Heat Transfer Handbook part 110. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | SWIRL FLOW DEVICES 1087 Condensing In-tube condensation of both steam and refrigerant vapor in the presence of twisted-tape inserts have been considered in the literature Manglik and Bergles 2002a . For describing condensing heat transfer with and without twisted-tape inserts Fig. for a once-through flow system is once again relevant but with the sequence of event reversed. That is entering from the right of the performance map in this figure the flow is initially desuperheated followed by condensation with a change in quality from x 1 to x 0 and subsequent liquid subcooling. As in the case of boiling phase-changer coefficients for condensation are inherently Puge. and twitted-tape inserts may enhance them further. Thus for their practical use due attention must be given to the controlling thermal resistance in a two-fluid heat exchanger as well as an assessment of the relative thermal benefits by considering the increased pressure drop. The latter generally entails a reduced saturation temperature and the driving temperature difference in the heat exchanger. Royal and Bergles 1978a b appear to have reported the only study on steam condensation in tubes fitted with twisted-tape inserts. They found that the average heat transfer conefficient was increased by 30 over the empty-tube values with snug-fitting tapes of y and where the hi l r elalance ne ll. waf ftth Hie tighter tape twist. Based on these data the following correlation has been given Nuh m L fiz Gdh xmpt ---- 1 - Xm 4------- Pg Pr033 1 160 H1 A1 91 Ld It may be noted however that the associated pressure drop also tends to be large two to four times the empty tube value at constant mass flux and inlet pressure and the relative performance enhancement should be ascertained by the appropriate evaluation criteria Royal and Bergles 1978a see also Section . In a somewhat related process the impact of a twisted tape on dehumidification of moist air has been .
