Performance Analysis And Optimization Of Thermal Storage Tank In Solar Heating System

Faced with the dual problems of energy storage and environmental pollution,the utilization of renewable energy is getting more and more attention,especially solar energy due to its advantages of wide distribution,green environmental protection,rich resources,etc.Solar thermal utilization system has been the focus of scientific research and engineering promotion.But on the other hand,the solar energy is unstable,intermittent and solar flux density is low,so the solar energy heat utilization system has disadvantages of mismatch between supply and demand,the early insufficient heating,and poor adaptability to the environment change,these problems can be summed as the heat control problems of system,so the effective solution to improve the performance of system is to improve the performance of the heat storage tank which is the control unit of system.At present,the method of improving the performance of heat storage water tank is mainly by enhancing the temperature stratification effects,to improve the collection efficiency and the ratio of high temperature water at the same time,the method of heat exchange in the simple structure of the layered heat storage water tank is mainly natural convection,so its thermalefficiency is low,the function of performance improvements for the system is limited,so we need improve the internal structure and the operation condition of water tank to address the shortcomings of the solar energy heat utilization system.In view of the above defects of solar thermal utilization system,this paper proposes a kind of instantaneous hot water storage tank for solar heating system.A small volume of corrugated tube heat water tank is placed in the top of the instantaneous hot water storage tank,which is connected by submersible pump with hot water tank,so the heat exchange process and heat storage process are separated,process of collector heating,room heating and heat storage can be acted independently or simultaneously,heating stability is the main purpose of system running,while ensuring system collection efficiency at the same time.Through theoretical analysis,experimental research and numerical simulation,the performance advantages of the instantaneous hot water storage tank and the operation of the solar heating system using the instantaneous heat storage tank are analyzed.Firstly,the components of system including the instantaneous hot water storage tank were analyzed,then we can know that the position for system heat exchange is the corrugated tube heat water tank with a small volume,heat transfer form is forced convection in a limited space,so its thermal efficiency is higher than traditional heat storage water tank of natural convection,on one hand,heating water temperature rise rate was improved,on the other hand,collector inlet temperature is reduced.Secondly,the engineering application of the instantaneous hot water storage tank is analyzed.The experimental results show that :(1)after the collector is opened in the morning,the temperature of the ground heating water supply can be rapidly increased to the design value,which has the effect of instant heating;(2)compared two sunny days in December,the collector reached the starting condition and the ground heating water supply reached the same temperature appreciation,the total solar radiation in low-temperature days was2.2 times and 3.2 times of that in high-temperature days,respectively.Therefore,the outdoor temperature was an important factor affecting the starting time of the collector and the temperature rise rate of the ground heating water supply.Then,TRNSYS software was used to establish the system model to analysis the operation of solar heating system using the thermal heat storage water tank and comply with reasonable automatic control system in heating season,results show that:(1)system can assure indoor temperature is relatively stable when the outside temperature is low and volatile which keep at 14 ? to22 ?,so the system has stable heating performance;(2)the average collection efficiency of the collector in the whole heating season is 0.37,and the highest value in a single day is 0.54,which ensures a good collection effect.(3)the average daily solar guarantee rate of the system in the whole heating season is0.67,achieving the design purpose of taking solar energy as the main energy.Finally,according to factors such as system energy consumption and actualconditions,the instantaneous heat storage tank is optimized,and the better value of the volume of the heat storage tank and the heat exchange area of the heat exchange tank is obtained.