Study On Optimization Design And Dynamic Heat Transfer Characteristics Of High-efficiency Energy Storage Tank Containing Phase Change Materials

The use of renewable energy such as solar energy is of great practical significance for energy conservation and environmental protection.Due to the intermittent and volatility of solar radiation,latent heat storage technology is needed to solve the imbalance between energy supply and demand.However,the low thermal conductivity greatly limits the heat transfer efficiency of phase change materials.As the most common means of enhancing heat transfer,fins can increase the heat transfer rate while also reducing the maximum heat storage capacity of phase change energy storage devices due to occupying space.Therefore,optimizing the fin structure has important research value.In order to further improve the performance of phase change energy storage systems and study their dynamic heat transfer characteristics,a novel set of bifurcated fins has been proposed based on the traditional longitudinal fins,and the three-dimensional numerical model of the vertical shell and tube energy storage tank has been established.Firstly,an experiment has been carried out to verify the accuracy of the numerical model,and the effects of finless,traditional longitudinal fins and novel bifurcated fins on the melting process of the phase change material have been compared and analyzed to verify the feasibility of the novel bifurcated fins.Secondly,the effects of bifurcation angle,fin number and fin thickness on system performance have been studied.Then,the effects of steady inlet temperature,steady inlet flow rate and thermal conductivity of phase change materials on system performance have been investigated.Finally,three sets of inlet temperature-time function conditions have been set on the basis of actual conditions,and their average inlet temperature values have been taken as the corresponding steady inlet temperature conditions for comparison analysis of the impact on the melting process of phase change materials.It is found that compared with the longitudinal fins with the same volume and number,the novel bifurcated fins can improve the heat storage performance of the shell and tube energy storage tank.The optimal branching angle and number of fins are60° and 6 respectively,and the effect of fin thickness on heat storage performance can be ignored.Compared with finless and longitudinal fins,the novel bifurcated fins reduce the melting time of phase change materials by 65.1% and 33.3% respectively,and increase the average heat storage rate by 174.1% and 48.8% respectively.Increasing the inlet temperature and velocity of heat transfer fluid and the thermal conductivity of phase change materials can shorten the melting time of phase change materials and increase the average heat storage rate.Compared with the corresponding steady condition,the melting speed of phase change materials is faster under the unsteady state condition,and the temperature field inside the energy storage tank is more uniform.The evaluation indicators of three groups of comparison conditions are3.1,1.3 and 3.6 respectively.The research results can provide a certain reference value for the structure optimization of the shell and tube energy storage device and the efficient utilization of solar energy.