| With the advancement of China's clean energy reform,the use of air source heat pumps in cold regions of China has become more and more popular.Among them,the air source heat pump household heating system and the central heating system are the system forms that have been vigorously promoted in recent years.However,due to the small water capacity of the household air source heat pump heating system,it is difficult to ensure the stability of the water temperature and the room temperature during the defrosting of the unit,and the heat pump unit starts and stops frequently due to the imbalance of heat supply and demand in the early and late stages of heating;The determination of the reasonable scale of the air source heat pump central heating system has not been studied before.Therefore,how to ensure the reliability and economy of the operation of air source heat pump heating systems with different heating scales is the focus of this paper.This paper has developed two criteria for judging the operational reliability of the system:first,during the defrosting period the heating system does not supply cooling to the room,and the room temperature and average water temperature drop after defrosting does not exceed 1?and 5?respectively;second,at the beginning of the heating period The unit does not start and stop frequently,and the duration of each operation and shutdown is no less than 15 minutes.First,the typical rural residential building form was determined.The thermal parameters were determined according to the standards of energy-saving,non-energy-saving and near-zero energy buildings,and the heating systems with geothermal coils,fan coils and radiators were designed.Secondly,the mathematical model of heat transfer of heating systems using three kinds of ends during the defrosting process is established,and the numerical solution is carried out to obtain the minimum tank volume that meets the requirements of room temperature and water temperature drop limit in the defrosting process.Then,5?is used as the typical outdoor air temperature in the early and late stages of heating.According to the actual heat load of the room and the actual heating capacity of the unit,the minimum tank volume that causes the heating and cooling units to start and stop infrequently is determined.Taking the larger value of the storage tank volume calculated under the above two conditions is the final reasonable tank volume.Finally,a quick calculation softwareof the tank volume was written in Python to calculate the tank volume under other different design requirements.In order to study the reasonable scale of air source heat pump central heating system,firstly,the physical model of high-rise and multi-layered communities of different scales is established,and the heat source and pump house land are reserved in the red line of the building.The calculation of the heat load and the design of the heating system were carried out according to the meteorological conditions of five typical cities in the cold region,followed by a technical and economic analysis of the heating system.According to the actual situation of the project,the cost of land for heat source is included in the consideration of initial investment.When the reserved heat source land is insufficient to place all the heat pump units,the cost of the land for the surplus unit will be included in the initial investment.When the building area is 34560 m~2,the multi-storey building has the smallest annual cost per unit of building area,and it does not fluctuate before the land for heat source billing.The annual value of the building area cost of high-rise buildings has not changed much within the area of 150,000 m~2,and the minimum value is obtained when the building area is 40,320 m~2.Therefore,for the residential plot model established in this paper,the reasonable heating scale of multi-storey residential buildings is not more than 100,000 m~2,and the heating scale of high-rise residential buildings is not more than150,000 m~2. |
PDF Full Text Request