Low efficiency of PTC in electrical vehicles would cut down its travelled distance

so it’s necessary to design high efficiency heat pump system. Two kinds of heat exchangers were used as outside heat exchangers (HX) in four-way-valve heat pump system

and experimental study was finished under both heating and cooling modes. The results showed

under low face velocity in heating model

small diameter tube HX had higher capacity by 10.5%

and the same COP compared with parallel flow HX. Under low face velocity in cooling model

small diameter tube HX had higher capacity by 3.8%

and higher COP by 22.8% compared with parallel flow HX. With the increasing of wind velocity

capacity and COP with small diameter tube HX increased little; however

the one with parallel flow HX had a higher increasing. It is concluded that heat pump system used small diameter tube HX had a potential prospect under low wind velocity.