Investigation of thermal stratification in a thermal storage tank with a curve edge obstacle plate

Abstract

Nowadays, thermal storage tanks have been widely installed because of high demanding for hot water in the production process or daily activities in a household. Numerous energy has been consumed to produce hot water. To reduce the energy consumption and improve the energy efficiency of the hot water system, the design of thermal stratification in a storage tank can play as an important parameter on its thermal efficiency. The basic concept of the thermally stratified tank is attempted to separate a layer of hot and cold water by means of density variation and gravitational effects which cold water is aimed to existing at the bottom and hot water is at the upper part of the tank. The level of temperature stratification significantly impacts on the thermal efficiency. The higher degree of thermal stratification, the better thermal efficiency of the hot water system. However, there are many factors strongly affected the thermal stratification such as height-to-diameter ratio, the inner structure of thermal storage tank, the water flow rate, and etc. Therefore, the purpose of this study is to design a thermally stratified tank by improvement the inner structural design of the tank. Two influenced factors are focused: i) the different configuration of inlet pipes which can impact on the flow pattern and flow velocity of the water and ii) the different design of obstacle plates which can help control a recirculation area of the water in the tank. To obtain a high thermal efficiency of the stratified tank, the computer simulation program Ansys Fluent is applied for the analysis. The results show that uniform distribution of water flow and lower flow velocity due to the appropriate design of inlet pipe and proper buffer plate design can enhance the temperature stratification in the storage tank which increase the thermal efficiency during discharging processes.