A new scheme using a separate heat pipe combined with the evaporator of a direct-cooling refrigerator is proposed. For a given heat sink temperature (?25 ℃) and different heat source temperatures (5

8

and 12 ℃)

the heat transfer rate of the separate heat pipe is tested. The result shows that the optimum filling amount is 120 g. Then

variation in the internal parameters of the system are studied and analyzed based on the cooling process. The experimental results show that after starting for approximately 10 min

the internal parameters of the separate heat pipe reaches a relatively stable state. The use of the separate heat pipe can reduce the temperature in the fresh food compartment from 16 to 5 ℃ in 60 min

which can satisfy the mid-range temperature requirements of a typical refrigerator. Meanwhile

it can also reduce the temperature in the fresh food compartment to 0 ℃ in approximately 135 min. Through automatic control of the solenoid valve

the temperature in the fresh food compartment can be maintained at 8 ℃

and the temperature fluctuation reaches to within 1.1 ℃

which is better than the 2.5 ℃ temperature of a direct-cooling refrigerator. In a on–off cycle

the running and stopping times of the separate heat pipe are approximately 6.5 and 42.8 min

respectively

indicating that the on–off ratio is approximately 15.2%. The good heat transfer characteristics and temperature control capabilities can meet the requirements of a new cool-storage refrigerator.