Study Of Pressure Drop And Heat Transfer Enhancement In Tube With Spiral Twisted Tape

Twisted tape inserted into the tube is a common equipment to enhance heat transfer, which is widely used in pipe heat exchanger. This study analyzes the pressure drop and heat transfer enhancement in tube with stationary and rotated twisted tape through experiment and simulation. Combining with the field synergy principle, a new comprehensive evaluation method is established to evaluate the performance of various twisted tapes.The tests are conducted using tapes with twist ratios Y=3～8 in the range of Reynolds number(Re) 4×103～4×104. The results indicate that, the heat transfer effect increases with the ratios’ reduction, Nusselt number(Nu) in the tube with stationary twisted tape is higher than plain tube, the increase ranged among 11-23%, Darcy friction factor(λ) are 2.28-4.60 times as large as plain tube respectively which comes to the dimensionless equations: Nu=0.0342 Re0.787 Pr0.333 Y-0.0983,λ=1.97 Re-0.187 Y-0.736; Nu in the tube with self-rotating twisted tape is higher than plain tube, the increase ranged among 7-22%, A are 1.71-3.54 times as large as plain tube respectively which comes to the dimensionless equations: Nu=0.0370Re0.777Pr0.333Y-0.128，λ=1.60Re-0.188Y0.770. As for self-rotating twisted tape, with the decreasing of twist ratio, the fluid velocity tape needs for overcoming resistance and starting rotation is reduced; the relationship between rotating velocity and the fluid velocity is linear. Simulation results show that after the twisted tape’ inserting in the tube, the secondary flow appeares and the synergy number of temperature field and velocity field increases. Accordingly, the effect of heat transfer is enhenced and it increases with the ratios’reduction. In addition, a new comprehensive evaluation method is made based on fitted equation and field synergy, and a method selecting twisted tape in engineering is proposed.