| In recent years,the increasingly serious environmental pollution and fossil energy consumption problems have attracted great attention from all countries.With the support of relevant policies,renewable energy power generation has developed rapidly,but renewable energy power generation has randomness and instability.In view of the above problem.At present,the configuration of heat storage tanks in a CHP unit to adjust the peak of thermal power flexibly and accept wind power has achieved excellent results.The efficiency of the charging and discharging process of the heat storage tank will directly affect the degree of accepting the heating load,that is the degree of adjusting thermal power peaking,and then affect the ability to accept renewable energy power generation.Based on the purpose of improvement the efficiency of the heat storage tank,the factors that affect the heat storage tank,the performance analysis of the inlet device,the influence of different structural parameters/forms of the inlet device are studied in this paper.Firstly,In order to improve the heat storage performance and optimize the structure parameters,one-dimensional unsteady state model was adopted to simulate the temperature distribution in heat storage tank.The influence of structural parameters,such as the inlet structures,the ratio of height to diameter,the ratio of inlet diameter to tank diameter and the volume of tank,on the thermal stratification performance were calculated.And the thickness of thermocline and the exergy efficiency were analyzed.The results show that the inlet structures have a maximum influence on the heat storage performance.The maximum exergy efficiency can be obtained by adopting the impingement inlet when the heat storage tank has the same shape.For all inlet structures,the thermocline appears a thick high-temperature part and a thin low-temperature part.Increasing the ratio of inlet diameter to tank diameter or decreasing the ratio of height to diameter can increase remarkably the exergy efficiency of the heat storage tank with the impingement inlet.The heat storage characteristics are barely affected by the volume of heat storage tank.Secondly,three factors of the inlet pipe diameter,the distance and diameter of holes on inlet device are taken into account in this paper,and a new evaluation index,namely the non-uniformity coefficient of water distribution,is proposed.The accuracy of numerical calculation is verified by experiments of operating in an experimental platform,and the related empirical formula is summarized finally.The results show that the non-uniformity coefficient is in good agreement with the temperature stratification and the exergy efficiency of heat storage tank,and it has strong universality.The thin temperature stratification and the higher exergy efficiency is achieved by the inlet device with small non-uniformity coefficient..When the flow rate of the inlet device is 0.5m/s,among the 9 kinds of inlet devices proposed,the temperature stratification produced by the No.8inlet device is 3 times that of the No.4 inlet device,which directly leads to the exergy efficiency reduction of nearly 30%.Finally,the heat storage operation of heat storage tank equipped with different inlet devices is calculated by numerical simulation,and the efficiency and the thickness of temperature stratification are taken as evaluation indexes respectively,which are verified by experiments.The results show that the distribution of temperature field inside the water distributor is different at each time under the conditions of different inlet devices,different nonuniformity coefficients and different diameters,which have different influences on the performance of the heat storage tank.When the octagonal inlet device is configured,the temperature stratification and efficiency are slightly higher than those of the flat inlet device and far higher than those of the tube-type inlet device.When inlet devices with different nonuniformity coefficients are configured,the increase of nonuniformity coefficient of water distributors makes the efficiency of heat storage tank very low.When the diameter of the inlet device is changed,the temperature stratification and efficiency of the heat storage tank are improved with the increase of the diameter,but for the pipe-type water distributor,the continuous increase of the diameter will lead to the decrease of the efficiency. |
