Effect of twisted tape inserts on pressure drop during R-404A condensation

An experimental investigation was conducted to find the influence of twisted tape inserts on the pressure drop during forced convective condensation of R-404A vapor in a horizontal tube. The test section was a double-pipe counter-flow heat exchanger. The refrigerant flowed in the inner tube and cooling water flowed in the annulus. Experimental tests were carried out for plain tube and four tubes with different twisted tape turbulators and several mass velocities and vapor qualities. Investigation clearly showed that using twisted tapes inside tubes increases pressure drop between 89 and 239% higher than that for plain tube. An empirical correlation was developed to predict the pressure drop during condensation inside twisted tape inserted tubes. Comparing the predicted and experimental data, it was found that the majority of the present data falls within ±20% of the proposed correlation.