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.

Data sets of internal resistances and open-circuit voltage of a particular battery are needed in ANSYS Fluent program to predict the heat generation accurately. However, one set of available data, called Chen’s original, does not cover all types and shapes of batteries. Therefore, this research was intended to study the effects of shapes and polarization chemistries on heat generation in Li-ion batteries. Two kinds of material chemistries (nickel manganese cobalt oxide, NMC, and lithium iron phosphate, LFP) and three forms (cylindrical, pouch, and prismatic) were studied and validated with the experiment. Internal resistance was unique to each cell battery. Differences in shapes affected the magnitude of internal resistance, affecting the amount of heat generation. Pouch and prismatic cells had lower internal resistance than cylindrical cells. This may be the result of the forming pattern, in which the anode, cathode, and separator are rolled up, making electrons difficult to move. In contrast, the pouch and prismatic cells are formed as sandwich layers, resulting in electrons moving easily and lowering the internal resistance. The shapes and chemistries did not impact the entropy change. All batteries displayed exothermic behavior during a lower SOC that gradually became endothermic behavior at around 0.4 SOC onwards.

Temperature stratification between outgoing hot water and incoming cold water is a key factor in diminishing energy loss during the discharging process and maximizing the useful hot water delivered from the tank or enhancing the thermal efficiency of the heating device during the heating process. In this study, the inlet structure and the obstacle plate were designed and modified based on two main factors, the reduction of inlet water velocity and the stipulation of the water recirculation area, to develop temperature stratification through the computational fluid dynamics method. The simulation model’s accuracy was validated against the experimental results. The results showed that using the equalizer as an inlet pipe’s auxiliary device was the best approach for decreasing the inlet water velocity, which resulted in enhancing temperature stratification. The discharging efficiency improved from 77.3% for the original tank model to 86.1% for the tank with equalizer IV model, which meant an additional 45 L of useful hot water was gained from the good temperature stratification storage tank. The installation of the obstacle plate for controlling the turbulence zone could not improve temperature stratification significantly, which resulted in an increase in discharging efficiency by only 4% more than the original tank model.