490-1040 W. Based on the results from heat exchanger investigations, compact heat exchanger configuration was preferred to be used in thermal energy storage system for utilizing waste heat in dishwashers to increase energy efficiency. Energy efficiency, economics and environmental benefits were determined for the thermal energy storage unit designed for dishwashers. It was determined that the energy efficiency of the dishwasher can be increased by 10,7% with the design using graphite and PCM together.