Numerical modeling of heat losses from hot water storage tank

Domestic hot water storage tanks (HWST) are widely used devices, and their daily operation can generate significant annual heat losses to the environment. Previous studies concerning HWST have mainly focused on the impact of insulation quality and thickness, stratification, and tank operation on total heat losses. Some studies have addressed these losses concerning different parts of the tank, including upper, lower, and side walls. However, the influence of insulating additional tank elements, such as connectors, on heat loss has not been analyzed. Therefore, experimental studies were conducted as a reference for the temperature distribution and heat loss from an insulated HWST equipped with 12 connectors. Then, CFD numerical calculations of heat loss were performed for various variants: an insulated HWST without connectors, a tank with connectors insulated in five different ways, and an uninsulated tank. It was found that, in extreme cases of poor insulation of the tank connectors, the heat loss increased by 92.5 % and 147.6 %, respectively, compared to the reference loss. This means an increase in heat loss streams by 62.0 Wand 98.9 W compared to the reference case. The latter value corresponds to an annual heat loss of approximately 3 GJ. The study also showed that insulating the bottom of the tank is crucial. With proper insulation, heat losses from this part account for less than 10 % of the total heat loss. The results highlight the critical role of proper connector insulation in minimizing standby heat losses in water storage systems.