Internal and external flow characteristics of multi-nozzle spray with liquid nitrogen

Abstract

The multi-nozzle spray cooling with liquid nitrogen can achieve high heat transfer rate and uniform temperature for a large-scale environmental simulation system. The understanding of the flow characteristics is crucial to the accurate control of the mass flow rates and the temperature distribution in a cryogenic system. This article combines the experimental and numerical approach to reveal the external and internal flow characteristics of the multi-nozzle spray with liquid nitrogen. It is found that a higher injection pressure is followed by an increasing mass flow rate under a given nozzle combination. The number and position of the low-temperature region in the downstream field correspond to the number and the arrangement of spraying nozzles under each combination. The pressure differences have little effect on the spray cone angle of a single-nozzle. The flow swirl is induced by the slotted swirl in the nozzle chamber and the cavitation is caused by the abrupt change structure at the orifice. In the absence of the friction and the resistance, the ratio of the mass flow rate in the multi-nozzles to that in the single-nozzle is basically equal to the ratio of the nozzle numbers. And the nearly equal amount of liquid nitrogen flows into each single nozzle of a multi-nozzle array under the varied injection pressure and inlet temperature conditions. The experimental research and the theoretical analysis are to provide insights on the practical engineering application of the multi-nozzle spray cooling in a cryogenic environmental simulation system.