| In the southern heating market,new heating mode with air source heat pump as heat source equipment,fan coil and floor radiation as dual-terminal has developed rapidly in recent years,but at the same time,many engineering application problems have arisen,which need to be solved urgently.In order to study the applicability of the air source heat pump dual-terminal system in the hot summer and cold winter regions,terminal heating characteristics,defrosting performance,the minimum flow,energy saving effect,comfort and stability of the system were studied and analyzed.Firstly,the simulation flow chart of the air source heat pump dual-terminal system was established on the platform of TRNSYS,and the indoor PMV-PPD,system energy consumption and performance index of heat pump unit were analyzed by numerical simulation.The results showed that the thermal comfort level of heating and air conditioning in air source heat pump dual-terminal system was at level I on the whole.The total annual energy consumption of the system adopting fan-coil unit terminal in the cooling period and floor radiant terminal in the heating period was 3860.61kW·h,and the total annual energy consumption per unit building area was 15.41 kW·h/m2,the SEER(Seasonal Energy Efficiency Ratio)of heat pump unit was 3.43,the HSPF(Heating Seasonal Performance Factor)was 3.64,the APF(Annual Performance Factor)was 3.52,the system average COPc was 3.00,and the average COPh was 3.33.Then,in order to further study the performance of heat punp units in winter,the effect of different terminal heating,the effect of system defrosting oin unit COP and indoor temperature fluctuations,an air source heat pump dual-terminal system was built in a residential area in Nanjing in the coldest month.The system was tested for 15 hours.The results showed that the outdoor air temperature varied from-1.32? to 4.53? during the test period(interval average value is 0.75?),and the heat pump unit heat capacity was 16.99 kW?26.47 kW(interval average 22.38 kW)and the maximum instantaneous cooling capacity of reverse cycle defrosting could reach 22.91 kW,and the average COPh of the heat pump unit was 2.56.After the system was started,the air temperature in the room at 1m below the floor radiation terminal rose from 12? to 18?,which took 4.31 times as long as that in the room 1 m below the fan coil unit tenninal from 12? to 18?.The floor radiant terminal provided a comfortable thermal environment with uniform temperature in the vertical direction,showing a relatively stable temperature field of warm in low and cool in high.As the hot air accumulated close to the ceiling,the indoor temperature difference in the vertical direction under the fan-coil unit was relatively large,showing a temperature field of warm in high and cool in low with a large temperature difference.The outdoor temperature and the temperature of the supply and return water of the unit were the main factors for the change of COP of the air source heat pump unit in the hot summer and cold winter zone,and the frosting of the system has little effect on the COP of the unit,but in the process of defrosting of the system for 4 minutes,the air temperature in the room at 1 m below the terminal of the fan coil decreased by about 4.5%,while the indoor temperature at the terminal of the floor radiation was uniform and had no obvious fluctuation.Finally,the heat dissipation capacity of different floor decorative materials was compared and the minimum flow rate of the system in normal operation was analyzed.The results showed that the time taken for the floor temperature of wood floor to rise from 18?to 25? was 1.67 times that of marble floor temperature from I8OC to 25?.After the ground temperature tended to stabilize,the heat dissipation capacity of the marble floor was about 1.27 times that of the wooden floor under the same flow rate.When the flow rate of the air source heat pump dual-terminal system exceeded 1.783 m3/h(The maximum flow rate of the system was 5.590m3/h),the system could operate safely and steadily. |
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