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

Abstract

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 62 mm and length of 1,200 mm. The conical injector type swirl generator has a conical shape, which is similar to a funnel, with angle (α) of 30°, 45°, and 60°. 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 (β = 30°, 60°, and 90°) 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 (β), and director diameter (d) but with a decrease in the conical injector type swirl generator angle (α). However, Nu_e decreases depending on the same independent parameters.

Keywords::

• heat transfer
• exergy transfer
• swirl generator