Speaker
Description
The cryogenic mechanical property tests of building elements are significant to ensure the safety of cryogenic-related buildings, such as LNG facilities, air separation plants, polar research station, etc. A cryogenic environment simulation chamber with large inside space, low temperature refrigeration and temperature control module is a key basic test facility for the construction of these buildings. A -120℃ cryogenic environmental test facility is developed and tested by the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences (TIPC, CAS). The facility consists of a cryogenic chamber, a mixed-refrigerant Joule-Thompson (MRJT) refrigerator and electric control units.
The cryogenic chamber is cooled by the MRJT refrigerator with inside dimension of 3m(L)×3m(W)×1.5m(H) and inner volume of 13.5 cubic meters. Building elements of concrete, steel or other materials could be tested in it. In order to handle the test elements conveniently, stainless steel slide rails with small rollers are installed on the floor of chamber, which are free of bears and oil lubrication. A full-width pneumatic chamber gate is designed for the access of large-scale testing elements. An optimized forced air circulation finned-tube evaporator is employed to cool down the air and testing elements in the chamber, driven by four motor split type centrifugal fans. 200 mm thick polyurethane foam board is used for insulation. Several temperature sensers are set at the center and corners of the chamber to test its cooling performance. A PID controlled electric heater is integrated in the evaporator for control temperature.
The refrigerator is based on a single-stage separation type MRJT cycle, driven by a 28 kW oil-lubricated semi-hermetic reciprocating compressor. The mixture of nitrogen, methane, ethylene, ethane, propane, isobutane and isopentane is used as refrigerant. High-pressure warm refrigerant is cooled through a recuperation process by low-pressure cold refrigerant in three stages of aluminum plate-fin heat exchangers. A dephlegmator is employed to separate the oil and high-boiling components in refrigerant before entering heat exchangers to avoid the clogging at the cold end. Cold mixed-refrigerant is sent to the evaporator of cryogenic chamber to supply cooling power. The refrigerator is cooled by a finned-tube after-cooler, free of cooling water supply. All the components of the cryogenic chamber and refrigerator are integrated on a skid, which is easy to transport.
In the performance test, chamber temperature of -80℃ is reached in 3.5 hours without load. The lowest temperature of -123.8℃ is reached in the cryogenic chamber after a 24 hour no-load cooling period. Concrete columns with total weight of 1.2 ton are used as the load, which are cooled to -80℃ in 11 hours, -100℃ in 15 hours and -111℃ in 21 hours (column center temperature). For normal utilization, it takes 2.5 hours to reach -60℃ and 4 hours to reach -80℃. The temperature fluctuation of cryogenic chamber is within 1.5℃. The temperature heterogeneity is within 2℃ (the temperature difference of the chamber center and corners). This cryogenic environment simulation test facility is successfully utilized in the research on cryogenic mechanical properties of a building technology laboratory, which is more economical than the former liquid nitrogen cooled test facility.
Acknowledgement
This work is supported by the National Natural Science Foundation of China under the contract number of 51625603 and 52006230, Autonomous project of the Key Laboratory of Cryogenic Science and Technology (No. CRYO20230303), QingDao CASFuture Research Institute CO., LTD. (21–8–1–1-qy), and the China Postdoctoral Science Foundation (2023M733584).
| Submitters Country | China |
|---|
