The Field Test Study Of Air Source Heat Pump Heating System In Cold Regions

In response to the national policy of "coal to clean energy",air source heat pumps have become an energy-saving technology that has received much attention in recent years and has begun to be used in large scale in the northern regions.At present,the research contented at home and abroad are mainly focused on the application of household air source heat pump or a single terminal control theory.From the heat source to the transmission and distribution to the end,there is little integrity analysis of air source heat pump in large and medium-sized buildings.This article plans to start from the actual heating effect of the air source heat pump in a teaching building of a school in Beijing and a factory in Shenyang,combined with theoretical analysis,and put forward constructive opinions on the application of air source heat pump in large and medium-sized buildings in cold regions.The results show that the air source heat pump has a good application effect in the cold area,and combined with the terminal regulation and transmission and distribution adjustment,the thermal comfort is higher and the energy saving effect is more significant.According to the results of the two heating seasons in Beijing and Shenyang,the possibility of applications of air source heat pumps was confirmed from the outdoor low temperature conditions and frost conditions.The results of long-term operations show that COP remains above 2.8,and the primary energy ratio is greater than 1.The most suitable unit load is 80~90%,which can not only ensure sufficient heating capacity,but also keep the unit performance at the highest value.The stability of the unit operation is also optimal.The terminal regulation can match the actual heating capacity of the heat pump unit with the actual heat load demand of the building.The test results show that the room temperature level can be basically guaranteed,but it is necessary to extend the warm-up time as much as possible,and in no one's case,the room temperature should not be set too low,so as to avoid the indoor temperature being insufficient under cold weather.The flow on the load side should be maintained at above 33.3% of the rated flow of the unit.in case the flow is too low,the compressor starts and stops frequently and the operation is unstable.When the flow rate is too high,the performance of the heat pump unit decreases.After the terminal regulation,the indoor environment is more comfortable,and energy-saving of the unit heat aera is 40.7%;COP falls from 2.93 to 2.64,but it does not affect the energy-saving effect of air source heat pumps.The transmission and distribution regulation can further deepen the energy-saving effect of air source heat pump heating systems.The establishment of the calculation model of the pipeline network verifies the great energy saving effect of the transmission and distribution system by the change of the pump frequency conversion and the pressure differential bypass valve setting.It infers the best differential pressure bypass valve settings and pump frequency value under different thermal load conditions.A water temperature control logic for matching the operation characteristics of the air source heat pump was established which saves energy by 29.1% and 27.3% on the working day and on weekends,respectively.When the frequency of the water pump is 40~50Hz,the performance of the air source heat pump is good.However,when the frequency of the water pump drops to 35 Hz,the performance of the air source heat pump unit is unstable and its overall performance is degraded.The paper is of great significance to the application of air source heat pump in cold regions.It provides a theoretical basis and data support for more energy-efficient and efficient use of air source heat pumps.