Simulation Research On Control Operation Strategy Of Radiant Heating System With Air Source Heat Pump

With the implementation of“coal to electricity”in cold regions,the air source heat pump has been increasingly used in rural residential buildings as a clean and efficient heat source device.As a comfortable and energy-saving heating equipment,floor radiant heating,combined with air source heat pump,can give full play to the advantages of low temperature and high efficiency of air source heat pump.However,due to the thermal inertia of the building envelope,the cyclical changes in the outdoor environment cannot be fed back to the indoor temperature changes in time,and the heat generated by the air source heat pump cannot be timely fed back to the indoor temperature changes.It would inevitably lead to a phenomenon in which the indoor temperature is too high or too low,the comfort is greatly reduced,and the energy saving and economy are inevitably affected.Therefore,how to use the thermal inertia of building envelope structure,formulate a reasonable operation control strategy,combined with the current peak and valley electricity price in Beijing,has a vital role in the further promotion of radiant heating system with air source heat pump.A transient simulation model of radiant heating system with an air source heat pump for a typical 100m~2 building in cold regions was developed by using TRNSYS software.The accuracy of the model is determined by the parameters such as the envelope structure and indoor air conditioning.If the settings are reasonable,the simulation results have higher reliability.In order to give full play to the low-temperature and high-efficiency energy-saving advantages of the air source heat pump,the control strategy of changing the water supply temperature of the air source heat pump was established.Through the system operation in the whole heating season was simulated,average supplied water temperature and average outdoor air temperature was obtained in the whole heating season and the fitted curve between supplied water temperature and outdoor air temperature was confirmed based on the outdoor temperature setting control regulation model under the premise of ensuring indoor temperature.The study results show that under this control strategy,the system energy consumption saved by17.9%,operation cost saved by 18.6%and system COP increased by 20.6%compared with the conditional constant temperature of the supplied water control strategy in the whole heating season.Through the system operation in the whole heating season was simulated by using TRNSYS software,and the operation cost in the whole heating season was taken as the objective to optimize the design which found the best heat-lag temperature and heat-lag time in the valley time under the premise of ensuring indoor temperature on the current peak and valley price of Beijing rural regions.The research results show that the optimal heat-lag temperature is 20?,the optimal heat-lag time is7 hours,and the operation cost is saved by 3.6%.The heat-lag temperature is 21?,and the whole valley period heat storage strategy can save the operation cost by26.9%when the peak period time electricity price is 0.55yuan/kWh,the electricity price in the valley time is 0.1yuan/kWh.Under the current peak-to-valley electricity price in rural areas of Beijing,the EPS insulation is added to the outer wall of the typical rural independent residential building.The external wall of the building is increased by 6-12cm EPS.The optimal heat-lag temperature is 19.5-19.6?,and the optimal heat-lag time is 5.2-6.2h.The optimal heat storage strategy operation cost is 3.5-3.9%less than the non-heat storage strategy.The external wall of the building is increased by 6-12cm EPS,the optimal heat-lag temperature is 19.5-20?,and the optimal heat-lag time is 5.5-7.5h.The cost savings ratio of the storage strategy compared to the non-heat storage strategy is4.5-5.5%.With the increase of the thickness of the external wall insulation,the operation costs of the non-heat storage strategy and the heat storage strategy are reduced.The proportion of operation cost savings for the optimal heat storage strategy has increased slightly.Studying the influence of building thermal inertia on heat storage strategy,it is found that the thermal inertia index of building exterior wall is 5.4-7.6,the optimal heat-lag temperature is 19.5-20?,and the optimal heat-lag time is 5-7h.The optimal heat storage strategy operation cost savings ratio is between 3.7%and 4.1%.As the thermal inertia index of the external wall increases,the heat-lag temperature increases slightly,the heat-lag time increases slightly,and the optimal heat storage strategy operation cost savings ratio increases slightly.Predictive control is used by using MATLAB software to develop predictive control on buildings.According to the difference between the indoor set temperature and the indoor temperature at the current time,the difference between the indoor temperature at the current time and the indoor temperature at the last time,the valve operation time was predicted in the next control cycle.The particle swarm optimization algorithm on GenOpt software was used to optimize the control cycle and the optimal control cycle was obtained to ensure the indoor temperature stability.The simulation results show that the best control cycle is 0.5h and the room temperature can be maintained in the range of set point±0.5?by using this control strategy.The law of the variable indoor temperature was studied under different indoor setting temperature,indoor air conditioning,fill layer thickness and radiant coil spacing.