| With the development of Chinese economy,the demand for energy is gradually increasing,resulting in a large number of uses of coal.The use of coal aggravates the pollution to the environment and the smog phenomenon.Therefore,the state strongly advocates“coal to electricity”.Therefore,electricity driven heating instead of coal-fired heating has become a hot spot,while air source heat pumps are favored due to a series of advantages such as small initial investment and convenient installation.However,air source heat pump heating is greatly affected by outdoor temperature,outdoor humidity and other factors during operation,so the application of air source heat pump in different regions is different.Therefore,the use of air source heat pump is regional.Many scholars have made a lot of research on the use of air source heat pump heating in different areas and have obtained many conclusions.However,few scholars have studied the optimal operation of air source heat pump heating in cold and low humidity areas.This topic mainly takes Baotou area as an example,and takes variable frequency air source heat pump heating system as the main research object in cold and low humidity areas.Firstly,the climate conditions in Baotou area are simulated and analyzed by TRANSYS.According to the climate conditions in Baotou area and the energy consumption characteristics on the building,the air source heat pump heating system is designed.Through consulting a large number of relevant documents and specifications,the specifications and models of air source heat pump heating system equipment and pipes are determined,and an experimental table is built.On the basis of setting up the experiment table,the constant flow is adopted,under different outdoor temperatures and by changing the water supply temperature of the air source heat pump unit,calculate the unit COP,the indoor temperature is recorded,and the characteristics and laws of the unit operation are mastered.The experimental results show that when the outdoor temperature is higher than-13?,the unit water supply temperature is set to 35?,which can meet the indoor temperature above 20?,and the unit has obvious energy saving effect.When the outdoor temperature is lower than-13?,the air source heat pump unit is difficult to reach the water supply temperature of 35?.This experimental study provides a basis for the air source heat pump to operate under different outdoor temperatures and determine the water supply temperature of the unit.The air source heat pump operates in a typical month,and the hourly analysis of the air source heat pump operating in a typical day and a very cold day shows that when the outdoor average temperature is above-7?(including-7?),the indoor average temperature can reach above 20?,which can meet the heating demand,and the energy saving is obvious.The average outdoor temperature is above-12?(including-12?),below-7?,and the average indoor temperature is about 20?,which can basically meet the heating demand,but the energy saving effect of the system is not obvious.The average outdoor temperature is below-12?,the average indoor temperature is below 20?,which cannot meet the heating demand and the system does not save energy.Under the same outdoor temperature,indoor initial temperature,heat pump water supply temperature and heat storage tank water temperature,different heat storage water tanks to assist the air source heat pump heating mode are adopted,namely the alternate heating mode of the heat storage water tank and the air source heat pump,and the mixed heating mode of the heat storage water tank and the air source heat pump.The indoor and outdoor temperature,the temperature of the heat storage tank,the flow rate of the heat storage tank,the change of the supply and return water temperature with the running time at the initial stage of the air source heat pump start up and the COP_s of the system are analyzed.The results show that the addition of the heat storage tank will cause instability to the initial operation of the air source heat pump,but it can make the indoor temperature less affected by the outdoor temperature,rapidly increase the indoor temperature and improve the COP_s of the system.When the water temperature of heat storage tank is45.3?,the COP_s of the heat storage tank and air source heat pump mixed heating mode system is about 4%higher than that of the heat storage tank and air source heat pump alternating heating mode,which has more significant energy saving effect.Therefore,the mixed heating mode of heat storage tank and air source heat pump is the best operation mode.Under the extremely cold outdoor temperature of-19?,the mixed heating mode of heat storage water tank and air source heat pump is adopted.Under different water temperatures of tank,the system operation time and COP_s are different.When the water temperature of the heat storage tank is increased by 5?,the operation time of the mixed heating mode of the heat storage tank and the air source heat pump can be increased by about 30%,and the COP_s of the system can be increased by about 10%. |
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