Improving the process of drying high-pressure air bottles after repair

Abstract

Object and purpose of research. To reduce time and air volume required for drying high-pressure air bottles after hydraulic strength tests; experimental studies for subsequent development of a new, more efficient, layout of drying the bottles. Materials and methods. The amount of compressed air and time needed to dry air bottles with volume from 1 to 650 l as per the technology currently applied at ship repair yards was determined through calculation. The results confirmed the necessity to develop a new layout for the drying process. To perform experimental studies and search an optimal technological solution to this issue, there were developed nozzles (“vortex generators”) of three different designs that swirl the air flow coming into the bottle. To find out the optimal design during the experiments, a test rig was made, consisting of a bottle model, a flow rate meter and a manometer (to regulate valves and connecting pipes). Part of the bottle body was made of a glass pipe to visualize the drying process in simulation conditions. Inside the bottle model, a steel tube was installed, with “vortex generators” and beacons (thin woolen threads) attached to it. Main results. Experimental studies have shown that “vortex generators” (with tangential nozzles and outer diameter equal to the one of the air feed tube) reduces the amount of both time and compressed air required for drying. The experiments have shown that heat & mass exchange is the most intense when “vortex generators” are installed at the distance of approximately 5-6 calibers (internal diameter of the bottle’s cylindrical part) from each other, whereas drying of the through bottom requires installation of “vortex generators” at the distance of approximately two calibers from air flow outlet from the bottle.Conclusion. Air vortices make it possible not to rotate the bottles at the factory rig during drying of their internal surfaces, thus making the bottles less costly to repair. This new efficiency drying layout based on “vortex generators” is suggested for introduction at ship repair yards.

Keywords

• high-pressure air bottle
• intensification of heat & mass exchange
• drying
• duct nozzles
• flow swirling
• internal surfaces