Experimental And Theoretical Study On The Explosive Boiling Of Saturated Liquid Nitrogen

The study on transient explosive boiling of liquid nitrogen (TEBLN) enlarges the conventional boiling research area, and plays the role as the fundamental investigation faced to the applications of superconducting technology, liquid nitrogen automobile, and so on. Therefore, TEBLN shows the great value both in academic study and in practical utility.As a new viewpoint of boiling heat transfer, this investigation aims at the behavior, influence factors, and the characteristics of the process about the low temperature liquids including liquid nitrogen impulsed by the transient high heatflux. This is a creative study and will make us on the cutting edge of the related research area. The below is the main contents of the thesis:1. The first TEBLN experiment system was set up successfully in China. With the pulsed laser heating and special Pt film to absorb the irradiation, the surrounding liquid nitrogen was heated to show explosive boiling phenomena. The process visualization was realized by the one-exposal-multi-repetition technique, and the transient temperature field was also measured. This experiment system is one of the rapidest visualization setups of the explosive boiling investigation in the world.2. TEBLN shows particular characteristics, such as super-rapid and violent nucieation, the obvious space boiling phenomena, new kind of boiling appearance of bubble group which is the mixture of lots of tiny bubbles and the internal liquid. Besides, there is a changeover from explosive boiling state to conventional boiling state on the heating surface, and the transition can be denoted by changeover time. By the experiments, the heating rate of explosive boiling was confirmed to exceed 10~7K/s, the evaluation system of explosive boiling and the meaning of changeover time were also analyzed.3. With the comparisons between TEBLN and the conventional boiling or the subcool explosive boiling, the essential differences were disclosed. The special factors describing the bubble behavior in the conventional boiling were not fit for the TEBLN. The existence of the changeover time and the persistency of the bubble...