FLOW VISUALIZATION USING HYDROGEN BUBBLE TECHNIQUE OF A FIN-AND-TUBE TYPE HEAT EXCHANGER WITH PUNCHED-OUT VORTEX GENERATORS

摘要

A study of the flow structure inside a fin-and-tube heat exchanger was performed by using hy-drogen bubble visualization technique to examine the effects of different vortex generator geome-tries on the flow field, understand the formation of vortices and identify the punched-out hole effect on the flow behavior. Flow visualization results clarified flow structures and the effect of the punched holes for the studied vortex generator configurations. It is found that the vortices are cre-ated in the installed or punched forms. The strength of the vortices of installed vortex generators is more prominent compared to that of the punched vortex generators but the punched vortex gen-erators showed smaller friction factors compared to the installed vortex generators.