To provide a return fuel cooling system for LPI vehicle and its controlling method in which LPG fuel returned from an engine is efficiently cooled to prevent a pressure of a cylinder from being increased.
An engine 3 and a cylinder 5 are connected to each other through a fuel supply line 7 and a fuel return line 9. This system comprises: a heat exchanger 20 installed at the fuel return line 9 for heat exchanging refrigerant of an air conditioner unit 10 and LPG fuel to each other inder to cool the LPG fuel of high temperature returned from the engine 3 to the cylinder 5; a bypass line 30 for bypassing the LPG fuel around the heat exchanger 20 to supply it to the cylinder 5; and a valve 40 for selectively opening or closing the fuel return line 9 in response to whether or not the air conditioner unit 10 is operated and a temperature of the cylinder 5, for flowing the LPG fuel into the heat exchanger 20 or bypassing the LPG fuel to the bypass line 30.
KIM MYEONG HWAN
CHO WAN JE
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