| In this paper, the cold climate of heat pump heating system design are studied, to solve the question of air source heat pump in winter can’t heating, to promote the use of air source heat pump. According to previous research conclusions on prototype design, the design method is proved through the performance test and the actual building heating test feasibly. Based on relevant research and engineering experience in China and abroad, found the affecting of low temperature air source heat pump operation factors including:high compressor pressure ratio led to decrease compression efficiency; oversize suction specific volume caused insufficient compressor cooling; frosting in evaporator caused heat transfer disable; low temperature start of compressor produced liquid hammer and so on. Influence factors of heat pump stable operation including:uneven distribution of evaporator reduced efficiency of the evaporator; unreasonable fin design caused frosting frequently; unreasonable condenser design increased condensing pressure inadequate expansion valve control brought about heating capacity frequent fluctuations and so on.In order to solve the above problems, in this paper prototype design include:The compressor system used refrigerant injection; economizer adopted heat exchanger in the system; throttling mechanism used electronic expansion valve. The refrigerant distribution in evaporator under low temperature conditions was checked, and make pointed references on prevent frost structure design. Condenser design according to the maximum working condition, for avoiding the problem of thermal efficiency decline under low temperature, at the same time can reduce the impact on refrigerant capacity under the different volume of evaporator and condenser. Other refrigeration parts were also designed at low temperature condition respectively.The COP of finished heat pump system could reach2.68at-12℃, the heating performance of synthetically part load could reach3.09. The COP of nominal working condition of refrigeration could reach2.7, the cooling performance of synthetically part load could reach3.02. Defrost used four-way valve, application proved that effect was ideal, after defrosting finished there was no water residual on the fin. Under frosting conditions, the ratio of the defrosting time and frosting time less the1:10. Drainage was smooth in defrosting process, and no defrosted water at the bottom of the unit. After adjusted the expansion opening number in low temperature, the startup performance is good, did not appear the compressor suction fluid or cannot be started.Through a heating period, the results showed that the unit satisfied the heating requirements with good working stability. There were only5days’ temperature below18℃over the whole heating period, because the holiday resulted the initial temperature of building was too low. Due to the poorer thermal insulation performance of building, power consumption in whole heating period were11702kWh, on the basis of calculating the construction area, the heating power consumption was38.76kWh/m2, operation cost was close to the central heating. |
