Diagnostics of a Domestic Hot Water Storage Tank under Operating Conditions

This paper presents a new method for the diagnostics of a hot water storage tank under operating conditions. Depending on the operating point of the tank, the method enables determination of thermal conductivity coefficients of the coil heat exchanger, which allows us to determine the intensity of heat transfer between the transfer medium and water in the tank as well as of tank walls, which consequently enables determination of heat losses to the environment. Furthermore, the dynamic properties of the tank may also be determined by applying this method. The advantage of this method is possibility of analyzing changes in the material constants of the coil heat exchanger, tank walls, and dynamic properties of the tank as a function of mass flow of the medium supplying the coil heat exchanger. The possibility of determining coefficients of thermal conductivity as well as the inertia of tank and exchanger, based on temperature measurements acquired in operating conditions is a novelty in this paper. Knowing the variability of material constants and of dynamic properties of the tank as a function of medium flow rate allows multicriteria optimization to be performed which, with a conventional design of the tank, results in a reduction of up to 10% in the time taken to prepare domestic hot water.

Automated summary

This paper introduces a new method for diagnosing hot water storage tanks under operating conditions, which enables the determination of thermal conductivity coefficients of the coil heat exchanger and the intensity of heat transfer, as well as the determination of dynamic properties of the tank. By analyzing the changes in material constants and dynamic properties of the tank as a function of medium flow rate, multi-criteria optimization can be performed, resulting in up to a 10% reduction in the time taken to prepare domestic hot water with a conventional tank design.