Effect of Swirl Generator Inserted Into a Tube on Exergy Transfer: Decaying Flow

This study experimentally investigates the effect of conical injector type swirl generator inserts on heat and exergy transfer in a uniform heat flux tube for turbulence regime. One hundred twenty watts of heat are applied by coiling a flexible silicone heater on the tube (copper pipe) with an inside diameter of 62mm and length of 1,200mm. The conical injector type swirl generator has a conical shape, which is similar to a funnel, with angle (alpha) of 30 degrees, 45 degrees, and 60 degrees. Circular holes are drilled on the conical injector type swirl generator as three different cross-sectional areas (A(h)). The total areas (A(t) =N.A(h)) of the holes on the conical injector type swirl generator equal each other. Because of this, the three different holes numbers (N) are produced. Flow directors having three different angles (beta=30 degrees, 60 degrees, and 90 degrees) to radial direction are attached to every one of the holes. This study is a typical example for decaying flow. Reynolds number (Re) was varied from 10,000 to 35,000, so the flow was considered as only a turbulent regime. All experiments were conducted with air accordingly; Prandtl number was approximately fixed at 0.71. The local and average heat transfer Nusselt number (Nu(h)) and exergy transfer Nusselt number (Nu(e)) are calculated and discussed in this article. It is found that the Nu(h) increases with an increase in Reynolds number, director angle (beta), and director diameter (d) but with a decrease in the conical injector type swirl generator angle (alpha). However, Nu(e) decreases depending on the same independent parameters.