Study On Operation Strategy Of A Convection-radiation Combined Cooling And Heating System

With the continuous improvement of people’s requirements for the quality of life,the cooling and heating system has gradually become an indispensable part of people’s production and life.The air source heat pump combined cooling and heating system is gradually favored by people due to its advantages of high efficiency,energy saving,health and comfort,and the average annual market growth rate exceeds 30%.Although the air source heat pump combined heat pump cooling and heating dual supply system is widely used,the understanding of its indoor comfort and system operation energy consumption is still in the engineering operation stage,and there is less research on its systematicness.In this paper,a set of air source heat pump cold and heating dual supply experimental system is built in the office building in hot summer and cold winter areas,and from the operation strategy of the system,the indoor and outdoor environmental parameters,indoor thermal comfort,system operation energy efficiency and energy consumption are systematically studied.Firstly,the effects of different water supply temperatures on the indoor environmental parameters,indoor thermal comfort,system operation energy efficiency and system energy consumption of the combined cooling and heating system are explored.The results show that the average indoor air temperature fluctuates between 20.19°C and 24.47°C during heating in winter,and the maximum indoor vertical temperature difference is 2.67°C.The overall indoor thermal comfort meets the conditions of Class II comfort zone.The energy consumption when the water supply temperature is 40°C and 35°C is saved by 13.65% and26.87% compared with the water supply temperature of 45°C.In summer,the indoor air temperature fluctuates between 23.14°C and 25.26°C,and the maximum vertical temperature difference is 2.91°C.When the water supply temperature is 15°C,the PMV value slightly exceeds the recommended value of the ISO-7730 standard,but the thermal comfort is still acceptable.When the water supply temperature is 7°C and 11°C,the overall indoor thermal comfort meets the conditions of Class II comfort zone.In addition,the energy consumption when the water supply temperature is 11°C and 15°C is reduced by 8.34% and 15.75%,respectively,compared with the water supply temperature of 7°C.Then,under the condition of the same water supply temperature,the variation rules of indoor environmental parameters,indoor thermal comfort,system operating energy efficiency and system energy consumption during the operation of convection end,radiation end and combined convection and radiation end were explored.The results show that the fan coil system can quickly adjust the indoor air temperature,and the floor radiant system has a hysteresis in regulating the room temperature,but the heating system with the radiant end can improve the overall indoor thermal comfort.When heating in winter,there is a significant weak correlation between indoor air temperature and PMV value,and the goodness of fit is 0.427.Therefore,it is recommended to use the operating temperature as the control index of the indoor thermostat.In summer,the indoor air temperature,average radiant temperature,indoor operating temperature and indoor PMV index are significantly and strongly correlated,and the goodness of fit is 0.979,0.991,and 0.991,respectively.Therefore,it is recommended to use the indoor air temperature and operating temperature as the control indicators of the indoor thermostat.Finally,experiments were conducted on the same heating and cooling system under different intermittent operation strategies to explore the effects of different intermittent operation strategies on the indoor environmental parameters,indoor thermal comfort,system operating energy efficiency and system energy consumption of the heating and cooling system.The results show that the intermittent operation strategy can save the energy consumption of the system,and the intermittent operation strategy is more suitable in summer than in winter.When the system is closed for about 60% of the whole day,the energy consumption of the combined cooling and heating system,the fan coil system and the floor radiant system can be saved by 25.48%,37.39% and 39.73% respectively in winter;The coil system saves52.86% and 44.48% of energy consumption respectively.In addition,in order to ensure that people enter the room to meet the conditions of the Class II comfort zone,it is recommended that the combined cooling and heating system and the fan coil system be turned on 1～2 hours in advance,and the floor radiant system is turned on 3～4 hours in advance when heating in winter.It is recommended that the combined cooling and heating system and the fan coil system be turned on 30 minutes in advance.