Abstract
The paper presents the analysis of thermal processes occurring in thermal energy storage tanks used for heating hot water systems. Three-dimensional Computational Fluid Dynamics (CFD) methods were used. The standard buffer charging stage was modelled for three tank inlets’ diameters DN20, DN40 and DN80. With a constant charging water flow and temperature the port diameter affects inlet velocity, heat storage dynamics, thermal stratification and thermocline thickness in storage tank. The smallest diameter causes unfavourable thermal mixing of accumulated water, and the largest diameter supports thermal stratification
Highlights
Thermal energy storage (TES) in heating hot water systems allows the stabilization between the variable heat demand and heat production
Computational Fluid Dynamics (CFD) transient 3D simulations can be successfully used as an effective tool to analyse and optimize the parameters of a water TES tank at a very early stage of design
The results of numerical analysis indicate that the adjustment of water inlet port diameter significantly improve the thermal stratification in charging stage
Summary
Thermal energy storage (TES) in heating hot water systems allows the stabilization between the variable heat demand and heat production. TES tank in water heating systems has two basic tasks: to store the required amount of heat, and to deliver the required water temperature to heat exchangers. The influence of TES tank volume and water temperature on thermal storage capacity is widely known and understood. The TES tank charge-discharge dynamic and the impact of water stratification is little known among engineers, and rarely considered in the design. In TES design process the storage volume, water flow and water temperature are determined by heat source and heat demand characteristics. The water inlet velocity of charging water is determined by diameter of TES tank connection ports. The inlet velocity impact on stratified heat storage should be defined and investigated in every project
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