| For the active solar heating system,the strategies not only should ensure safe and reliable of the system,but also have the effect of improving heating performance and then improving heating user satisfaction.With the certain heat collecting area,how to effectively utilize the limited heat of solar heating system to improve the system cost is an important problem that should be solved by the strategies.However,there is no research on the relationship between heating efficiency and operating energy consumption in the on-off modes of active solar heating system,and no the use of variable flow mode to improve the heating effect of the active solar heating system at night yet.Therefore,by means of studying the effects of the operating strategies on the heating performance of active solar heating system,we could explore effective methods to optimize the heating effect of active solar heating system.In the paper,the method of experiment and theoretical analysis was used to study the performance of the active solar composite heating system under different operating strategies.The variations of indoor temperature and mean temperature of the kang surface,the heat supply,the average heating efficiency and operating energy consumption under different operating modes are analyzed,and the factors affecting the heat supply are analyzed.The main conclusions of the heating performance of the active solar composite heating system under different operating strategies are as follows:(1)Under the same ratio of on-off time(50%),in the similar environment conditions,with the initial supply temperature of about 70 ℃,the shorter the supply water durations and intermittent durations of the circulating pump,the more heat is supplied to the single building.The long-term heating results of the system also reveal that the shorter the on-off time length of the circulating pump,the higher the average heating efficiency of the system,and the order from high to low mode of the average heating efficiency is: 15/15 min>20/20 min>30/30 min.Without increasing the running time of the circulating pump,the average heating efficiency of the system is increased by 4.15% from 30/30 min to 15/15 min;(2)With the initial supply temperatures of about 61 ℃ and 56 ℃ under the similar environmental conditions,the heat supply in the same on-of cycle of 30 minutes of the system can be increased by increasing the running time of the circulating pump.The calculation of energy consumption of the system with the on-off cycle of 30 min shows that the running time of circulating pump is increased from 10 min to 20 min,the operating energy consumption of the system is doubled,and then heat supply is increased by an average of 79.24%.Therunning times in the anti-freezing model is reduced from 5 min per hour to 2 min per hour,and the average proportion of heat supply per day in the period of 18:00 to 8:00 is increased by about 16.72%,the heating efficiency was increased by 13.56%;(3)Comparison of the heating effects of the system in the three variable flow modes shows that the temperature changes more slowly of the living room in the variable flow mode B,in which the average room temperature decline amplitude of the living room at night is1.8 ℃,which is 1.7 ℃ and 1.1 ℃ lower than the average temperature of living room in the variable flow mode A and mode C,respectively.In the variable flow mode B,the average heating rate of the kang surface is 2.7 ℃/h,which is 1.1 ℃/h lower than the mode A and1.7 ℃/h lower than the mode C,respectively.The average cooling rate of the kang surface of the variable flow mode B is 0.25 ℃/h,Which is 0.3 ℃/h lower than variable flow mode A and 0.5 ℃/h lower than variable flow mode C,respectively.The main conclusions are as follows: in the on-off regulation mode,the living room temperature is less fluctuating at night,and the temperature fluctuations are in accordance with the ASHARE-55-2004 standard;reducing the the length of on-off durations can improve the heating efficiency of the system effectively;With the fixed on-off cycle,changing the running time of the circulating pump can adjust the heating capacity of the system;using the variable flow rate mode from small to large can reduce the temperature decline amplitude of the heating room,and the kang surface temperature in the heating process.Temperature changes on the kang surface are more uniform in the mode B,which improve the sleep comfort at night.For the on-off time ratio of 50%,under the constraints of the system,the optimal operating mode of the system is 15/15 min mode and the variable flow mode B from small to large is adopted,which can simultaneously take into account the system,Energy efficiency and heating comfort. |
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