二、柴油機為應用廣泛的船舶發動機，請說明它有那些優缺點？（20 分）

⑵ The fresh water cooling system is a closed cooling system, in which the fresh water first passes the fresh water cooler, where it is cooled by sea water, and then is circulated through the cooling water jackets of the main engine by fresh water pump to cool cylinder liners, cylinder heads and exhaust valves.