Numerical Analysis Of Exothermic Stablility Scheme Of Basalt Fiber Bundle Thermal Energy Storage Tank

Based on the consensus on the carbon neutrality goal,the utilization of renewable energy has attracted attention,among which the mobile thermal energy storage system has has been widely concerned because of its heat supply method that is not limited by time and space.In this paper,a mobile basalt fiber bundle thermal energy storage system is designed based on basalt fiber,a high-temperature sensible heat material,and the following works is carried out based on the system:First,a basalt fiber bundle thermal energy storage tank with two-stage flow channels was designed,and air was uesd as the heat transfer fluid.The working principle of the thermal energy storage box is introduced and the corresponding numerical model is established.On the basis of model simplification and assumptions,a two-dimensional numerical calculation model is established,and the grid-independence solution verification and validity verification are carried out.Secondly,an evaluation index system for the exothermic properties of the basalt fiber bundle thermal energy storage box is established.The topological structure parameters of the secondary flow channel of the thermal energy storage tank are studied and analyzed,and the exothermic properties of the thermal energy storage box under different secondary flow channel spacing is explored.The results show that the exothermic power per unit volume of the thermal energy storage box is greatly affected by the lateral spacing of the secondary flow channels,and the power per unit volume decreases linearly with the increase of the lateral spacing.Other evaluation indicators such as stable exothermic time,stable exothermic efficiency,pressure drop and pump consumption are greatly affected by the longitudinal spacing of the secondary runners.After judging by several evaluation indicators,the optimal arrangement spacing of the secondary runners is:s_x=1.2d,s_y=1.6d.In addition,the flow rate of the heat transfer fluid is an important operating parameter that affects the exothermic properties of the basalt fiber bundle thermal energy storage tank.Therefore,six different flow rate schemes are designed to analyze the effect of fluid flow rate on the exothermic properties of the thermal energy storage tank.According to the visualized cloud map,it can be found that during the flow process,the flow field of the fluid in the thermal energy storage tank exhibits obvious periodic changes,and the pressure in the flow channel gradually decreases with the flow,and the greater the fluid velocity,the greater the pressure drop.The change of the exothermic power per unit volume is linearly related to the flow rate.The increase of the fluid flow rate will obviously increase the exothermic power per unit volume,but at the cost of shortening the stable exothermic time.The increase of the flow rate is also unfavorable for the heat exchange between the fluid and the solid.According to the evaluation index system,different flow rate schemes were analyzed.The 0.5 m/s flow rate scheme and the 1 m/s flow rate scheme performed better,and the 0.5 m/s flow rate scheme was considered as optimal flow rate.It should be pointed out that the rated exothermic power per unit volume of the thermal energy storage tank reaches 0.138 MW under the 0.5 m/s flow rate scheme,and the rated exothermic power per unit volume under the 1 m/s flow rate scheme achieves 0.277 MW.Using different flow rates of exothermic fluids,it can provide heat users with a higher upper limit of exothermic power per unit volume and achieve a wide range of power supply.Finally,based on the optimal secondary channel spacing and optimal constant flow rate scheme,a scheme to improve the exothermic stability of basalt fiber bundles was explored.A variable flow rate scheme and a preheating relay variable flow rate scheme are proposed.When the exothermic power at the outlet of the thermal energy storage tank drops to 99%of the rated power,the flow rate starts to increase,and the flow rate is automatically adjusted to maintain the stability of the exothermic power.The calculation results show that the stable exothermic time of the basalt fiber bundle thermal energy storage box using the variable flow rate scheme is more than twice that of the constant flow rate scheme.Taking the 0.5 m/s basic flow rate scheme as an example,the stable exothermic time of the constant flow rate scheme is 1603 s,and the stable exothermic time of the variable flow rate scheme reaches 3353 s.The preheating relay variable flow rate scheme further increases the stable exothermic time on the basis of variable flow rate,reaching 4477 s,and the stable exothermic efficiency also reaches83.16%.The scheme of preheating relay and variable flow rate makes the overall heat utilization efficiency of the thermal energy storage box reach 99%,of which more than 80%of the heat is directly released in a stable form,and the remaining heat is released in the form of indirect preheating.