As one of the three major energy sources, natural gas has been increasingly favored at home and abroad in recent years. After natural gas is liquefied, its volume shrinks by about 1/625, which has huge advantages for storage and transportation. When users use natural gas, LNG needs to be gasified and used. The atmospheric storage temperature of liquefied natural gas (LNG) is 111K (-162℃). Its vaporization and reheating to normal temperature of 300K (about 27℃) will release a large amount of cold energy, which is about 883 kJ/kg. The recycling of this part of cold energy is of great significance to improving LNG use efficiency and saving energy consumption.

At present, the cold energy utilization of liquefied natural gas can be used in various occasions and fields, such as thermoelectric power generation, air separation, refrigeration and dry ice production. In addition to low-temperature utilization, in accordance with the principle of cascade utilization of cold energy, LNG can be used in low-temperature quick-freezing warehouses (-60℃) and low-temperature freezers (-35℃) according to cascade recycling from the point of vaporization to normal temperature., high-temperature freezers (-18℃), as well as fruit and vegetable pre-storage rooms and central air-conditioning systems (0℃~10℃) temperature zones.

The LNG cold energy utilization research team of the Institute of Refrigeration and Cryogenics of Xi'an Jiaotong University is in a leading position in China in its research in this field and has a good research foundation and results.

At present, the team mainly has important theoretical support and key application technologies in the following aspects.

(1) Air conditioning technology used for refrigerated and refrigerated trucks (cold chain) or compartments of liquefied natural gas vehicles (LNGV);

Vehicles using natural gas as fuel are divided into CNG (compressed natural gas) vehicles and LNG (liquefied natural gas) vehicles. The latter is gradually accepted by the automobile market because of its large unit volume capacity, its ability to provide longer-distance power for vehicles, safety and reliability.

(2) LNG cold energy is used in the air separation unit process.

It can provide a low-temperature cold source for the air separation process and input a large amount of high-quality low-temperature cold energy into the system, thereby reducing the energy consumption of the air separation process and achieving the purpose of energy conservation and efficiency improvement.

The LNG cold energy recycling technology studied in this topic has applied for many invention patents. Simulation experiments have been carried out in refrigerated trucks, and the cold capacity can fully meet the requirements. At the same time, a series of studies have been carried out on refrigerated trucks 'cold storage technology, temperature field inside the box, etc., and the efficient recycling of LNG cold energy has been achieved.

This research group will further carry out experimental research, theoretical basic research and more important application research on LNG cold energy recovery. It is hoped that this technology can be successfully applied to automobile air conditioners, refrigerated trucks and large-scale air separation processes as soon as possible.

(1) Improve the refrigeration recovery system of LNG refrigerated trucks;

(2) Research cold storage technology for refrigerated trucks;

(3) Improve the technology of utilizing LNG cooling capacity in carriage air conditioning;

(4) Strive to apply and promote LNG cold energy recovery technology in the air separation industry.