Household dishwashers are home appliances that perform washing processes using electricity and water as inputs, thereby increasing household comfort. Between 70% and 90% of the electricity used in a washing cycle is consumed for heating water. The wastewater, which can range in temperature from 45°C to 60°C, is discharged into the drain without being utilized. In this thesis, a thermal energy storage (TES) unit was developed to utilize the thermal energy of the wastewater. An additional air duct was integrated into the TES to interact thermally with the wastewater. Air at 23°C with 55% relative humidity, drawn from the external environment, passes through this duct with the help of a fan, is heated by the energy from the wastewater, and is directed into the washing chamber. As the temperature of the air increases, its moisture-carrying capacity rises, and since its relative humidity is lower compared to that of the chamber, it enhances the drying performance. To increase heat transfer in the air duct thermally interacting with the TES, five different types of fin designs were developed and analyzed using computational fluid dynamics (CFD). Firstly, the effect of fin designs on flow resistance was investigated, and the air outlet flow rates were compared. Subsequently, the impact of the fins on heat transfer was evaluated by conducting time-dependent simulations under the initial conditions of the drying phase. A prototype was produced with the fin design that provided the most efficient results, extending along the length of the duct. Drying performance experiments were conducted with the prototype TES integrated into a dishwasher according to the EN 60436 standard. According to the results, when the developed TES system was integrated into a dishwasher with a B energy class (0.595 kWh/cycle), it was upgraded to an A energy class (0.544 kWh/cycle).