Thermal Characterization of Turbulent Flow in a Tube With Discrete Coiled Wire Insert

Abstract

The present study aims to investigate the effect of adding discrete coiled wire to enhance the heat transfer in the heat exchanger. The coiled wire used in experiments was made from steel circular cross-section wire with (b = 4 mm) diameter. The outer coil wire's diameter was (B=36.5 mm) and length after been winding is (l = 100 mm), the discrete distribution of coil wires, by different spacing (S) between them with (S/l = 0.22,0.57 &1.2), which require to distribute 10, 8 & 6 coiled wires along test section respectively, were considered in the experimental study. The experiments have been carried out at constant heat flux rate and different flow rates of air that started from (Re=6000) and increased gradually to reach the following Re. (7500, 9000, 10500, 12000 and 13500). The results show that the use of the S/l=0.57 results in the augmentation of pressure loss around 33.2% higher than that of the S/l=0. In addition, it can be found that for using coiled wire turbulator with spacing ratios(0, 0.22, 0.57,& 1.2 ), the improvement of average heat transfer rate is, respectively, about 112%, 119.3%, 141.3%&132% higher than those the plain tube while the friction factor is 300%,392%,432%, and 322% times of the plain tube.