Abstract: The temperature of cooled water is high when using the traditional water cooling method in freezing construction. Therefore, in this study, a secondary water cooling system is designed and developed for the freezing construction of long tunnels. This system comprises a secondary water refrigerator and medium and hightemperature water pumps. The primary cooled water is transferred to the secondary water refrigerator through a mediumtemperature water pump, and the cooled water is reproduced. During the secondary water cooling process, the highpressure liquid refrigerant cools again, and the entropy of the refrigerant and cooling capacity per unit mass increase, whereas the compression work remains unchanged. The engineering practice reveals the superiority of this system over the conventional water cooling method, including a higher cooling efficiency of brine that can reduce the crossing time of the freezing wall, a lower temperature of brine, a higher strength of the frozen curtain, a better freezing effect, and lower energy consumption.

Key words: long tunnel, freezing method, cooling water, secondary cooling system, refrigerator