Experimental study on cool down characteristics and thermal stress of cryogenic tank during LN2 filling process

Abstract

During the filling processes of large-scale tanks with cryogenic liquids, the tanks experience non-uniform cool down processes and could suffer from significant thermal stress. An experimental study is performed to investigate the cool down characteristics and transient thermal stress distribution of an aluminum tank during LN2 filling processes with different feeding rates. The varying wall temperatures and induced thermal strains during filling processes are measured, and the local thermal stresses are evaluated. Test results indicate that when LN2 is fed into the tank, remarkable temperature gradient exists in the local wall region at the liquid level. The thermal stress at each point experiences a tension-compression cycle as the liquid level passes by. The maximum thermal stress at each point is proportional to the local maximum cooling rate, and the peak value emerges at the bottom of the tank. Moreover, the non-uniformity of the temperature distribution and the thermal stress level within the tank wall increase with the LN2 feeding rate. Under the largest feeding rate (0.08 kg/s) in this study, the peak value of thermal stress is about 41 MPa. This work could be beneficial to the design and safe operation of cryogenic tanks.