Simulation Analysis On The Discharge Characteristics Of Compartmental Solar Heat Storage Tank

As an important part of solar hot water system,the performance of heat storage tank has a great influence on the whole system,in recent years with the development of solar energy market,the new-style compartmental water tank appeared in the solar industry,which is divided into double or three-compartment water tank by some clapboards,but there is not much research about the specific performance of the compartmental water tank.Therefore,a series of experiments and three-dimensional numerical simulation are carried out on the compartmental water tank in this paper to provides accurate data support for the application of solar energy practical engineering,the specific details go as follows:.In this paper,the most common compact vacuum tube solar water heating system in the market is adopted in the experimental analysis.Firstly,in the initial stage of preparation for the experiment,the water in the water tank was firstly adjusted to 333±1K,and the cold water inlet was adjusted to 293 ±1K.According to people's demand for hot water flow rate at different times in daily life,this paper selected 2.5L /min,5L/min and 10L/min as three inlet flow rates to conduct water discharge experiments on the single,double and three-compartment water tanks.The flow trend of hot water in the tank and exothermal efficiency at different flow rates were obtained by experiments.Secondly,through CFD numerical simulation technology,geometric simulation,grid division,model selection and parameter setting of the single,double and three-compartment water tanks are carried out.Simulation experiments were carried out on the two-compartment water tank at the flow rates of 2.5L/min,5L/min and 10L/min.At the same time,the simulated and experimental discharge curves were compared,and the results showed that the discharge curves were basically consistent.All above proved that the model parameters can be used for simulation and analysis of water tank.Then,numerical simulation was carried out for three kinds of water tanks at three flow rates through numerical simulation technology,and the temperature cloud diagram in the water tank at different times was compared by Fluent post-processing technology,so as to analysize the flow trend of hot water in the water tank more intuitively.The discharge curves and heat release efficiency of three kinds of water tanks at the same flow rate were compared.In addition,temperature stratification in water tank at different times were compared through the non-dimensionless exergy.The results show that different structure of the water tank at the same inlet velocity will indeed affect the mixing of water in the tank,the discharge curve will be also different;And at the lower limit of water intake temperature of 310 K,the exothermic efficiency of single-compartment tank is the best.However,the mixing degree of the compartmental water tank shows an upward trend in the later stage,even exceeding the mixing degree of the single silo water tank.And at the lower limit of water intake temperature of 310 K,the exothermic efficiency of single-compartment tank at three flow rates has the best performance.The mixing degree in the water tank will increase with the increase of inlet velocity,However,the mixing degree of the compartmental water tank shows an upward trend in the later stage,even exceeding the mixing degree of the single-compartment water tank.From the point of the maximum value of non-dimensionless exergy,double and three-compartment water tanks can indeed reduce the degree of mixing tank.Finally,the numerical simulation on three different clapboard position in the double-compartment water tank was carried out at three flow rates and compared the temperature cloud diagram,discharge curves and exothermic efficiency,non-dimensionless exergy at different times.The results show that different clapboard position in the double-compartment water tank will also affect the mixed water situation and discharge curves;Similarly,at the intake temperature of 310 K as the lower limit,exothermic efficiency of double-compartment water tank,which clapboard is on the left,is the highest at three flow rates.From the point of the maximum value of non-dimensionless exergy,maximum value of non-dimensionless exergy of three kinds of tank are very close,maximum value of non-dimensionless exergy of double-compartment water tank,which clapboard is on the left,is the lowest,the result indicates that the double-compartment water tank,which clapboard is on the left,can better reduce the mixing degree in the water tank.