Active solar water heating systems typically include hot water storage tanks. The selection of the storage system strongly affects the performance of the entire system. This article presents a ...detailed analysis of a hot water storage tank during charging and dynamic charging-discharging mode. A numerical model using computational fluid dynamics for the storage tank was developed to investigate the temperature distribution inside of it. Transient thermal analysis was carried using ANSYS Fluent. The numerical model was validated with the experimental results. The energy and exergy analysis as an important tool for the evaluation of the thermal systems quantitatively and qualitatively was performed. The calculation procedures were described. The energy and exergy efficiencies, heat losses were calculated for steady and dynamic processes. Effect of mass flow rate was analysed. The results from parametric analysis showed that charging dynamics reduced the thermocline and efficiency of the hot water storage tank. The dependency of the exergy efficiency of the heat storage tank on the reference environment temperature during the dynamic operation was analysed. Exergy efficiencies for two cities with different climates were compared. This indicated that the higher environmental temperature gave lower exergy efficiency of the storage tank.
The authors have improved the test equipment of the multi-tank-combined water heat storage tank, which was earlier mentioned in the first report, for the purpose of facilitating tests of the parallel ...stratified heat storage tank. Using this experimental equipment, the authors have conducted tests in accordance with the varied flow distribution in each of the two parallel systems with a view to finding characteristics of inside temperatures of the heat storage tank. In light of the operating methods of air-conditioning systems, the authors have conducted tests additionally based on such factors that might have an impact on the heat storage efficiency of the combined fully-mixed heat storage tank as the diameter and placement of connecting pipes, gaps in secondary circular temperatures, drain pipes and residual heat storage volume in order to discover thermal characteristics of the heat storage tank.
The thermal energy storage (TES) system installation provides the optimization of energy source, energy supply security, flexibility of power plant operation and energy production. The aim of given ...research is feasibility analysis and evaluation of thermal energy storage system installation at Riga cogeneration heat power plant (CHPP) Nr. 2 with P el = 832 MW and Q th = 544 MW (cogeneration unit Nr. 1 and Nr. 2). The six modes were investigated: four for non-heating periods and two for heating periods. Different research methods were used: data statistic processing and analysis, forecasting, financial analysis, correlation and regression methods. Finally, the best mode was chosen with aim to increase of cogeneration unit efficiency during the summer period.
This paper will present a new type of heat supply system, which provides both fresh air and heat. It helps save much more energy and greatly reduce the waste of heat than ever before, other than ...that, it also realizes the dynamic regulation of the outlet air temperature in this system. First, solar-powered water heaters heat the cold water in the pipes, and then it flows into two branch pipes. One flows over the fan coil exchange heat with the outlet fresh air. The other flows over a tank and stores the additional heat temporarily. According to the data detected by sensors on the CAN bus, this system will call the fuzzy function to keep the balance between heat exchange and heat storage. In this way, the air in room will maintain a stable temperature and fresh. This system is completely different from the traditional ones, it has been greatly improved. The new type of system makes inlet air temperature much easier to control and provides fresh air all the time.
Phase-change heat storage device is the key equipment for the heating technology's application of solar heating technology, industrial waste, etc. Based on the analysis of the characteristics of the ...current phase-change heat storage device, the capillary phase-change material heat storage tank was proposed. And with a composite phase change materials, whose thermal properties were tested and the results showed that the composite phase change material meets the requirements of solar heating technology. Meanwhile, the effect of water flow and temperature to the capillary phase-change material heat storage tank were investigated and the optimum flow was got, which provides credible data for the design of the capillary phase-change material heat storage tank.
The relationships among solar radiation intensity, volume of heat storage tank, heating load and heat storage temperature difference has been revealed by the theoretical analysis on heat storage tank ...in active solar water heating system. Heat storage volume can be concluded with the simulation and analysis on solar water heating system in northwest area of China. And then, the nodal model of heat storage tank is simulated in different conditions with the help of CFD. The results show that the heat storage volume is diminished with increasing of heat storage temperature difference, and for practical project, the recommended values of heat storage volume in different cities are given. The lower water velocity at the inlet of heat storage tank is, the more obviously the layers are, and the recommended water velocity is between 0.01 and 0.05m/s.
A mathematical model of the all-glass vacuum tube solar collector-heat storage tank system of a new solar-air source compound heat pump has been developed, and the heat storage characteristics of the ...system have been simulated in Zhengzhou City at winter solstice. The changing regularity of the solar radiation intensity in one day, and the influence of the heat storage medium flow on the temperature variation of the heat storage tank and the heat-collecting efficiency of the solar collector have been analyzed. The simulation results reveals the dynamic heat-collecting features of the solar collector-heat storage tank system, and forms a solid basis for the combined operation of the solar collector-heat storage tank system and the heat pump system.
A mixing model with simple one-dimensional diffusion, for a temperature distribution in a heat storage tank of the multifunctional heat pump hot water supply system, which middle warm water (30〜60℃) ...returns to the tank central part is presented. The feature of the model is assuming the thermal diffusion under buoyancy effect in the tank to be change of thermal resistance. Temperature distribution in tank calculated with the mixing model is compared with experimental results in an actual multifunctional heat pump hot water supply system with a floor heater. And the accuracy of the model is validated. Applying the model, the best point for low energy consumption of floor heater circuit return position is studied.
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